Geometry lessons for the AARP set
A Bit Of A Reach
Initially, this started out as a progress report about the teal-toned double-dip I am experimenting with; the back to back review of Yeti’s SB120 and SB140. I’ll get to that at some point soon, but not here. Today, because of these two bikes, I want to talk about reach.
Full confession: I am a regressive curmudgeon with just enough brainpower to be a menace to myself. Meaning, I think I know things. I can get pretty far down my own confirmation bias wormhole, to the point where I am convinced that I REALLY know things. This brings up a premise from the Kurt Vonnegut novel, Galapagos, where humankind has evolved/devolved to something akin to fur seals and the book is being narrated by the ghost of Leon Trout. Much of the book expounds upon the idea that our brains are too big for our own good, and that we would be much happier, and would make less questionable choices, if our brains were smaller:
“When I was alive, I often received advice from my own big brain which, in terms of my own survival, or the survival of the human race, for that matter, can be charitably described as questionable. Example: It had me join the United States Marines and go fight in Vietnam.
Thanks a lot, big brain.”
“And people still laugh about as much as they ever did, despite their shrunken brains. If a bunch of them are lying around on a beach, and one of them farts, everybody else laughs and laughs, just as people would have done a million years ago.” ~ Kurt Vonnegut, Galapagos. Image thanks to Wikimedia Commons.
Aaaanyway, my own questionable grey matter has been convinced that reach isn’t really a very important measurement as far as bicycle geometry is concerned. Let’s refer to this mindset as “Crusty Old XC Nerd Syndrome”. COXNS is best evidenced in men of a certain age who tend to view ever slackening geometry with suspicion, and who, it might be fair to say, are inflexible in their thinking when it comes to vehicle dynamics. The COXNS afflicted will assert that effective top tube and effective seat angle measurements are the real important stuff, and that reach is some new school affectation put in place to try and obfuscate the fact that wheelbases are becoming almost comically long. Or something like that.
Doing back to back rides on these two Yetis however, has me thinking that it is time for me to gently set aside my COXNS and maybe hobble stiffly into the 21st century. To recap: I am testing a large SB120 and a medium SB140. Each bike has exactly the same componentry, wheels and tires. Each bike has exactly the same wheelbase; 1217mm. Chainstays are almost identical – 438mm for the SB140, 439mm for the SB120. The SB120 is a degree slacker in its effective seat angle, at 76.5 degrees as opposed to the 77.5 degrees of the SB140. The SB140 is a degree slacker in its head angle, 65.4 degrees to 66.5 on the SB120. In spite of these variations in head and seat angle, the front center measurements of these two bikes are also almost identical – 779mm for the SB140, 778mm for the SB120.
It could be assumed, from looking at the geo charts, that these two bikes would ride just about the same. Sure, one has more travel and a beefier fork, but in terms of the bending them around turns, the distance between the wheels and the placement of the meat spinning the cranks is so similar that they’d have to ride about the same, right?
But they don’t. At all. These bikes are both teal in color, made from carbon fiber, and have the same bits bolted onto them, but they behave very differently from each other. And I suspect that much of this difference comes not from the extra travel or the slacker head angle, but from a paltry 10mm that I’ve been omitting to mention until now. That 10mm is the difference in reach between the medium SB140 and the large SB120; 465mm vs 475mm.
By the numbers, SB140 first. Size medium...
And SB120, in grande. Or is it venti, if we are using the Starbuck's sizing parameters?
The SB120, so far, has proven to be a versatile and adaptable long-XC rig. Don’t say downcountry. Just don’t. It’s a stupid word. The SB120 is a sweet pedaling, beautifully proportioned bike for grinding out long bite-the-stem climbs, but it has enough plushness to the suspension and enough room between the wheels to remain stable and fun when the going gets chunky. It’ll still run out of suspension at some point, but up until that point, it is a very capable bike in almost every situation. It is calm, predictable, comfortable to stretch out on, and it doesn’t try to do anything sketchy.
The SB140, meanwhile, is a fucking riot. Loose drifts entering high speed turns, bring them on. Wheelie drop into poor line choices, no problem. Finesse the pedal strokes between the rocks and roots or just smash into everything, have it your way. Ironically, it pedals and climbs almost as well as the SB120. I mean, it’s close enough that in terms of pedaling performance I would have trouble determining which bike I was on if blindfolded. There’s more travel, so there is inevitably a little more body induced motion, but if one wanted to sacrifice some top of travel plushness for a little more pedal stomping glory, a few extra PSI in the Float DPS and I am willing to bet they’d be even-Steven. The pedaling kinematics are right there, but the distance between the nose of the saddle and the handlebars is that crucial skosh shorter. And when it comes time to bite the stem, that’s when the SB140 reveals its limitations.
But is it a limitation, or is it a size choice? This is where I am running smack dab into my own preconceived ideas about bike fit and bike handling. As an aging XC burnout, and a cusp sized rider, I have always opted to size up to a large instead of downsizing to a medium. I blame this on a too-small Bridgestone MB2 in 1988. Sort of. But really, for most of my life, I have opted for more effective top tube, and more room to breathe. This was all fine and dandy until mountain bike geometry really started to evolve away from old paradigms during the past decade. And now, I think my old way of thinking is hampering my enjoyment of riding.
That 10mm shorter reach, combined with the extra degree of seat angle, means that the distance from the nose of the saddle to the center of the bars is 495mm on the SB140. That same measurement is 515mm on the SB120. Same saddles, set to the same height, with the same setback. Same stems, same bars. I suspect that this 20mm difference has more to do with why the SB120 feels like a gentleman climber and the SB140 feels like a teenage renegade than any difference in fork stanchion diameter or wheel travel.
So similar in so many ways. But there's 20mm in there that speaks volumes...
Reach is measured by going vertically upward from the center of the bottom bracket, then drawing a line horizontally forward to the center of the top of the headtube. Effective top tube length is just that – the measurement horizontally from the center of the top of the headtube back to where it intersects the seatpost. The higher a given seat extends, the slacker the effective seat angle may become (that’s a whole other column!), but when comparing different geometries with the seat heights the same, ETT is a consistent point of reference. For seated, bite the stem dynamics, effective top tube length is still a great measure. It determines how much you can stretch out and suffer while laying down the watts. Reach, meanwhile, which along with stack basically tells you where your hands and feet will be, is probably a more valid harbinger of overall bike handling – of the potential fun quotient.
I have, in my dinosaur way, tended to weigh my preferences more upon effective top tube length than I have reach. I’m kind of embarrassed to admit that. And, similarly, as bikes have entered the new school of stretched out wheelbases, I have continued to opt for as much reach as I can get. “Yeah, 480 sounds about right for me, bro.” I am a little embarrassed to admit that as well. I suspect that maybe I have been reaching too far, so to speak, for the past few years, and in so doing, have been robbing myself of fun.
I don’t know whether I’d like a large SB140 as much as I like the medium. It may not be as much fun. And dear god, that SB140 is fun! Conversely, I am pretty sure that a medium SB120 would lose out on its red mist capability, and would feel too cramped as well as a hair more sketchy. But I am dead certain that moving forward, when I am looking at any longer travel bike, I am going to need to contemplate sizing down instead of dumbly selecting “large” and calling it good. More to think about. Or maybe less. Shit, now I am confused again. As the ghost of Leon Trout would say; thanks lot, big brain!
Comments
albert03
10 months, 1 week ago
This reminds me of many similar discussions of home building and efficiency, where various aspects of the building SYSTEM are discussed in isolation. To me, Effective Reach and Stack, defined horizontally and vertically from BB to middle of handlebar GRIP, much more accurately define how you’re going to fit on a bike. You don’t grab the center of the top tube to position yourself on a bike, you grab the grips. By using simple frame dimensions, you’re more likely to confuse your thinking.
[Edit: "...we're more likely to confuse our thinking." That's what I meant to write, but I forgot, because I'm part of the AARP set ;) ]
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Landonarkens
10 months, 1 week ago
Yep, you’re describing Lee McCormack’s RAD measurement
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Mike Ferrentino
10 months, 1 week ago
In this case, the reach number difference measured to the center of the headtube works fine - the stems and bars are identical between the two bikes. But yes, you are right. Bar width, bar rise and bar sweep all impact the reach and stack of a bike.
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Brian Tuulos
10 months ago
SYSTEM huh? By that logic, can a big dude make a small frame work using a 80mm high rise stem? No.
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Cee Cee
10 months ago
How about a 230mm riser bar?--BMX
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Justin White
10 months ago
Boom!
Yup. Completely depends on what said big dude wants to do on said small frame.
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Brian Tuulos
10 months ago
Stem length, stem spacers, and bar height are just for subtle tuning of fit. Not to make a 6FT dude ride a small frame, comfortably. Slopestyle applications are an outlier. Frame size needs to approximately match body size.
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Cee Cee
10 months ago
6FU
TristanC
10 months, 1 week ago
I thought I knew what I wanted/what fit me, but then I got another bike and re-confused myself. I have a bike that I spent years tinkering with, and fits me like a glove, my Ice Cream Truck. 80mm stem. Then I bought a Stooge Scrambler, which on paper is a slightly smaller bike. I put a longer stem on it - crippling neck pain. I put a 60mm stem on it - feels great. How can the smaller bike fit better with a shorter stem???
I think all this taught me is that I should keep that bucket of stems and just iterate through, since I clearly can't reason through what fits. Thanks, big brain.
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Bikes
10 months, 1 week ago
Possible measurements are taken differently. Also possible neither bike matches its geometry chart perfectly.
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TristanC
10 months, 1 week ago
That's very possible. The two bikes are on different continents so I can't physically compare them side by side, but I'm very interested to do that when I can.
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Cr4w
10 months, 1 week ago
I've experience this too. I keep a bunch of old bars and stems around so I can at least move my experiments in the right direction. It's amazing what a few millimetres here and there will do.
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Burgess Langshaw Power
10 months, 1 week ago
I think terrain and intended bike purposes matter in a huge way. I'm only 5'10, but I ride an XL enduro bike (previous gen Orbea Rallon) for riding in the Canadian rockies, and a size M Banshee Enigma for ontario. Why? Partly the terrain - I need stability for long, fast descents in the rockies - hence XL, long wheelbase, stretched body position etc. Partly the trails and intended use - for Ontario riding, its short trails where I wanted something stupid fun, that I could do all sorts of silly things on (somewhere between DJ and trials type riding).
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Skooks
10 months, 1 week ago
That makes total sense to me. I mostly ride slower speed, janky trails and my shorter bike works great for this. If I was riding higher speed trails or bike parks I would prefer a longer frame.
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Kenny
10 months, 1 week ago
Agreed. I get the desire to reduce the determination of "proper" bike size down to a formula, it'd be nice to just say "I used the formula, therefore, my bike fits me", and remove bike fit from the list of variables going through our heads when riding.
Reality is, how and what you ride, body proportions, flexibility, and personal preference in terms of handling characteristics are all going to play a part.
The other side to that coin is, humans are pretty adaptable and cockpit setup also adds room to alter fit, so most people can realistically ride a couple sizes with decent results.
All I know is, for me, the whole "RAD" doctrine puts me on a bike that is way too small for my use case.
I finally went from 465 reach, 75 degree seat tube angle, to 510/79, and couldn't be happier. Yes I got the odd corner where it feels like an 18 wheeler, and bunny hops and front wheel lofts require more focus, but overall the bike is just way easier to ride, especially in gnarly terrain.
Is this compensating for the fact that I am a desk worker who lacks the fitness and flexibility to be able to consistently hold a low deep hip hinge? Probably. But the point is the bike fits ME. Not a theoretical ideal version of me.
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Morgan Heater
10 months, 1 week ago
I think the idea that pros are continuously in a deep hinge is pretty untrue. They are usually in a pretty neutral balanced position so that they can use their limbs to respond to terrain and move the bike.
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Kenny
10 months, 1 week ago
I'd agree, I was more saying that because thats the argument people make for these small bikes, and it is a position that, the better you can hit it, the less likely you are to go out the front door when things get spicy.
The wild thing is, I have probably at least one "moment" a month where the longer bike saves me from what most certainly would have been certain doom on my old bike.
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Brian Tuulos
10 months, 1 week ago
You CANNOT compare the reaches of two bikes accurately when they have different stacks. I drew your example out in CAD, the actual difference in reaches (corrected for the same stack) is 14mm. Not insignificant.
I also think stems have gotten too short for how capable bikes are. We arent in danger of going OTB as easily anymore, so 33mm length stems are overkill and just dont weigh the front end as much, and push people to bigger frame sizes. 45-50mm stem is still a sweet spot.
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BadNudes
10 months, 1 week ago
It's better than using ETT and STA, but I think we still got it wrong with reach and stack. Were it up to me, we'd measure the distance between feet to hands (or BB to top of head tube for frames) and the angle from horizontal that that distance is measured. The distance tells you the fit, the angle tells you the intention of the bike (more vertical for relaxed riding, more horizontal for the racers).
And yeah, I seem to always get along better with a 50mm stem, even on different bikes where the reach varies +/- 20 (but ETT is pretty similar because of different STA). Something about the stem being similar to the fork offset intuitively feels right but might just be a coincidence.
There's a lot going on in the shape of a bike, but the best way to find what you like has always been trial and error... too bad those errors can be so expensive when riders aren't able to test ride...
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Justin White
10 months, 1 week ago
Any stem to fork offset relation is completely a coincidence, because the bar also plays a large part in where you hands are, both its sweeps and width. You average 760mm wide, 8 degree backsweep, bar is going to put your hands somewhere around 25mm back, making a 50mm stem behave like a 25mm with a straight bar. So no useful relation to fork offset, especially when you start taking into account head-tube angle and front-wheel trail.
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Tehllama42
10 months, 1 week ago
As long as the bar is an apples to apples comparison, I'd say that just comes out in the wash. Same, I agree with the trail measurements being mostly coincidence, but it's actually pretty neat overall that those roughly 1" changes can actually be so directly affecting ride experience in mostly quantifiable ways.
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Bruce Mackay
10 months ago
That's b/c ETT tells you how you body "fits the bike" length wise (all other things equal like STACK and stem and bar). So still valid. Reach is a good to indicate where you be located. In the bike. (Again ATB=). They are all guides. But a leg over still wins, to fit. If you geek over numbers, and understand how they work for you. You can get a good fit off a sheet of paper.
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Justin White
10 months ago
ETT alone can tell you how your body fits the bike length-wise when seated. Without knowing the BB location, ETT alone tells you very little about how the bike will fit when standing. So yes, ETT is still valid, but not any more or less valid than reach, since we (pretty much) all sit and stand at various times while riding.
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Mike Ferrentino
10 months ago
The hypothesis I am slowly arriving at is that, for me, if seat angle geometry is more conservative (maybe sub 75 degrees or thereabouts), then ETT is still a really good barometer for understanding how I will fit, especially with regard to seated pedaling behavior. However, as we move deeper into bigger travel and more radical seat angles, I am realizing that reach/stack matters more, and that those bikes are probably not designed to optimize seated pedaling (no, really?), and are more likely to be ridden with the seat slammed out of the way except for when they are being winched up climbs between the downs, and therefore maybe should be viewed in the framework of reach/stack fit instead of worrying about ETT at all.
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Justin White
10 months ago
Agree: steep seat tubes are meant to optimize that one very specific seated pedaling situation: long and relatively smooth uphills where traction is not really an issue; as you said, the "winch" part of winch & plummet. If traction or technical moves come into play, they stink.
I still think ETT really only provides seated fit. You might know that with a narrow range of seat-tube angles that a given ETT should fit you well both standing and seated, but really you're just deriving reach (and stack?) estimates based on your experiences.
ETT is simply not a driving factor for standing (descending) fit: reach and stack are (given the rest of the components are same/similar), and for standing feel it's those plus wheelbase, front-center, out-front, trail, etc.
Tehllama42
10 months ago
Mike, I could probably put together a decent 18 paragraph rant on why the set of measurements we're using is about half right... and very definitely half wrong for the ways in which we actually ride bikes and try to understand why the handling characteristics are the way they are.
If Andrew wants, I can probably actually commit some of that to paper with some of my thoughts, since it might actually be somewhat more useful.
My TL;DR on that is that we really only care about bike geometry with a pretty small subset of broad measurements (HTA, A2C, Pythagorean Reach/Stack and Angle from BB, BB Height, and Chainstay Length, with just needing to understand the combined leverage/force curves and braking ratios through travel). We can even simplify it with a given fork travel to just a HTA value, a stack/HTA adjusted offset applied to reach, then add BB height, and CSL (since we're probably going to want a basically fixed bar height relative to the BB and front contact patch)... and in light of that very simplified measurement set, it starts to feel really silly to have the same CSL across a wide range of bike sizes (until you're a logistics chain manager trying to keep people in bikes, and realizing that tall/long and small/short edges are much low volume units).
To add climbing performance, the actual measure we care about is the horizontal offset from BB, which is why the specific seat tube angle and location is quite relevant for seated climbing, and arguably STA can only be understood in light of CSL anyway, but will vary based on leg length because that can really shift around what is happening with each of those segments. Again, the only relationship we actually care about there is how the inclination angle and rider-input on CoG affects the weight distribution between those two patches, and for how broad a range of upper body positions does that keep a rider within the easier to pilot bounds of maintaining traction and avoiding looping out or having to be too low to let the front wheel come up over trail features.
Tehllama42
10 months, 1 week ago
Absolutely can compare across the different stack values - but the right pair of values really is the pythagorean reach/stack, and the inclination angle from horizontal at the BB up to the headset top point (although the way we actually supplement stack with spacers on a steerer tube is kinda sub-optimal.
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DancingWithMyself
10 months ago
Seeing as we pretty much have to have this discussion in generalities, I'd argue a longer stem is a poor solution for weighting the front wheel. I never feel very comfortable when my hands get that far in front of the steerer axis. I've got a bike where a 50mm would give me a better "fit," but I just can't get used to it versus the 40mm to which I'm accustomed.
Instead, I'd suggest that rear centers are too short on most L and XL bikes, and because of the short rear center dogma, the industry has been lengthening and lowering the front of the bike to achieve stability at speed and get enough weight on the front wheel. If rear centers grew and front centers shrank, we'd have more balanced bikes and you wouldn't struggle to get weight into the front wheel. And as we age, our backs would thank us for the more reasonable stack we could run.
Bikes with Transmission drivetrains but not size specific rear centers are emblematic of the consumerism-without-knowledge that plagues our sport.
I think Lee McCormick's "formula" errs on the short side, but I do think he's absolutely correct that too much distance between feet and hands limits your ability to handle the bike well. As to whether a shorter distance is a faster or a little bit slower, I don't know or care.
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Tehllama42
10 months ago
It definitely trends towards the short side - having had the luxury of running a 452mm CSL bike for the last decade, it's a properly amazing thing for anybody north of 6' to run, especially when the terrain trends towards chundery but enabling speed, there just isn't a substitute for the stability it enables. Whatever I give up in maneuverability (and that is the tradeoff), tends to be really easy to accept after coming out of a section of trail on a 130mm bike at speeds more talented riders on full on enduro rigs are struggling to achieve, and do it repeatedly.
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Cr4w
10 months, 1 week ago
I'm going through a bit of a revelation these days around these questions as well. It's good to question all the things you thought you knew about your numbers. I've been reminded that everyone has a range for each number, and within that range the ideal number varies depending on how it is paired with all the other numbers.
And you can't ever get the full story from geometry charts and suspension diagrams. I've spend the last few years of two very extreme bikes (the Geometron G1 and the Forbidden Dreadnought) and the last few months on a not so extreme bike (SC Hightower) and guess what? They're all really different and really great. For different reasons.
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fartymarty
10 months, 1 week ago
I'm in no way a golfer but see bikes like golf clubs. Every one has a use that is slightly better suited to an application that the other.
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Velocipedestrian
10 months, 1 week ago
You bring up golf a lot. Blink twice if we need to send rescue.
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Skooks
10 months, 1 week ago
I'm between sizes and sized down for my latest bike. The reach is shorter but because the stack is also taller the span from the BB to the center of the bars is identical. I like the taller front end, and the slightly shorter wheel base makes the bike noticeably more nimble. It's a great bike for the slow speed technical style of riding I prefer. If I spent more time riding high speed trails I would prefer the stability of a larger frame.
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Lynx .
10 months, 1 week ago
@Skooks, that sounds just like my Large Phantom, super sweet on the seriously slow or tight tech trails, bit "thrilling" when speeds really pick up, that's when I sometimes start to think having chosen to ride the Prime would have been the better idea, but for what I ride and like to ride, the L Phantom works well.
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Skooks
10 months, 1 week ago
Yeah the shorter bike felt a little squirrelly on steep downhills at first but I'm getting used to it. I think it handles better than a longer bike everywhere else.
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FullSend
10 months ago
Same here! For my latest bike I also went to a model with a shorter reach but taller stack. What the new bike loses in reach, it pretty much exactly gains in stack. It makes for an awesome setup IMO.
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MTB_THETOWN
10 months, 1 week ago
I've been mountain biking pretty seriously for 20 years, but only recently started get coaching to learn how to ride properly. Basically everyone rides with their weight too far forward, which makes a longer reach seem comfortable, and that longer reach helps save you from you from crashing when your body position is wrong. Now that I know what I'm looking for, i can tell the pros have their butt almost comically far back by the rear axle with an aggressive hip hinge that balances their weight over the pedals with chest super low. I watch experienced but non pro riders (including videos of myself), and their butt is by the saddle and they are super upright.
At 5 10 I am always between a medium and large, and going to a medium is usually the right move. I used to ride a large, with big riser bars, but that made me sit too upright and was slow around corners. In a proper position I'm now much more comfortable on a shorter bike and am dropping my bar height.
However, this new position requires a strength and flexibility that I am still working to achieve, and a lot of people who ride casually probably can't hold it. For them, the bigger bike may still be better overall. It will feel comfortable and confident in a straight line through whatever comes up, although is slow to corner.
I occasionally race xc somewhat poorly, but I really care about descending, so if your primary concern is climbing your fit needs may vary.
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Andy Eunson
10 months, 1 week ago
Therein lies the rub. What works in terms of bike fit for one discipline does not work for another. We are always looking for the balance between going up and coming down. What works in terms of geometry of a cross country race bike will not work at all for enduro racing. Plus individual body sizes and proportions also play a significant role. Many riders set up a bike for how it looks. Road riders have slammed stems for years because it looks race yet they rarely ride the drops because they can’t reach them comfortably.
I think the reach measurement started out as a good thing. What we wanted was a bike that we could ride with a short stem to get our weight behind the front contact patch. A bike that fir well with a 100mm stem fits the same as a bike that is 50mm longer and a 50mm stem. Increasing reach but steepening the seat tube angle to keep the effective top tube length similar or even shorter for a given size can have a negative affect. The recommended size for me at 5’4" is a small. But many current designs will have a tt that is too cramped for me by a few cm. Knees get close to bars on hard uphill switchbacks. So I size up. Steep seat tube angles encourage a more upright position but many current bikes seem to use dinky little headtubes. Must suck for tall guys. That may be why you see tall riders angle their seat down. Too low of a bar height leads to leaning on the bars with more weight and the riders is sliding back off the saddle so the tip it down to alleviate that. Or they think they need different grips because their hands hurt or a compliant bar (whatever that means) when the better answer may be a higher bar.
I do think really tall and really short riders are more challenging to fit a bike on. Because we are at the extremes of average.
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MTB_THETOWN
10 months, 1 week ago
It sounds like a small sized bike needs to have a slacker seat angle so you can pedal without bashing your knees, but still have a good fit for cornering aggressively on descents. I think some brands do this, but probably not enough. I can't believe that we are six inches in height difference though and ride the same sized bike. That tells me that bike companies are not doing a good job with sizing for actual human shapes as opposed to just building the bikes so the geo chart fits the latest fashion trends
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Andy Eunson
10 months, 1 week ago
Yes but the 78° seat tube angle is the problem. My medium Fuel ex has a tt of 584mm which is a length I’ve ridden on numerous bikes but with less steep seat tube angles. The reach on the Fuel is 450. But the steep seat tube angle puts my feet further under my butt. First rides were clumsy particularly around uphill switch backs but I have adapted nicely now. I do have long legs and arms. Inseam is 31". I’m pretty sure I’m an outlier in terms of size and proportions so what I prefer won’t jive with normal people with average proportions. I’d love a dropper with a set back head. But I don’t like the 9point8 or other offerings that have that.
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MTB_THETOWN
10 months, 1 week ago
That makes perfect sense. Bike sizing is clearly a struggle with unusual proportions. Maybe a good justification for something more custom like an Atherton bike?
Custom sizing is much easier to get on road bikes for obvious reasons, but hopefully with additive manufacturing coming down in price, and mtb bike geometry and kinematics stabilizing, it will become less of an extravagant option.
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Muesliman
10 months, 1 week ago
MTB_THETOWN You're absolutely right about the body position thing. It was a revelation to me after seeing a Lee McCormack video about the importance of 'the hinge'. You're also right about the flexibility needed which I struggle with a bit as an older rider. Still I'm happy to have a wee bit more reach in my bike than I used to.
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BenZ
10 months, 1 week ago
Not trying to invalidate anyone's opinion here, but whenever someone (seems like it is usually one that thinks of themselves as a coach...) calls one riding style 'right' and another 'wrong' I take issue. An example with the hip hinge: Jackson Goldstone, very much a rider of the moment, rides incredibly upright with very little hip hinge (polar opposite to the likes of Rude). Another case was elbows up (ala Gwin) vs elbows down (ala Gee Atherton) with some coaches calling up a 'strong' position and down a 'weak' position. To call anything about Atherton's riding 'weak' is frankly comical.
What is great about technique discussions, is they always remind us to try different things. You are the only one with your exact dimensions, trail preference, strength/joint mobility, and gear setup, so try some different techniques out and find what works for you!
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Dogl0rd
10 months, 1 week ago
Yes! Just as all aspects of geometry are connected same with body position.
Elbows out or down, doesn't really matter. Jordan Williams is elbows down.
I wish no one ever told me to put my outside foot down in turns. Useless information taken on its own
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MTB_THETOWN
10 months, 1 week ago
While people should ride what and how they want (since we do this for fun) if you have certain goals, like racing downhill or enduro, there are fairly universal techniques that help achieve those goals. If you want to produce power and traction to go as fast as possible downhill, you need to harness power from your core. You can tweak around the edges based on your body type (as you make a good example of the slight elbow tweaks of Gwin and Gee), but it all comes back to a body position and movement that is similar to a deadlift (or kettlebell swing), aka a hip hinge. You can call it different things, and I've had different coaches describe it differently, but the general point is the same.
Here is a picture of Jackson riding (first I found): https://www.vitalmtb.com/photos/features/PHOTO-BLAST-Andorra-Race-Day,13710/Jackson-Goldstone,152871/sspomer,2
Here's another from his redbull bio: https://www.redbull.com/us-en/athlete/jackson-goldstone
He may not appear as hinged as other riders because he is so short, but his hips are back and his weight is low and balanced over the pedals so he can use his core to generate power and traction. Every top downhill pro does their own version of this.
But again, all that really matters (for non pros) is if you are enjoying the ride and not hurting yourself. If you prefer a super long stable bike and a relaxed upright position, as long as you're having fun that's great. Try out a few things and see what you like best.
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Jonny Calder
10 months, 1 week ago
To me it’s about proportions. I’m 6’1 and ride a Kona process large which is 490mm reach. The steep seat tube is great for our steep climbs here and the reach means it’s not too cramped.
I initially really struggled with weighting the front wheel when in the short chainstay setting (435mm). Now in the long setting (450mm) the bike feels so balanced.
It’s a big bike but super stable and feels like the right size. I’m sure I could downsize for a more lively, nimble ride but don’t have the strength and skills to feel as comfortable in those fast, rough situations.
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Dogl0rd
10 months, 1 week ago
Yeah I think if you feel comfortable when it's nasty, that's what is going to keep your confidence high and keep you coming back. Easy to lose confidence in a crash and slow to regain it sometimes.
Greg Minaar is a big guy and runs a super huge bike. It shows to me that you can just ride what you feel good on and not worry
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Justin White
10 months, 1 week ago
More people need to hear, and experience, this chainstay story.
The old numbers game of "shortest chainstay" has kept its inertia in the industry, and it's why you still see new bikes with 120mm of front-center change through a size range and 0mm of rear-center (chainstay) change. Those XS and S sizes are going to struggle getting weight off the front (CS relatively very long), while the XL and XXL are going to struggle getting weight on the front wheel (CS relatively very short). Same bikes, very different riding experience just because of the sizing. It's so stupid.
My height and bike size actually line up pretty good with yours: 5'10", 460 reach, 435 chainstays. Very balanced for me: enough room to move around inside the fore-aft stability window, but still easy enough to get out of the window for endo-turns (batting like .150 on those, haha), manuals, or hops. I could def go longer and still be comfortable, especially if my terrain had more extended downhills, but I'd want both ends longer, not just the front.
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Landonarkens
10 months, 1 week ago
As a 5‘11“ human being on a 435 mm reach bike, this satisfies my confirmation bias very nicely. 😉
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mk.ultra
10 months, 1 week ago
All I know is I fucking love my XL Cotic FlareMax with obscene reach and wheelbase. I LOVE the rock solid stability of a long bike. 6'2" for reference.
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fartymarty
10 months, 1 week ago
Cotic make big bikes. I'm on a L Solaris Max but borderline XL. The L is great for a HT but XL probably better on FS.
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Lynx .
10 months, 1 week ago
Hey Mike, sorry to say, but you had me face palming there a few paragraphs in, had to close the browser and take a break. There's no real problem, would never expect those 2 bikes to not handle quite differently with a difference in Reach, HTA and ESTA.
Easiest way to me to try to figure out the climbing/descending thing is to put a longer stem on the SB140 and lengthen it's effect Reach to match the SB120, see if that helps/works, then, try putting a shorter stem on the SB120 and see if that helps it's descending prowess.
Note that I DON'T talk about moving the saddle forward or backward to match whatever ESTA, because, well honestly, there's really only one "right" ESTA for each person and what the frame manufacturer decides they think is best is irrelevant. I put ALL the saddles on ALL my bikes in exactly the same place, relative to the BB, then I adjust Effective Reach with stem/bar.
I have 4 main bikes, all have almost the exact same Effective Reach, but one runs a 70mm stem, another 50mm stem and the other two 40mm stems, but the saddles (all WTB PureV) measurement vertically down from the back of the saddle to intersect the CS is less than a cm and they're all VERY different bikes with different usage.
Also of note the front centers are within a couple MM on the 2 I mainly ride off road/on trails, 760mm and that's for my '18 XL Kona Unit with a 485mmReach and 2014 L Banshee Phantom with 750mm Reach, the other 2 are quite a bit shorter and longer, with my 2012 XL Prime measuring 785mm and the XL '08 Monkey measuring only 680mm.
Edited this just to add, I'm 6'2.25", 35.25" inseam, i.e. a pretty hefty Ape Index.
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Justin White
10 months, 1 week ago
"The COXNS afflicted will assert that effective top tube and effective seat angle measurements are the real important stuff, and that reach is some new school affectation"
Except those are all related. Knowing effective top tube, effective seat tube angle, and seat tube length (or wherever ETT is measured from) and seat height (personal not frame geo), reach can be derived. So the afflicted aren't wrong, they're in fact kinda saying the same thing: the horizontal relationship of BB and bars is quite important.
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fartymarty
10 months, 1 week ago
Mike - in the name of science you must also compare the L140 and M120. My hypothesis is the L140 wont be as riotous until you reach a certain speed - then it's game on.
I'm 6'1" and have an XL Starling Murmur. I was on the cusp of L(485) / XL(515) and went with a XL as I wanted to try a longer bike. On a mellower trails it gets on with things and is maybe a little boring but when the trail gets rowdier it's got your back and wants you to push on. It has allowed me to push my riding. I suspect a L would be more "fun" on mellower trails but less confidence inspiring when things get spicy.
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Mike Ferrentino
10 months, 1 week ago
Asking for two more bikes from Yeti, as well as a spare month of riding time, isn't in the cards. But I suspect your take is about how things would shake out.
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fartymarty
10 months, 1 week ago
It is a shame but would be worth the science.
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Vincent Edwards
10 months, 1 week ago
Or just trade that LG 120 for a LG 140 and ride the same bike in Med and Lg for a month.
What I mostly came here to say is Bravo for doing some real bike TESTING… not to be confused with bike ‘reviewing’ which seems to be the majority of what is served up these days. I think testing equates to looking at the various factors that make a bike ride a certain way, and employing some loose science to A/B changes. Reviewing = riding a bunch of bikes and commenting on their merits as a product.
I’m gearing up to teach a frame-building class next year, which has me thinking a lot about all these numbers, and how they relate to different riders and styles and past vs future. I have several articles from NSMB saved to serve up as required reading… this one just made the list.
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Cee Cee
10 months, 1 week ago
Testing the author's unsubstantiated suspicion about the special significance of static reach would have involved using a +10mm stem and +10mm of saddle offset on the 140. This is two bike reviews prefaced with an impertinent literary reference
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Mike Ferrentino
10 months, 1 week ago
As far as cockpit dimensions and "fit" go, using a different stem would get things in the ballpark, as would the seatpost offset. lynx alluded to that as well upstream. it would be a way of checking fit, but i don't think it would be totally relevant to bike handling, since reach and ETT are two aspects of a puzzle that also involves head angle, stack, wheelbase and front center.
One of the key reasons I wanted to test these two particular bikes was because they each have exactly the same wheelbase, and almost exactly the same chainstay length. I wanted to see where the similarities and differences lay within that wheelbase. One thing that surprises me right now is that the large SB120 with a steeper head angle "feels" like a longer bike than the SB140. I don't think it is actually any more stable, and given the wheelbase and head angle, it shouldn't be, but the extra cockpit tells my mind something that physically isn't really true. I may need to go ahead and futz around with stems just to see how that works.
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Tehllama42
10 months, 1 week ago
"Feels longer" doesn't actually surprise me... it doesn't take a very big shift in CoG relative to the contract patches or leverage points (BB, stem- headset) to actually make a meaningful change in kinematic response. Head tube angle is almost a secondary metric, and too intertwined with trail measures to really be evaluated in isolation in the small adjustment range... it is telling that even Mondraker didn't go that hard on HTA, despite pushing >500mm reach figures nearly a decade ago. We don't really perceive the horizontal difference between our front contact patch and bars, so much as the difference in load carriage between upper and lower body, and since rider mass is still >80% (a truly embarrassing 87% in my case) of the equation, THAT just plain matters more.
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Cee Cee
10 months, 1 week ago
Well, don't waste time on my account--I'm responding to people going gaga about something having been tested. Anyone can see from geo that 120 has a longer rider compartment, and you've already figured out that you've been robbing yourself. Until recently, longer travel bikes have had more compact compartments--hmmm. One's a riot and one ain't.
P.s. I should mention that I've been using two bikes for the last few years with more similar dimensions than these Yeti except for reach and STA--429mm/75d and 447/77. Even out of saddle, the shorter reach unit feels bigger. Its four-tenths degree slacker HTA and 3mm longer chainstay have a greater effect than 18mm of reach. RAD people should know that mine is 82cm theoretical but 90 actual, though I'm 183cm and riding size Mediums--go figure.
A companion piece for A Bit of a Reach could be 'Base Instinct [1196mm], but I'm struggling to conceive more stem-bitten cockpits as well as to find a literary reference for the intro.
If you want to increase the riotousness of 140, drop the saddle a cm or two and use flats foot-forward. Bar can also be dropped. Shorter crank is funner too
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Vincent Edwards
10 months, 1 week ago
I think this is part of what you’re getting at with your testing, but I’m very curious about the difference between a slacker HA with a longer stem vs. a steeper head angle with more reach and a shorter stem. Consider this two ways to achieve virtually the same position of handlebar and front axle relative to saddle and BB.
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Tehllama42
10 months, 1 week ago
In my admittedly sample size limited experience... really just depends which direction and speed you're going. Low speed and climbing, the steeper HTA and longer stem is meaningfully better... and the reverse is very much true as speed gets added on. With the luxury of lots of wide open trails, I will choose the shorter stem slacker HTA option ever time, but I did develop an understanding of where a 50-60mm stem can be a lot better, especially when paired with a 67-68° HTA if you're mostly dealing with speed limited jank... but the more optimal setup would still be more reach and less stem length. 35-50mm stems still work a fair bit better to me, and produce what feels like a more direct steering response, especially when descending slow/janky/switchback filled stuff.
ackshunW
10 months, 1 week ago
Yes, I’ve thought about this a lot too, and we two aren’t the first - - - my details might be off, but I think it was Joe Breeze and Charlie Kelly made some experimental bikes based on that idea- consistent wheelbase & bar position, but varied head angle, reach, and stem length (all the way up to like 80 degrees / zero mm stem, if I remember correctly….). I’ll post back if I find a link to the article.
taprider
10 months, 1 week ago
Genesis geometry
https://singletrackworld.com/forum/topic/gary-fisher-got-a-lot-right-early-on/
Lynx .
10 months ago
Good link Taprider, Gary was ahead of his time with the G2 geo, especially for MTBs, but nothing even close to what I'd call radical. Also remember, Gary's "short" stays were 440mm, which by todays standards are more like long/regular.
AlpineMTBTraining
10 months ago
Great to see discussion exploring the different measurements and adjustments that can be made to tweak bikes for specific circumstances.
If you adjust reach, stem, HTA like you said to have your handlebar, BB and front axle in the same position you have created bikes with comparatively the same fit. The steering of the bike will change (your hands are in different places compared to the steering axis, the steer tube basically) and the bike will interact with the trail differently, mostly because of the change in HTA and trail that goes along with it.
Bikes are a sum of their geometry, travel, components etc which we can can adjust what is adjustable to fine tune the ride fit ourselves and our preferences.
I love to nerd out on what adjustments can be made to change the ride experience of a bike.
Muesliman
10 months, 1 week ago
fartymarty - I'm a smidge under 6'1" on a Starling Twist in size L and it feels spot on although I never tried an XL. I'm pleasantly surprised how well it climbs steep technical stuff with no hint of front wheel lift despite its unfashionably 'short' 435mm chainstays. Probably the steep seat angle and coil shock grip I guess.
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fartymarty
10 months, 1 week ago
I could ride a L but wanted to try a properly long bike and got the XL. I do run a 31mm stem and 12 degree bars and seat pushed forward so have "shortened" it a bit. There were a few other bikes geo I was looking at before I got it - Pole and Nicolai spring to mind. The L is a similar size to my Cotic Solaris Max.
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Justin White
10 months, 1 week ago
The coil shock grip would probably be more conducive to front wheel lift. And it's definitely the seat tube angle helping to keep it down. Axle-to-ass position is the driving factor for seated climbing and the trade-off between traction and keeping the front wheel tracking well enough.
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Lynx .
10 months, 1 week ago
Mike, while making my evening "cuppa" I got ot thinking about this and the essence of your discussion ETT vs Reach, which is the better one to use when trying to pick the right size bike and thought I'd share my story when I realised and switched from ETT to Reach.
The switch occurred back in 2014 when I received my new to me Banshee Phantom, V1, size large coming from a 2012 pre-production Banshee Prime XL. The XL Prime had the ETT I was used to, 25.4", so that was the size I chose when asked what I wanted to test.
I was coming off learning to ride MTBs with 120mm stems as the norm, I'd gotten an XL Paradox V1 in 2009 with a 25.4" ETT and I made the "monsterous" switch to a "super short" 90mm stem and 685mm wide bar and it worked just fine for the type of riding I was doing back then, it was a massive change from the old school 120mm stem/640mm bar I used to run. When I was getting ready for the Prime, Keith told me I had to give a wider bar a go and somewhat reluctantly, I did, I got a 750mm FUNN Fatbar and it felt insane, it was so wide, but it felt "good" coupled with the still 90mm stem.
So, a 2005 Giant Trance XL, 2007 RIP9 XL and then the 2009 XL Paradox were my gauges, I was always told I was a tall guy, definitely XL and so that's what I got when I got the Prime, but I refused to think that anyone, unless they were doing Rampage type stuff, "needed" anything shorter than a 60mm stem and so, that what I ran, but I always had trouble controlling the front, never could figure out the full why, always put it down to the much slacker HTA of the new bike compared to all that came before. When Keith designed the Phantom, he lengthened the reach compared to the Prime by 10mm for the Large and 4 or 5mm for the XL, so I thought the XL would be way too big and the Large had the same 450mm Reach that the XL Paradox had, but almost an inch shorter ETT, but that should be good, right.
The plan, as with nearly all my builds was just a straight parts swap from Prime to Phantom, then down the line build back up the Prime. Well, I built the Phantom up with all the parts, but opted for a 70mm instead of 60mm stem and gave that a go and it was pretty good, but not perfect. On a chance I gave the 60mm stem a go and that was really good, no issues with pushing the front, climbing or the like and so I realised that I had been running too long a stem on the Prime and going by ETT to match my earlier XLs, that had much slacker ESTA, had been a mistake, or at least a mistake with the intention of running a 60mm stem shortest. I then rebuilt the Prime using a 40mm stem and any problems I had had initially were gone, yet it still climbed just as well.
So about then when I made that switch from Prime to Phantom, I realised using the Reach w as better than ETT, BUT, you also need to look at Stack as well. It was also about then that I realised that ESTA wasn't something to pay attention to with regards to my actual riding, only to know if I'd need a straight or setback post to put the saddle where I needed it.
Don't know if all that makes any sense to anyone or is even helpful to this piece, but thought I'd share, because for me, it was a big "Aha" moment.
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Andy Eunson
10 months, 1 week ago
I get it. When 29er were starting to be a thing I bought a Giant xtc 29er and built it up. They didn’t make a small nor did any others at the time so I simply used a stem that was shorter by the same amount the new bike was longer. Revelation time. From then on I went by tt measurement and not the letter size which is kind of stupid. Thing is you shouldn’t select a frame size based on one parameter. You need to see the whole picture. And like someone smarter than me said, bike fitting is like a spider web, pull here and it moves there. If you change one thing you’ll change the fit somewhere else.
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fartymarty
10 months, 1 week ago
Andy - your spider web analogy is the best i've heard re geometry. I guess you could extend it to cover the use of the bike.
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Andy Eunson
10 months, 1 week ago
Not my analogy but that of this Physio/bike fitter on Cam Nicholls YouTube site. https://youtu.be/vMmbXAWcgh4
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XXX_er
10 months, 1 week ago
At 5'8" I did a 1 hr demo on a yeti 5.5 in Large, i liked the bike but the cockpit did feel long so I ordered the medium and it felt just right, the medium Bullit also felt just right in fact much like the 5.5,
I think I'm right in the middle of the medium sizing, I don't pay much attention to the figures I just get on the bike
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Timer
10 months, 1 week ago
I'm not sure if I should be glad or annoyed that I'm totally unable to feel such small differences between bikes. When I'm on the trail, I'm only focused on the terrain. The bike just kind of disappears into the background.
Sure, I notice if I'm riding an Enduro or XC bike. I can feel if the suspension is vastly over or undersprung. Wrong tire pressures too. But that's where it ends.
I recently put on a new rear tire of a different type. Didn't notice a thing. A couple of psi more or less in the fork? No change. Rode with a 820mm bar for a while because I didn't notice that the new grips weren't pushed all the way in and stood over by ~20mm. Swapped in a shorter stem at some point. If it didn't look different I wouldn't have know.
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Skipaul
10 months ago
So, as I understand you set your setback on the saddle according to the saddle marking and therefore you are effectively further behind the bottom bracket on the SB140. Your pedal position and muscle utilization are therefore different. Seems to be about 10mm in your measurements/analysis.
What would be really useful is to do the analysis with the same actual saddle position relative to the bottom bracket on both bikes, so push the SB140 saddle 10mm forward, or whatever it takes to have the same distance from the nose of the saddle to the center of the bottom bracket.
I don't think reach is as big of a differentiator on the uphill as you think, I think it is because you have introduced a 10mm different pedal position.
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Mike Ferrentino
10 months ago
Other way around. I am further forward over the bb on the 140, and further back with a more relaxed seat angle on the 120. In this instance, the 140 seat would need to go back 10mm, to counteract the effect of it having a steeper seat angle. This would roughly even up the seating/pedaling positions but would still be a gap between saddle and bars on the 140. (edit in there because I accidentally downvoted you when I was futzing around with the voting toggle. Sorry about that. Hope it is fixed now!)
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Tehllama42
10 months, 1 week ago
You'd be amazed at how much these measurements can be boiled down to a simple vector metric (pythagorean reach/stack and stack inclination angle). When actually comparing those, you start to see how big the actual frames are.
The tricky part of this is how stack, A2C, and HTA really play a part in setting since vertical height for a travel value effectively sets a real stack height target which then isolates reach as the true metric, until you start monkeying with things like Long-shock & mullet combinations which can rapidly shift the Z height starting point for the bars, then you do have to actually go back to the ultimate frame size pythagorean measurement.
For my part, mountain biking only ever started to be fun was the first time my 6'2" idiot self got on something with over 450mm reach, then I actually discovered there entire notion of shifting weight between contact patches, and not just teetering between looping out or ejecting myself over the bars. There actually are good ways to give up a little bit of effective reach (add a little A2C with an air shaft, lower the stem; slide the seat forward; roll the bars back slightly; or the ever present rider mod). The outlier answer is reducing weight... a light long setup (plus slightly stiffer tube) can do acting things with regard to winning back agility, and keep the ride much more engaging, all with side benefits of increasing the upper limits of capacity. I realize there are limits, but the reason bike sizing has experienced such a seismic shift after droppers normalized as because of those things. More reach is a wider trade space that works when you use the other adjustments around it. Insufficient reach just leaves you stuck and giving up performance in ways that just plain suck to varying degrees. This is why I bought the same bike I already had, just 54mm longer.
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Velocipedestrian
10 months, 1 week ago
>For my part, mountain biking only ever started to be fun was the first time my 6'2" idiot self got on something with over 450mm reach, then I actually discovered there entire notion of shifting weight between contact patches, and not just teetering between looping out or ejecting myself over the bars.
Yes. This was a revelation for me too, now when I get on a shorter bike I feel trapped - there's only one spot to put my weight without tipping over the whole apparatus.
It's a wonder we ever got hooked at all.
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