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Dang. Spot on. I will check out the interview. I didn’t connect the dots but my geo journey started when I switched to flats and adapted my bike to my new riding position/style.
Maybe a little bit, but him not being very tall is good for highlighting my point, and that him liking longer stays on some bikes while feeling a bit off on others is also great to show that it isn't the end all be all fix that a lot of people online make it out to be. When I started the thread, it was in response to long chainstay talk, but I did want it to be about geo in general, what we like and don't like, how we experiment with it and how it's going, and general complaining about it.
Honestly, I'm really interested in talking about stack height right now since that's what I've been trying to experiment with the most. Most of us ride mid to big travel bikes (140-170mm rear) so a lot of us are going higher stack, but what about the xc and short travel riders? How have they been experimenting with stack height?
The one downside I've noticed with taller stack (as a medium sized rider) is that while it feels great on steeps, I find it harder to lean over rapidly and pump/pull. I'm not saying it's not possible to do those things, just that like many others there's a sweet spot that works for one's height. I feel like there's an optimal amount of arm bend to be at in the default riding position, and if you raise stack too high, it becomes harder to, say, pull up on the bars. I'm sure you can adapt to it eventually, but with 3 bikes, I've found that I need to get the stack within a couple mm of each other in order to be able to ride them interchangeably without conscious adjustment.
Stack and HA adjustments seem like the next variable to tackle. Just stumbled on an insta post by the Raise and Reverse stem guy that seems relevant. I don't really understand wheel flop as a characteristic and its relationship with stack and HA, but this is interesting because his point is that tweaking those things you can have a more extreme rear weight bias and still keep front end grip with his unique setup.
"You might think that with such a long 920mm front center and short 423mm chainstay for a 1343mm wheelbase combined with the tall Gen 1 150mm RR stem with a -15mm Reversed offset putting the rider over their feet with less weight on their hands that there would be such a small amount of weight on the front that it would always understeer and wash the front with no front traction. In practice much like with cars, a rearward weight bias will actually tend to oversteer with a rear wheel drift or even tailspin. On a traditional forward offset stem, you have a lot of wheel flop at the hands, and unlike with cars where if you understeer you just track a wider arc, with bikes you have to balance in turns by steering and counter steering to keep from standing up or falling over leading to you washing the front with your weight falling off from loading the tires. With so much wheel flop at the hands with a forward offset stem, it’s harder to get good feel of your traction and balance point to know if you are falling over leading to a front wash unless you are aggressively on top of it with weighted hands. This is the main reason you feel you need to get forward and keep weight on the front to keep it from washing. That washing out isn’t so much a lack of traction from a lack of weight on the front, it’s a lack of balance making you fall over unless you keep on top of the floppy balance point by weighting the bars. With the RR stems Reversed offset steering geometry, you get much less wheel flop at the hands and a much calmer steering response. This means that even with a rearward weight bias to overload and drift the rear to oversteer, you can still keep good feel of the bikes balance and traction points."
Would love to see a vid of him drifting his mtb
Ironically, I've seen plenty of videos of him understeering off a corner using that stem.
Wheel flop is really only a factor when riding slowly with sharp turns. It's the tendency for the front end to drop down when turning the wheel relative to the bike. Slacker head angles cause the wheel to flop over since the rotational axis is more angles relative to the ground, causing the front end to drop. When you're riding fast and linking corners that stops being an issue because you're leaning your bike into the turn. Honestly not sure how stack height factors in to wheel flop, since it's determined my your effective wheel radius and head tube angle.
No, my elbows just have a little more flexion in a neutral position. It's as or more effective for pulling (i.e. more lat activation, less bicep activation) and way more effective for pushing the bars (i.e. an extra 60mm of range of motion). And if I'm in an active stance, I'm not trying to support my bodyweight with my triceps — I'm standing on my feet and using my arms to pull and push the bar.
I think a lot of folks are trying to weight their hands to increase traction on the front wheel, but it's a mess biomechanically. Triceps aren't postural muscles, and as they fatigue we unconsciously extend our arms to reduce the leverage on them. On a bike, that means you're pushing your weight back (i.e. unloading the front wheel) and reducing the distance the front wheel can travel down before your arms are fully extended and the bars pull you forward over them. A short front center and a long rear center increases the weight on the front wheel as long as you're standing on the pedals.
A short reach means the range of motion in your arms, from locked elbows to pulling the bar to your chest, maps to a greater degree of frame rotation around the bottom bracket. The bottom bracket is the vertex of an angle where the line of the direction of gravity intersects a line from the handlebars. The linear extension and flexion of your arms form a chord and the handlebars form an arc as the bike increases or decreases in pitch. The range of motion in your arms is constant, so the trigonometry question ends up being: what is the maximum central angle you can create with a cord of a given length? It's 180 degrees, and the chord is the diameter of the circle. Every increase of that circle's radius results in a decrease of the central angle of that chord.
Damn, geometer
Are there any elite riders / coaches / engineers lurking here who can explain current or changing schools of thought on optimal body positioning? Do you start with body position & balance, then build/adapt the bike from there? I remember Minnaar talking about trying to adapt to the more upright modern position you see from riders like Jackson, Asa, Loris, etc but at a certain point over-elongated wheelbases and additional drag might prevent setups from scaling accordingly for large riders (ex Coulanges/Kolb are more hunched-over).
I'm imagining that many many riders (including myself) are very poorly fit into our cockpits but have no realistic starting point or target to work with aside from trial and error with different setup options- I could see bike-fitting services making a comeback but for descending rather than pedaling.
I am curious how much the hunch over is from proportions on those bikes of people you list and then the upright folks having better bike proportions, higher stack, and the ability to weight the front a lot more naturally all while being more upright still. I mean look at all the changes that Minnaar was trying to do to his old XL SC to have a better fit. Mega stack, +10 custom chainstays, higher bars.
I think Jackons bike came out to 1.79 at the time and Minnaars was something like 1.86. BIG difference in ride characteristics between the two and body positioning needed to ride em. Jackson has the ability to drastically change cockpit set up(stack, bar rise, etc) and still maintain good positioning AND good front end balance/weight while Minnaar is having to do a heap load of changes just to get it acceptable but still not optimal. He made the best with what he had.
I think its the comparison of bike geo and balance between Mediums and XLs. XL is way behind the curve for balance for the most part for bikes produced cerrently (forbidden and few others being the exception).
As a decently tall person (6'2"), this stuff gets me all sorts of frustrated and fired up. Just want to ride good balanced stuff too in a better ride position!
Brands sell alot of Medium and large sizes, a few small and hardly any XL.
It makes zero sense to try make an XL ride like a Medium.. for starters the damn thing is long wheelbase, youll never change that.
We ride the same trails, why should you take your XL bike down the same trail as a person on a small? the trail may suit the smaller bike...then what? youll change the trail to suit your Trail train?
at 6'2 youll find a size large will naturally balance because you will be able to ride it.
Im 6ft and many of my friends are over 6ft and they stopped riding big bikes - many have tryed longer rear centre bikes and ended up back on proper bikes.
If you look at the youth in any developed country, they are getting taller.
I'm 6'1 and every 18 year old male towers me in Australia it seems
must be the chicken
You're conflating wheelbase and rear center length. If you shorten the front center of a bike, you can lengthen the rear center without increasing the wheelbase. "Long rear center" bikes are not necessarily bikes with long wheelbases.
Also, to reiterate what's been said a thousand times — a medium Hightower has a ~1.83 ratio of front center to rear center, an XXL Hightower has a ~1.98 ratio. Those might as well be entirely different designs given how completely different the geometries of the two are. Now, if you assume the 1328mm wheelbase of the XXL is proportional to the rider, an XXL which preserves the riding dynamics of the medium frame would have 470mm chainstays and a 500mm reach. But it doesn't. It has a 525mm reach and 445mm chainstays.
Thats most Certainly not how it works, you cant just shorten the reach an extend the rear - its been trialed before - We've tried it.
When I read through this thread Someone's already touched on it, but Rear Centre length and Actual chainstay length Play vital rolls in leverage and where the BB is in relation to the axles through travel(then you need to account for axle Path, shock leverage, Shock tune, Fork tune and travel)
You can Chirp on about Balance but Have you ever watched a Pro ride? they don't stand there in the middle of bike looking like a damn scarecrow
Alot of Non-green riders don't generally ride Just flatter trails on a Hardtail with a 6'5ft rider with 470mm rear centre in XXL... However you put a rider on a medium frame with the same Ratio and the trail is suddenly alot more fun.
No XXL will ever ride like a Medium, you would literally have completely different bikes.
No, you cant get your XXL bike around a tight 90deg like a Medium frame - however you can Ride the bike different, Lean into the front of the bike and allow the rear to 'flick' around and drift.
You cannot ride a medium bike the same as a Medium regardless of what any theories say about 'ratios'
I'd like to add something personally, Im 6'3, And i tried to chase this long rear centre theory, but overal the bikes just sucked, It got so extreme I made Many of my Own steel frames to Confirm my Own experiences.
I learned to Ride properly, I can get my XL spectral around some Very tight corners and its chainstays are short. I have a roomy cockpit and the bike will 'whip around' no worries.
I dont normally comment on Here or Pinkbike but you guys are chasing a theory that in the end youll resort back to shorter rear centres because they just work.
Feel free to Chat via FB - Angus koleston.
@The Serious , that’s interesting to hear. Can you elaborate some more on what geometries you tried and what your experiences with them were?
Lol @ drunk rambling: “You cannot ride a medium bike the same as a Medium”
Dude no one is chasing a theory. These bikes are working in practice. You are correct that long front center bikes need to have the rear whipped around, but a lot of riders don’t like that!
Anyways, feel free to come and discuss your ideas in the geo thread. We aren’t allowed to talk about this stuff here in tech rumors anymore
Edit: who’s drunk now?!? I didn’t even see what thread I was in lol!
also worth noting: every single anti-proportional cs person talks incessantly about tight corners, as if thats the best part of mountain biking. "how will you steer your bike through 180° switchbacks?!?" dude i don't look forward to those types of turns on any length cs or wheelbase. when we are talking about suspension performance we hear the same thing about pedaling efficiency, as if pedaling uphill is this incredible experience that we are all looking forward to. Why are we designing bikes around moments that at best are bearable on a bike rather than optimizing our bikes for absolutely sick parts of a ride? i want suspension that feels great riding fast through the rough and I want geo that lets me ride balanced and fast and turn at speed without tucking my front or needing to lean over the bars to get the front to hook up.
we get that there are different styles of riding, but there is a large contingent of riders chasing a different experience on the bike than the one that was pushed on us for the last 5-7 years or so.
See, this is the thing. I started off on a medium bike despite being 183cm, and I've been chasing that balanced feel ever since. It was something like a 455 reach and 430 rear centre. My large e-bike has a rear centre of 455 and a reach of around 470, it handles damn near the same as my old medium bike despite the large difference in reach and wheelbase.
I was a lot more upright on the medium, and once I adjusted the stack to be more upright on the large bike, not only did it get a lot more comfortable to pedal, it felt a hell of a lot more agile on the trails.
I think a large part of it is being able to pivot the bike around the CG, which becomes harder when you're more over the front, as your weight is more spread out, being upright concentrates your weight, and your strength more, making wheelbase less relevant for tight turns.
Every bike I have upgraded to has been longer than the last, yet I feel I am cornering better than ever (which is still poorly), even on tight turns.
So I agree that I am not willing to sacrifice handling on most of the terrain (by lengthening wheelbase) to improve in the very tightest of corners.
For me the real question is:
Do “more standard” chainstays, or proportional length chainstays work better for the largest bike/rider sizes?
My suspicion, based on theory and limited experience is that closer to proportional would be better.
I have a stumpy Evo, so I can adjust cs length, but it’s a tiny adjustment, that also adjusts BB drop and head- and seat-tube angle, so it’s not been very informative.
It would be cool to ride a bike and be able to change just CS length, in a noticeable amount, to test this.
Aligns with my experience in a bike with longer chainstays. I think 3-5 years ago, as reaches were getting longer, folks just assumed that the new required body position of being hinged and over the front was just… the new required norm. But I am really liking being able to be in a more neutral or even defensive position that’s afforded with longer rear center.
I have the stevo in s4 and put an xl seat stay on it to give it a 10mm longer CS measurement (I think that was the difference...) The improvement was night and day.
I’ll be honest with you: your writing style makes it very hard to understand what you’re saying, so I don’t have much in the way of a specific response.
But my current bike has 525mm chainstays and a 460mm reach and it rips. I’ve taken it on pump tracks, dual slalom tracks, jump trails, flow trails, punchy rolling XC trails, sketchy loose fall line trails, big ass rock gardens, fast open trails, tight techy trails, poached hiking trails, and paved bike paths. It’s felt better everywhere than any other bike I’ve ridden since I started riding as a kid in the early 90s.
I’m not chasing a theory, I’m riding an actual bike.
I just want to say, I have never been able "whip around" my bike better than when I put on the longer 460 chainstays. Turns out, when you increase front end grip, you can then drift the rear end in an extremely controlled fashion. My bike turns tighter than it did before, and I think it all has to do with front end confidence. I know I can turn a tighter radius because the front end is not going to wash. I often feel like the people who cannot fathom riding longer chainstays are the same ones who bemoaned the geometry changes of the mid to late 2010's. You'll get there one day.
This guy gets it.
It’s like riding skinny skis. Why?
At least for backcountry skiing, I’m a lot more worried about breakable crust than hard snow, so my heavily rockered fat skis are great for that, too.
I’ve definitely been doing some experimentation on my 120/140 bike (REEB SST). Having spoken with the man who designed the bike, he is a low stack enjoyer and rides a medium (so the FC/RC ratio is more like 1.78 vs my Large’s 1.83). I’ve run everything from a 40-50mm stem and 20mm to 50mm rise bars, and I’ve settled on a 50mm stem and 35mm riser bars with 15mm of spacers as being the best combination between feeling “safe” on the bike and getting good front end grip without going out of my way to ride the front. A low stack seems to complement a shorter rear end, and encourages you to ride leaned/hinged into the bike to push the pace and keep the front planted. I love the SST, but I honestly wouldn’t mind an extra 10mm or stack and chainstay length to feel a little safer and more stable. Riding with flat pedals actually seems to help for me, because it makes me think about where I’m putting weight instead of ending up with heavy hands and light feet.
In general, it seems like chainstay length and stack need to be proportional to each other to an extent, and long chainstays are no good if the front of the bike is too long or too low as well. At 6’ even, two of my least favorite bikes I’ve spent time on were my S5 Stumpjumper Evo (1.86 FC/RC) and my friend’s XL Dreadnought (exact same FC/RC). I was running a short stem and lots of spacers on the Evo to make it more comfortable, but it took even more weight off the front - friend with the Dreadnought is just an inch taller than me with a similar set up as my Evo had. Both bikes felt like uncomfortable freight trains, without much ability to control the front but with waaaay too much bike behind me. I’m sure I’d have a great time on a Large Forbidden, though. On the opposite side of the spectrum, I found with the Canfield Lithium that the high stack was very confidence inspiring on steep downhills, but ultimately the slack STA and short chainstays made it climb horribly and feel a little sketchy in turns that weren’t incredibly well supported.
I'm a bit late to the party here, and not coaching elite Dh racers, though some of my former riders have gone on to race at that level...
One of the big reasons for higher bar height/stack becoming popular is overall speeds have increased. Most riders adapt to a setup and run it mostly the same, but change minor details for each track. Most of them live/train in steep fast areas, where the high stack is hugely advantageous. It may not be helpful on the motorway at Ft.bill, but they aren't going to change their entire riding style for one section. Riding taller also makes it easier to see further down the track without craning your neck, look at the size of their eyes during a race, their eyes and brain are 100% engaged, a tiny advantage is huge. Longer wheelbase bikes also require more leverage to engage the rear tire. There are limits to everything, but I don't think we've seen the end of stack heights and wheelbases increasing.
To briefly touch on the "feel" and preferences most riders on our lovely forum here have, in essence, they don't matter. A racer doesn't care if it feels fun to manage their limo through a tight switchback, as long as it's faster it's good. Racers are experts at ignoring their feelings for speed, that's why they aren't scared to go twice as fast as me. Winning feels good.
Riding today and realized as I was pumping and carving through rolling turns why I love long cs bikes: I can pump and carve through rolling turns at the same time and keep traction at both tires. Before I made the change to my bike I kind of had to pick one: if I was weighting the rear I lost the front, and if I was weighting the front it made it hard to actively pump. Being able to weight my feet and carve through turns means I can actively pump in and out of the turn. Lower grade turns are so much more fun as I’m maintaining speed if not actively generating speed through turns. Big ups to all the people before me who worked this stuff out!!!
Alright, I’ve just read through the last few pages of this thread, and I have a question:
Have you considered that your strong preference for a particular setup might be matched—or even outweighed—by an equally strong preference for something different among a broader group of well-informed riders?
It seems possible that what you're seeking is a very specific riding feel that simply doesn’t align with what the majority of riders want. In that case, it's less about the bike industry being misguided or behind the curve, and more about you needing to seek out the brands or builders that cater to your particular niche.
The impression I get from some of the responses is that when others disagree, there’s an implication that they just “don’t get it” or that they didn’t implement the setup correctly.
For what it’s worth, I’ve tried the long chainstay / short reach setup with high stack. While it technically worked fine, I found it to be an unengaging riding experience that dulled much of what I enjoy about the trails
^My preferences and ideas don’t always seem to work out for me let alone everyone else. And yes geo is incredibly user dependent. And you’ll probably adjust to anything if like me your goal is to have fun and get a little better year to year. And your preferences will probably change the more opportunities you take to really try new ideas. Or they will solidify around something if that’s what you constantly ride and commit to.
But it’s way more fun to tell your buddy he’s an idiot for riding with Dak stack or still riding a 420 reach bike when they are 6 ft. Or to wind up your friend on whatever bike gear related rant he’s likely to spiel if provoked.
Post a reply to: Modern Geo Talk: Chainstays, Stack, Reach, and Bitching About It