Hello Vital MTB Visitor,
We’re conducting a survey and would appreciate your input. Your answers will help Vital and the MTB industry better understand what riders like you want. Survey results will be used to recognize top brands. Make your voice heard!
Five lucky people will be selected at random to win a Vital MTB t-shirt.
Thanks in advance,
The Vital MTB Crew
The funny thing is what turned me onto this idea was in fact 29ers with "longer" (compared to my other bikes) stays. I was cornering better, riding faster and just generally having more fun - feeling more comfortable on the bike. I thought it was the bigger wheels, the head tube angle, the BB - until I rode a 27.5" bike with nearly ***identical*** geo numbers less the stays (and rear travel). Then it all came together when I put both bikes on the scales. Bar height, head tube, reach, stem, sweep etc were all the same. Chainstays were the only noteworthy difference.
So yeah, I never ever would have thought bigger wheels with longer stays would allow me to smash corners harder - but sure enough, in this particular case, it did.
But yeah, I'm not trying to say "make all bikes chainstays super long" - what I am saying is now that bikes have grown in front center, perhaps some bikes rear center needs to grow as well (or maybe just the larger sizes - or bikes intended for racing...)
Yes, I'm talking in circles.
How about 18.22 with the custom link!
yeah, I guess we were talking slightly past each other. I'm trying to look at single variables, so either CS or front center. In your case, your variable is the BB, aka the body anchor point at constant wheelbase. Fair enough. I would still maintain though, that a shift in BB location alters the weight balance of the bike. After all, isn't that what Minnaar did effectively on the XXL V10? I'm saying effectively, because of course they lengthened the bike altogether. But by first increasing reach, and then CS, and maybe going back and forth a bit, they were basically experimenting with different, relative BB locations.
But yeah, the body measurements must be the foundation to all this. It's astonishing how different the experiences are. And then there is the whole short bike is better movement in the 2000s, cramping Steve Peats and Greg Minnaars onto BMX bikes. Is anybody out there aware of any database regarding variability in human body measures?
To be fair, last 29' bike I had felt like the concept of changing directions was stupid and a sign of weakness. Needless to say, I don't own that bike anymore.
If you are shorter, maybe spend more time in a bike park or on fairly gnarly trails, maybe the Patrol is right.
Too many variables but without a question I'm more balanced, more comfortable and riding faster on the Smuggler than the Patrol.
I will say, in my experience, going north of 60 really isn't (ever) good. Unless you are andre the giant and running an uncut steerer tube
Usually, a stem around the length of the fork's offset is a good place to start (40-50mm)
J
To correct all that, I'd used Fork Offset x 1.190476 to generate a stem length
You speak of balance, but balance can be found with short CS too. Compared to a Ripley, 17.4" CS, a Intense Spider 275c has a 16.5" CS and feels far more balanced and centered to me, both size med and me 5' 7". I found myself cornering from behind the saddle on the Ripley, while I'm centered 2-wheel-drifting on the Spider. I wasn't setting KOMs on the Spid, but it definitely was radder. Not too self-conscious about actual speed... the feel of going fast is pretty satisfying, even if it's not proved by the clock.
Interested to know the OP's views on bikes like the Ibis HD3 and Pivot M6? Both have short stays but also keep the reach sensible which should put the rider centred but between a shorter wheelbase than something like an SB6.
Many people like long chainstays, and I bet the same amount swear by short ones. Count me in the second group. I'd trade stability for maneuverability any day. It all comes to your riding style. I like my bikes to turn over a dime, you might feel at home with a different geo.
Both at the top and both short chainstays
So...here is the point to this half-baked rant. I've raced bikes for awhile in a number of disciplines. And yes, I ski. For both skiing and road bikes, there are a number of objective ways to determine mount point, ski length, shaping, stem length, frame size, seat position etc. For mountain bikes, we're still sort of using the "guess and check" method to determining what works and what doesn't. This makes some sense being the modern mountain bike rider is far more "dynamic" than that of the static (in one position more or less) road racer.
Put another way, if anyone has had a real road bike fit, you can attest to it being more of a science and less of an art. I'd like to bring this level of objectivity to mountain bike fit and geometry to get more riders on the best tool for the job. For a number of manufacturers, it really wouldn't matter as this level of customization is beyond their reach from a dollar and sense perspective. (though I still say growing the rear center slightly in the longer sizes will create a more balanced bike no matter what). That said, if you could better explain to a rider what sort of numbers to look for in a bike, you could steer them toward better buying decisions. As someone who has tested a lot of bikes, I can promise better fit/geometry will always trump better suspension. (as suspension can always be improved)
I've run formulas to try and figure out how much the rear center should grow in proportion to front center. As a number of people in this thread have noted, its different than skiing for the reason that there are two weighted points on the bike (handlbar and pedal). The proportion to how this is weighted is going to differ person to person and largely be determined by style, arm length, proportions etc. which is likely why some tall dudes may love short stays and some hate them (me).
If this bias between pedal/bar can be better quantified based of body proportions, perhaps we could arrive at a better fit system that goes more in line toward each rider getting on the right rig than simply following "internet trends"(low bars rule! short chainstays are the truth! Long bikes are the best! Slack HT angles rule! Stiff suspension is the best! etc)
Again, as I noted elsewhere in this thread, the ultimate would be some sort of group of sensors on the bike that could actively determine weight bias while riding and objectively explain what tweaks to geometry/suspension setup etc are doing to the the overall ability for the rider to stay in control.
I know, making a lot of leaps here. Its the internet. And this is a forum. Isn't this what its (internet forums) are for?
J
With a large helping of different body shapes and muscle densities, there is a lot of room for varying preferences. Add in just how big the differences are between terrain and the speeds people take it, there actually should be quite a decent range in preferred CSL.
Similarly playfulness has a few different meanings, and really depends on how people want to dick around on a bike, as well as the trail. For being able to quickly reposition on low speed technical stuff, and quickly modulate the pitch and yaw of the bike, shorter chainstays do carry advantages, particularly for less brawler-shaped riders. For others, being able to set a shock tune with minimal rebound damping to send hops off bonus lines without giving up stability in chunky stuff and being able to modulate weight balance in big drifty cornersis better, and to those riders a longer chainstay setup is going to be more playful. For riders that like both, it may be a terrain dependent preference.
As far as the weight distribution delta - a move of 0.6" of the bottom bracket on a fixed wheelbase is actually non-trivial. Considering that the axle to axle wheelbase of bikes is usually in the 46" range for a medium sized bike, with a chainstay length around 17", this puts a front center length at 29". Moving to half inch longer chainstays, and taking that out of the front center, it's about a 5% change in center of mass location between the two contact patches.
Also consider that in terms of a properly fitting bike with properly located rider that the pedal axle to ankle location is going to be ideally constant (especially when going downhill), therefore the bottom bracket sets the location of the rider's lower body. When in attack position, the only other contact points are the grips, and consequently moving those forward to achieve proper fit is going to move the rider either farther forward also, or rely on adding some stack to keep the overall pythagorean reach-stack sizing the correct size for the rider (basically rolling the rider back @ the hip to get the same fit happening). Especially when adding inclines, the ramifications for these changes on weight distribution at the contact patches are significant.
As far as I know there isn't a manufacturer who broadly maintains stack to reach ratio across sizes. I know for some very small sizes it's hard not to have an extreme high stack relative to reach but in general it's the L/XL/XXL that have the problem of very low stacks that riser bars can't cure.
That means that there's almost no point in asking a tall dude and medium sized dude to compare thoughts because the tall dude already has his weight forward due to the lower relative stack.
People talk about keeping the weight on the front wheel.... I've never had this problem! I wonder what it's like?
JUST on CS.....
I've had bikes with CS ranging from 415 to 450mm (including one with 15mm of adjustable CS) and I've tried a 455 bike. There is no doubt that balanced CS is important and my hats off to Norco for trying to produce what felt like a balanced bike. The adjustable CS was a real eye opener and I agree it's a great idea for letting a tuner ride a bike to their riding needs and size.
Proprotionate CS aren't just needed for balance and high speed but also for climbing if your tall. A steep post is only part of the solution to this issue. I did a bunch of calculations and the balance angle (when the seat is over the rear axle for arguments sake) varied massively for so called All mountain bikes for large sizes. The range was 10 to 17 degrees and I'm sure I didn't find the lowest!
I mean, you ride a unsuspended bike differently, right?
More laid-back, less aggressive?
Would love to hear some thoughts about it.
Sam Hill: NukeProof Mega (guessing a medium) 17.5" chainstays"
... I guess this argument is now moot
I bought a Kona Explosif with adjustable dropouts earlier this year and despite the fact i dont believe shorter=better, i slammed them to the front (425mm). I ride techy, steep, rough trails and this definitely gave the bike a skittish character, felt very reliant on the forks doing their job and letting the rear end bounce around and hopefully follow suit.
After sliding the dropouts back (445mm) i feel a lot more comfortable descending in terms of position and weight distribution on the bike, also, being a hardtail, increasing CS length gives a little more flex and therefore more small bump compliance.
My opinion is that whether HT or FS, the CS length should be proportional to the reach in order to give a balanced riding position, riding with a higher weight distribution over the either wheel is not as efficient as riding with even weight distribution.
I'm not saying we need the longest stays on every bike to go fast, but I am saying when looking at the application and overall bike size, going longer in a number of cases really would help the bike work better under the rider.
Alternatively, everyone can go get two scales and check your weight distribution in your neutral position. Stack, head angle, reach, bar sweep, stem, fork pressure, rear shock pressure, tokens etc all play into this but this is number I'm driving toward equalizing. Regardless of the characteristics short/long stays might bring forth, getting the weight distribution nearly 50/50 (with a trail bike) while keeping stem length close to fork offset, reach numbers around 18.5-19 and head angle between 67-66 (29" application) is what I'm after first and foremost. Wish we could bring back adjustable stays for this very reason...
How well would a human work if the legs never grew proportionally with torso length?
Last year I had to rent a Stumpy Evo 29 in Moab after my roof rack failed sending my L Transition Covert tumbling down I-70. Similar reach to my Covert but a massively longer CS. I instantly felt faster in the corners on that bike. Could be other things, low BB, bigger wheels are obviously faster. But since then I've definitely been a skeptic of the super short CS camp.
The Yeti's I've demoed of recent felt insanely balanced at least in the Larges I tested. They weren't as easy to manual but cornering felt much more balanced and I suck at manualing anyway.
Post a reply to: The Internet Was Wrong: Short Chainstays Suck*