Modern Geo Talk: Chainstays, Stack, Reach, and Bitching About It

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 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.

I just don't want to be spread out over a bike. The more leaned over I am, the more pressure it puts on my hands and the less control I have over the bike's movement. I shouldn't be experiencing something completely different just because of my height. I should be getting the same experience on my size L bike as someone who fits a size S. 

Reach changes too much between sizes in proportion to stack height, and rear centre lengths don't change enough. Right now, there's more difference in ride feel between the same bike in two sizes than two different bikes in the same size. 

There's a reason Jackson is doing so well in the DH at the moment. He's able to be way more upright on his bike and take impacts through his legs rather than his arms, and your legs are much stronger, so he's able to push through to the end where other riders are starting to experience fatigue. I believe some tweaks to geometry, dialling down reach numbers a little (literally no size L bike needs to have a reach approaching 500mm, that's absurd) and increasing bar heights/stack heights would lead to a lot less rider fatigue. 

I don't believe anyone is calling for any crazy revolutions in design, rather some small tweaks so that the stack:body height and front centre:rear centre ratios are more consistent across sizes.

I think that's a solid observation and I think a lot of it also depends on each rider profile (strengths, weaknesses, build, etc).

I went the long cs, shorter reach, high stack route and found myself riding faster and with more control on the terrain that I enjoy - steep & technical. Interestingly, when going from an Enduro to Madonna, I found the Enduro to be more of an unengaging riding experience that dulled too much of the trail for me. Which isn't to say the Enduro is a bad bike, but maybe not best suited to me, my preferences, skill, etc.

So I chose a bike with geometry that lets me ride the terrain I enjoy, more "better" - which I think is a pretty common statement for all?

For discussion sake, I'll throw out a half baked opinion - I think dynamic riders tend to prefer the longer reach/shorter chainstay setups as they're able to move their body around the bike as needed. As opposed to less dynamic riders who prefer the long cs/high stack and ride by positioning and bracing the bike for different maneuvers (insert skiing metaphor).

People are asking for size L and XL to have the same proportions as size M. 

Ignore the total WB length number, there is no too long, and scale up the CS and stack to match the same proportion when increasing reach. 

This is the way. Once again I'm reposting this video from Steve at Vorsprung because its just so... damn accurate. 

https://www.youtube.com/watch?v=i5R60JHJbxI

 

Did you find yourself having your back more upright on the Madonna than on the Enduro? 

Also regarding EDR riders sizing down. These guys are getting longer CS's relative to the WB and stack is roughly the same. Yes the WB is shorter, but the balance is better. 

I would assume so... setting up the Enduro to have as much stack as the Madonna made the bike feel awkward.

a lot of the pro-balanced weight distribution folks are saying just this: hey, this is how we like to ride. but then the argument gets confused when people say "no those bikes don't turn." so yeah, when they say "those bikes don't turn" the response is 100% "you don't get it" as in, thats not a valid criticism. it might be your opinion, but its be presented as fact.

agreed til the last part, had to downvote due to a very beautiful counterpoint to the dynamic bit: Goldstone. He is the most active rider right now and he has a set up that confirms the tall stack/long cs crowd. I think you mean "active on the bike" but the progressive geo folks want to be active on the trail. 

After watching La Thuille, I was thinking Jackson’s bike is very active and he is very active laterally. But he may not be as active as others fore and aft, which makes sense to me. 

He also looks crazy slow compared to how fast he is going. I would attribute this to his relaxed stance and hovering over everything. 

I think it's more those "bad habits" leave you in a position where potentially necessary skills are unlearned and left on the table. 

If you never have to bunnyhop higher than 4 inches then it's not a "bad habit" to learn to hop up and lift the bike with your feet. But if you ever come up to a 15-inch thick branch laying across the trail, then you're going to have to get off and walk over it or do the full compress->front wheel lift->explode upward to hop->level bike by pushing forward and rotating wrists->land bunnyhop technique. With flats, you basically have to do a compress->front wheel lift->explode upward to hop->level bike by pushing forward and rotating wrists->land bunnyhop in either "thing requires hopping" scenario (adjusting intensity for varying heights). A clipless pedal setup can lead you to learning one very limited technique while never forcing you to learn the other more useful technique.

You don't need to learn to ride heels down and with a soft bend in your knee if you only ever ride a 8-foot-long rock garden with four-inch height variation. Clipless pedals will keep the bike with you and you can keep on riding after holding on for that short bumpy spot. A person with flats will lose the bike if they don't drop heels and soften their knees on that same rock garden. If the rider then takes their riding to a 30-foot long rock garden, they'll need that dropped heels and soft knees technique either way and that stiffened up but clipped-in rider will have to learn that dropped heels and soft knees technique.

In both of the escalated scenarios above, the flats rider and the clipless rider have access to the same techniques to make it through those obstacles/features. The difference is the flats rider had to learn it early in their riding and the clipless rider might have to learn a new technique later in their riding while simultaneously breaking themselves of the habit of calling on an old technique that won't work for them in those escalated scenarios.

They're not "bad habits" as much as they're "techniques that are useful in fewer scenarios and a related techniques might have to be called on more often."

Related, I kind of wish I felt more comfortable with the idea of clipless pedals. I'm just too frugal to spend a bunch of money getting pedals and shoes if I'm going to find out I don't like it. I don't live in an area where I'd be able to easily sell that pedal/shoe combo so I'd be stuck with unuseable and unsellable parts. I ride my fixed gear bike with toe clips and it's perfectly fine in that scenario. I think riding my mtb clipped in would force me to be a little less wild in corners...which is something I really should do. As of now, if I overcook the entrance to a corner I can just stick a foot about and be mostly fine. Clipped in, an overcooked corner is a more crashy prospect. I hate the feeling of struggling to get into my toe clips and I think I'd really hate the feeling of not getting clipped in to a quick-start scenario on mtb.

As a side-note: I'm kind of blown away by how many mtb riders can't really bunnyhop. I learned to hop riding a bmx bike 20-some years ago. I picked up a mountain bike the first time 3 years ago and the first thing I did was bunnyhop it. It's such a useful technique that I think I'd be very scared to be out on trails without a full bunnyhop in my back pocket.

Something else I have been wondering about. As you raise handlebar height, do you have to increase cockpit reach to maintain balance between the wheels? When I raise my handlebar height but keep stem length the same, I find that I end up riding off the back of the bike and have trouble weighting the front wheel. I guess it would make sense that as handlebar height is raised, cockpit reach (not frame reach) should increase, whether through stem length increase or sizing up a frame? Would be curious to get other people's experiences

i was introduced to this whole topic when i overforked my bike. I loved the way the front end felt but the higher stack and longer front center deleted a lot of grip up front. essentially I threw the geo out of balance. I looked at ways to get that front end grip back and a lot of folks talked about longer chain stays to balance out the rear-bias that comes with a higher stack/shorter reach. Luckily I have a stumpy evo and was able to just buy a s5/s6 seat stay that increases the rear center. bike designers have the option of just stretching the front, but that will radically change the character of the bike overall. 

it seems to me that the balance is finding a front end long enough to feel stable, a stack high enough to give good leverage and allow a more heads up, playful command over the entire bike, and a balance front to rear to maintain grip through varied terrain. when we look at this set of variables we realize that within all of the different setups possible there are also varying riding styles and terrains that will favor some over others. incredibly shitty riders and incredibly good riders might be able to make any combo work, but therein lies the door to the qualitative: how does each setup feel? what type of riding style does each setup reward? what experience are you looking for on the trail, and which combination facilitates that experience for you? 

sorry, just went on a ride and i am pretty inspired right now

Glad I took a look at this... Informative thread .. As I do more research into this, I'm thinking that a longer CS might be what I'm looking for in a bike. Front end grip has been an issue for me as I tend to ride with a bit of a rearward weight bias..

It's nice to see people looking at frame geometry as a whole. For so long, it would be like people would focus on one number without realizing how other things might need to change with that..

Also, I can't help but wonder if the first decade of getting 29ers to feel like 26in bikes set back the development curve..

But then do n't forget the variable of taller bars vs flatter bars. If you're stacking spacers or stem height, then the bars come back. Then you also have Bar Roll, which for me makes a much bigger difference in how the bike feels. If I my bars rolled back, my elbows flatten and I find myself off the back. Slightly forward (and pared with a resonable up and backsweep), my elbows come up and I can attack the front of the bike. 
I mean obvi Jackson saw my set up and it's working well 🙃

I;ve also found that for me personally the new style geo's tend to require an attacking riding style, and holy crap can they make you fast. But they mute everything, dumb stuff down, and require a pace that makes the sudden stops way more brutal. 

Posted by noideamtber:

chainstay length itself is also the distance between rear axle and pivot point - this is why the actual length matters so much, that pivot could be infront of the BB or behind it.  which has quite a role in anti squat, leverage of the stay etc - it also directly relates to where the BB ends up.

That's nonsense though, and nobody else I've ever talked to considers that word to mean that. There's no way to define that length for a virtual pivot bike in a way that makes sense unless you want to pick and choose your definition of what a chainstay is and what the word means for each suspension layout. And that kinda means the word has no definition at all.

A DW link bike is topologically identical to a horst link bike, so either the chainstay length of the horst bike is only a small handful of centimetres long because it's the distance from the axle to the chainstay pivot, or you include the other frame member too and arbitrarily say that the chainstay length is defined by the pivot connecting the main frame holding the bb to the adjacent lower frame member... but then you're including the short link for the DW link bike too. So Giant's Maestro has longer chainstays than an Ibis with DW because the lower link is mounted in a different location? Where's the logic there? How is that a useful thing to define?

And if you're going to do that, because as you say it affects the AS, AR etc, then maybe we should consider the switch infinity. With switch infinity simulating a lower link of infinite length, then by your definition then the chainstay length of a yeti is infinite. wow, that's pretty long. What about high pivots like Forbiddens? now your definition of chainstay is unfortunately defining the seatstay, because the seatstay is doing the heavy lifting in defining the suspension behavior and wheel path, while the chainstay has no definable length, it's just pulling on a link to actuate the shock. What about I-drive?

Every time you mention this random ass definition of what a chainstay length is, i can't help but think about how it doesn't make any sense and how everyone you talk to is going to misunderstand you anyway. The fun thing about language is that words mean what people understand them to mean, not what you want them to mean.

it's almost as physics dont exsist to you........
Have you ridden a high pivot bike? Moving the damn pivot changes the bike..... 

Bikes with Bone links(such as DW/Giant) are less effected depending on link length + upper link as the axle path can be controlled more.

I almost wish I never Worked on Race Car suspension as a job for 15 years + contract Job's in the RC Industry for a couple of brands - It's like explaining  the meaning of life to a new born here.

Side Question, Do you notice Offroad cars have long Arms and road cars have short arms?

2nd question, what happens when you have 3 rocker/pivot locations?... Long lever from the seat stay and short lever on Shock side (which means frame pivot is Closer to the shock pivot) Do you know how leverage works?

The picture below doesnt care if its a Shock or a frame pivot, It's all about triangles.

But hey. Your right and physics are wrong.
Cant wait untill we debate Dynamic ride height vs static and how the bike's CG is effected by it + the Puzzle of suspension Tuning that effects it aswell - That'll make your head explode then as theres sooooo much going on.

Oh ok you're one of those. Cool.

Please define what you consider a "chainstay" succinctly  in a way that actually covers all suspension layouts.

I understand suspension dynamics and the concept of leverage quite well. The final year of my degree was mostly concerned with mountain bike suspension design and a fair amount of my experience in engineering has involved linkage systems. You're just assuming I'm a moron because i said you had a shit take on something, and I'm a guy on the internet.

Nobody in mountain biking understands that word to mean what you insist it means, and I doubt you can even define it properly.

can we agree that there are two different ways that chainstay length impacts bike handling and performance? it matters how long the chainstay is from axle to bb as the rear center figure. it also matters for suspension behavior how long the axle to pivot point is.

i don't know how much this matters but there does seem to be a distinction that is getting muddied by a singular term to cover both instances...

I thought we were discussing chainstays, not kinematics...