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

No matter how you do it, either moving the bb and pivots forward or back or actually making a longer chain stay will change the leverage rate and therefor rear travel no? That's why in a lot of cases (I think RAAW is public about it) there are different travel numbers on the Small vs the XL bike.

Altering chainstay length, altering pivot location: Leverage Ratio/Travel changes

Altering BB location: Leverage Ratio/Travel doesn't change

Because all the moving parts stay the same and in the same location. You only change the non-moving part (BB )

Its been awhile since we’ve discussed high rise handlebars. I’ve run out of stem spacers on my bike and want my bars even higher so Im eyeing going from a 35mm rise to a 50mm rise. 

What are some fit and handling considerations from doing this aside from just hands being higher up?

People will judge you and ask stupid questions?

Nah , it's all personal preference..

A higher rise bar usually moves your hands higher up directly vertically while adding spacers does it along the steering axis. In short, adding spacers shortens the reach, high rise bars don't change it. 

I've seen some people say that the higher rise could affect the reach, but it would seem that would really only be an issue if you roll the bars back..

Not everyone agrees but in my opinion having the rise inline with the fork is the neutral roll position. (Gwin made a video on this btw). Why? Because it doesn't affect the steering geometry as you increase or decrease rise. If you run the bars straight up then as rise increase your hands move further away from the steering axis. The steering axis is inline with your head tube angle so it's pointing back about 64°. This has the same effect as running more spacers and a longer stem. 

You can't cheat the reach! Moving your bars around doesn't somehow give you more reach or stack. Running higher rise bars vertically "preserves reach" the same way a longer stem does.

Not really. If you swap your bars for higher rise bars that have the same (negative) reach or setback, but have a higher stack, you grip reach won't change, the stack will. 

On the other hand, running a longer stem will increase the reach and stack and vice versa for a shorter stem. 

Same thing with spacers, adding spacers under the stem will increase the stack but decrease the reach. And vice versa for removing the spacers. 

Hell, cutting the bars will increase the reach and decrease the stack unless you're running completely flat bars. 

As for angling the rise to the steering axis, careful with that, you're negating the designed for upsweep and adding backsweep. In my experience that affects the riding posture negatively. Adding upsweep or lowering the backsweep opens up your elbows. Lowering the upsweep or adding backsweep closes your elbows towards the body and makes you look like a praying mantis (or a T-Rex). Isn't Jackson running his bars rolled forward that much precisely to open up his elbows? 

Not if the stem is only long enough to offset the decrease in effective reach caused by adding spacers. It does not matter how you adjust your hand position, the effect is the same. A higher rise bar that's not inline with the steering axis will change your effective stem length.

Re: the rise of the bar inline with the fork as the neutral position - this seems a bit odd to me since the angle of the fork changes bike to bike.

How does everyone else set their bar roll? I've always eyeballed the rise to be perpendicular to flat ground.

edit - looks like we posted at the same time, I see what you mean wrt to neutral. But that setup always feels weird to me, feels like i'm riding like a praying mantis

I mean you can run them however you want. I'm mainly referring to neutral effects on steering and how higher rise bars don't magically bypass the negative effects of stem/spacer changes.

I specifically mentioned stem spacers or the stem in isolation. You could use a longer stem AND add spacers to get to only a vertical change, but good luck finding a combination of both that will make this possible.

I never said a high rise bar will not change the effective steering. I only said that changing stems OR stem spacers affects both reach and stack while a higher rise only handlebar will only change the stack.

Obviously, the caveat here is that this vertical only change will work with a higher stack bar ONLY if we're talking about two different rise handlebars that otherwise have the same sweep angles and the same setback and width. I'd be willing to bet there are VERY few options like that available on the market, especially considering only BikeYoke actively publishes their stack and setback values.

Regarding roll, I guess some people might like more backsweep and less upsweep. Testing different sweep values without affecting other dimensions is incredibly hard as most handlebars are just bent back/up a bit more to get a higher angle and thus get a longer setback (and stack). So much so I had to at one point run a 12/8 degree handlebar with a 70 mm stem to get to a half decent position relative to the steering axis. I also had the chance to try a handlebar with a 12/8 degree sweep vs. a more standard 8/5 degree variant where the hands stayed in the same position (same rise and setback) and I very much did not like these higher sweep angles, specifically the backsweep. It was amazing riding up, but going down the praying mantis effect was too much to handle.

I can't believe I have to say this, but there is no "right" position to set a handlebar. I put it in whatever position feels most natural and effortless for my wrists and hands. For most bars, that's means i roll them pretty far forward (like Jackson G), but YMMV. I know tons of people who think the bars feel more comfy rolled back. There's no wrong answer.

I guess the only wrong answer would be to deliberately run an uncomfortable setup because you read online that it's "the right" way to run your bars.

And yes, changing your bar roll will change your effective steering position, similar to changing stem length. In practice, this change matters almost not at all. You will notice the effects of your hands and wrists hurting from running a whack bar angle long before you'll notice a minor change in steering geometry from rolling your bars forward or back. And if you do notice a change in steering geometry after adjusting your bars, and you really don't like it, you can get a different length stem to compensate. And this isn't just about comfort- your hand and wrist position will actually travel up the chain and influence your forearm, elbow, shoulder, back, and hip position on the bike, so if your wrists are in the wrong place it's likely going to make all of you be in the wrong place.

TLDR: put your bars wherever they're comfiest for your hands and wrists. Your wrists will thank you.

On the latest Bikes and Big Ideas podcast, the subject of BB drop came up while talking about 32in wheels.. What was discussed kinda makes me wonder if that's what can tie it all together.. More BB drop, more of the stable in the bike feel.. Reduce the amount of drop, length the HT to keep stack similar (or cheat with a slightl  taller bar) and you should get a little more of the nimble feeling as that would raise the COG a bit..

Paul Aston has done this for his crazy long bikes. The idea being that bb drops were used to add stability to bikes when they were shorter/steeper, so when you’re getting that stability from the wheelbase, larger wheels, etc. you can reduce the bb drop to gain some agility back.

For 32” bikes I can see the benefit of this being massive ground clearance. I think it was Jordie on the quarter HP podcast who said that a big benefit of 32” seemed to be the traction on the rear that if gives you when climbing. Combine that added traction with more ground clearance and that seems like a big benefit for technical XC racing.

Sounds like my theory has already been proven by people smarter than myself..

Daniel at Neuhaus was saying a lot of the same.. He is feeling that standover will be a bigger issue, especially with suspension still being figured out.  He did however bring up 750D as a way to go... Which measures out to roughly, wait for it.... 30.5...