Enduro/AM - The Weight Game

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Enduro/AM - The Weight Game
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Posted: Jan 28, 2020 at 15:33 Quote
All the reasons to run a coil still apply on short-travel bikes. The difference in weight is smaller on short-stroke applications, so you might say it makes even more sense.


PHeller wrote:
seraph wrote:
A lot of short travel bikes I've ridden have this initial shock stiction that makes it seem like they have even less travel than they do. And if you reduce the air volume they just bottom out too easily. So I think a progressive coil sounds nice.

This is usually because the initial stroke leverage ratio of XC bikes is super high, which means high pressures in the shocks for most riders, although the intended markets can usually do ok (150lbs riders). For the rest of us it's not ideal.

Obviously the leverage curve plays into this as well.

I kinda wrote about this in a little blog post a few years back: https://www.pinkbike.com/u/PHeller/blog/low-leverage-ratio-bikes.html

Yikes, there's a lot of misunderstanding to unravel here.

• Reducing air spring volume will generally increase the compression ratio, reducing the tendency to bottom out.
• Higher leverage ratios - especially at the beginning - reduce the feeling of stiction. The static friction force is the same, so the greater leverage overcomes this force more easily.
• The average of average leverage ratios are below 2.7:1 for trail / all-mountain / enduro bikes.
• It is not necessarily true that a lower average leverage ratio means heavier riders do not have to modify the damper, as a different damper tune may have been chosen for that application, so all riders - including heavy riders - are in the same situation as they would be in if the bike had a more average leverage ratio. It does, however, mean a heavier rider could easily buy an off-the-shelf Mid-Mid tuned shock and put it on a bike that came with a Low-Low (or similar) tune.
• A light rider running a low pressure does not have an increased risk of bottoming out. If a heavy and light rider both set their spring pressure such that they have the same sag, the light rider is less likely to bottom out because he or she has the same damping force resisting his or her lighter weight, relative to the heavier rider. The compression ratio of the shock is the same, regardless of initial pressure.
• It is incorrect that "An obvious alternative is to run a progressive heavy-weight coil shock on a higher leverage frame. This would allow a supple initial stroke with significant ramp up." Even progressive coils do not have as much ramp-up as air springs. The only way this could be of any benefit is if a heavy rider cannot achieve sufficient spring support at maximum air pressure. In this case, the heavy rider can remove any volume reducers - yes, reduce the ramp-up - and use spring pressure above the rated maximum. The actual maximum pressure, at bottom-out, can still be within the allowable operating range and there is more "area under the curve" of the spring curve, representing total spring support.

Posted: Jan 28, 2020 at 15:47 Quote
Running a linear spring on a short stroke is pretty silly. If you don't compromise on sag you'll be bottoming the living shit out of the "downcountry" rig

Posted: Jan 28, 2020 at 15:49 Quote
iggzdaloc wrote:
Running a linear spring on a short stroke is pretty silly. If you don't compromise on sag you'll be bottoming the living shit out of the "downcountry" rig

It's fine if the motion ratio is sufficiently progressive. Same as with a long stroke.

Posted: Jan 28, 2020 at 16:26 Quote
R-M-R wrote:
iggzdaloc wrote:
Running a linear spring on a short stroke is pretty silly. If you don't compromise on sag you'll be bottoming the living shit out of the "downcountry" rig

It's fine if the motion ratio is sufficiently progressive. Same as with a long stroke.

That is why Kollys work really well with coils

Posted: Jan 28, 2020 at 16:29 Quote
dchill wrote:
R-M-R wrote:
It's fine if the motion ratio is sufficiently progressive. Same as with a long stroke.

That is why Kollys work really well with coils

The leverage curves on Knolly models are pretty typical for modern bikes. Fine for coil shocks, but no more so than many others.

Posted: Jan 28, 2020 at 17:44 Quote
Yeah they are average if they where more progressive I wouldn’t be running 2 volume spacers in my float X2 at least on my warden.

Posted: Jan 28, 2020 at 21:19 Quote
R-M-R wrote:
iggzdaloc wrote:
Running a linear spring on a short stroke is pretty silly. If you don't compromise on sag you'll be bottoming the living shit out of the "downcountry" rig

It's fine if the motion ratio is sufficiently progressive. Same as with a long stroke.

This. Is. Correct.

Posted: Jan 29, 2020 at 0:16 Quote
R-M-R wrote:
iggzdaloc wrote:
Running a linear spring on a short stroke is pretty silly. If you don't compromise on sag you'll be bottoming the living shit out of the "downcountry" rig

It's fine if the motion ratio is sufficiently progressive. Same as with a long stroke.

Could you give some examples of short travel frames that feature progressive motion ratios?

Posted: Jan 29, 2020 at 1:33 Quote
seraph wrote:
Could you give some examples of short travel frames that feature progressive motion ratios?

I don't closely track bikes under 130 mm. Several interesting ones make it into the database, but if I filter for less than 130 mm and moderately to highly progressive motion ratio, my data is too incomplete to make generalizations or to provide a decent set of examples.

For just one example, Cotic's motion ratios are quite progressive and the FlareMAX would suit a coil nicely.

Posted: Jan 29, 2020 at 1:53 Quote
Supposing that a coil fit, is there any specific reason why it wouldn't be a good choice for a Tallboy 4?

Posted: Jan 29, 2020 at 2:23 Quote
seraph wrote:
Supposing that a coil fit, is there any specific reason why it wouldn't be a good choice for a Tallboy 4?

FINE, I'll do a model for the Tallboy. It's an important bike, so I probably should've already done this.

Okay, even with less than ideal confidence in my accuracy, it's clearly very progressive. Coil approved.

A general comment on Santa Cruz: Early Santa Cruz VPP bikes had some of the worst kinematics of all time. Kinematics were starting to improve by the mid-2010s, but geometry remained conservative through 2018. The 29ers introduced in 2019 show a big leap forward in both areas, even compared to the 27.5" bikes introduced in 2018. Santa Cruz is finally up to speed on geometry and kinematics.

Posted: Jan 29, 2020 at 7:16 Quote
R-M-R wrote:
• Higher leverage ratios - especially at the beginning - reduce the feeling of stiction. The static friction force is the same, so the greater leverage overcomes this force more easily.

My thought, and I think this is what I saw when I was doing research: is that higher pressures generally work against initial sensitivity, which is why so many prefer coils on higher leverage frames. Even my 2.4:1 Trail Pistol requires nearly max pressure for my 250lbs ass. I'd think that puts a lot of pressure on those seals, creating friction.



R-M-R wrote:
• It is not necessarily true that a lower average leverage ratio means heavier riders do not have to modify the damper, as a different damper tune may have been chosen for that application, so all riders - including heavy riders - are in the same situation as they would be in if the bike had a more average leverage ratio. It does, however, mean a heavier rider could easily buy an off-the-shelf Mid-Mid tuned shock and put it on a bike that came with a Low-Low (or similar) tune.


The slightly lower than average leverage ratio of my bike also allows me to run exactly this setup. I'm running a Mid-Low tune on a bike specced for Low-Low.

Posted: Jan 29, 2020 at 12:35 Quote
PHeller wrote:
My thought, and I think this is what I saw when I was doing research: is that higher pressures generally work against initial sensitivity, which is why so many prefer coils on higher leverage frames. Even my 2.4:1 Trail Pistol requires nearly max pressure for my 250lbs ass. I'd think that puts a lot of pressure on those seals, creating friction.

I'm afraid that's incorrect. The seal pressure is not greatly different. The greater leverage that requires the greater air pressure helps overcome the friction.

Posted: Jan 31, 2020 at 16:28 Quote
Just ordered up a a Liv Intrigue 2 to do a custom build on for the ole lady! How light do you all think it will be? Funny the intrigue has better geo than the trance imo. Which I found kind of odd.

Posted: Jan 31, 2020 at 19:40 Quote
Tsoxbhk wrote:
Just ordered up a a Liv Intrigue 2 do do a custom build on for the ole lady! How light do you all think it will be? Funny the intrigue has better geo than the trance imo. Which I found kind of odd.

34lbs with pedals


 
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