Enduro/AM - The Weight Game

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Enduro/AM - The Weight Game
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flag fantaman
Posted: Jul 6, 2020 at 12:42 Quote
Circe wrote:
I'll let Ian Collins from MTB-Mag explain:

"If I had one major gripe with the EVO, it’s the same gripe that I have with most Specialized bikes. They’re a bit over-leveraged in their rear suspension. To explain further, the ratio between the wheel travel and shock travel is quite high – 2.85:1, to be exact. This means higher spring rates (or more air pressure) and a shock that’s being taxed harder.

At at 180 pounds, I was running a 600 pound spring and bottoming out fairly frequently, despite things riding a little harsh and feeling oversprung. That begs the question – how does this work out for a 230 pound rider who actually shreds?

....

The leverage rate curve is also quite linear, so while I’m a huge fan of coil shocks on trail bikes, I think this bike might actually be better suited to an air shock, or at least a more supportive damper than the DHX2, which is notoriously linear in nature, and needs a much bigger bottom out bumper."

https://www.mtb-mag.com/en/tested-specialized-stumpjumper-evo-pro-carbon-27-5/

One word ''Sprindex''
flag PHeller
O+
Posted: Jul 6, 2020 at 13:14 Quote
That's interesting because of the huge debate surrounding the benefits of high leverage ratios for better damper performance...shaft speeds or something.

The comments surrounding the Norco Sight or Optic is where this came up. Lots of debate about whether it's higher leverage ratio was ideal for bigger riders.
flag badbadleroybrown
Posted: Jul 6, 2020 at 13:44 Quote
PHeller wrote:
That's interesting because of the huge debate surrounding the benefits of high leverage ratios for better damper performance...shaft speeds or something.

The comments surrounding the Norco Sight or Optic is where this came up. Lots of debate about whether it's higher leverage ratio was ideal for bigger riders.
I'd tend to think it'd be the opposite... I don't think shaft speeds are getting high enough that it's beyond the ability of the damper to manage it and a lower leverage ratio gives more fluid and more space over which to transfer the kinetic energy to thermal energy, which I'd think would entirely offset the benefit of less aggressive damping on a higher leverage ratio. You're effectively getting better thermal dispersion and more consistent damping in spite of the higher shaft velocity with a lower ratio so I'd assume it would either balance out or be advantage low ratio. I'd think running higher leverage ratios has a lot more to do with packaging a smaller shock into the frame than they do with performance.
flag bikerboywill
Posted: Jul 6, 2020 at 13:58 Quote
Yeah bblb is surely right. There’s more energy having to be damped because of the higher spring rate which overworks the damper. I’d really like to try a 160mm bike with a dh sized shock on. Wonder if the stiction would outweigh the fact the damper has less work to do
flag PHeller
O+
Posted: Jul 6, 2020 at 14:06 Quote
Here's the comment that stood out to me on the Norco Sight's "behind the numbers":

"You realize that the new Spesh Enduro runs virtually the same average leverage ratio? No one is acting like that bike can't hang. These dampers see lower oil velocities than a low-leverage bike, not higher (just as Dan mentions in this article). Damper oil velocity/friction is what produces heat more than damper force. The higher leverage ratios we're seeing from every major manufacturer in 2020 are designed to bias the suspension action toward the spring rather than the damper, which is exactly what they do. This is why it is so critical to take the time to get the spring force curve dialed on these bikes."
flag captainbringdown
Mod
Posted: Jul 6, 2020 at 14:39 Quote
Hardtails solve all these problems.
flag badbadleroybrown
Posted: Jul 6, 2020 at 14:47 Quote
PHeller wrote:
Here's the comment that stood out to me on the Norco Sight's "behind the numbers":

"You realize that the new Spesh Enduro runs virtually the same average leverage ratio? No one is acting like that bike can't hang. These dampers see lower oil velocities than a low-leverage bike, not higher (just as Dan mentions in this article). Damper oil velocity/friction is what produces heat more than damper force. The higher leverage ratios we're seeing from every major manufacturer in 2020 are designed to bias the suspension action toward the spring rather than the damper, which is exactly what they do. This is why it is so critical to take the time to get the spring force curve dialed on these bikes."
That makes no sense to me... the piston moves through the oil as the damper compresses so there's no "oil velocity", there's shaft and piston velocity. Heat production is a byproduct of energy transference where you're taking the kinetic energy of motion and transferring it to thermal energy by forcing it through a viscous fluid... so the amount of thermal energy is going to be dictated by the force put upon the suspension driving the damper, not the action of the damper itself. With a higher spring rate it may take more energy to overcome the counter force of the spring but you also have less fluid volume and overall piston travel through which to dissipate that energy and you get a higher return force on the rebound side which is then going to require more damping to control. I mean, I haven't done any legit testing, or even non legit testing, but just thinking it through I don't see how higher ratios would come out on top.

And I'm sticking by the higher leverage ratios we see from bike companies is a function of wanting a compact stand over and it being a shit ton easier to fit a 7.5" x 2" shock into a frame than a 9.5" x 3" shock without linkage and tubes getting in the way of one another... and shocks are also inherently a heavy component. Just look back at the Foes 2:1 frames and imagine trying to cram one of these shocks in a modern 5" travel multi-link frame.

photo
flag Circe
Posted: Jul 6, 2020 at 14:51 Quote
isaacschmidt wrote:
Hardtails solve all these problems.

Shutup Dad
flag captainbringdown
Mod
Posted: Jul 6, 2020 at 15:05 Quote
Circe wrote:
isaacschmidt wrote:
Hardtails solve all these problems.

Shutup Dad

I'll just be riding off in the comfort of my new Shimano Sandals.
flag PHeller
O+
Posted: Jul 6, 2020 at 15:15 Quote
badbadleroybrown wrote:
And I'm sticking by the higher leverage ratios we see from bike companies is a function of wanting a compact stand over and it being a shit ton easier to fit a 7.5" x 2" shock into a frame than a 9.5" x 3" shock without linkage and tubes getting in the way of one another... and shocks are also inherently a heavy component. Just look back at the Foes 2:1 frames and imagine trying to cram one of these shocks in a modern 5" travel multi-link frame.

I agree with you...but

That being said, the difference in overall length of a 230mm shock vs a 210 or even 190 isn't huge. Why wouldn't more manufacturers find that extra 20mm of space to dramatically lower their leverage ratio and better suit a larger variety of rider weights?

If space was an issue, we've got Trunion mount now, which reduces overall length while retaining stroke.

Could you end up in a situation where air pressures are so low that damper does all the work? Like, a really light rider on a 2:1 frame?

I know that lower leverage bikes sometimes disappointed coil shock users because they require very small increments of spring rates, so they were pretty particular about spring rate. Maybe the same is for lower leverage and air - small differences in air pressures can end up really impacting performance.
flag PHeller
O+
Posted: Jul 6, 2020 at 15:17 Quote
Here's this from Steve at Vorsrpung:

"Higher leverage ratios do have some advantages - more leverage over the friction of the seals in the shock means less stiction, smaller shock means less weight, and making the shock smaller usually makes it easier to package. Specialized also run relatively high leverage ratios on a few of their most popular bikes. The downsides of the higher leverage ratios though are more stress on the shock, requiring higher damping force, which in turn has to dissipate energy in a smaller amount of oil/aluminium, and therefore reduces the thermal mass and the thermal stability of the system as a whole as a result. In theory, you can achieve identical spring curves and damping curves at the wheel with almost any leverage ratio, but in practice it becomes more and more difficult as you go to one extreme or the other (ie very high or very low leverage ratios). Back in the day it seemed to be commonly accepted that around 3:1 was a good number to work with, nowadays we are seeing numbers usually somewhere around the 2.5:1 mark. Companies tried shocks with leverage ratios as low as 2:1 (eg the Foes 2:1, and the Morewood Makulu got fairly close to that as well) but at that point the weight of the shock, the space it was taking up in the frame, and the difficulty valving existing damper architectures lightly enough seemed to push designers back to higher leverage ratios."
flag PHeller
O+
Posted: Jul 6, 2020 at 15:20 Quote
So yea, high leverage is really only a product of packaging constraints and tune options.

Therefore, all these bikes with 3:1 leverage ratios still suck for bigger riders. It sounds like the industry still believes any low leverage bike will end up looking like the Foes 2:1.
flag fredro
Posted: Jul 6, 2020 at 15:35 Quote
photo

This took a nice wack yesterday at the bike park. I cringed when it happened, but it was fine. AXS not as delicate as one would think. Takes a licking and keeps on ticking. Or in this case, shifting.

I LOVE MY AXS Fab
flag fantaman
Posted: Jul 6, 2020 at 15:39 Quote
fredro wrote:
photo

This took a nice wack yesterday at the bike park. I cringed when it happened, but it was fine. AXS not as delicate as one would think. Takes a licking and keeps on ticking. Or in this case, shifting.

I LOVE MY AXS Fab

Battle scars have to be earned Beer
flag swan3609
O+
Posted: Jul 6, 2020 at 15:47 Quote
isaacschmidt wrote:
Circe wrote:
isaacschmidt wrote:
Hardtails solve all these problems.

Shutup Dad

I'll just be riding off in the comfort of my new Shimano Sandals.

Let me know where you pick them up.. Ill be right behind you to get a pair too

 


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