Ask the experts

[sethschmautz]

Duh, you're right. I wasn't thinking about how the shock would move in that orientation.

For what it's worth I figured that was a slam dunk originally until we looked at it - then it became obvious. :-/

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[toast2266]

Would those be these?

"Zipp’s 3ZERO MOTO carbon 27.5 and 29 enduro/trail wheelset is inspired by moto to provide riders with the control and durability required for pure trail speed. Already this wheelset and its MOTO Technology are proven with multiple victories in the Enduro World Series with our pioneering partnership with Lapierre Zipp Collective.

While other wheel brands limit their focus to traditional box-section rim designs, Zipp engineers—uninhibited by legacy technology—took a different approach. They looked to motorsports as a model. Zipp’s Moto Technology’s single-wall rim is the optimal approach for an enduro/trail wheelset. The resulting rim provides something we call “ankle compliance.” Imagine a runner rounding a sharp turn, the ankle naturally flexing to maintain grip as the runner leans. The 3ZERO rim can locally flex to stay parallel to the ground during cornering, increasing traction like a human ankle adjusts while running. This ability to twist locally allows it to deflect during single bead impacts without the rider getting bounced offline. 3ZERO MOTO helps you take the most direct route, saving seconds when and where they count most."

Yeah, that sounds just great, doesn't it? MOTO weight and you have to change the lean angle to get the side knobs to bite thanks to "ankle flex." I'm gonna go out on a real short limb here and say SRAM figured out they could make single wall rims cheaper than box section.

Yeah, that's them.

I've never even fondled them in real life, so I dunno. But pinkbike seemed to like them (https://m.pinkbike.com/news/review-z...s.html?pbref=p). I thought someone on here had a set, but I might be misremembering.

But regardless of the execution on that particular model, it seems like pretty much every decent rim manufacturer is working on tuning rim stiffness. Lots of wheels are coming with different rims front and rear for that exact reason.

[J. Barron DeJong]

Yeah, that's them.

I've never even fondled them in real life, so I dunno. But pinkbike seemed to like them (https://m.pinkbike.com/news/review-z...s.html?pbref=p). I thought someone on here had a set, but I might be misremembering.

But regardless of the execution on that particular model, it seems like pretty much every decent rim manufacturer is working on tuning rim stiffness. Lots of wheels are coming with different rims front and rear for that exact reason.

I seem to recall reading/hearing about those rims (maybe Marginal Gains podcast?) and they were saying that they had had the idea for a while, but there was some manufacturing hurdle that needed to be overcome? So maybe cheaper isn’t actually the reason. But also, I could be totally misremembering, and manufacturing wasn’t actually an issue at all - I can’t think of what would be so complex about it.

I’m not going back to listen to all the MG podcast so mostly just hoping that by throwing this out it might trigger someone else’s memory.

[jono]

Yeah, that's them.

I've never even fondled them in real life, so I dunno. But pinkbike seemed to like them (https://m.pinkbike.com/news/review-z...s.html?pbref=p). I thought someone on here had a set, but I might be misremembering.

But regardless of the execution on that particular model, it seems like pretty much every decent rim manufacturer is working on tuning rim stiffness. Lots of wheels are coming with different rims front and rear for that exact reason.

Yeah, and snark about the ad copy aside, the real world is definitely the question. On further reflection (and ignoring their plan to keep the rim flatter to the ground) there may very well be something to this when the wheel isn't in plane with the load. As is the case when we lean past that point to get the side knobs to dig.

What if the reason separated side knobs work better is because the knobless channel forces you to lean further, which makes the rim a lot more vertically compliant and better able to track the terrain?

The conversation about wheel stiffness in-plane is completely different from what happens when there's a lateral load on the rim. I'd expect any wheel to be at least 10x softer laterally than in-plane (and many to be more like 500x softer).

I was ready to say those probably work fine just because they aren't really as different as the marketing guys claim, but I can see an advantage to letting the tire move a little more--depending on the tire. (How to best achieve that is the marketing guys' next challenge, I'm sure.)

[J. Barron DeJong]

Yeah, and snark about the ad copy aside, the real world is definitely the question. On further reflection (and ignoring their plan to keep the rim flatter to the ground) there may very well be something to this when the wheel isn't in plane with the load. As is the case when we lean past that point to get the side knobs to dig.

What if the reason separated side knobs work better is because the knobless channel forces you to lean further, which makes the rim a lot more vertically compliant and better able to track the terrain?

The conversation about wheel stiffness in-plane is completely different from what happens when there's a lateral load on the rim. I'd expect any wheel to be at least 10x softer laterally than in-plane (and many to be more like 500x softer).

I was ready to say those probably work fine just because they aren't really as different as the marketing guys claim, but I can see an advantage to letting the tire move a little more--depending on the tire. (How to best achieve that is the marketing guys' next challenge, I'm sure.)

Allowing for some lateral flex to gain traction is absolutely a real thing - at least on motorcycles.

In Moto GP they went trough a period where they were making the rear swing arms as torsionally/laterally stiff as they could. But when the bike is leaned way over, bumps aren’t acting in-plane with the motion that the rear suspension allows, so they started backtracking and reduced lateral/torsion stiffness of the swing arm so the that the swing arm deflection allows for bump absorption to increase traction.

[toast2266]

It's not clear to me how much those zipps actually flex. My impression that most of the engineered flex is torsional, so when leaned over the rim stays more square to the ground. And I can definitely see some benefits there, but it also makes me wonder if it could also reduce the the ability for the tire's side knobs to really dig in. Like there's kind of a minimum lean angle for a dhf to work right, and if the rim is flexing, then is it effectively increasing that minimum lean angle?

I dunno. Mostly this is just a "it's winter and I'm half way through my annual 5 month biking hiatus" kind of conversation.

[jono]

It's definitely that kind of convo. But forget the SRAM claim and think about which way the force is actually applied when you over-lean. Less torsional rigidity doesn't actually keep the rim flat to the ground, it does the opposite. (ETA: over-lean the wheel, that is--SRAM-speak is true for roadies tipping a knee and shoulder into the turn and keeping the bike more upright.)

[schuss]

Yeah, that's them.

I've never even fondled them in real life, so I dunno. But pinkbike seemed to like them (https://m.pinkbike.com/news/review-z...s.html?pbref=p). I thought someone on here had a set, but I might be misremembering.

But regardless of the execution on that particular model, it seems like pretty much every decent rim manufacturer is working on tuning rim stiffness. Lots of wheels are coming with different rims front and rear for that exact reason.

I mean, the line "Zipp's engineers experimented with over 112 different laminate configurations and six different resins on their way to creating the final product." seems to indicate they weren't just price-engineering these. It also makes sense as the typical cycle with carbon seems to be "look how much stiffer we made it while being lighter!->We've experimented with layup to make it flex more so you aren't beaten to shit."

[jono]

If you're selling more than a few of these things you can afford to do a lot of engineering (both design and manufacturing) to bring the piece price down. The cost advantage of open section rims is in making them without the hollow portion.

Not to discount the challenges to making it work, either, I'm just saying the end goal could be performance despite a "disadvantage" rather than because of it.

[toast2266]

It's definitely that kind of convo. But forget the SRAM claim and think about which way the force is actually applied when you over-lean. Less torsional rigidity doesn't actually keep the rim flat to the ground, it does the opposite. (ETA: over-lean the wheel, that is--SRAM-speak is true for roadies tipping a knee and shoulder into the turn and keeping the bike more upright.)

I mean, if I lean right, my weight is on the right knobs on the tire, which presumably puts more force into the right bead of the rim. If there's less torsional stiffness in the rim, that right rim bead would flex upwards, which would make the rim profile more square to the ground.

I picture it kind of like those t-motion skidoo sleds, which keep the track more square to the ground as the sled is leaned.

[sethschmautz]

Would an offset bushing in the top eyelet give you enough clearance?

I reached out to an offset bushing manufacturer and their response was that on compression the offset bushing wants to rotate to the opposite configuration of what I need (hole away from the shock body). If there was a way to prevent that somehow I think this could work.

Seth

[jono]

I mean, if I lean right, my weight is on the right knobs on the tire, which presumably puts more force into the right bead of the rim. If there's less torsional stiffness in the rim, that right rim bead would flex upwards, which would make the rim profile more square to the ground.

I picture it kind of like those t-motion skidoo sleds, which keep the track more square to the ground as the sled is leaned.

Ok, I definitely skipped a step, let me see if I can fill it in. Think of the rim as a beam that's being held in position (mostly) at the middle*. As you push on one end of it the beam flexes all along its length and at the support, causing a rotation (upward, in this case--clockwise as viewed from behind if you lean to the right). Also, note that the upward force is not applied at the rim bead, but at the center of the contact patch. The tire carcass imparts a torque and the best way to look at that is to take the distance from the centroid of the rim section (let's just call that the middle of the rim's cross section) to the point where that force is applied.

So when you lean right the tire is to the left of the rim and the farther you lean the more torque is created. The direction of that torque is up on the left of the rim, twisting it clockwise (both in the local sense and for the whole beam), so less upright.

Does that make sense?

*mostly at the middle because the spokes mostly balance each other out, so resisting a torque (parallel to the bike's axis) means the rim's support appears to be near its center--approximately

[toast2266]

Yeah, that makes sense, mostly from the perspective of the forces on the tire being rotational. So yeah, agreed with what you're saying.

So I guess that rim flex would mean it'd be easier to over-lean the knobs on the tire. I've had a few tires that felt like they ran out of lean angle too early, so I wonder if those zipps would make that even worse.

[jono]

If you're over-leaning the bike, yeah. I think their whole concept was based on road tires where that risk is common and encourages over-leaning the rider instead of the wheel (marketing-speak-wise, that is--still kind of expecting it to work fine or maybe better on a mountain bike if we want/do the opposite).

[evdog]

Has anyone installed a rebuild kit on a pair of HT Pedals? (AE03 - 2017+ I think). I've taken one side apart, but can't get the two bushings out. They are jammed inside the pedal body. Just sprayed with some penetrating oil, fingers crossed that will help. Any tips would be appreciated. I see on HT's website they sell (expensive) rebuild tools. Hoping those are not required to remove the bushings.

[HAB]

Has anyone installed a rebuild kit on a pair of HT Pedals? (AE03 - 2017+ I think). I've taken one side apart, but can't get the two bushings out. They are jammed inside the pedal body. Just sprayed with some penetrating oil, fingers crossed that will help. Any tips would be appreciated. I see on HT's website they sell (expensive) rebuild tools. Hoping those are not required to remove the bushings.

I've only done T1s and X2s but HT recommends just threading a tap into the bushing and using that to yank it out. I forget what size I used, but their instructions should say. It's not an HT specific tool per se, though likely not one that the average home mechanic has on hand. But you can get a cheap one for <$10.

[homemadesalsa]

Hoff’s is an authorized Fox repair center.

So is the Hub. Can do all shocks in-house.

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[evdog]

I've only done T1s and X2s but HT recommends just threading a tap into the bushing and using that to yank it out. I forget what size I used, but their instructions should say. It's not an HT specific tool per se, though likely not one that the average home mechanic has on hand. But you can get a cheap one for <$10.

Awesome, thanks. Was hoping the answer would be easier than that! Don't recall where I got these, don't have a manual nor do I see one on HT's site. Hopefully re-build kit has instructions. 2 different size taps will be required. Glad it doesn't require a proprietary tool, those start around $100 on the HT site.

[sethschmautz]

It was recommended to create a template of what kind of clearance that the shock needs. I printed a few plastic "bolts" and fit them into the shock first, then the frame to see how much material would be to be removed. Looks like 1-1.5mm on the end of the support and probably 2-2.5 elsewhere.

The little black dots on the bolt are the spots where the shock head goes from a radius (between the dots) to flat and clearance is less of an issue.

I think I might do this. Am I gonna die (specifically from this)?

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[jono]

Did you already try just flipping the shock to check leg clearance?

Guessing how overbuilt that spot is is complicated by not knowing the way the composite is laid up there. I don't do enough of that to try to guess about that part, so I can't add to what you've already heard. Not sure if I'd try it or not, but maybe after all reversible options were exhausted.

And it begs the question: are you better off modifying the frame or the shock? Cheaper to screw up the shock? From your first pic it looks like you're closer to having enough clearance on the bottom but maybe rotating the shock and carving out a little clearance on the non-valve side would mean minimal frame changes? Just spitballing. I'd flip and rotate the extra hardware to the bottom first.

[toast2266]

My vote is don't do it.

I'm sure that manitou is great, but you already have a perfectly good Fox that fits in that frame and works fine. If there's some specific aspect of the Fox's ride that you don't like, send that shock off to get tuned.

[jackstraw]

It was recommended to create a template of what kind of clearance that the shock needs. I printed a few plastic "bolts" and fit them into the shock first, then the frame to see how much material would be to be removed. Looks like 1-1.5mm on the end of the support and probably 2-2.5 elsewhere.

The little black dots on the bolt are the spots where the shock head goes from a radius (between the dots) to flat and clearance is less of an issue.

I think I might do this. Am I gonna die (specifically from this)?

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Man, pretty balzy attempting to do what you're doing, but man, you're gonna die!

I think I'd get with an engineer or two...maybe you are one...but that is a pretty critical component of a vehicle that travels at high speeds an failures have severe consequences.

[J. Barron DeJong]

Man, pretty balzy attempting to do what you're doing, but man, you're gonna die!

I think I'd get with an engineer or two...maybe you are one...but that is a pretty critical component of a vehicle that travels at high speeds an failures have severe consequences.

I think one engineer has already spoken. Second chiming in here:

I don’t work with composites, but it seems to me that the area your looking at is one where you’d have a hard time ensuring consistent high quality results from the layup. It’s a small area, tight radius, a hole right in the middle. So while it looks like there’s more material than you need to meet the strength requirements, you don’t know what you’ll actually find inside: maybe a lot of resin, maybe fibers not oriented ideally, maybe voids.

I’m with Toast. I can’t imagine liking a shock so much to be willing to risk doing something like that.

[skaredshtles]

<snip>
I’m with Toast. I can’t imagine liking a shock so much to be willing to risk doing something like that.

I'm going to third this.

[joetron]

Fourth it.


Also, I rode a demo set of the Zipp Moto wheels for a few weeks when they first launched. Here is my math/physics-free anecdotal review.
They had different tires than I usually run (Conti vs Maxxis). I never noticed anything specifically related to rim flex when leaning the bike on smooth-ish turns (but this could be related to unfamiliar tires).
What was very noticeable was the way the wheel tracked through off camber roots/rocks. Noticeably less deflection and better traction. They held my preferred line with less effort and finesse compared to the Enve M7 I was riding at that time.
They didn’t feel super quick trying to get on the gas and accelerate out of corners if I did make a mistake or used too much brake. But as I got used to them, I found myself braking less into turns and could carry more speed through chunky turns because they tracked well and inspired confidence.
I’ve found that the thermoplastic Revel RW30 fit somewhere between the Zips and Enves in terms of ride quality/deflection/smoothness and impacts.


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