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I came across this retrofit 15mm axle on PB Buy/sell. Has anyone tried this? Could be a good option that is likely cheaper than swapping hubs.
https://www.pinkbike.com/buysell/4072641/
Interesting! Just cause I'm a nerd, it would be cool to do a back-to-back with this 15mm axle and the stock 20mm steel axle and a 20mm wheel. Curious if I'd be able to notice a difference, and how noticeable it'd be.
How many different Allen keys does it take to remove the wheel?
was vital also approached to write such an article?
https://www.pinkbike.com/news/comment-fork-alignment-and-friction-in-th…
Did some quick CAD maths. Feel free to correct:
Given a 400mm stanchion height and 20mm press distance into the axle/stachion union, a 1mm offset at the non-axle end as observed means the concentricity between the base and the top of the stanchion press union is .05mm or .002". That does not included the perpendicularity between the effective stanchion press interface axis and effective axle axis (axle + threaded sleeve concentricity and size tolerances). If the concentricity is perfect then the resulting stanchion to axle axle angle to get a 1mm offset is 0.144deg.
In reality both of these tolerances are varying simultaneously. These are tight tolerances to hit as is and if the claims of 3% friction difference are true they are perfectly acceptable IMO.
The whole stanchion misalignment thing did seem more of an exercise in rage marketing. The whole thing is designed to work as a system and the person making all the noise has both financial incentive to do so and skipped installation steps because they weren't possible to prove their point.
The air spring being on the rotor side of the fork bothers me more than a 3% increase of friction vs a best case scenario.
Reading between the lines it seems to me like Jessie-May had the idea and approached Fox. It's a great idea for an article, and I wish I'd written it! I'm guessing she tore down her fork for an apples to apples comparison with the "bad alignment" videos floating around on the internet, and when she discovered it was out of alignment she said, "damn, this WOULD make a good story" and reached out for comment. I'm jealous! It's a good story.
Someone in this forum even suggested the same thing, asking if I'd be willing to tear down my Podium and check the alignment, but I didn't have time. Also, there hasn't been tech documentation from Fox for servicing yet, so I was also a little apprehensive of tearing the fork apart without being 100% certain I had all the tools, parts, oil, and torque specs to put it back together.
I love her article because it addresses one of the things I've been wondering for a while, which is how much alignment or bushing stiction on the work bench actually translates to perceivable friction on the trail. If her fork felt great and had measurable alignment and friction issues on the work bench, it's worth asking how important those measurable differences are on the trail. Not everything you can measure is significant.I'm open to two possibilities, which I think are both equally likely, and I'd be curious about the peanut galleries thoughts:
Option 1 is that it doesn't matter much and you'd be surprised how little bushing friction translates to ride feel. Bushings are specifically chosen to slide under intense friction and load, so it's possible that the friction you feel on a work bench pales in comparison to the friction fork bushings experience in heavy braking, flat landings, etc.
Option 2 is that every little bit of friction in the fork chassis is immediately perceptible on the trail. This is similar to the old adage that a fork lowers service is one of the best performance upgrades you can make, or to rumors about super ultra aligned pro forks with .01mm axle spacers for minimum friction. I'll be honest, I don't think I've ever felt a difference after a fork lowers service, but maybe my forks aren't dirty enough when I make the change?
The air spring being on the rotor side of the fork is in fact very annoying. Annoying like a paper cut, or a loud fly circling your head, because it doesn't actually matter, but it feels so wrong and annoying. And it could matter, if you don't know or forget to shield your rotor and pads and blast a bunch of float fluid onto your brake.
I live in Colorado and frequently travel up to 10k feet to ride so setting my air pressures after a huge change of altitude, either up or down, is something I do frequently. So having to flip my bike upside down and remembering to shield the brakes and rotors every time sounds like a huge hassle.
Option 1 with the caveat that there may be some situations where that 3% matters (World Cup DH), but the vast majority of riders are not in that situation.
Mainly wanted to highlight the following:
> I'll be honest, I don't think I've ever felt a difference after a fork lowers service, but maybe my forks aren't dirty enough when I make the change?
I'm not that convinced that swapping out just the oil for most folks does all that much, as I think the oil change is mostly there to prevent things from going way south if it gets too dirty.
However, I have made a point of taking some extra time to clean and re-grease the air spring when I swap my lower oils and that makes a HUGE difference, and I think that's due to the friction nature of sliding seals eventually just wearing out/removing all the grease/oil on the sliding surfaces. My wife's smashpot can go much much longer between services than my air sprung 38, and my guess is that its due to the lack of sliding seals on the spring side.
Going to chassis flex, I believe the biggest issue with the added friction is not between the fork stanchions and the lowers, but the added friction incurred by the air spring trying to deal with the flex. The fork stanchions and lowers don't need to be air tight, or even all that tight to work (as the rubber seals at the top do a good enough job keeping oil in the fork and water out of it. Fox's 38 "air spring in a tube" and the 36's glidecore air spring are prime examples of how much better an air spring can be if its less impacted by chassis flex.
I'd bet you dollars to donuts that the air pressure changes you see are more due to the air temp inside your fork than the outside atmospheric pressure. Ideal gas law and all that. The column of air serving as your spring is a closed system, so its not impacted by barometric pressures (however, the air in your lowers for sure is, that's why we have lower bleed valves now.
Don't believe me? Set your fork pressure when it's in the 50s outside and then check it again when it's in the 80's.
It's more about a rule of thumb for me than a hard scientific truth. I reset my pressures when going to and from high altitude and when there was an outside temperature swing of more than 20F. I agree that temperature swing has a bigger effect than elevation, and that aligns with my anecdotal experience, but setting my pressures under those two circumstances has helped things stay consistent.
The more I read these stories of minor issues that could have been easily prevented if someone paid attention to detail, the more I appreciate the no-bullshit approach of Herr Cornelius.
The big question is this. Just how much better would the fork feel if it was perfectly aligned?.
Do I like mine? Yes I do, is it like the ones seen online? Yes it is. Just how much better could it actually be if it was perfect? No one will ever know as Fox seemingly don't give a shit!
I suspect that normal variations in ambient temperature and tire pressure are way more impactful than a tiny difference in bushing alignment.
That was actually a really good article - well done Jessie for taking that step, I wish there was more of this from media sites
I would roughly guess the friction from bushings and the air spring are 50/50 - there is potentially a ton of bushing friction under high loads/bending, and the air spring has a big impact on smaller, high frequency movements. I believe there is a lot more bending on the air shaft than you would think - my theory on buttercups has always been that they do more for allowing the air shaft to stay properly aligned than they do for vertical compliance, so a single butter cup on the air shaft probably makes 80% of the benefit of having them on both sides (I haven't fully measured that yet but thats my hunch)
You can also make a bone dry fork bind much easier than one with oil still on the bushings.......
@Dickscruttock - from everything I have seen, most of these forks are built to a completely acceptable tolerance for the real world. The diminishing returns means that making them any more precisely would cost twice the price and need a proprietary hub, for almost zero noticeable improvement on the trail. Nearly everyone who has ridden the podium seems to think it is incredibly sensitive so clearly this supposed friction isn't translating to the trail. I do believe this has all been rage bait to get clicks (which it certainly has!) but it is good that pinkbike took the time to do some proper education on it!
I used to go from the Bay Area (sea level) to Northstar (around 6600ft).
You can absolutely tell the difference if you don’t bleed your lowers. It’s a pressure increase of about 3psi with no negative chamber to counteract it.
Also, you have to use absolute temperature in your scenario. 50f to 80f is only like a 6% increase in absolute temp.
That can still be noticeable, and its common to have even wider changes in temperature than that. Shocks have a larger change due to their small volume, but also heat up more in use so on a cold day probably operate closer to what it would on a hot day.
Point is I wouldn't overthink it too much, and just change things based on how it feels on the trail. Just maybe try to make those changes at roughly the same ambient temp, and also ignore what the pump says when you put it on
Also use the bleeder buttons whenever you feel like it - it doesn't hurt
For what its worth, I wasn't blown away with the two I've had from a sensitivity perspective. I didn't take the fork apart and "check" alignment, but even buddies who rode it agreed it was very "meh". I don't know what is going on, but I am starting to think there is more variance fork to fork than maybe we want to acknowledge.
One thing I am starting to question is if the hub I have (DT Swiss) is part of the problem (or rather, Fox didn't leave enough "float"). The hub measures a hair wider than boost and I've noted the fork flange that floats is right against the hub endcap (can't go "in" further). When I get it back from Fox I'll consider "machining" 1mm off the end cap to see if that doesn't improve things.
Did a lower service for a friend that was probably 200hrs+, verging on abuse. Parking lot test, the reduced stiction was noticeable. The oil that came out was the worse condition I have seen so far.
Some food for thought… let’s assume each leg is a cylindrical joint where it can slide linearly and rotate around the axis of said cylinder. A cylindrical joint on its own is equivalent to four points of contact. Six points of contact fully define the position of something in space. Two cylindrical joints is eight points of contact. Both right side up and upside down forks are technically over constrained and rely on flex and/or bushing clearance to move smoothly. In the world of aligning linear rails with bearing cars, you pretty much always have to float in at least one of the rails. What this often looks like is bolting one rail down against a reference edge to ensure it is straight and then sliding the stage along and using it as a guide to tighten the opposing linear rail. This is effectively what snugging all your bolts and then compressing before fully torquing is supposed to do more or less. That is the only way you can ever have lower bushing clearance and smooth action.
"Some food for though" and then proceeds to give a huge Thanksgiving meal.
Are you telling me fox engineers might be smarter than the average bear when it comes to sliding things up and down?
Well at least end caps are easily and relatively cheaply replaceable.
Rule #1, always modify the cheapest/ most easily replaceable part first.
Rule #2, have replacement part in hand before starting.
Or if you can borrow a 20mm front wheel from someone for diagnostics, even just pushing up and down in the parking lot seems like it would answer that question. It'd be a bummer if the hub width is the problem but it'd also be an answer. Weird that your second fork was "meh" as well. Subscribed to your ongoing Podium travails.
Before machining anything I'd measure the hub flanges with calipers first to see where you stand. Then maybe add some shims to get even worse alignment and see how that feels. Less impactful than than hogging out alu.
The other way to have lower bushing clearance and smooth action is to design and manufacture the product correctly, including the necessary alignment and clearance between bushings/stanchions. Other companies don't seem to have a problem doing this.
The difference felt between a fork with correct clearance and one that binds is absolutely noticeable. Of course it all depends on how "bad" the misaligned one is, and also rider weight. Smaller, lighter riders will notice it more. I have felt it myself on numerous occasions, most recently with the PUSH 9.1. If you are not working on suspension and come across this issue on a regular basis, you may lack the frame of reference. You don't really know how bad something is, or how good it could be, until it isn't bad anymore.
Diaz Suspension has a spring rate tester with a load cell that is big enough to put a whole fork in. He ran a poorly aligned Fox 34 that showed 10-18lbs of force required to overcome the friction from misalignment.
Fox's response to the Podium debacle that it is only a 3% increase in friction due to the misalignment and not a big deal is almost comical when one of the selling points of the Podium is the "floating" air spring piston that is supposed to reduce friction. All the time and money spent designing this new air spring, only to lose 3% right off the bat due to poor chassis alignment?
A $2000 fork should be perfect, I bought $250 RS Lyrik this year that has excellent chassis alignment/bushing fit. It’s not that hard.
It is my opinion that 3% "added" friction because fork misalignment is probably negligible because 3% is. Let's be honest, in a dynamic ride situation, the various level of twisting and buckling forces applied to a fork is going to misalign it.
You referenced fox's floating air piston and the whole goal of reducing friction in an air spring; stating how somehow that goal is diminished due to fork misalignment, and I strongly disagree. As I mentioned before (somewhere on vital), air springs are particularly vulnerable to added friction issue due to the issue of needing to seal air AND slide around. Fork lowers/stanchions do NOT need to be air tight, so they operate at a much wider window of tolerates and just do not have the same friction levels as rubber seals going against metal.
The reason things like the 38, new 36, work so well (in my opinion) is that their air spring are more tolerant of fork twisting and buckling due to either their tube in tube nature or the elastomer "flex" of the piston. Hell, I'd even venture that's kinda what buttercups do as well to some extent.
I'm not trying to let Fox off the hook, I just feel like people are so quick to go into this tribalistic mentality around things they deem important without a clear understanding of WHAT the issues actually are. Is 3% important? probably not. Is the reduction in friction from the air spring in the new fox stuff important? Undoubtably.
The whole thing around fork misalignment seems so click-baity, and frankly it seems like a few people who are trying to sell their services are creating all the hubbub. I hold people like @TheSuspensionLabNZ and @Vorsprung in high regard because they don't seem like they are trying to sell me on their services, but more solving problems that people actually have, and if neither of them are screaming about misalignment from the rafters then neither will I.
"The reason things like the 38, new 36, work so well (in my opinion) is that their air spring are more tolerant of fork twisting and buckling due to either their tube in tube nature or the elastomer "flex" of the piston. Hell, I'd even venture that's kinda what buttercups do as well to some extent."
I think the seals in my 36 air spring are in need of replacing (seems to be slowly leaking air into the lowers). I may just buy one of the new air springs and try it out. Worst case I have a spare, best case is it improves the fork with no other changes. Should be a good back to back comparison with no other changes.
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