Ask the experts

[toast2266]

I'd LOVE to see their process for doing this.
The factory forges/casts these things with massive fixtures throughout the manufacturing process to keep everything lined up. I can't imagine how Diaz can tweek these to the minute amount it takes to "improve" on the factory straightness (% of mm) without an enormous investment in machinery.
I hope he's not just doing it by hand and feel.

From watching his videos, it seems like how the hub interfaces with the fork is a significant factor. I don't know how much of that is variations in different hubs vs. misalignment of the fork. But it seems like it'd be pretty tough to account for variations in the hubs.

But I wouldn't be surprised at all if the solution was essentially just to bend the lowers a bit with some basic tools, then check the fitment with the CSU. Cost and fancy equipment aside, I'm not sure there's realistically a better way to do it.


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[Andeh]

I'm pretty sure there's something to whatever he does. I have a Zeb that I got from Joetron which Diaz had worked on that is amazing. I have another Zeb that I bought new, honed the bushings myself, upgraded to SKF seals, etc. and it never feels as good. Same 3.1 damper upgrade on both, same oils, etc. The only other difference is the Diaz one is set to 170, the one I worked on is 160. The one that wasn't worked on by Diaz feels like it ramps a lot more in the lower 1/3 of stroke, which I assume is actually some sort of binding.

[frorider]

It’s getting a bit frustrating to read the dozens and dozens of comments on Diaz’s instagram asking him to explain more about what he’s actually doing to ‘align’ and his answers are always variations on ‘yes I am aligning’.

If he wants to omit the details on the actual process that’s fine, but to stubbornly avoid any explanation of what is getting aligned is kinda weird.

I vaguely recall a fork test years ago in which small variations in hub width affected binding force. Is he just trying micro shims (or end cap sanding) to fine tune hub width?

[jono]

That's a legit question, but the answer "yes I'm aligning" seems to imply that he's bending stanchions, doesn't it?

In which case, ok, you could do that with max expense and minimum geometric expertise. But you could also do it a million other ways, including a few carefully mounted dial indicators.

However you do it, once you have the ability to measure alignment accurately you should be able to measure how much you're bending them. Then you build a database for each fork so you know how much "spring back" to expect (a la sheetmetal brake) and it gets you pretty close and adds one to your database each time. If you can improve alignment by 50-90% people will notice.

[rideit]

Let’s get Hambini on the case!

[toast2266]

That's a legit question, but the answer "yes I'm aligning" seems to imply that he's bending stanchions, doesn't it?

That's my take.

I'm also guessing that work voids the warranty (or at least could be used an excuse to not honor a warranty), so it's maybe better left as a "don't ask don't tell" kind of procedure.

It's kind of like pivot bindings and Cast. People want what cast is offering, but pivot definitely doesn't approve of the alteration, and they don't want people to do it even though it makes their product better.

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[Roxtar]

Yeah, there are so many variables to stanchion alignment (direction, angle, material springback, distance, which side is off, etc) that I can't imagine just manually pulling on it would possibly improve anything.
One possible low-tech/lowish-$ solution might be to insert very long rods into the stanchions which would extend far enough to be able magnify any misalignment.
That would still require buying 34mm, 35mm, 36mm, and 38mm (Don't think he works on Manitou) sets of these rods.

[sfotex]

Diaz was talking about facing the dropouts in their last video.
The lower are cast magnesium and soft, so they are going to distort with the hub,
I bet they align the axle holes to stop the lowers from twisting and get the dropouts square and go from there.

Trying to 'cold-set' stanchion tubes without destroying coatings, creasing things, etc. ,not to mention liability, seems like a moon shot to me...

[Andeh]

That makes the most sense out of all of this speculation. The lowers are going to get twisted/bent to line up the axle once the axle gets inserted and tightened down. From the factory, the droputs are probably squared with the holes that are through them, but not necessarily to the opposite side. Like you said the lowers are a really soft material so it wouldn't take much to knock them out of true between casting & final assembly. So it makes more sense to reface them when they're fixed in place by the axle, as that's the actual working condition.

[jono]

Trying to 'cold-set' stanchion tubes without destroying coatings, creasing things, etc. ,not to mention liability, seems like a moon shot to me...

Liability is always arguable, but coatings and creases would be non-issues within this range. It takes about the same force/deflection to put them right as what (theoretically) messed them up.

ETA: I'm thinking of this relative to the steps needed to measure and straighten paired tubes that are about 10x the size of a fork stanchion. During manufacture those get measured and straightened as much as possible before coating but they can be bent as needed afterwards, too. Lot more options on small stuff.

Best reason to think there's no bending needed is that they wouldn't necessarily stay straight for real long. In reality, this would represent a strain relief exercise, so it would take somewhat more force to mess them up again (aside from any cold working increase in YS, but that should be minimal). But the whole prospect is more reliable if we're talking about stress that is well below yield in normal use and can be corrected by machining/shims.

[jono]

This post is probably only interesting to a few of us. You were warned.

My previous post notwithstanding, we're talking about a forged component. Show me a forged, formed or in any way bent component that never leaves the manufacturing process with meaningful residual stresses and I'll show you a process that includes strain relief.

It's not uncommon for manufacturers to accept the best tolerance they can get rather than the one they need. So it's not unlikely that there's a strain relief cycle needed, without which there's a little more variation in alignment and some of the forks will move a little when subjected to large but typically acceptable forces. Given the weight requirements, I'd be surprised if it's all that rare for a fork to yield slightly in use, so I'd expect anyone doing what Diaz does to check and try to correct that. Wouldn't have to be perfect to be better.

[sfotex]

Liability is always arguable, but coatings and creases would be non-issues within this range. It takes about the same force/deflection to put them right as what (theoretically) messed them up.

ETA: I'm thinking of this relative to the steps needed to measure and straighten paired tubes that are about 10x the size of a fork stanchion. During manufacture those get measured and straightened as much as possible before coating but they can be bent as needed afterwards, too. Lot more options on small stuff.

.

If the stanchion wasn't pressed into a crown.. but as it is you would have to grab the crown and bend the stanchion, or hold the stanchion and bend the crown on a 'Kashimi' coated tube that's sensitive to any small knicks in it, etc. And I imagine the uppers are pretty straight when they manufacture them anyways,

I would guess this issue is more of a tolerance stacking thing between the uppers and lowers, seals, and bushings vs. one piece being out of tolerence....

C'dale claims on the Lefty is better because with 2 stanchions when the front wheel gets a twisting force on it it twists the legs and introduces a bunch of friction in the system, and that seems to be true in garage testing at least, so if the dropouts were misaligned I guess it could cause a similar issue?

[jono]

Assuming it's minor, it probably depends on the misalignment, I think. Some would resolve pretty well into the axle. One bad issue would probably be an incorrect length that pinches or spreads the dropouts.

That actually seems like a good thing to check yourself before sending a bind-y fork off for work: how close is the fit without the axle vs. with tension?

I also think C'dale is right, FWIW. By the time you account for flex the over-constrained nature of a dual stanchion fork is almost certain to bind sometime.

[toast2266]

I'm impressed that this discussion devolved into extolling the virtues of the lefty before at least dabbling in some inverted fork talk.

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[XXX-er]

The Lefty Max with SPV worked really well IME especially compared to the forks that were around 20 yrs ago

When I rode the earliest Giant Reign , the rear end worked pretty good but whatever fork was on the front absolutley sucked dead goats while buddy at the C-dale demo just asked me what I weigh adjusted air on a prophet and it was great

but I'm pretty sure a lot more Reigns were sold than prophets cuz of the anti-christ factor

[jono]

Before we really get into the Lefty (and obviously before we point out that it's inverted) I want to come back to this:

If the stanchion wasn't pressed into a crown.. but as it is you would have to grab the crown and bend the stanchion, or hold the stanchion and bend the crown on a 'Kashimi' coated tube that's sensitive to any small knicks in it, etc.

I was thinking this would be an issue in your garage, but not with a set of soft jaws and the set of custom tools you'd build if you were doing it for money.

Then I remembered we all have 3D printers for our soft jaws. So you just need to make up an easily adjusted but solid-ish stand/frame for your straight edges and indicators and a very solid vise. When you're not keeping your dick in there (whatever happened to that guy?) the steerer tube gets chucked up and away you go with your 3D printed soft jaws.

Dammit. I already have access to a shock dyno, too. I think I'm gonna have to log out. Lemme know how the Lefty bits turn out.

[sfotex]

I'm impressed that this discussion devolved into extolling the virtues of the lefty before at least dabbling in some inverted fork talk.

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When do we bring up linkage forks as the future?

[toast2266]

When do we bring up linkage forks as the future?

Ha!

Linkage forks have been the future for 30 years. I think they'll be the future for at least another 30.

[rideit]

As are IG drivetrains for meat-powered bikes.

[frorider]

Ok Diaz posted this: https://www.instagram.com/reel/DAjwU...RlODBiNWFlZA==

And in the post & his comments a lot more is revealed. Sounds like stanchion tube measurement and alignment is part of it. And facing the dropouts. And the shimming of hub axle ends, as I mentioned earlier, if really needed.

He also made it more clear that his concern about the ‘reaming the bushings’ fix used by many shops is it can often result in an overly large bushing to compensate for the stanchion misalignment.

[Yukonrider]

This looks to me like something that was solved in motos a long time ago with a floating axle.

Install axle, tighten one side, compress fork to "align" the legs, tighten pinch bolts on other side.

My 36 had something pretty similar. I would guess this guy is just using shims and selling it as snake oil.

[joetron]

This looks to me like something that was solved in motos a long time ago with a floating axle.

Install axle, tighten one side, compress fork to "align" the legs, tighten pinch bolts on other side.

My 36 had something pretty similar. I would guess this guy is just using shims and selling it as snake oil.

The Fox forks have floating axles.
They still bind.
I can assure you it’s not just shims. Diaz gets forks sent to him from all over the country and they don’t have the rider’s hubs with them, so he can’t just shim them. Sometimes he’ll come up and borrow wheels and hubs from my shop to try and match the brand and model that a mail-in customer has, to get better in the zone for alignment on that hub.
Can you call something snake oil if it actually works?



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[toast2266]

I'm sure some of the work he does is at the hub / fork interface, but I'm also sure there's some amount of alignment that can be done on the lowers (or possibly even the csu) themselves.

I've had a lot of forks over the years, and I've had plenty of different copies of the same model. Some are noticeably good, some are noticeably bad. Most are somewhere in the middle. But the good ones are good regardless of what hub / wheel I put in there - they're just aligned well from the factory. I don't doubt that it is possible to tweak average / bad forks to make them work as well as the good ones.

Fox's floating axle helps, and it removes one variable from the equation, but it doesn't fix all potential problems.

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[jm2e]

Fuck the floating axle. There, I said it.
As much as I love Fox, each 40 I’ve owned has play at the hub after doing the silly compress then tighten routine. Feels like there’s a 0.25-0.5mm gap and zero preload. Rides like the headset is loose or the bearings are shot.
So my solution has been a three handed routine of pulling the lowers together before tightening the pinch bolts.
Maybe making it bind? Still feels better than the rattle.
Maybe a great system for motorcycles that weigh 5x more and have way lower tolerances.


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[east or bust]

Fuck the floating axle. There, I said it.
As much as I love Fox, each 40 I’ve owned has play at the hub after doing the silly compress then tighten routine. Feels like there’s a 0.25-0.5mm gap and zero preload. Rides like the headset is loose or the bearings are shot.
So my solution has been a three handed routine of pulling the lowers together before tightening the pinch bolts.
Maybe making it bind? Still feels better than the rattle.
Maybe a great system for motorcycles that weigh 5x more and have way lower tolerances.


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Huh, so you’re saying this could be the source of a rattle on the front end of my Enduro (w/ 38) that I haven’t been able to track down for 4 seasons?


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