After all these years. It's misaligned!
Each leg individually slides off the stanchion perfectly smoothly under gravity, without seals in the fork. But put both legs in, and it's stiff to pull off. However if I pull the lower legs apart slightly, it frees up.
Next thread is likely to be something like "Can anyone sell me some 66 lowers as I've broken mine trying to realign them"
What happens if you put the hub in and retry your experiment? How about adding spacers to the axle to open the legs up a bit?
Bushes? Sounds like they could be the problem
It's not the leg end, I don't think. If I splay the legs, it doesn't free up, I have to pull at the brace. I think it's the brace that's too narrow.
I will try again with the hub in though.
The bushes are fine I think because with only one leg in it slides almost friction-free. Unless you are suggesting the bushes aren't aligned correctly somehow? Is this a thing? They were done a few years and not many riding hours ago by Loco.
Without knowing what the problem is, it sounds like they could still easily be within expected manufacturing and operational tolerances. You would need to compare them to a pair you know were working correctly to know for sure.
Surely loco would have mentioned if they were misaligned?
Unless you are suggesting the bushes aren’t aligned correctly somehow?
If the bushes are not aligned together then it would be an issue, so if one is set slightly out the symptoms will be that, worth a try before swapping them out or just ebay spares/repairs
It seems unlikely that this cast part is out of alignment really, otherwise a large number would be affected.
Everyone else is reading this thread in their internal Kenneth Williams voice, right?
It seems unlikely that this cast part is out of alignment really, otherwise a large number would be affected.
It's a 2007 66 SL ATA - from reading forums, it seems that some pairs were smooth and some not. So it's possible there was a QC issue.
If the bushes are not aligned together then it would be an issue, so if one is set slightly out the symptoms will be that, worth a try
Not sure what you mean..? How are they meant to be aligned?
Could the CSU be out of alignment?
Maybe but I thought this less likely than the lowers. I can't do anything about the CSU anyway.
Not sure what you mean..? How are they meant to be aligned?
Firmly seated and parallel, if one is off then the uppers will slide properly in one leg but not both together, or they are properly buggered, got some lasers?
Or for the cost ebay something newer
I can't afford to replace them. eBay has nothing sensible.
The thing is though it frees up if I pull the lowers apart slightly. That's why I think they are too close together.
Have you tried with the axle and preferably a hub in???
Didn't read everything but just trying to save possible tears.... 😀
It might even be the hub? (If its a fraction off tolerance over time bending the lowers?)
I'd have thought you stand a chance of getting a creak in the CSU as well....
How much can you actually pull the sliders apart at the brace/top end though? - I’d have thought next to bugger all. If that tiny amount makes a difference then just get the bushes sized a few thou.larger and see if that sorts them.
I have been known to hand scrape fork bushes to cure this but I appreciate that not everyone has bearing scrapers lying around...
How much can you actually pull the sliders apart at the brace/top end though?
About a mm or two at maximum force. However I only need apply slight force to get it to slide, so the amount of misalignment must be tiny, less than .1mm I'd guess.
Then I’d get a triangular scraper and take a tiny amount at a time off the outer part of the bush ID until you get free movement. As you say, even 001” makes a difference.
I’ve done this with a set of 55 RC3 Ti’s and it didn’t tske much to make a big difference.
This is an interesting idea - ta.
What triangular scraper are you talking about? I was thinking of a round file...
A triangular bearing scraper - if I could post photos on here I’d show you what I mean
Like the triangular one of these here -
You can just take off the smallest amount and doesn’t leave a rough finish like a file does.
I can’t do anything about the CSU anyway.
Are you going to try re-aligning the lowers? I can't see how you would do that.
https://www.pinkbike.com/news/race-prepping-a-fox-40.html
Fox have a bushing slackening tool (tube with a good tolerance)
Andy that link doesn't work somehow.
Are you going to try re-aligning the lowers? I can’t see how you would do that.
Well it turns out the lowers are pretty soft. I can splay the bottom easily enough, but I can also widen the top, by the brace, by putting the axle in (it's a bolt through) and jamming a piece of wood up into the brace. Actually works pretty well.
Spent an hour in there fiddling about - managed to improve it, but it's quite hard to work out exactly what to do since my calipers can't measure accurately enough as I can do nothing but offer them up in awkward positions which isn't repeatable enough in most cases.
Currently, with the lowers on the uppers and no internals or seals, they are nice and loose at the very top of the stroke (as if bottomed out). They will slide down about 5cm on their own and then stop. I was able to increase this by adding a weight and then pushing the legs in or out to see if they slid a bit more. But no matter what I do I cannot get them to slide all the way off under gravity. They are significantly stiffer on the lower part of the stanchion. The internet at large led me to believe they should slide right off under gravity, as they do when I put only one leg in. Of course it's mostly dry since it's in bits.
Another possibility is to try and hone the bushings with a device I have made for honing the inside of brake master cylinders on cars. The active parts of it are like a fine sharpening stone, not crumbly and pretty smooth so shouldn't leave any particles. It's meant to be used with a drill but I'll probably start with my fingers. One side is every so slightly tighter than the other.
Ok, so with the alignment as good as I could reasonably get it, I had another look at the bushes. Tried the single leg slide test again, and actually only one leg was super smooth - the other a little stiffer. So I got out the honing thing and tried it with my fingers before using the drill gently. And it worked brilliantly. Dead smooth now and the lowers do now slide all the way down under gravity. They don't fall off because as the lower bushing loses contact it twists and jams, but that's not an issue really.
They are way way smoother than they were with an air spring in. Here's hoping that when my SKF seals arrive I'll have a proper buttery smooth fork!
Let's hope the warnings about leaving abrasive particles in the bushing material don't apply...!
They are way way smoother than they were with an air spring in
Have you put a coil spring into it ?
No, I mean when I put in an air spring to compare the feel directly, they were way smoother than before 🙂
I'd be tempted to convert them though, they made a kit but not for that exact model.
Just reassembled it with SKF seals and ridden it around the street.
It is properly smooth and supple now, finally! I've probably made more posts about these damn forks than I have my Passat. But now they are lovely.
The alignment helped a bit, but the real issue was simply the bushes being too tight, despite my initial thoughts. I honed them til they dropped straight off the lowers, and I was a bit worried there'd be too much play, but there's absolutely nothing detectable when they are back on the bike.
The SKF seals have not added any stiction at all but added some friction damping. All nice and greasy though so no issue really. There's more gap between the oil seal and the wipers (which are separate in this fork) and I packed it with grease as before but I think the seals are tighter because the grease doesn't come pouring out like it did on the last ones.
Not sure if I should be using silicone grease between the two seals or oil and a foam ring, but who cares, it's all working really well now.
