sticky fork seals

ludwig · May 27, 2024

A late reply, 'cause just back from a 3000 km (wet) trip, but I have done some testing on fork seals.
Break off force ( stiction):
New original : 5 kg.
Used original : 4 kg. ( leaky, didn't know km..)
New Ariete : 1.5 kg.
Used Ariete: 1.5 kg. (not worn, only 10000 km, or so..)
This is a HUGE difference.
Friction force is hard to measure ( depends on speed), but the difference is comparable.
All seals were lubed with Ohlins fork oil for testing.
With the special Ariete lube, the difference might even be greater.
Ari 003T has an od of 48 mm, which makes it a ( too) tight fit, so best to remove some of the rubber coating.
If you make slider extensions ( a good thing), you can machine them for Ari 149 , which have an od of 46 mm.
The Ari seals are intended for 35 mm stancions, but they seal better and last longer than the originals.

(edit: beware for fakes..)

o0norton0o · May 27, 2024

ludwig said:
A late reply, 'cause just back from a 3000 km (wet) trip, but I have done some testing on fork seals.
Break off force ( stiction):
New original : 5 kg.
Used original : 4 kg. ( leaky, didn't know km..)
New Ariete : 1.5 kg.
Used Ariete: 1.5 kg. (not worn, only 10000 km, or so..)
This is a HUGE difference.
Friction force is hard to measure ( depends on speed), but the difference is comparable.
All seals were lubed with Ohlins fork oil for testing.
With the special Ariete lube, the difference might even be greater.
Ari 003T has an od of 48 mm, which makes it a ( too) tight fit, so best to remove some of the rubber coating.
If you make slider extensions ( a good thing), you can machine them for Ari 149 , which have an od of 46 mm.
The Ari seals are intended for 35 mm stancions, but they seal better and last longer than the originals.

(edit: beware for fakes..)

Thanks for all your input. I'm going to order a set of Ariete seals and see if I can fit them. The slickoleum fork seal lube made a noticeable improvement on the AN seals. Every little bit helps!

fiatfan · May 27, 2024

o0norton0o said:
In my case the bushings are Turcite from JSmotorsports and have been consistently in the forks throughout all the other changes. A lighter oil has can give less resistance to slider movement given the same valve settings. (my dampers have adjustable valves and I tried to open them to see if fluid resistance was causing the decreased travel issue) My point with mentioning the change in fluid viscosity to a lighter fluid was just to mention another variable change, but highlight that it was a change that wouldn't cause more resistance to slider motion. That only leaves the other 2 changes I made, which are the dampers with the progressive springs, and the fork seals which were both changed.

The fork seals are part of the problem without a doubt. Whether their stiction will change with the addition of the slickoleum grease, and also loosen up over time is not being ruled out at all. It was surprising to me at how much more stiction the new seals had, compared to the used ones that I removed, which did not leak. I know I have to remove the current dampers because if I put the best damper set up back in their place, then any stiction has to be from the new fork seals...

I'm on the fence whether I should just put the old seals back in when I swap out the dampers, because I do want to try the slickoleum product too. The more variables I have, the more elements my testing covers, but unfortunately that also means many more disassembling and reassembling to test that many more permutations of parts.

Thanks for your interest. I'm mostly back channel with people who are interested in my current project, and only mentioned it here to get some feedback because I was surprised at how sticky new fork seals are compared to the worn in ones... and was looking for confirmation that this is widely agreed upon as the standard situation. "New seals start out a bit sticky"....

I have the JS bushings too, have big problems with sticky forks. Have cut off one lip off from the seals to test, but my prime suspect is the bushings. Did yours work fine before? I just got a pair of original bronze bushings in the mail which I will put in tomorrow, exited to see the difference. Hope there is one....

o0norton0o · May 27, 2024

I thought my turcite bushings were ok. In my case, the dramatic change in happened when I put the new fork seals into the slider.

Its easy to test which parts are sticking. remove the slider so the bushing and seal pop out, then assemble the slider and bushing on the fork tube with the seal up on the fork tube out of the way. Lube the slider with a bit of fork oil and move the slider up and down. Does the slider move freely with just the bushings installed??

Now engage the fork seal in the slider and tighten the cap, wet the seal and try moving the slider again. Did the friction increase? Dramatically?

When you engage the turcite upper bushing into the slider with the turcite on the fork leg, it might be a little tight. I think Jim recommends wrapping the fork tube with fine sandpaper and giving just a few strokes with the turcite bushing to micro adjust the fit. Then try the fit again and continue until it's just right.. You don't want any play, but neither do you want too tight of a fit because that will cause a sticky slider too....

hope that helps. If you try any of this report your results please, thanks

jseng1 · May 28, 2024

When chasing down friction its best to work the leg up and down before installing the oil seal as a pre-check. Some fork tubes such as Forks by Frank are out of spec and can be too tight. Tubes should not measure larger than 1.359" because 1.356 to 1.358 is the ideal original factory spec. Be sure to tighten the axel and check for binding before pushing in the fork seals (leave them loose on the tubes and push them home as the last step). Fender mounts and fork braces will put a lot of binding on the forks if they pull the legs out of parallel even the silghtest amount - this happens more than it should and it ruins the ride.

The Turcite bushings have much less friction than bronze. The bronze will eventually wear the chrome off your fork tubes but the Turcite will not.

Another low friction XNBR fork seal is available from Pyramid #FOS-012 It measures 47mm x 10.5 but needs a shim and maybe some silicon sealer because the OD is undersize.
The original Norton seal measures 47.63mm x 11.3mm

ozcruiser · May 30, 2024

ludwig said:
A late reply, 'cause just back from a 3000 km (wet) trip, but I have done some testing on fork seals.
Break off force ( stiction):
New original : 5 kg.
Used original : 4 kg. ( leaky, didn't know km..)
New Ariete : 1.5 kg.
Used Ariete: 1.5 kg. (not worn, only 10000 km, or so..)
This is a HUGE difference.
Friction force is hard to measure ( depends on speed), but the difference is comparable.
All seals were lubed with Ohlins fork oil for testing.
With the special Ariete lube, the difference might even be greater.
Ari 003T has an od of 48 mm, which makes it a ( too) tight fit, so best to remove some of the rubber coating.
If you make slider extensions ( a good thing), you can machine them for Ari 149 , which have an od of 46 mm.
The Ari seals are intended for 35 mm stancions, but they seal better and last longer than the originals.

(edit: beware for fakes..)

Ordered a set thank you

concours · May 30, 2024

fiatfan said:
I have the JS bushings too, have big problems with sticky forks. Have cut off one lip off from the seals to test, but my prime suspect is the bushings. Did yours work fine before? I just got a pair of original bronze bushings in the mail which I will put in tomorrow, exited to see the difference. Hope there is one....

I had the same experience.

concours · May 30, 2024

Best answer, by far, to eliminate stiction

Fork Bushing Kit

As new upgrades are developed for our beloved Nortons,

nycnorton.com

jseng1 · May 31, 2024

concours said:
I had the same experience.

Concours - The problem was because your fork diameter was out of spec. The diameter of your tubes ("Franks" I think) was too large and beyond standard tolerance according to the measurement you sent me. The first bushings I sent to you were sized for stock tubes with a max spec of 1.358" I explained this to you and offered you a free exchange of bushings to accommodate your oversize tubes. You refused the free exchange and continue to blame the problem on the bushings when it was obviously the tubes that were at fault. I offer one size of bushings to fit the stock diameter and another size to fit the oversize diameter of the Frank or other out of spec aftermarket tubes. To offer one size that fits all would be to offer a bushing that is too sloppy and loose on the original Norton factory tube.

Note that I have also offered teflon bushings since 1984 as described in my race manual as shown below (copyright 1984). Both the Teflon and the Turcite are much more slippery than the bronze and I offer both types to fit the stock fork tube diameter spec of 1.356 s 1.358" as well as a second option to fit 1.359+" Frank and other aftermarket tubes.

The Teflon bushing Suzuki part mentioned above is no longer available. Teflon bushings are an earlier technology. Turcite was developed more recently as a slippery but more durable alternative as used on heavy machine tool ways etc.

sticky fork seals

Similar threads