[Codeman00]

My friends and I have debated for a long time now about fork seals. Our fork seals never seem to last as long as they should before they start leaking. Many times, it's that one ride in the mud with new seals where the mud dries on the forks and the fork compression drives the dry mud past the seals into the upper tube...and all of a sudden there's leakage all over the place. We try and try to use the "film negative cleaning technique" which seems to stop the leak temporarily...but the seals start leaking again. I have read that seals leak because of "micro-cuts" and "micro-abrasion"...but is this really true? Or is it just dirt between the seals that cause a gap and thus a leak? Can the seals be re-used? Have the seals really been compromised?

I've read from the experts that "seals are cheap", always replace them...but $45 is $45...and some people would rather spend that $45 somewhere else...especially a couple of times a season. I know I would like to save money...especially since I do my own bike work at home.

So since I have a few microscopes at work in our Quality Lab (in addition to one that's hooked up to a computer for photos), I decided to look at my leaking seals under the microscope and see if the seals were nicked or scratched in any way. I first looked at and photographed the sealing surface on my new seals as a baseline. The old seals were about 6 months old and only began to start leaking with grainy dirt that came out of the cavity between the two seals with every swipe of a film negative. I expected the old seals to have obvious nicks in he seal surface.

After careful examination under the microscope, I couldn't find any evidence of any kind cuts in the old seals. In fact, I declined to take photos of the old seals because they looked exactly like new seals. Exactly like new seals. In fact, I saved my old seals, cleaned them and the next time my fork seals leak, I'm going to replace them with these old seals instead of buying new ones and inspect the ones I take off with a microscope again. My guess is that one set of fork seals can be used a lot longer that previously thought by cleaning the seal / forks and replacing the oil with fresh oil. I know most people don't have access to a microscope, but a 20X-30X jeweler's glass will get you the similar results (purchased for about $10 on ebay).

Anyway, I know your dealer will mandate new seals so as not to accept any liability...but if you are a DIY guy like I am, this little inspectiion and a reuse of seals might save you some money in the long run...especially if you are one of those guys that seems to have leaking fork seals many times in a riding season. My opinion is that it's the dirt in between the seals that constantly pulls the seal lip up and causes the leak...not a cut in the seal. The seals might not be bad after all, they just might need a little cleaning.

(of course, this method is at your own risk...but definitely worth thinking about)

[madmax]

After 5 years both my 250s are on the stock seals, my 450 has been changed once.

I`ll have one of the six leaking from time to time, but i`ll just run a .005 feeler gauge up there. sometimes they`ll last a month sometimes a year before it leaks again. Nothing wrong with a seal thats leaking just a little dirt up there.

[Leardriver]

Those are great observations.
When I'm fixing friend's fork seal that I know to be fairly new, we just pull the snap ring, pop them apart a few inches, wipe them out, and drive the formerly leaking ones back in. That seems to work 75% of the time, and is worth the 15 minutes and $0 that it takes.