How to recognize busted fork seals

[DeepBlueRider]

During my last trip I've ended up in the middle of nowhere on very bumpy dirt road. I've met local old lady and she told me road is bad only for 1 more mile. I don't know if I've screwed up or she didn't know what she was say but anyway I've ended up riding over 20 miles that road

I've change fork oil in august but after giving it so hard ride I've wanted to check how suspension components looks like. Oil have now consistency of water. I've drained fork (without disassemble) and it looks like it's only 400ml. I don't remember how much I've put last time as I believe I've went directly to fork oil level. Also I don't remember if I've used 134mm or 130mm levels so I cannot tell if there was any oil lost but according to manual I've should put ~467ml.

Only way I know to lose oil in fork is by leaking fork seal. All my bikes leaves little residue on the forks. Kind of thin film - not like oily drops or something similar. It's so minimal it doesn't even attract a dust after riding. While it's possible all bikes have busted seals chances are very low

How do I recognize if seals are busted ?

 

[trepetti]

A thin film of oil on the fork. If I understand correctly you should have no residue at all.

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[DeepBlueRider]

A thin film of oil on the fork. If I understand correctly you should have no residue at all.

Thats what I was told also.

However I haven't seen yet bike that haven't left ANY residue. All I've seen left something - I could wipe it with finger and even finger didn't felt oily but there was something.

 

[Nelly]

Are you confusing the polishing that the seals do as they move up and down the stanchion as oil residue? Even a small particle of dust breaking the seal will cause a noticeable leak. You will see fresh oil running down the fork leg and dripping. This has come from my recent experience with a leaking seal. If your unsure you could invest in the very cheap and excellent sealmate to make sure there is no dust or debris caught in the seals.

Nelly

 

[FinalImpact]

IMO there should always be a boundary layer or film of oil on the stanchion tubes. Completely dry it will wear from increased friction and SOON WILL LEAK oil (think of it as your knee on gym floor). It should not however, leave a noticeable film at the edge of the seal.

In short if you dry it constantly it will increase the wear. If its rock hard and not pliable but not leaking, I'd replace it. As in, push on the lips edge and see that its pliable. It should be soft enough to deform slightly and then return to shape.

If your tubes have lots of minor scratches, they may seep a bit more and be harder on seals. 2200 grit wet dry paper can remove very fine surface scratches (forks apart). You must be very careful and not leave edges/solid stops or do any shoe polishing like action (in circles). Go up and down with at least 180 degrees of coverage (just a few passes) rinse remove any grit, do the other side.

 

[Hellgate]

Is oil running down the fork leg? If not you're good. If it is try the 35mm film trick.

 

[DeepBlueRider]

It could be polishing Nelly mentioned. For sure there is no enough oil to run down fork. Even there is not enough oil to make seal wet.

Also what FinalImpact mentioned, makes logical sense. My gut says if seals would be dead dry it would tear them in a blink of eye.

I've noted what oil level I've used so I'm going to ride it and see how much will be there in a month. If there is any lost, I will replace seals (or I will replace them anyway .

Thanks for answers guys.

 

[Nelly]

For sure mate if the fork is leaking depending on which leg you will see oil on the fork leg and possibly the brake lines and even caliper as I did.
Especially if you don't ride the bike daily.
Nelly

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[Water Bear]

For what it's worth my experience is exactly the same as Nelly's. There was oil all over everything, down the fork boot and even on the brake pads.