Fork breather?

[rustyrider]

Hi folks, not been on here for ages but have now the need to ask a question of the great and wise.  Is there a breather hole anywhere on the front forks?  I ask because I've got a leaking right hand fork leg but not when being ridden, only when it gets hot.  I keep it in a sort of mini-conservatory so it gets quite warm in there and after a couple of days of sunshine I found this

That's fork oil and it's dribbled down the fork leg, over the caliper, pads and disc and dropped onto the wheel.  It's only the RH leg and has only appeared since we got hot weather.  So is there a breather somewhere that has got blocked so as the temperature goes up, the pressure in the leg increases and is pushing the oil out past the seal rather than through a breather?

[cl1ve2004]

somebody wiser than me will tell you for definite, but I've never seen a breather hole on the forks.. reckon you're right fork oil is getting past your seal there ..

[Fazerider]

No there is no breather hole.
The pressure variation in the fork with temperature is trivial compared to that due to compression of the suspension anyway.
What you have there is a leaky fork seal.

[rustyrider]

I've ordered a set of fork seals so will be changing them as soon as they arrive and see if that cures it.  I'm intrigued that I can ride it and nothing gets past the fork seals, yet if I leave it sitting on the sidestand somewhere hot, it pisses past the seals.  I've pulled the top dust seal out and it is definitely coming past the seal, just not when I'm riding it, only when it's parked up.

[robbo]

If the fork oil has dripped over the caliper, you'll be looking at new pads as well.

[kebab19]

Strange.  Are you sure it's not coming out of the bottom of the fork lower, where the underside oil drain bolt attaches the inner damper rod?

[rustyrider]

Nope, definitely not coming out of the drain, but from the seals.  I lifted the dust seal (which is covered in oil), there's oil laying on top of the fork seal and I can see it dribbling down the fork leg, caliper and disc.  Yes, I know I'll need new pads as well as a lot of degreaser to clean the disc off too.  The only thing I can think of is the fork leg is pitted at the very bottom where the seal will be when there is no weight on the bike so the fork leg is fully extended but when being ridden the seal is higher up the leg and seals at that point.  I'm thinking that if I can see any damage on the leg when I get it apart to fit the new seals, I fit the seals with a spacer under them so they bear on a different area of the leg.

[His Dudeness]

Nope, definitely not coming out of the drain, but from the seals.  I lifted the dust seal (which is covered in oil), there's oil laying on top of the fork seal and I can see it dribbling down the fork leg, caliper and disc.  Yes, I know I'll need new pads as well as a lot of degreaser to clean the disc off too.  The only thing I can think of is the fork leg is pitted at the very bottom where the seal will be when there is no weight on the bike so the fork leg is fully extended but when being ridden the seal is higher up the leg and seals at that point.  I'm thinking that if I can see any damage on the leg when I get it apart to fit the new seals, I fit the seals with a spacer under them so they bear on a different area of the leg.

The fork's not fully extended when the bike is parked. The weight of the bike is still being transferred through the suspension compressing the fork. If you did a wheelie and took the weight of the bike off the fork it would extend out further than it is now. If you dry off the around under the dust seal so there's no oil and then pull the front brake and compress the fork a load of times simulating riding along a road you will probably see some oil weeping past the seal. Don't put a spacer under the seal.