Causes for Blown Fork Seals

I just blew my right fork seal the other day while riding in the cold. I am not sure when the last time they were replaced was, but what are the usual reasons for why this happens? Could it have been the cold, lack of bleeding them (forgot :/), or just being old?

I'm sure the cold can stiffen up the rubber and aid in the leaking process.

Best I recall, every seal that I changed had no damage to them. Usually it's sand/dirt caught on the lip of the seal, holding it away from the tube and letting fork oil by. If I have new seals and one of them show some leakage, I just clean the debris from the inner and outer seals area. If they are older I just change them so cleaning will work.

I'm sure the cold can stiffen up the rubber and aid in the leaking process.

Best I recall, every seal that I changed had no damage to them. Usually it's sand/dirt caught on the lip of the seal, holding it away from the tube and letting fork oil by. If I have new seals and one of them show some leakage, I just clean the debris from the inner and outer seals area. If they are older I just change them so cleaning will work.

+1. Just clean the seals, unless it's a KTM and in that case you probably need new ones.

Try pulling away the dust seal and cleaning inside the actual oil seal with a 35mm film negative. I cleaned them out and they havent showed any signs of leaking yet.

If you ride them awhile without bleeding them then strap it down with tie downs. It puts too much pressure on them.

Dirt/grit is the reason 99.999% of the time. It can either hold the lip of the seal away from the tube or scratch the seal, effectively cutting a small notch in it. A seal in good condition can withstand well over 60 lbs of air pressure, so for pressure to be the cause, there has to be an additional factor. Old seals loose elasticity, but then you are talking about seals five plus years old. Over filled forks can cause the pressure to exceed the max the seals can withstand too.

I just blew my right fork seal the other day while riding in the cold. I am not sure when the last time they were replaced was, but what are the usual reasons for why this happens? Could it have been the cold, lack of bleeding them (forgot :/), or just being old?

Old seals, cold seal, dirt below the dust seal. Also mis-aligned fork tubes. Anytime the forks are moved, wheel tweaked (crooked after a crash) or the wheel removed, you have to align the fork tubes. Do this by loosening the pinch bolt, and lower triple pinch bolts. Now compress the forks about 4 times, tighten the lower triple pinch bolts, then compress it 4 more times and tighten the front axle pinch bolts. This ensures both tubes are parallel with each other.

Old seals, cold seal, dirt below the dust seal. Also mis-aligned fork tubes. Anytime the forks are moved, wheel tweaked (crooked after a crash) or the wheel removed, you have to align the fork tubes. Do this by loosening the pinch bolt, and lower triple pinch bolts. Now compress the forks about 4 times, tighten the lower triple pinch bolts, then compress it 4 more times and tighten the front axle pinch bolts. This ensures both tubes are parallel with each other.

Thanks everyone for the input, I will get out there and do all of these things once I am able to. I am kinda set back here...I broke my femur on Monday playing hockey :busted:

Thanks everyone for the input, I will get out there and do all of these things once I am able to. I am kinda set back here...I broke my femur on Monday playing hockey :busted:

Ouch! Good luck getting back to action soon, that injury is said to be one of the worst! Hope they gave you some good pain killers....

Thanks everyone for the input, I will get out there and do all of these things once I am able to. I am kinda set back here...I broke my femur on Monday playing hockey :busted:

All good advice.

One more thing to add, water spots are like little teeth to seals so get some lube on the tubes after each wash (just don't get any on the brake pads or rotor).

A Pro-Action tech once told me worn bushings will cause seals to wear faster. I'm not sure how significant a part that would really play though. There's always some play even with new wear parts installed.

IMO seals fail because your dust seals wear out and let dirt by, this lets dirt into the seal and pulls it away from the fork tube which in turn lets oil come out. Which is why its always a good idea to replace the dust seal

with the fork seal.

IMO seals fail because your dust seals wear out and let dirt by, this lets dirt into the seal and pulls it away from the fork tube which in turn lets oil come out. Which is why its always a good idea to replace the dust seal

with the fork seal.

I agree. If you have your forks apart it makes no sense not to replace both.

All good advice.

One more thing to add, water spots are like little teeth to seals so get some lube on the tubes after each wash (just don't get any on the brake pads or rotor).

You lube your fork tubes? That would just cause dirt to stick to the tube, i would suggest wiping the fork off after a wash with a clean rag, but lube IMO does not sound like i good idea.:busted:

You lube your fork tubes? That would just cause dirt to stick to the tube, i would suggest wiping the fork off after a wash with a clean rag, but lube IMO does not sound like i good idea.:busted:

Well..it is true that some lubrication products will attract and sometimes hold on to dirt. But in this case, the point is make sure that there are no water spots left behind as that is more of a problem than what some dirt build-up would cause.

Additionally, a dry silicon spray or a PTFE lube does not really hold dirt.

That said, all forks and shocks will exchange some fluid and air as you ride so there will eventually be more of that on the tubes than whatever you use to clean up the water with. Not a big deal, really, as the purpose of the wiper is to keep the tubes...well...wiped. They just don't hold up to mineral spots and the seals are soon subjected to the torture.

:moon:

Dirt/grit is the reason 99.999% of the time. It can either hold the lip of the seal away from the tube or scratch the seal, effectively cutting a small notch in it. A seal in good condition can withstand well over 60 lbs of air pressure, so for pressure to be the cause, there has to be an additional factor. Old seals loose elasticity, but then you are talking about seals five plus years old. Over filled forks can cause the pressure to exceed the max the seals can withstand too.

Forks when fully compressed create about 300-400psi depending on your fluid height. Just making a note:ride:

It`s in my Honda manual.

Additionally, a dry silicon spray or a PTFE lube does not really hold dirt.

d up to mineral spots and the seals are soon subjected to the torture.

:busted:

I personally like a lube like dry silicon myself, though I can't say I use it as often as I should...

I mostly keep the fork legs whiped down after washing, and just expect seals to go eventually....because they eventually will:banghead:

Speaking of putting a lubricant on the fork tubes I have heard people recommend packing grease into the dust wipers and I have heard others argue against it. The MSR wipers come with grease-like substance in them already.

Any thoughts on this from the suspension pro's here?

Speaking of putting a lubricant on the fork tubes I have heard people recommend packing grease into the dust wipers and I have heard others argue against it. The MSR wipers come with grease-like substance in them already.

Any thoughts on this from the suspension pro's here?

I have tried it....but can't say I thought it any better or worse....and certainly accumulated dirt.

But if you clean it often, it may help out some.

If your forks are installed correctly, with a good fork seal (most really are decent these days...OEM is very good) they will last a long time on properly cared for bikes.....the biggest reason I see forks leaking is improper installation that puts it in a bind.....

i was impressed today with some seals, i always think kyb and showa seals will last 3 months if you are lucky, a friend who rides a lot came in with his 07 rmz, it must have been 6-7 months on the same seals and this is riding in sand and our mud sometimes 3 times in a week.As a side note the bike must have done way over 150 hours, the ex and inlet valves are dead in the middle of the range, its never had a shock service i know of, the only thing he has done is replaced one clutch, he is now getting a piston kit as well.

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