Ceriani 38mm fork seals

  • Thread starter Thread starter Davo
  • Start date Start date
D

Davo

Guest
OK, so the first pair of new fork seals I fitted turned out to be so fat that the retaining circlip would not fit. No I did not measure their thickness prior to fitting - idiot that I am assuming that as they were bought for this purpose they would be the same as OEM. So, now I measure the other new pair and find them to be 7.5mm thick, parts book says they should be 7.00mm, go through the old parts bin and find the originals I had removed - 6.75mm, measure another set that I had ordered when the first new pair didn't fit and they are 6.75mm.

Inquisitive I start to research fork seals and in the very informative "Guzziology" Dave Richardson states that:-

1.  Older design fork seals as were OE in our ancient forks were actually designed to seal against rotational movement rather than longitudinal and hence were prone to leak with the stanchion movement and that is why two fork seals were used per leg.

2.  The newer design fork seals are much more efficient at sealing against longitudinal movement due to their tighter fit on the stanchion but because of this tightness also increased the friction between seal and stanchion and therefore increased stiffness.

He went on to recommend using a single seal only.

Now, the first set of seals I got were from a Guzzi dealer, the second (and correct thickness set) were from a Ducati dealer.

Should I use 1 each per side of the fatter "Guzzi" seals or go as per original with 2 seals per side?

Your expert opinions would be much appreciated.
 
Think that's the recommendation for Marzochi forks as well. Got single seals in my forks (RGS) and they don't seem to leak any more than when two seals were fitted, but stiction is much less. Just cut the seal out of the old seals (if they haven't been distorted too much by the removal procedure) and use them as spacers. Don't know if its better to have the cut seal above or below the new seal, maybe somebody will have an opinion. HTH

Terry
 
If you cut the lip out of the old seal to use as a spacer, then you're probably better off putting it under the new seal so there isn't so much of a well on top of the seal for dirt to collect in.

However, a better solution is to leave the lip on the old seal, remove the circular spring that's inside the lip, then fit it on top of the new seal so it'll act as a dirt wiper and protect the new seal. Taking the spring out will reduce the seal's grip on the fork so there will be bugger all additional friction.

The difference between rotary and linear action as far as a seal is concerned is that linear movement will drag dirt into the seal, so the wiper lip does actually perform a valuable function. Seals designed for this type of service (eg. for hydraulic rams) generally have a dust exclusion lip built into them.

Cam
 
I was right, didn't take too long for somebody to come up with an excellent suggestion.
Thanks Cam
 
You must log in or register to reply here.
Back
Top