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Tillerman6

Fork seals too tight in sliders

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Kind of a generic problem I think. the fork sliders are from a 75 DT 250 and the seals are aftermarket from "All Balls Racing".  The online instructions say to use a fork seal driver.  Or if you don't have one of those, use a piece of PVC pipe split in half and put back together with a hose clamp. It looks like the fork tube is also inserted into the slider at the time that the fork seals are driven home. Well, I did it another way with a male plug with a shoulder at the top just slightly smaller than the seal OD on the top end and just slightly smaller than the inner bushing on the inside of the slider.- Then hammered on the bushing I made which should have driven the seal in straight. It was well lubed and so was the fork tube, but the seal refuses to seat all the way. I'm hitting the driver I made pretty hard, but the seal is stuck about flush with the top edge of the slider.  Any ideas? Are all seals this tight? 

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No idea why your seal is tight because you haven't said much about what you've done in preparation but here are generic suggestions:

Check to see if the bore in the slider is completely round.

Clean out the bore with a scotchbrite pad until it is shiny metal all the way to the bottom.

Warm up the slider to about 80 degrees C.

Put some anti-sieze in the bore.

It's normal practice to fit seals in that type of fork with the sliders removed from the tubes.

I usually use a 1/2 drive socket that has an OD slightly smaller than the bore and tap it with a small hammer. Plastic coated seals don't usually take much force to get in place

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After reading and replying to Tillerman6 today, I fitted a new set of All Balls fork seals and they are a different design to what I have seen before. They have a ridge near the bottom of the OD and fitting them required a slightly different technique than previously. They were much harder to keep straight than previous times until they were in the bore. They were no tighter than normal and took little force to move them axially once their whole width was inside the bore.

I'm not sure if Tillerman's seals were like this with the ridge near the bottom because mine were a different size (36 x 48) for a Suzuki SP370

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I've fitted All balls seals to my roadbike forks, and they were definitely much tighter than the stock seals. 
Hammering them into the tube couldn't be achieved with a PVC pipe. (it broke)

After hours of frustration, I changed tactics. Took a piece of paint stirring wood, which had a nice rounded fillet at one end, so it didn't damage the seal. 

Used a 2 pound hammer to drive in the seal using the piece of wood, slowly going round to achieve an even movement down.

I even had to use the wooden driver for the dust seal. 

(I then noticed I had forgotten to mount a metal bushing inside the tube, and had to do the whole operation again, killing my sliding bushes in the process....)

  

 

 

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Sorry it took me so long to get back to the question of seal replacement- You guys are great for making these comments! I feel a lot better after reading that I am not the only one having difficulty putting in the All Balls Racing seals. - I am lucky to have some precision tools to scope things out. So after getting one seal stuck half way in and half way out, I decided to measure everything and see what was actually going on with the fit between the seals and the slider inside diameter.- As Feeetup fun said, the new seals from AllBalls racing have a moulded ridge near the bottom which protrudes out around the circumference .This protrusion seems to be mostly "flashing" from the plastic moulding process, and I managed to trim most of it off with sandpaper at first.  I wanted to get a micrometer reading on the OD.  Much to my surprise it was .008" oversize for the bore of the sliders!  And the sliders were not out of round, but the seals are not concentric.  So after much dissapointment and considering my options, I decided to grind down the plastic seal OD to a point where it would go into the slider tube without destroying itself or the slider tube.  I have a Dremel hand piece with a flex shaft and I put a standard coarse sandpaper drum on the handpiece and then put the handpiece in the tool holder for my Southbend Lathe. This gave me a steady and controllable way to reduce the diameter of the seal( oh I forgot to mention I made a 34mm mandrel on the lathe and mounted the seals on it while grinding down the OD of the seals.  I was pretty surprised to find that the seals were several thousandths out of concenticity as well as being oversized.  So as the grinding progressed - very quickly I was down to just .0015" oversize and I decided to stop there.  Good thing I did becase any more and the seals would have probably been too loose of a fit to withstand the oil and air pressure changes that they will see in use.

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You are not the only one that has had issues with the relatively uncomplicated fitting of fork slider seals, especially aftermarket types. The actual tooling used by most bike dealers is like a pair of large collets and quite weighty too! With a little rubber grease on the seal lips and on the fork tubes and using the tool it usually only takes a few strikes sliding the tool to the top of the tube and bringing it down with just hand force. The retainer internal circlip is then installed job done. Your seals were most probably the wrong ones.....close but should not have required all the effort that you put in.

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