by Bob Love and Russ Drake
Bob was recently performing some work on his R100GS which required him to remove his Fox shock absorber. Much to his surprise, he found that the rubber bushing at the rear drive end had failed. The unit was on the bike for 2 years and about 20,000 miles. His riding is mostly on the street with a fair amount of dirt mixed in. Generally ridden pretty hard with reasonable loads. Calling various local dealers (Cal, San Jose) resulted in no replacement parts available. He called Fox and was disappointed in their response. First they had no parts available, second they would not supply him with a drawing of the part (he offered to go to the factory) so he could have one manufactured, and third they could not tell him when a part would be available. The Fox rep he spoke with offered the fact that the design was not good and in fact that Fox was working on a redesign. Again no date was given for availability.
His temporary solution was to install a bushing made from delrin. He made his part with the inside diameter .005" greater than the shaft diameter, the outside diameter .002" greater than the shock eyelet inside diameter, and the length the same as the metal bushing from the original part. He views this as a temporary solution to get him through the Death Valley trip, though he expects it will last a lot longer than the original part. He plans to install a spherical bearing at the drive shaft end. Unfortunately this will require a new eyelet to be manufactured and welded to the shock as the eyelet currently is too small for a standard bearing that will fit the mounting shaft. He will provide details after that work is complete.
He would like to suggest that all owners of bikes with Fox shocks with rubber bushings in the mounting eye perform an inspection. You may well be unpleasantly surprised.
Russ adds "In addition, anyone that has a few miles on his bike should check the upper mount on single shock bikes. On my R100 (1991) the tube that is welded to the frame, which has a bolt going through it to the shock, was worn to an oval shape. Since the shock rod end is only supported on one side, the force of the shock had elongated the mount tube."
There was noticeable play at the upper shock mount when the bike was on the center stand and the tire was lifted up and down. His cure was to run a reamer through the mount tube and press a manufactured aluminum bronze bushing into the tube with the inside diameter .002 larger than the mount bolt.
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