FF: Forks Girdraulic spring boxes

highbury731

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To reduce friction and wear (particularly, abrasion of the plating), some members have made plastic liners for their outer spring boxes. I think teflon and delrin (nylon) have been mentioned. I would like to know exactly what they did.

Is teflon or nylon better? Should the liner be just the larger diameter portion (the lower 2" or so) of the outer, or longer? What clearance works best between bush and inner spring box?

Where do I get the necessary plastic?

If the clearance is close, the air inside the spring boxes will be trapped. Some means of escape will be needed. A slot in the bush, or perhaps a drilled hole in the bottom clevis of the inner spring box? How big?

Paul
 

vibrac

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You should have a hole in the side of the upper spring box (towards the top) anyway especially any remaining adherents to bantam gaiters so popular years ago when people actually used Vincents in the rain.
 

timetraveller

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I would have thought that a hole between the two lower legs would be better as this would let out, not just air, but also any water which collected in there. Comments from anyone who has actually done it please.
 

stu spalding

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Hi Paul, I should treat plastic lined spring boxes with caution. I had a pair and the plastic, probably nylon, was hygroscopic and swelled up, gripping the inner and stiffening the fork action. Cheers, Stu.
 

highbury731

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I mentioned delrin (a sort of industrial nylon) which is not hygroscopic, and teflon, ditto. Nylon is also slowly dissolved by hydrocarbons. It's best not to use oils on it thicker than GT85 or TF2 for this reason - such as on nylon-lined control cables.
Paul
 

Vincent Brake

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Indeed delrin.
Or
POM.
Play i used about 0.2mm, machined after pushed in.
(Machined the stainless bottoms as well)
As the air(containing water) is pumping in n out drill a hole in the bottom as well.
But rust will set in.
On springs.
 

timetraveller

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But if you have the 36 lbs/inch springs then they are stainless steel. All the others are spring steel. The 36s are the normal ones supplied for riders of twins who are medium weight, 12 to 15 stones, 75 to 95 kgs. You can tell if you have the 36s as they are the only ones which are a light grey colour. If this is a real problem for many people then it might be possible to get other strengths made in stainless but the firm could not match my specs with normal spring steel for the 36s.
 
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