By Peter Caldwell - World Wide Auto Parts
First. What fails in a lever shock? Almost all of the (non-traumatic) failures
result from lack of oil in the shock. The manuals always recommend checking
or topping-up your shox in various intervals 3000 miles or so. Why? Because
they leak!.. what a surprise! They don't leak just because they are British,
they leak by design (now there's a bumper sticker). Speaking here of the rear
shox... the shaft that protrudes from the body of the shock is rotating in the
body without a bearing. To ensure sufficient lubrication there is often a channel
or groove in the shaft bore. At the outside there is a rubber packing retained
by a thin metal washer. A packing needs some lubrication to work at all and
the weeping of oil acts as a deterrent to dirt getting in.
Dirt getting in will score the shaft at the seal area hastening the demise
of the packing and wearing the bearing surface in the body.
The solution that all of us rebuilders use is to machine the body and install
a bearing. We use Delrin, others use bronze. Bronze requires oil, Delrin doesn't.
We also machine the body for a rotary oil seal (others don't) (in fact we use
a double lip seal with dust excluder). One guy does, now out of business did
use a rotary single lip seal and the others use several rubber washers held
in place with a steel washer or two. To solve the pitted and scored shaft problem,
others sand or grind the shaft down.(you don't need to be precise with rubber
washers) We have manufactured for us, to our specs, stainless steel sleeves
that allows us to have a 3 micron finish and consistent diameter and concentricity
of the shaft. After many years, we have found this to be very reliable. Our
shox don't leak.
The process... step by step. Receive grimy old shock, tumble clean in a deburring/tumble
cleaner. Glass bead blast entire shock. Disassemble. Tumble and hot wash in
ultrasonic tank internals. Bead blast the rest of the arm. Machine for the bearing
and for the seal. Wash again. Press in bearing and seal. Press on sleeve. Inspect
and repair/replace as necessary the pistons and the valving. Reassemble components
using all new hardware of proper thread and style. Fill with oil and bleed.
Compare valving with NOS shock, adjust if necessary. Wash AGAIN. Paint 2 coats
primer and 3 coats high heat black enamel. Date code and ship.
There you have it. I can provide details of the valving and design changes
over the years, etc. But my carpel tunnel is acting up.
Peter Caldwell
