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Jul 18, 2005
Can the APPROXIMATE condition of the isolastic condition be checked by checking sideways movement of the rear wheel relative to the frame?

For example I'm thinking of when you're looking at a bike that is for sale and want an idea of the isolastics condition. I guess swingarm wear would enter into it making it a not very viable idea!! On my 1970 roadster side to side movement is about 1/2" each way from center at the far side of the rear wheel when holding the frame rigid. I've only had my bike a short while and haven't got around to checking with feeler gauges yet.

Having a 1/2" of movement at the rear wheel would indicate a LOT of wear in the swing arm bushings and spindle, and perhaps the isolastics,at a clearance of .010" total in the rear iso's. my rear wheel has at the most a 1/16" of movement side to side.
I replaced the old bronze swing arm bushings with Torrington B1416 needle roller bearings, packed with grease, no more trying to get 140 weight oil into the tiny nipple, I also modified the s/a tube as detailed in the INOA Tech Digest, two additional bolts that bear against the s/a spindle to prevent the side to side "rocking" motion in addition to the single factory installed central bolt,these mod's. seem to work well in stiffening up the rear end.
CAUTION: if you decide to fit the Torrington bearings you must get the spindle hardened, I made a new one hardened to 58 Rockwell C scale,I then ground the spindle to size to fit the bearings i. e .8755" / .875".,if you use a "soft" spindle it WILL get chewed up by the bearing needle rollers . Good luck, James.
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