Dear Listers,
I am going insane.
I replaced the TR7's front wheel bearings about 2 years ago. The
instructions in Haynes did not work ("tighten to 5 ft-lbs and back off 1
flat"): they were way too loose, so I tightened them to 5 ft-lbs, which felt
snug, but allowed the wheels to rotate easily.
About 1 year later, the car developed a shimmy (between 73 and 77 km/h). I
checked the wheel balance, bushings (all were new 2 years ago), and steering
rack tightness, finding nothing wrong. After some months, I discovered that
the wheel bearings had loosened.
I've tightened them to 5 ft-lbs twice since then. I put them at 10 ft-lbs on
Saturday, after ensuring that no grease was where it needn't be, and that
the castellated nut/cotter pin assy. was not going to move. They are already
acting loose again.
I can think of 4 possibilities:
1. the bearings have failed in some strange way that allows temporary
adjustment, which subsequently reverses itself;
2. the bearings have moved outward in the hub, so that every time I tighten
them, they're only good until they relieve the compressive stress by moving
further into the hub (thus increasing the clearances and getting loose
again);
3. there's something wrong/worn in the hub;
4. I have gravely offended the marmots.
I have to fix a leaking caliper, but I don't want to tackle that until I
know how to deal with the bearings. (Of course, having no other vehicle
means I have to sort everything out at once, and have all parts on hand!)
I will happily entertain any diagnosis, conjecture, or anecdote.
Allen Nugent
Graduate School of Biomedical Engineering
University of New South Wales
Sydney 2052 Australia
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