> Every TR6 I've owned have shimmied at around 62 MPH. The
> only time they haven't is when I've had the tires balanced on
> the car.
That sounds like exactly the problem I have been looking at recently. When
I went to service the front brakes on TS13571L, I noticed that the hub/rotor
assemblies were badly enough out of balance that they would turn by
themselves. Didn't have time to investigate, so I swapped in the hubs from
the wrecked TR3A and went to TRfest. The lug nuts on the LF came loose
twice, once on the way to SLO and once during the Fun Rallye; so I
determined to investigate further when I got home.
Using an old spindle & vertical link clamped in the bench vise, I have
verified that 3 different hub/rotor assemblies are out of balance enough to
turn by themselves. The problem appears to be mostly in the brake rotors,
as one of the hubs would not turn at all and another would only barely turn,
without the rotors mounted. And both times, the heavy spot was on a
different side than with the rotor mounted. I also tried spinning them up
to speed (unfortunately no way to measure what speed), and noted that they
shook my entire workbench hard enough that things started to dance off the
top.
The two original hubs (one from TS13571L, other from TS39781LO) also had
significant runout at the hub face.
The third hub has much less wear apparent, and may actually be unused. It
came from a complete TR4 front suspension I bought from a shop many years
ago; apparently unclaimed after being rebuilt. It only had about .002" TIR
runout on the hub face, and .004" at the brake disc, which is passable. The
assembly was still out of balance, again apparently mostly the rotor. Same
thing happened with a brand new TR3 brake rotor mounted. I got the rotor
runout down to .002" and then drilled a series of dimples around the edge of
the rotor to balance it. Balance still isn't perfect, but it's much better
than before ... I can feel the vibration in the vice, but things don't dance
around on the bench.
Hopefully in the next few days I'll try it on the car.
I've bid on the on-car balancing gizmos several times, but always been
outbid. Apparently they are no longer sold new.
HF also sells a motorcycle wheel balancing tool that might do for balancing
hub/rotor assemblies; but I haven't tried it for that.
-- Randall
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