Hello the list:
My 72 TR6 has an irritating habit. Between 65 and 70 mph (measure on my
slightly wavering speedometer) 2800-3000 rpm on my o/d transmission (o/d
off), the front of the car shakes. Not very hard, but definitely enough to
be irritating. It feels very like one of the wheels is unbalanced. That is
to say like the front of the car is hopping in a twisty sort of fashion.
Left up right down, left down right up. etc... You can feel it through the
steering wheel. Accelerate above 3100 and it starts to fade, at 3400 it's
dead smooth.
First the machine state:
- new redline Coker classic radials (205/75 15)
- front and rear suspension all rebushed and rebuilt this spring
(Brittanicar in Montreal)
- new shocks
- front and rear wheel bearings all replaced
- rims good but not great
- everything re-aligned (runs absolutely straight on the road)
The mechanics tell me that the wheels took a fair weight to balance, but
that they are definitely in balance. I haven't pulled them off for
independent testing, I may have to.
Is there something that I should know that could create this situation. In
the past, I have had out of balance tires (lost weight etc..) usually the
out of balance situation extended over quite a speed range and was quite
horrible before it got better. This is in a fairly tight speed range and is
definitely close to wheel frequency. I looked at cars going alongside and it
seemed that the frequency of vibration was about the same as their wheel
turning rate.
I have examined the tires and can find no broken belts etc. As I said they
are brand new. Because the car is just now on the road after many years
mostly off it, I don't have a good baseline comparison. However I do not
believe this activity is native to the machine design. Memory says that she
was very smooth on the highway at any speed. I always could feel the paint
lines on the road, but this is different.
I may swap the tires about a bit just to see if something changes, but would
like to get opinions before wasting time.
Mark Hooper
72 TR6 (temporarily named "Hoppy")
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