bearings or bad tire?

["Eric Billing" <eric.billing@metaphasetech.com>]

Greetings,

I recently put new Potenza RE930 (with allignment) on our '93 100 CSQW. The
car rides real well and is considerably more comfortable to drive than
before--the Pirellis were well worn and we were out of balance.

Bad news, is that while the new tires and allignment make things
considerably quieter, I have discovered a "throbbing" vibration which occurs
at about 65mph (which is 2800RPM in 4th on the auto-tranny).

Some additional diagnostics:

a) 2800rpm in 3rd (about 50mph) has similar noise but much less noticable
and a different frequency.
b) below 65 (say 60 mph) there is no noticable noise. Above 65, the ambiant
road noise drowns out the throb...
c) 65 mph in 3rd (about 4000 rpm) results in too much engine noise, so throb
may not be present
d) no shake in the steering wheel

So, I'd be interested in hearing suggested courses of finding the source of
the problem. Currently the car is back at the tire shop having the wheels
re-balanced and rotated. Hopefully the noise will go away or move in someway
as to indicate a tire defect.

Other ideas?

Thanks,

Eric

--

Eric Billing
Eagan, MN

'93 100 CSQW Pearl w/ 57K miles
'91 Accord EX w/ 115K miles

eric.billing@metaphasetech.com