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Re: steering wheel shake

To: "DenverD" <>, "David Councill" <>,
Subject: Re: steering wheel shake
From: Barney Gaylord <>
Date: Mon, 25 Jun 2001 15:56:38 -0500
At 09:34 AM 6/25/2001 +0200, DenverD wrote:
>its not all the time...but almost all the time..
>sometimes...say there is a slight bend in the road and a pressure is
applied to turn ever so slightly the shake *might* go away during the turn..
>or, sometime for NO apparent reason it just fades away to completely
smooth...and then maybe five seconds later comes back..

This is an indication that there is a bit of a problem with both front
tires.  It may be either out of balance or out of plane.

Tires are not exactly the same diameter, so as they rotate one will turn
slightly faster than the other.  When the two wheels are in sync the shake
from each is reinforcing, and you notice the shake in the steering wheel.
When the two tires are out of sync by 180 degrees the shake can be
self-cancelling, and it can run perfectly smooth for a while.

The frequency with which the shake comes and goes depends on the difference
in diameter of the tires, but it will be a regular pattern while driving in
a straight line.  You may expect this to repeat at intervals of 10 to 30
seconds.  Also traveling around a gentle curve changes the differential
rotation of the tires because of the different travel radius, so the time
pattern will also change.  Under the right conditions through a curve the
car can run smooth continuously until youi exit the curve, or it may shake
continuously in the curve, or the repeat frequency may change to much more

Jack up the front of the car and spin the wheels by hand.  Check to see if
they wobble latterally or radially at the tread.  If they run true within
1/8 inch, then the problem is probably out of balance.

However, in rare cases a tire can run appearently true when suspended in
the air, and then thump or wobble when it has a load on it.  This is a
problem with a carcass failure or abberation of carcass construction.  For
a mild condition of this type there are some tire service shops with
computerized equipment that can map the rotation and "lift" of the tire
when running under load, and then selectively grind some of the tread in
order to make the tire run true under load.  This can work to cure a radial
wobble, but not for a latteral wobble.  The service can also be cost
prohibitive, so as long as yout tires are not too expensive you may do as
well just buying new tires.

Barney Gaylord
1958 MGA with an attitude

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