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Re: Rear Wheels not straight...why?

To: Ben Burnweit <a1972tr6@hotmail.com>
Subject: Re: Rear Wheels not straight...why?
From: "Robert M. Lang" <lang@isis.mit.edu>
Date: Wed, 21 Nov 2001 16:04:31 -0500 (EST)
On Wed, 21 Nov 2001, Ben Burnweit wrote:

> TR-6 er's,

Hi.
 
> My '72 TR6 has just had a rear wheel bearing replaced.  But I notice from 
> the rear the rear wheels stand with the tops inward ( / \ ).

This is "negative camber".

> Is that normal or should I worry about this?

Well, this depends on what you need by "normal". The alignment specs for
the car indicate that teh camber should be 0 degrees plus or minus 1. So,
if the camber measures to -1, then you are technically within spec.

How do you change rear camber?

There's a couple of things that effect camber on TR6 - the brackets that
the trailing arm is bolted to, the effective spring height and the
integrity of the frame.

Assuming that the mechanics left the trailing arm on the car, all your
camber we likely already there before you had the work done. Howqever, if
the shop removed the trailing arm from the frame and then (by chance)
removed the swivel brackets and then (by further chance) re-installed them
in reverse or flipped around or whatever - then your camber may have
changed.

There are 36 combos (total) using the three brackets available from the
suppliers, so-called 1-notch, 2-notch and 3-notch. The amount of camber
change using all the combos of brackets is approx. 11 degrees.  Armed with
a stack of brackets and an aligment machine, you should be able to dial
out the negative camber if you deem it to be excessive.

If your springs are "sagging", then the car might appear to have more
camber than others, but you have to resort to spacers or new springs to
remedy this. Does the car bottom out on the rear bump stops??

Finally, make sure the frame is okay where the trailing arm brackets bolt
to it. If the frame integrity is compromised, then you need to deal with
that. In fact from a safety standpoint, you should look at the frame
first.

A lot of folks with TR6's with old original springs still in 'em can take
on this excessive camber look. But before jumping to any conclusions, get
some real measurements and find out of the shop that did the wheel
bearings took the trailing arm off.

Hmm. I just thought of something. You might also want to check to make
sure that the six studs holding the rear brake plate and hub carrier is
installed properly. It's not uncommon for gorilla mechanics to overtighten
the nuts and pull the studs out.

> I've looked at a couple other TR6's and they don't seem to be as slanted as 
> mine.

I hear you.

> Is it possible that 185/15 tires are too big for my car?

NO NO NO. 185/15 is the stock tire.

> Should i go to 165/15's?

Absolutely no. There is no reason to go to a smaller tire.

> Or should I replaced the coil springs with heavy duty ones?

If you want to go this route, tread carefully. There are several
"competition/heavy duty" spring sets available. Not all of them give you
the correct "fitted length" and therefore need to be "tuned". The warning
is that many of the springs are too long and therefore change your problem
from excessive negative camber to excessive positive camber. This is bad.

Then folks hack one or more coils off the springs to lower the installed
hieght - the problem with tis is that it _increases_ the spring rate. Can
you spell "buck board"??

At any rate, depending on how you intend to use the car and how much
"stuff" you bring with you in the car, you should be able to get an ideal
combo of springs/aligment.

Note: when you change the camber by gross amounts, you very likely effect
the rear toe measurement. SO if you play with the springs or the brackets,
you want to get an aligment by a competent alignment shop before you drive
very far on the new setup... failing to do so may lead to premature tire
wear.

> Any advice  is greatly appreciated.
> Thanks,
> Ben

yer welcome,
rml
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