Wes Dayton wrote:
> Under our racing rules, we are allowed to run up to 2 degrees of
> negative camber. After reading accounts from earlier FOT questions, we
> have unsucessfully attempted several mods (shortened upper control arm,
> etc) but have been less than impressed with our results. One problem is
> clearance of the ball-joint bolt/nut and the top of the spring tower,
> etc.
>
> Yesterday we were looking hard at a TR6 front suspension that just
> happened to be on the shelf. It would appear that we could use the upper
> arms, vertical link and trunnion etc. We'd need to modify the TR3A lower
> arm to accept the trunnion, but that looks to be pretty
> straight-forward. It looks as though the 3A caliper plate would still
> bolt up, etc. This would also appear to end up with a stronger overall
> set-up.
>
> Without going into any further details, maybe someone out there has
> already "been there, done that" and has some advice/direction?
(Hope you brought your lunch for this answer.)
Been there, done that.
Last winter I purchased a front suspension software package and spent many
hours trying to find a way to provide negative camber and improve the front
end geometry in a practical manner, using stock suspension pieces and
pivots. Maybe someone out there has come up with a nice improvement, but I
have not. However, I have successfully provided parts for 1-1/2 deg negative
camber for a number of Triumphs.
There are three ways to do this that I know of, each with pro's and cons. I
hope that someone who has implemented a better solution than what I'll
describe will chime in and add to our collective knowledge.
One method is to weld internally threaded receptacles to the upper a-arms in
place of the current inboard ends, and install Heim joints. It has pros and
cons that you can imagine, one of the cons being that it's illegal in most
vintage circles to put a Heim joint there, so I won't do it.
A second way is to bolt a piece of angle iron to the top of the front tower
where the trunion is now bolted. Then you turn the top trunion 90 deg and
bolt it to the vertical leg of the angle iron, providing opportunity to shim
between the trunion and the angle iron, for adjustability. There is at least
one TR in the midwest using this approach and it is successful. I like that
idea, exept it requires either raising the pivot axis of the inner trunion
which makes theoretically undesirable changes in the dynamics of the front
suspension geometry, or else you cut off two of the trunnion ears to get the
pivot line in about the right vertical position but that leaves only two of
those little ears holding the top trunion on, which makes me nervous.
The third way is one that I've either done myself or provided parts for, now
installed on maybe ten TR's that I know of. It is not an original idea, lest
anyone should be offended.
This involves using TR4 upper a-arms and shortening them.
For a TR4, This is pretty straightforward. You use all the stock suspension
members, saw a section out of the upper a-arms, and weld them back together
in a safe manner. I Mig weld them and then weld another piece of steel to
the open side of the c-section, thus boxing in the joint, just for safety's
sake.
For a TR3, you replace your current upper a-arms, upper ball joints, and
vertical link with TR4 parts. This gives you the TR4 caster angle, and it
gives you upper a-arms that are more easily shortened.
The obvious disadvantage of this method is lack of adjustability. That, plus
you must saw the right amount out of the upper a-arm, and that amount varies
with the amount that you have lowered your front suspension.
The combination that we're using on TR4's, and that should work on TR3's, is
to
1) Remove the upper aluminum spring spacer block
2) install MGBGT front springs which are 480 lb / in, more or less
3) shorten upper a-arms by 3/8"
This gives 1-1/2 degrees negative camber (if nothing else up front is bent).
I have built a weld fixture to hold the parts exactly right and have made a
number of sets of these upper arms for friends. It's very time consuming. If
interested, contact me off-list.
Hope everyone has finished their lunch.
--
uncle jack and New Blue
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