Marcus Tooze speaks to the issue of bump steer on his homepage:
http://www.calmit.unl.edu/tooze/tvr/
Look under Front Suspension, and the note regarding changing the steering
arm. I have emailed him and asked if this fix is specific to the M cars, or
to the Vixens as well. Keep you posted.
Somebody else on the list recently asked about a heavier roll bar. Note the
section on roll bars off the same webpage . Marcus recommends replacing the
rubber sockets with heim joints (known more commonly in N.A as rose joints,
I think. Sounds like low cost change that really stiffens things up. Stephen
> ----------
> From: Malaboge@aol.com[SMTP:Malaboge@aol.com]
> Reply To: Malaboge@aol.com
> Sent: Saturday, September 12, 1998 3:21 PM
> To: TVR@Autox.Team.Net
> Subject: Bumpsteer (long)
>
>
> A fellow lister asked...
>
> << What is my best bet for the bump steer fix? I bought some aluminum
> steering rack mounts, but haven't installed them yet. Seems to me they
> won't
> cure the problem by themselves. >>
>
> And of course the ever opinionated Nickster has to toss in his 2 cents
> worth...
>
> TVR's have used one style front end (excluding the early VW stuff) with
> only a
> few differences up until the M chassis. The components of that system were
> commonplace origins for kit cars, one-offs and race cars of the day. Some
> manufacturers just got it a little better than others. TVR unfortunately
> wasn't one of them. You can look at it either of 2 ways; they got the
> steering
> rack too high, or the steering arms weren't high enough.
> Anyone who has ever driven one of the pre M cars has noted the dreaded
> "kick
> back" in the steering wheel, and the fact that ot takes 2 hands on the
> wheel
> at all times to drive the car as it hunts and darts all over the road.
> Some
> cars are way worse than others, but they all could have been better. (One
> of
> my cars had a total of over 2 inches of toe out through a "normal" amount
> of
> suspension movement...very scary ride)
>
> OK, here's the Nickster fix. It's easy, cheap, will make your car fun to
> drive
> again, but takes a bunch of time.
> First you have to measure the amount of bump steer. There are lots of
> fancy
> bump steer gauges around, but I'm too cheap for that. Scrounge around the
> garage and find a couple of pieces of plywood and a piano hinge. One piece
> of
> plywood has got to be at least 20" square, the other can be smaller. Use
> the
> hinge to attach both pieces together at the edges so that you can form a
> ninety degree angle with the 2 pieces. With your car on the flattest
> section
> of your driveway, measure the static ride height. Jack up the car and
> remove
> the bottom bolt that holds the shock/spring unit to the lower a-arm, and
> swing
> it out of the way. Put the wheel back on and lower the car back to its
> static
> ride height while still on the jack. Place the big piece of plywood
> tightly
> against the tire and put something heavy on the other hinged part to keep
> it
> from moving around. Lower the car on the jack (the tire now goes into
> "bump")
> and measure the space between the wood and the tire.If the space is in the
> front of the tire, you have toe in. If the space is in the back you have
> toe
> out. Continue lowering the car and measuring as you go, and you can graph
> the
> amount of toe change per change in ride height. Ideally there will be no
> change in the space as you lower the car. Most TVR's I have seen will toe
> out
> "a bunch". Toe out under bump is much harder to drive than toe in under
> bump,
> but excesses of either are no fun.
>
> Most cars will be found to have toe out, so I will address the fix in that
> direction. If you find toe in, move everything in the opposite direction.
>
> If you ever wanted to fix/change rack mounts, now is the time. Be sure to
> remove any shims under the mounts as you want to get the rack as low as
> possible. Some cars have used the Triumph steering arms, but most TVR's
> have
> some odd longer Stanpart steering arm. Anyone know what the heck it came
> off
> of? What you need to do to this arm is to raise the front end of it where
> the
> tie rod attaches. Note that the very end where the tie rod hole is, is
> parallel with the ground and when you are through with the mods, it still
> should be parallel. Remove the steering arms and heat them cherry red
> between
> the tie rod end hole and the first attachment hole. Using judicious
> leverage
> (do not beat on the arms), pry the arm up in the front. Depending on the
> amount of toe out, the amount that the steering arm must be bent will
> vary.
> Try starting with about 1/2" higher, and don't forget to bend the very
> front
> part of the arm back down so that the tie rod end hole is still approx
> parallel with the ground. Let the arm air cool, do not quench it.
> Reassemble
> the car and measure again. You may have to repeat these steps a few times
> to
> get the bump steer as close to zero change as possible.
> Do not just duplicate the amount of bend for the other side as it will not
> be
> the same, measure both sides and deal with them individually.
> Once you have the readings you want (we haven't even considered the amount
> of
> toe change under "droop", but it is not nearly as important as the amount
> under "bump") take the steering arm to your local heat treater and have
> them
> heated and cooled to a "normal" state, then heat treated to the proper
> Rockwell hardness (any heat treater should know these specs, if not lemme
> know
> and I'll dig them out, but I can't remember the number at the moment). Do
> not
> just put them back on the car without the heat treatment as they will be
> softer than they were and could have lots of new stress points, neither of
> which are good things.
>
> Depending on the amount of bump steer, when you bolt this puppy back
> together
> it will seem like a completely different car.
>
> So much for another OPINION...just remember, you get what you pay for...
> Nick in Nor Cal
>
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