I don't know if the frame rails were ever supposed to be parallel to the
ground. On both my cheater TR3 and Peyote they slope upwards from one to
two inches, front to back measured from beneath the front inboard
suspension point to the joint where they kick up. About every TR2 I've
ever come across has stiffer and shorter front springs than original spec
and softer rears. I can't find anything in the manual that indicates what
standard is, but I don't know if it matters much since no ones car is like
that.
By the way, before you bend anything to solve the bump steer issue you
need to look at roll center. Ugly. If you don't want the front end
pitching all over the place you need to bring the roll center up to about
the same place as the rear roll center. The rear roll center for any car
without some form of stabilization will be the centerline of the axle. The
stock front end is about three feet underground. The standard solution of
moving the inboard pivot of the lower A arm outward will exacerbate the
bump steering problem. Moving the upper pivot inwards and lengthening the
arm a little both raises the roll center and reduces bump steer. The upper
pivot bracket is offset to begin with. I'd love to make a more offset part
and a new upper arm that would solve the problem and look totally stock.
-----Original Message-----
From: Larry Young [mailto:cartravel@pobox.com]
Sent: Thursday, January 23, 2003 6:18 PM
To: Bill Babcock
Cc: fot@autox.team.net
Subject: Re: Suspension/Handling Questions
Bill,
The frame rails are straight until they start to kick up at the rear
wheel. If they slope, then the ride height is different at front and back.
That was my original question. Mine slopes up about 1 1/2" from the front
wheels to the back. I don't know if that's ok, or whether I should try to
get it level.
I agree with you about the difficulty of making accurate measurements.
The biggest problem is measuring the dimensions involving the ball joints,
i.e. where is the center of the ball? On my 4th attempt, I think I've
finally got the program dialed in. The early Service Instruction Manual
for TR2 (with TR3
supplement) has valuable information and scaled drawings. I took a lot of
dimensions from there and compared them to mine. I can now match the
vertical variation of camber from the manual and from my direct
measurements. It's virtually impossible to get the steering pivot
locations accurately enough to predict bump steer, so I fudged the height
of outer joint to match my direct measurments. Currently, the toe angle
changes almost 1 degree for a 1 inch bump. That's a lot. I thought I was
going to need a dial indicator with 2 inch travel. According to the
program, I need to bend the steering lever upward only 0.4" to almost
completely eliminate the bump steer. Now that I've got it dialed in, it
will be interesting to play some what if games. I too would be glad to
share any of this information, if you give me a chance to put it in an
understandable form.
Bill Babcock wrote:
> The frame rails slope, so it's always a little hard to derive a
> correct ride height. It's also hard to make good measurements to enter
> into suspension calculations.
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