Help, twitchy drive

[dogwood]

Took my car out for it's first spin today..


Seemed a bit twitchy to me
I know the tracking is ok.
And it self centres fine.
So any ideas, obvious or obsure.
I thought the setup was right.

[AshG]

100% sure.... not enough toe in. guess how i know that.

[tex]

check your castor angles first.
Check your rear toe parallel or slight toe in should be pretty near. Tyre pressures.. Not too high? Check ride heights too.. Unloaded the rear would be good slightly higher than front so when you get in it then goes levelish..

[spud69]

As Ash says, 2 to 3deg toe in at the front (main one), some negative camber will help, rear wheels parallel and no toe in, corner weighting the car can make a big difference, tyre pressures only need to be about 18psi - too high will make it skittish. Are your wheels balanced and true, with a light car it doesn't take much to put it out of balance.

Hopefully the wheels will be okay Dogwood and it only needs setting up, if you prop up the rear end and get the wheels spinning up to 40mph you'll soon find out if they are true and balanced.

Good Luck...AndyH

[dogwood]

Ok,
So I have reset the tyre pressures to 20 at the front and 18 at the back.
I have also redone the toe in to 1.5deg .
Seems a lot better.

Still room for improvement.
Might try a little more toe in.

Someone mentioned bumkpsteer.
Not quite sure about this, had a look at the rack to see how it lined up.
It s dead level looking from the front.
But looking down from the top, the rods go forward towards the wheels.
Have a look at the dodgy sketch. Angle not as bad as pic, just done it like that to show what I mean
If I lower the rack on the mounts it will improve the angle forwards but make it worse looking from the front
(Does that make sense?)
Is it worth altering, or am I starting to loose the plot??

The rear end is pretty good, very little toe in.
Perhaps 1/2 a deg and no camber

[tex]

look at your ride heights! that can make a big difference.. if you get in and the car chassis drops lower the the back your running lighter on the front end.. corner weighting principles aim for weights to be equal or as near as over the 4 wheels..
aim for around 15-20mm higher at the rear and try that.. then get in or add weight to your own body weight - measure it again see what you get..

[Big Vern]

David - 1.5 degrees toe in are you sure no wonder it's twitchy as hell I would have thought 10 minutes total toe in for the front and 10 - 20 minutes total toe in at the rear at the most.
I've looked up dozens of car geo specs but could find nothing that drastic on toe!
If the Haynes roadster needs that much toe in then theres something seriously crapped up with the suspension design
I would treat 20psi for tyre pressures as a max value as well, my MX-5 is only 26psi and it's nearlt twice the weight

HTH BV