toe plates accuracy?

[matt p]

i am about to set my toe with some toe plates, but my only problem is that they read total toe, so technically one side could have 1/4 inch toe out, and the other 1/4 toe in, and you would get a reading of zero on the toe plates.
i set my toe to zero (for the front) so i was thinking a way to ensure total and each side toe is zero, would be to also measure diagnally on the toe plates, and if the front measure=back measure on the toe plates, and the front to back of toe plate both ways are the same (cross measure) then it would truly be 0 toe in every aspect of the front.

i am not talking about having the wheel off center, but the toe pointing in one direction.

hopefully this made sense,it does to me but sometimes i have a hard time communicating random ideas like this.
thanks
matt

[John Valerio]

at the front it doesn't really matter if your toe is offset to either side, you'll correct with the steering wheel naturally and won't even notice unless its a huge offset (which damn hard assuming you build equal length links left and right and can count threads). of course you'll notice it alot more with steering wheels which have LCDs in them and such.
in the rear however it is very important because a toe offset will crab the car in one direction, causing understeer when you turn one way and oversteer when you turn the other. for the rear (and front if you want) you can just measure from chassis reference points and then double check the pair. most people have tubes that run straight down the chassis at the suspension mounts anyway.

[Igor]

You could also string a wire around the car at axle height. You can then visually check or measure with a ruler the rear toe. Not very scientific, but rather effective.

Igor

[Patrick W. Crane]

i think there is a picture of a champcar team using some string to do setup. Simple and effective.

[matt p]

i tried to square the car but it took forever. so i just did it with toe plates and it feels ok. i had teh guy that does my alignments check it, and he said its fine. its a little off total, but since its the front its fine i guess. i still hit the steering stops both ways so no need to adjust for more angle. i want to change my ackerman!
im leaving tonight for willow springs event tommorow. hopefully it works out alright.

[PatClarke]

Matt, If the toe is offset as you describe, the vehicle tracking is affected, and as John has said, the steering will centralise as you drive. I have to disagree with John though about the effects.
Firstly, it takes very little difference in front toe offset to put the steering wheel off centre. This can be irritating or even dangerous.
Secondly, offset toe will have a detrimental effect on your ackermann effect, changing steering performance left and right.

There are several ways to centralise toe, but the string method mentioned is probably easiest. I remember writing a newsletter on this subject, so it should be available in the archives on the FSAE-A site.
Good luck
Pat Clarke