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race tire allingment


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Yes and no. Increasing tire width (thereby increasing track) has some affect on toe and camber. Given that toe is the biggest cause of tire wear, I frequently change toe when I get to the track with my car and then change it back when the day is over.

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I was going to try running strings to adjust my toe. and make a gauge like this

0238_1_b.JPG

 

Now do you set your toe at the track by x number of turns gives me x toe from measurements you took at an earlier date?

 

I really need to go back to the drawing board on my front end and change the CA inner point to fix my geometry. I need to do some research. As I see it I should move my point 7/8" up and 1/4" out and add "bump steer" spacers

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There is a FAQ post for bumpsteer, you might want to read it before you move your pivots.

 

What I did on my car was to make a mark on the tie rod that corresponded to 1/8" toe in for street driving, then another that corresponded to 1/4" toe out. I'd only adjust one side, which makes the steering wheel very slightly crooked, but it was an easy adjustment to do at the track.

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I have been reading some of your posts about slotting the cross member to set the control arm in the perfect spot. I need to re-read it again so I set up my dial indicator correctly. I wont do this until july so I have plenty of time to get ready. Am I adding extra stress to my ball joint by having the control arm not right?

 

One other thing I did take your advise on the air hammer to get the rear stubs out. Except the air was my arm with a sledge and a cold pointed chissle in that nice hole. That worked great. If I had the air chissle it would have been even better.

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Back to alingment...I set my toe 1/8" out at the rim. Like the picture above. I got everything finished up took my string lines off the car and realized I may have screwed up.

 

Let me see if I have this right. A 1/4" difference measured between the front of the front tires compared to the back of the front tires = 1/8" toe in or out depending on where the difference is front or back. So if this is right I nailed the 1/8th inch toe out that I wanted....but its at the rim.

 

Where is the right place to measure for toe? Im assuming now that Im done, it should be at the outside edge of the tire.

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When we talk about toe we are generally refering to total toe. Meaning 1/4" of toe out is 1/8" of toe out on one wheel. In your example above you've got 1/4" of toe out which is a whole bunch. Probably OK for autocross but too much for the track, especially a high speed track.

 

Over time I tended to settle on 3/16" toe out for autocross and 1/8" toe out for track use - measured using Longacre toe plates. That's with 6 to 7 degrees of caster and 3 to 3.5 degrees of front camber.

 

YMMV

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At the track you really don't have time to setup strings so I use toe plates. In your example, measuring at the rim, you're toe number will be greater if you use toe plates because the angle is extended out past the edge of the tire using plates. My guess is that if I put toe plates on your car I would measure about 5/16 to 3/8" of total toe out.

 

Strings are really good for squaring the car and getting the thrust angle correct. When I string a car I:

 

1. Set the ride height.

2. Set the center of each hub square to the strings.

3. Set the front and rear wheels square to the strings at zero camber.

4. Set the thrust angle.

5. Set camber.

6. Remove the strings and use toe plates to set toe.

 

I usually end up going through steps 2 through 4 a few times until everything measures right. Sometimes it takes 6 hours to get through steps 2 through 4... :cry2:

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