Toe question, very theoretical.

This thread seems to be kinda all over the place. I think you are trying to learn but don't exactly know what to ask. In general what you want to do is set the car to factory ride height then corner balance the car with how it is to be raced with 1/2 the fuel load of the race. For street it is the number of passengers and 1/2 the fuel level. There is no desired corner weight except all equal which is not possible unless you move weight around the car. So the best you can get is a compromise between left and right turns with a 50/50 cross weight and straight line even braking with equal LF and RF corner weights. So if my choice as a racer to have a 50/50 cross weight and LF/RF unequal by 100lbs or 49.7% cross and equal corner weights LF/RF I would take the later. But then again as a racer you might set up a car to make better right turns if a track has more right turns. See that is clear as mud!

After that you adjust thrust, rear toe, and camber finally front toe. You adjust caster depending on road crown or desired amount of return to center force vs. ease of turn-in. Then you check all the settings again because each setting can have a small effect on the other. Then you race and tune all of these elements for desired effect on important aspects of the race track like a juicy passing zone. Then if you have adjustable shocks....

 

I'd guess my neighbors didn't much appreciate my "dialing in" the DMS coil-overs on my Celica GT-Four by running it around the condo circle.

But after four hours of tweak, test, back on the lift to tweak, test again, etc., I wound up with what may have been the only Celica GT-Four with completely *neutral* handling.

The factory tunes them with massive understeer for "average" drivers.
I set mine so I could control over/under steer by how much throttle I applied.

Which came in handy, as I was cut off in traffic *twice* within a week of setting up the car.
With the old suspension, either of them would have resulted in a crash.
With the new set-up, I was able to avoid both of them.

 

Also consider a tire can also make a car pull to the right or left.

 

Very important to check for even tires as above. Make sure pressures and wear are even. Alignment may be perfect and frame perfect but tires can throw it all off.

Note: pay no attention to the position of the steering wheel at all (more on this later).

Roads are almost always leaning away from center and castor settings correct for this. It is usually set to keep the car in the correct lane even though the lane is tilted off the road a little. But on a perfectly flat road the car should actually pull slightly to the theoretical middle of the road.

After all settings are proper the steering wheel may be off center. This is corrected last. It will take somebody who knows what they are doing but actually easy to fix. It is purely cosmetic.

aehaas

 

Also, like DGS stated, factory settings are for the "average" driver. The first thing I do is change settings for the way "I" drive my big sedan cars as they are rarely set up the way I drive. They are set up for "old folks" drivers not for the truly sporty driver.

Lastly, if a car dealer wants to "check" your wheel alignment, stop them. If your tires are wearing perfectly well then the alignment is perfect for the way you drive. They can only mess it up by "checking" it. Plus you can save the unnecessary costs involved.

aehaas

 

Yes, indeed.

My F355 is setup such that all 4 tires go slick within 100 miles of each other. Brand new tires, never rotated, with or without track events (where tires ARE rotated L<->R 1/2 way through the day) all loose their tread <essentially> simultaneously.

 

Yes but in scenario 2 you should check the toe-adjusted lengths of the track rods are equal before correcting the wheel centering. If one track rod is longer than the other it can cause bump steer and could also cause scenario 1 owing to unequal load on each side (ie the driver sitting on one side) although scenario 1 could be many other factors as already discussed.

 

It depends

 

Respectfully, I think you need to do more book research before you start experimenting on the car. Based on your posts I don't think you have enough academic understanding on how alignment works and are more likely to make things worse rather than better.

Here is a start but it is more complicated that that like you alluded to the ride heights and even corner weights.
Correcting Steering Pull

 

I would suggest less emphasis on theory, and more on experimentation.

You can do a crude alignment yourself with some fishing line, and 4 jack stands. Make sure to find the center line of the car first, or else it will be going down the road like a crab.

IIRC, we setup our road racing cars with toe out, and negative camber on the fronts. Toe in on the rears. This makes the car turn in better.

 

It also makes it pretty unstable on the straights. Good for the track, bad for the street.

 

Don't forget to rule out mechanical drag. Brakes, wheel bearings, tires - pressure/defects etc

 

Caster definitely will cause a car to pull. Generally you can have slightly less caster on the drivers side of the vehicle to compensate for road crown.

 

If your alignment proves correct, try swapping tires from left to right side to rule out a radial-tire-pull, assuming the vehicle is not equipped with directional tires

 

Not true. If the track rods are adjusted to different lengths, even if the toe is correct, the car will bump steer and also tend to steer under braking dive.