Oversteer Under Hard Braking

[sluflyer06]

Originally Posted by learnerspermit

That was from the Toyota dealer this morning. When they tested it in the service lane. Also I know the old trick to tap the paddle to make the screen show it's in spec.

seems reasonable to say that you should find someone to do a quality alignment and see if your problem still exists. I would bring that toe a little inward in back, I'm running just 1/32(in) in back and no stability problems (about 1/32 out up front).

[Racecomp Engineering]

Just my opinion but "in spec" is generally meaningless to me.

Take it to a shop that can get you specific numbers. 0 toe in front, maybe a hair of toe in for the rear and you'll be happy.

- Andy

[solidONE]

Originally Posted by Racecomp Engineering

Just my opinion but "in spec" is generally meaningless to me.

Take it to a shop that can get you specific numbers. 0 toe in front, maybe a hair of toe in for the rear and you'll be happy.

- Andy

Yeah take it to a shop specializing in alignments. With the sheet you posted it could be that you have the left side toed out while the right toed in and it would still be "within spec" as long as the total toe is inside of the specified range. Also the bit of toe out you have will increase after you put a driver in the seat. Add a passenger and it would likely be out of "spec".

Which dealer is this? Please post so maybe people around you area will know not to go there for alignment if they find this thread lol.

[wheelhaus]

Another question after seeing the alignment report (assuming it's somewhat in the ballpark of accuracy) does the oversteer typically happen more in the same direction (i.e. steers left, you countersteer right)?

I think the right rear is the biggest red flag here. If it's pointed outward (positive toe), and it has one more degree of negative camber than the left, not only would it want to steer wide, it may have a slightly smaller contact patch than the left when the rear end is "light" under braking.

This would lead me to believe that it's generating slightly less friction than the left, and would then allow the car to pull left (like L/R differential braking in an aircraft). Also with your driver weight adding slightly more weight on the left side, could exacerbate the effect.

Just a theory...

And I also second the notion of a good alignment shop that will work with you and not just "get it into spec" and spit you out the door. The car from the factory doesn't have much adjustability besides toe, so it might be of interest to pick up some bits such as camber bolts, etc.

[dradernh]

Originally Posted by Racecomp Engineering

Just my opinion but "in spec" is generally meaningless...

This.

[CSG Mike]

Originally Posted by learnerspermit

Hawk Hp plus, 4 piston Spoon Calipers, steel braided lines, and Motul fluid

They just checked my Alignment this morning

Looks like you have some toe-out, but it doesn't specify what the individual toe is, only the total.

How hard are you braking when you get your instability?

What pads do you have on your FRS?

Is the instability only in a straight line?

[Ubersuber]

That alignment "report" is incomprehensible.

For the rear axle "total toe" is meaningless as the toe has to be adjusted individually to be equal on each side.

Total toe is the only number that matters on the front axle because toe divides equally automatically by shifting the rack one way or the other until steering forces are equal. Toe MUST be adjusted separately and equally at the front axle also but that's because the steering wheel will go off centre if only total toe is adjusted and measured.

I think you will experience rear end wander under hard braking if you have any static toe out at the rear. I also think toe at the front is better set at zero or a small amount of toe in for a rwd car. If you track or autocross only then can toe out be desirable depending upon how you like the car to handle.

That rear camber doesn't look correct either. If rear camber is different side to side then under heavy braking the rear of the car will feel very strange. You get quite a bit of camber change under braking and it is critically important that left and right camber be as close to exactly the same as is possible. It is more important that it be the same than it be correct although obviously correct and the same side to side is what should be provided.

Camber settings and toe settings also should be measured for thrust angle in a full alignment report. You want the thrust angle to be as close to zero as possible, to avoid the dogtrack problem.

I hope you didn't pay for that crap alignment report.

[Ubersuber]

Typical OZ plain speak:

http://www.whiteline.com.au/articles...WL%20ALK_b.pdf

Basically, you can divide weight transfer between spring loads and direct leverage loads through the alignment of the suspension arms but the total is the same and not related to spring rate.

Weight transfer is braking force acting through the CG. The forces either go downwards directly through the springs by compressing them or directly to the hub through the leverage exerted by the angle of the suspension component travel to the forward direction of the momentum.

Roll forces and acceleration forces transfer weight in the same fashion: partly through spring compression and partly through suspension arms.

This is one reason changes to your suspension arms are very tricky to do correctly as compared to just changing spring or roll bar rates.