steve40th

Just curious as when you change your rear camber for dragstrip to autocross it is quite a bit of camber change, but does your Toe change too?

steve40th

one mo' time

Curveit

Not sure, although i think the front would some. You might try posting over in Autocross section; if you haven't already. Somebody there should know.

STEVEN13

Yes the toe will change. I think the more negative camber the more it will toe out.

Steven

P.S. I do my own alignments

steve40th

Thanks, I was wondering if the car went through a toe change as you went through the range of the suspension travel.
I know people have just taken shims out in the front for autocross and not changed their toe.
But if it is easy to check and do, I would like to know how.
But on the rear, for drag racing you want it to be positive on C4's so when you floor it, the tire is flat. But on roadracing and autocross you want lotsa negative camber.

CentralCoaster

Suspension travel also effects the camber, which in turn effects the toe.

When the rear squats, you get more negative camber. BUT... the angle of the toe rod is now different, so I'm not sure if you still get toe out.

In fact, I think you get toe in on squat, because the half shaft gets a little shorter in the horizontal plane, while the toe rod gets longer. Also, my drag radials set at zero toe are scuffing towards the outside, which seems to agree with this. It all depends on the starting angles of the three rods.

Z51L9889

The toe will change with camber. Since the toe link is located behind the center of the wheel, increasing negative camber will make the rears toe in, decreasing camber will toe them out.

STEVEN13

Yes the the toe (and camber) does change during suspension travel. For auto x adding more negative camber (taking out shims) and in turn adding toe out is not a bad thing. On a high speed road course I would reset the toe to zero or in about 1/16"+ total. For the rear I run between 1/16 to 1/8 toe in. Under braking the rear toe will change and want to go out.

If you want I can email you how I do my alignments or post here.

Steven

STEVEN13

That makes sense as when you brake the rear will rise and the toe will start to go out.

The front is the opposite.

Steven

steve40th

Thanks, Email me at Steves396lt1@yahoo.com
Thanks again, Steve

STEVEN13

Email sent.

Z51L9889

I was referring to what happens to the rear toe statically when you change the camber setting.

Toe change during suspension travel is a totally different situation and each suspension design will have a different characteristic based on the suspension geometry and how the suspension bushings deflect. Independent rear suspensions are usually designed to make the toe change curve as small as possible, especially on a rear wheel drive vehicle. If anything, you want the suspension to toe-in under braking. Toe-out during braking is a VERY undesireable condition on a rear suspension, especially at high speeds.

STEVEN13

Understood. This is why for high speed the rear toe is set in. Underbraking the rear toe will change and tend to go to zero or out depending on how the car is set up. I don't think the rear on any or most cars will toe in.

Steven

VetNutJim

Would you mind sending me your alignment info?
I, also do my own, but I, want to know how you do yours.
alfordjim@earthlink.net

STEVEN13

Email sent.

Steven

CentralCoaster

No, when you increase negative camber, the toe rod behind the wheel stays the same length. Since the camber rod attaches in front of the toe rod, lengthening it will cause toe out.

Z51L9889

No, it's the other way around. The bottom of the knuckle moves outward as you add negative camber. The knuckle pivots about the wheel center at the outer halfshaft u-joint leaning the top part of the knuckle inward. On my '89, the center of the outer toe link tie rod end is slightly above the center of the outer u-joint. If the toe link wasn't present, the attachment points would move a tiny bit closer together when you put in negative camber. The rear side of the knuckle at the toe link attachment can't move closer together because of the toe link, so the front part of the knuckle rotates inward, causing toe-in.

Hope this helps.

steve40th

So, then why dont we just make our suspensions real stiff so you have little movement so it will maintain the alignment you want.
For example, There was a very well known Corvette that ran tens, and to keep his suspension flat, for drag racing, he ran coil overs AND leaf spring.
In autocrossing you could do the same, and this will keep your tires planted?

Z51L9889

Keep in mind that we are talking about pretty small changes in toe, especially on an 88-up car.

Stiffening up the suspension so it won't move defeats the purpose of having an independent rear suspension. You want the camber angle to change as the wheels move so that you can maximize grip during cornering. Ideally, the camber would change such that the tire is always able to generate its maximum grip no matter what the suspension is doing.

The only real disadvantage to an independent rear is that they tend to have little to no anti-squat geometry which is not ideal for drag racing. When the rear squats on a Corvette in a drag race start, you get negative camber which reduces the effective contact patch of the tire and thus reduces traction compared to a solid axle car. This isn't really a problem for those of us with relatively stock cars that aren't running slicks. For the 10 second car you gave as an example, my guess is that he was trying to keep the rear from squatting so it would keep the tires square to the track.

CentralCoaster

Yer right, the vertical position of the toe-rod dictates that. I assumed it was between the ujoint and camber rod pivot.

On a perfectly smooth road, that'd probably work. You'd still need a little castor to gain camber in turns to make up for the tire rolling over though. But what about in rear? You'll want those flat for braking and accelleration, but why not let the car lean and use that movement to increase negative camber back there? You end up redesigning the wheel.