Rear Toe???

[nomad]

Wondering how critical it is to have exactly matching toe from one side to the other. I believe that both sides are with in specs but one has more than the other.

Kurt.

[fattogatto]

As long as they are both zero or positive - i.e. fronts of both tires pointing inward, a slight variation should not be a big deal. Assuming no handling issues noted. Watch the tire wear.

[tesprit]

You probably will not notice anything other than accelerated tire wear from the offset toe if the difference is only a degree or so between the rear wheels, but if the difference is greater it will effect the thrust line and cause the car to "crab" down the road and the handling will feel off. This will look like the car is pointing slightly left or right while you are driving straight down the road. Ideally the thrust line of any car should be directly straight down the center line of the chassis. This is only possible if the rear wheels are both pointing directly forward or have the same amount of toe in or toe out on each side. When you get a four wheel alignment done, the thrust line is the first thing they check because it indicates a bent chassis or suspension components and they can't perform a proper alignment until this is corrected. Do you have something bent in your rear suspension or frame damage?

Dan

[vincereynard]

Given the limitations of the chassis and suspension, without some form of adjustment, I doubt many are truly symmetrical.

If you cannot detect any dubious handling characteristics, and both are within limits, it's probably not worth worrying about.

[john.p.clegg]

Mine forms a perfect trapezoid , and handles great...

John

[nomad]

It's not terrible and I think within specs. So far just using the string method and eye ball. The car had encountered something while at the hands of the PO. I had to do some straightening and trust everything I did but I didn't check the A arm to see if the mounting holes are still perfectly parallel. I suspect they are not and will check that when I tear things down for other work. Was just wondering about the difference though.

Kurt.

[tesprit]

One cheap and easy way to visually check if the car is going to have a problem is to have a dusty floor in your garage and starting from outside drive the car straight into the garage over the dusty floor without turning the steering wheel from straight on. Get out and take a look at the tread marks left in the dust to see if the marks from the front tire treads follow the ones from the rear tires. If the rear tire tread marks are offset to one side from the fronts, this indicates you will have a problem.

I learned this trick from the owner of an old time alignment shop that always had an empty dusty service stall with nothing in it. I asked him one day I was there why he never had any cars in that stall and he showed me this trick using another customers car that had damage to the rear suspension. He said when his alignment machine showed something was wrong with the thrust angle or the car had a weird pull that he couldn't correct sometimes he would have to resort to rolling it over the dusty floor to visually check the tread patterns left in the dust.

Dan

[bitsobrits]

From tesprit: "You probably will not notice anything other than accelerated tire wear from the offset toe if the difference is only a degree or so between the rear wheels"

Measured at the rim as per normal practice, for a 13" rim 1 degree is about .23", which is a pretty large variance. I would be looking for toe to be +/- 1/16" side to side (relative to spec). So if both sides were off positive or both off negative (again, relative to spec) you could have a total 1/8" variance, or about 1/2 a degree.

Put another way, I'd be looking for 3/16" toe in per side (most sources recommend 3/16" rear toe in for a street car on stock sized tires), with a max variation of plus or minus 1/16" per side.

You definitely won't like positive rear toe on an Elan, so avoid that for sure.

[rgh0]

The manual say 3/16" to zero rear toe -in. This is probably per side but that is not certain. You definitely don't want to stray into toe out and the bottom end of this specification of around zero to 1/16" toe in is a bit to small on modern tyres and can in some circumstances lead to to much over steer

I would normally run 1/8" toe in each side +/- 1/16". Most original and un-bent A frames will give you this without further adjustment assuming your chassis mounting points and bushes are good also.

cheers
Rohan

[nomad]

Well, I've experienced toe out on a Miata. Interesting driving characteristics!!

Using a string over the front wheel [narrower track] I have one rear parallel to the string and one that appears to have no toe but approx straight ahead. Somewhere I read that a perfect symmetrical trapezoid is what one should aim for.

Kurt.

[john.p.clegg]

Something like this?

John