Thread: Rear Left Tyre Wear

Originally Posted by letherm

I had the same problem following a bad wheel alignment after hitting the rear left against a round about kerb. Asked dealer to check for damage out of caution (there was none) and his local wheel alignment source did the alignment. Following this the car pulled slightly to the left and the rear left tyre scrubbed the outside edge. Took it to an indy LR specialist and he found that the rear was out to blazes. Now runs straight as a die and no more unusual wear issue. So your problem may be simply alignment. Then again it may not. The joys of owning a car.

Martin

You may be onto something here as well as I have noticed it pulling to the left more recently.

Originally Posted by vee8auto

Repeatability is the potential chaos factor in this process, so the setup steps such as full tank of fuel and recommended tyre pressures are important.

Also, the step: Put it in Tight Tolerance Mode. Raise the car to off-road height, while rolling slowly, then lower to normal height while rolling slowly. .. is all about controlling mechanical hysteresis, which is a real thing when setting up positioning actuator control loops.

I just googled that as I've never heard of it. Decided to get a degree in something so as to try and understand what it means. I must be dumb or something.

Martin

I also googled it before posting comment but couldnt find a good explanation.

It is a concept to do with mechanical engineering and industrial instrumentation and control. It describes the drag or load in a (hydraulic or pneumatic positioning) system that creates an error which is dependent on the direction from which the device is driven.

Otherwise described as the concept of overshoot or undershoot depends on the direction from which the object has been moved by the actuator, or driving force.

If not factored in when trying to calibrate a positioner to tight accuracy you will end up chasing your tail.

Ok, I didn't get to start Mr vee8's calibration process yet, but I did fiddle with my IID tool some more!
I reset the rear calibration to 190 and noticed (not unexpectedly) that the ride height is now 30-40 mm difference left to right. Mmmm strange I thought but then I realised that when the ride heights were the same, the calibration was different by this amount (as per the previous pic), so not unexpected.
So I deflated all corners for a look and found that fronts were both the same, yet even on the stops, there was 30-40 mm difference in height L-R on the rear.

As I said, I do have to replace at least the sway bar bushes, but I am starting to think that there must be some damage or hefty component (bush) wear to account for that much difference.
Being a graphical kind of guy, I went for a drive whilst watching the height graph and IMO, both rear sides went up and down by the right amount when they had to. I mean by this that when going over a speed hump, both rear sides contracted by the same amount then extended and contracted again by the same amount each side.

Tomorrow, I'll do Mr vee8's calibration, but I fear I'll be up for bushes or an arm.

Cheers
Ralph

I also had a play, at least until the compressor overheated and found that I ended up back near the original settings. I do wonder why I have the disparity left to right however they’re only numbers related to the output value of the height sensor so it’s not the end of the world, unless it relates to an issue, and if it does, I’m stumped as to what.

And if you change the sensor it will be different again.. just a tolerance thing!

Originally Posted by Ralph1Malph

Ok, I didn't get to start Mr vee8's calibration process yet, but I did fiddle with my IID tool some more!
...
So I deflated all corners for a look and found that fronts were both the same, yet even on the stops, there was 30-40 mm difference in height L-R on the rear.

As I said, I do have to replace at least the sway bar bushes, but I am starting to think that there must be some damage or hefty component (bush) wear to account for that much difference.
....

Cheers
Ralph

when you say 'ride height' are you measuring axle centre to top of wheel arch?

And yes, if something is badly worn or bent then thats your most likely cause. I only suggest checking your height calibrations when nothing else is making sense.

Also, after all my control arms were replaced and before getting the wheel alignment I did a height calibration , and after wheel alignment I rechecked it.