Wheel alignment - Caster

KCross

Hi

I have a 202 car (RWD). I got 4 wheel laser alignment done and I have some questions as the report shows a problem which the tyre guy said he couldn't fix.

• The guy doing the job said the Caster is out and that that is unusual for a relatively new car. More importantly he said that that's a main dealer fix and not something he can easily do. Is that true, that Caster is a bit more involved than typical 4 wheel alignment?
• Is the Caster being out unusual?
• If I go to the dealer (car still under warranty) are they just going to tell me I hit a pothole and I'll have to pay for the fix or is this likely to be something that was setup wrong at the factory and they should fix it under warranty? Im OK either way, just don't want them to pull the wool over my eyes here if it is a manufacturing fault.
• I got 20k+ km's out of the rear tyres so its not eating the tyres at the back (it is RWD) and the fronts have another 4mm or so to go BUT the two fronts are wearing heavily on the inside (on the curve of the type, not left to right of the thread) and will need to be replaced long before they get to legal limit on thread depth as a result. Is the Caster issue the reason for the inside wear or will the new alignment figures address that now?

• Basically I'm unclear what effect Caster has on tyre wear and need to know how big an issue this is and if Im wasting my time putting two new tyres on the front without getting the Caster issue addressed first (or are the new alignment figures good enough since they were out also and are now fixed)?

Report attached which shows the before and after figures.

IMG_0440.jpg

The Continental Op

My (limited) understanding is you can't change the caster angle, it is fixed and there is noting adjustable to change it on your average car. When you'd need to change it or worry about it is on an accident damaged car where the steering has taken a knock.

Caster doesn't really have any affect on tyre ware provided its the same on both sides and is positive.

This may help explain

https://www.youtube.com/watch?v=Gh7gWJAvOvs

KCross

Thanks, that helps, I think.

It sounds like the inside wear has nothing to do with the Caster setting and as long as the car is driving straight the Caster is probably alright as is.

And crucially, the new alignment figures, which are now within tolerance, should sort out the inside wear and so it should be OK to just put on two new tyres. Hopefully that's the case.

Hopefully one or two others can confirm that here too?

GalwayMan74

"I got 20k+ km's out of the rear tyres so its not eating the tyres at the back (it is RWD) and the fronts have another 4mm or so to go BUT the two fronts are wearing heavily on the inside"

That is absolutely awful for a set of tyres.

KCross

https://www.boards.ie/discussion/comment/119275756#Comment_119275756

Well, that was why I got the tracking checked/done! 😉

sundodger5

https://www.boards.ie/discussion/comment/119275756#Comment_119275756

it is at the bottom end of the mileage you should get out of tyres but not ridiculous.

A lot depends on the cars use.

The Continental Op

OP why not google your car and see what the caster angle should be? As in <make of car> caster angle. Always a chance the guy doing the test picked the wrong model off the computer database.

KCross

https://www.boards.ie/discussion/comment/119276025#Comment_119276025

I did try that, couldn’t find the spec online.

He did pick the right car from his database as I saw it on the screen.

The Continental Op

I've looked up my Ford and can easily find the details and I've looked up a few random cars to see what average caster angles are. Yours seems to be quite high if the 7.38 degrees +- half is to be believed. Mk 4 Golf (not your car I know) seems to have very similar geometry and that high caster angle but many other cars have a caster angle of just over 3 degrees. I couldn't find any data for RWD BMW's (seemed an obvious mark regarding RWD to look up) except that the difference between left and right should be no more than 30' which is 0.5 in decimal and yours is well within that.