Thread: Tread Depth difference between tyre pairs.

Originally Posted by brad72

Hi, I had one of my front tyres fail a couple of weeks back and had to replace the tyre. I changed the front pads today and thought I would check inspect the tyres more closely. The new tyres tread depth is about 2mm more than the other front tyre but circumference is 15mm more meaning it will rotate 2 revolutions less per Km.

Question is will this discrepancy cause issues to the diff and should I order another tyre or am I over thinking things?

Thanks for your advice

This would be true only if your tyre was solid steel and perfectly round. The reality is that every radial tyre at a sensible pressure has a flat contact patch on the road and the rolling diameter is mainly determined by the length of the steel belts just under the tread. I.e. you are over thinking things.

Even with same size tyres - You’ll soon know if it’s too much. The vehicle will balk at the difference and DSC will show up more often. This shows up at 10% tread wear in many cases...

So yes, running a different size tyre is a really bad thing for your diff... especially one 15mm different... also bad for your insurance

Originally Posted by bee utey

This would be true only if your tyre was solid steel and perfectly round. The reality is that every radial tyre at a sensible pressure has a flat contact patch on the road and the rolling diameter is mainly determined by the length of the steel belts just under the tread. I.e. you are over thinking things.

Not on the discos he’s not....

I’m going to guess he has a 255/60 spare and 265/60 primary tyres... that will cause the vehicle issues.

Originally Posted by Tombie

Not on the discos he’s not....

I’m going to guess he has a 255/60 spare and 265/60 primary tyres... that will cause the vehicle issues.

All the tyres on the car are the 255/60R18 Wranglers. Just the new tyre has deeper tread. No fault codes or other warnings have shown up

So a bit like going around a corner then where 1 side travels further than the other. I wouldn't worry.

Originally Posted by Milton477

So a bit like going around a corner then where 1 side travels further than the other. I wouldn't worry.

And that action causes wear...

Imagine driving endless corners for hundreds of kilometres. Not a good thing!

DSC and TracControl will detect it.

I wonder if a small air pressure difference between tyres on opposite sides would cause similar concerns.
Same sort of argument?

Originally Posted by Tombie

And that action causes wear...

Imagine driving endless corners for hundreds of kilometres. Not a good thing!

DSC and TracControl will detect it.

Sounds like living in the Adelaide Hills, nothing bad about that.

Anyway, you haven't given us a good theory why tread depth influences rolling diameter. Most radial tyres have a flexible blocky tread pattern that runs parallel to the ground AND the steel belts during the contact phase, unless it's massively over inflated. Do you run your tyres at double or triple recommended pressures?