Thread: Mixed tyre sizes - can I drive it?

Originally Posted by Aussie Jeepster

I need to replace 2 rear tyres on my D3 this week - 2 punctures which are not repairable.
I currently have 255/60/R18's fitted (previous owner, not my choice) and I'm going to 265/60/R18.
Would it be OK to drive with the 265's on the back for a couple of weeks while the budget sorts out 2 new tyres on the front???? The diameter is 1/2" larger with the new rubber - is that going to be ok, or do I ground the car until I get all 4 done?
Alan

Hi Alan.

The 265 is wider not higher. The 60 is the profile of the tyre from rim to tread so it should be ok.

Martin

It's still bigger.
I was speaking to a relative recently who has a D4. His spare was smaller than the other tyres and it upset the ABS , being fitted on the back.
He had to drive slowly and stop often and turn off and restart.
However this may not happen front to rear.

Regards Philip A

Originally Posted by letherm

Hi Alan.

The 265 is wider not higher. The 60 is the profile of the tyre from rim to tread so it should be ok.

Martin

Great.
My tyre size guide said it was 1/2" more in diameter. It does also say .4" wider which does not really worry me.
al

Originally Posted by letherm

Hi Alan.
The 60 is the profile of the tyre from rim to tread so it should be ok.

Err. Really?
I've always taken it as the "Aspect Ratio". It's the width to height ratio of the sidewall, so a wider tyre on the same rim with the same aspect ratio would be taller (have a larger circumference).

I'm happy to be corrected, but every tyre size calculator I've ever used seems to agree with me. You want wider on the same rim, you need to go for a smaller aspect ratio to keep the diameter the same.

Your calculator is correct. One set will be about 1.5% bigger than the other. I wouldn't do it.

wrong information about aspect ratio.

if you don't know something don't say anything.

giving people incorrect information is wrong and it can damage their vehicle if they heed your advice.

the aspect ratio is a percentage of the tyre width measured on the tyrewall. vis 265/60 x18...the tyrewall height is 159 mm...on a 255/60x18 the tyrewall height is 153mm ....the rolling radius of the 2 tyres are significantly different and depending on the vehicle can produce transmission windup, which can damage your driveshafts/universals/axle splines and differentials

Both tyres are being put on the same axle . ie rear .. why would it upset the car ?

Cheers Ean

Abject apologies for wrong information. I genuinely thought what I said was correct. Thanks for correcting me. I never mind being told when I'm wrong. Sorry for misleading you Alan.

Martin

If you had a viscous lsd in the centre differential then front to rear would cause trouble. I did this once on my AWD turbo by simply having new on the rear and old on the front. The centre diff banged its head off trying to jump out the car as it locked up and unlocked thinking one set of wheels were spinning.
In the LR though, the centre is open so it’s less of an issue. As has been said the abs will struggle with it until it learns the difference, and in some cases I’d expect the difference will be outside tolerances and will cause error.