Quattro question

[darich]

Hey guys
I discovered I have a nail in one of my rear tyres so need to take it to a local garage for puncture repair.
My spare is brand new and the exact same size as my other wheels...... All are 235x40x18.
The spare is brand new with 8mm tread while my other wheels have around 4mm.

I know the quattro system doesn't like different sized wheels.
Am I being paranoid about driving less than 30miles with the spare on?
Is it likely to cause any damage to the quattro system?
I'm probably paranoid but would be grateful for confirmation of my paranoia!!

If forced I could possibly cut the mileage to about 7.

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[Guest 2]

You should be fine, lots of people out there with different treads/makes on quattro so 30 miles won't be a problem.

[darich]

Great.....thanjs

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[darich]

Thanks
Trip made and wheel changed back without incident.

I did figure it would be ok. If not, then Audi would have had to design a variable size spare wheel....or use the tyreweld and pump setup.
Puncture repaired and wheel back on.

thanks again

[jdp1962]

I would have a similar dilemma myself if I ever had a puncture. The car originally came on 235/45 X 17s, so that's what in the boot as a spare. But I've got the car running on 235/40 x 18s which, according to a tyre calculator, have a 0.3% bigger rolling circumference. And that's before any differences in tyre brand and tread depth.

[Doc B]

I would have a similar dilemma myself if I ever had a puncture. The car originally came on 235/45 X 17s, so that's what in the boot as a spare. But I've got the car running on 235/40 x 18s which, according to a tyre calculator, have a 0.3% bigger rolling circumference. And that's before any differences in tyre brand and tread depth.

Get yourself a can of tyreweld for emergencies......

Isn't it illegal to run different sized wheels (as in rolling diameter) on the same axle?

[Guest 2]

0.3% wouldn't really worry me too much for a short time.

[darich]

Get yourself a can of tyreweld for emergencies......

Isn't it illegal to run different sized wheels (as in rolling diameter) on the same axle?

Despite asking the initial question, I did carry a different sized spare for a long time. 4 wheels were 235 x 35 x 19 with a spare of 235 x 40 x 18.
I never had need to use it but my car went through 3 (i think) MOTs with the spare a different size. If it really was illegal I'd imagine the garage would've told me....and it wasn't a "friendly" MOT :p

[discobarry]

Your car doesn't even need a spare for the MOT Darich so i wouldn't worry about that.

[darich]

Your car doesn't even need a spare for the MOT Darich so i wouldn't worry about that.

I know...my last car had run flats (until I ditched them of course). The point I was making is that my spare was a different size from the 4 wheels on the car. So while the spare isn't an MOT requirement, it presumably doesn't need to match the other ones for size either.
I know many cars have larger/wider rear wheels than fronts so the spare can't match every wheel.

[discobarry]

Why did you ditch the run flats, too expensive?

[darich]

Why did you ditch the run flats, too expensive?

Yes...partly.
The ride was also smoother. It was a BMW Z4 3.0SE so it was quite a sporty car with stiff suspension. Coupled with the run flats, it was quite stiff. I put Vredestein Ultrac Sessantas on it and it made a massive difference.

If I remember right, I got all 4 Vredestein tyres for the price of 2 Bridgestone run flats, give or take a few quid.