Driving 4wd with odd tyres

Herzlos

I had wondered if uneven wear would cause problems. Any one know if I'll have the same issues with the AWD X-Type? I've just been replacing the tyres in pairs across the axle, potentially can't swap them front/back as they've got different weight ratings (94W front, 91Y back)

daveyjp

Herzlos wrote: »

I had wondered if uneven wear would cause problems. Any one know if I'll have the same issues with the AWD X-Type? I've just been replacing the tyres in pairs across the axle, potentially can't swap them front/back as they've got different weight ratings (94W front, 91Y back)

I would be checking with a dealer/owners club that this is normal. Has someone at some point saved money by purchasing a cheaper pair with different load and speed rating?

Iceweasel

Herzlos wrote: »

I had wondered if uneven wear would cause problems. Any one know if I'll have the same issues with the AWD X-Type? I've just been replacing the tyres in pairs across the axle, potentially can't swap them front/back as they've got different weight ratings (94W front, 91Y back)

Different load ratings doesn't make sense on an X-Type with the same size tyres all round.

I'm guessing they are the normal 225/45 17 size which are made in 91 or 94 - with the 91 usually being cheaper.

What does it say on the tyre info label on the driver's door post?

Herzlos

The post indicates that either is allowed, though no mention of what should be on what axle. I'd assumed the slightly heavier ones were on the front due to the engine weight.

Iceweasel

I don't think that being on the front or rear makes any difference to the load rating.

I would think that it's more likely to be the speed rating.

The 225/45 17 91 would likely come with a V speed rating and the 225/45 17 94 would have a W speed rating.

I assume you haven't owned the car from new so I guess that a previous owner fitted whatever he found was cheaper.

So unless you are going to be doing fully loaded high speed autobahn trips I wouldn't worry about the difference between them.

I'd swap them around to equalise the wear.

marlot

The worst ever car for diff/transfer box problems was the cavalier 4x4.

TO avoid issues, all tyres had to be within 2mm of each other. Garages often replaced all 4 tyres when one had a puncture! I don't suppose many have survived - but they left a trail of owners' tips on how to keep the car alive

eg.
http://www.cav16.co.uk/transfer/dosdonts.htm

rich13348

So here is the maths for anyone interested.
285/35R22 circumference is 2382.27mm in 1 mile that is 675 revs
285/40R22 circumference is 2471.81mm in 1 mile that is 651 revs
Given that the smaller back tyres will be more worn that the brand new front tyres this will be more exaggerated.
Mobile tyre fitter might not be a bad idea.

facade

So driving 5 miles to get tyres fitted will cause the front propshaft to rotate 120 times the diff ratio, call it 3.5, so 420 turns more than the back, it wont hurt the torsen. There is no viscous coupler with the torsen centre differential.

It might cause premature wear over 100,000 miles though.