Staggered Tyres

[Rusty]

Why did you move away from 225/40? More grip?

[Sonic]

New alloys are 8J vs 7.5, 235 have slightly more sidewall, and they were the better price.

[Rusty]

Fair enough, price is always a good motivator. I'd try and source a correct size spate, although I think you'll struggle to git it in the wheel well...

[Sonic]

Hah yeah i've been using the entire boot for the spare since changing to 18's.

If push came to shove, would it be ok to trundle home on the spare then, or time to call european recovery?

[Rusty]

Difference in diameter is 8mm larger, so if it's a new spare and the 235/40s are well worn, then it shouldn't be too different but if the spare is very worn and the others are very new, then the difference will be more. For what a used 235/40R18 will cost, it would seem a better idea to get one of those but in the absence of any other option, it should get you to the ferry OK.

The issue here is the centre diff's reaction to difference speeds on the axles. I can't see that it's going to be much of an issue for such a small difference on one wheel but it's not something that I'd run around on a more permanent basis with.

@Error. You and your 255s

[Sonic]

Difference in diameter is 8mm larger, so if it's a new spare and the 235/40s are well worn, then it shouldn't be too different but if the spare is very worn and the others are very new, then the difference will be more. For what a used 235/40R18 will cost, it would seem a better idea to get one of those but in the absence of any other option, it should get you to the ferry OK.

The issue here is the centre diff's reaction to difference speeds on the axles. I can't see that it's going to be much of an issue for such a small difference on one wheel but it's not something that I'd run around on a more permanent basis with.

@Error. You and your 255s

Cheers Rusty - this is what i wasn't sure of, the diameter difference and the effect on the diff.

Sounds like it should be safe to trundle back to the tunnel with rather than leaving me stranded at the side of the road though

[Rusty]

Yeah, it's all pretty close ATEOTD. You could always get a smaller spare, a pseudo spacer saver, like a 17x7 and stick that on the rear, plus it'll fit in the spare wheel well! Would need to look at tyres but 215/50 is close.

I may get a 17x7 and run a 205/50R17 on it, although a 16 is also an option with the right tyre on it.

[Sonic]

That's a pretty good idea actually.

[Rusty]

I do have them every now and again

[Rusty]

Michelin Primacy HP tyres, I have these on my 16s and they're very good for daily duties - Ebay Linky

[Sonic]

Yeah, it's all pretty close ATEOTD. You could always get a smaller spare, a pseudo spacer saver, like a 17x7 and stick that on the rear, plus it'll fit in the spare wheel well! Would need to look at tyres but 215/50 is close.

I may get a 17x7 and run a 205/50R17 on it, although a 16 is also an option with the right tyre on it.

Interestingly a 205/50/17 compared to a 235/40/18 is exactly the same difference as a 225/40/18

[Sonic]

215/55/16 or 215/50/17 seem right as you say with -0.31% or 2mm difference.

[Rusty]

RTFP 215/50R17 for you

http://www.ebay.co.uk/itm/MICHELIN-P...item2c6f3ce41e

[driftin jo]

While I agree its not good practice to mix different rolling diameter tires, consider this.

The difference between a new 225/40/18 and an old one that needs
changing due to tread wear is about 1.5 %, the difference between a 225 and 235
is 1.3%.
Tire manufacturing tolerances are about +/- 0.5 % so going from one make to another could in theory could give you 1% difference even with 2 brand new tires of the same size !

Imagine you are driving down a country road for 50 miles that has no straights to speak of, the tires are never turning at the same speed, do you worry about your diff then ? I don't


I would be more concerned about differencee between front and rear through the torsen diff, on the same axle it's just an open diff, I fail to see how its going to bother it at all.

[Henkjan]

.... although I think you'll struggle to git it in the wheel well...

anything wider than 205 will make it a struggle. my 215/45-17 spare (Nokian wintertyre) does not fit