S4 Tyres 235/45/18 switch to 235/40/18 Any problems?

[BasilAudi]

I have a 2004 S4 which, given the car and the way I drive is ready for replacement tyres, especially at the front. Reading through the threads on here I have settled on Michelin PS2's. However, I am being told that they dont do them in a 45 profile only 40. What I would like to know from you guys is, if I change to 40 profile from 45 is it going to screw up the diagnostics of the car, or any consequenses on ride etc?

My life in your hands guys.... no pressure, lol!

I would be grateful for any advice

Cheers, Basil

[Mike_K]

I have a 2004 S4 which, given the car and the way I drive is ready for replacement tyres, especially at the front. Reading through the threads on here I have settled on Michelin PS2's. However, I am being told that they dont do them in a 45 profile only 40. What I would like to know from you guys is, if I change to 40 profile from 45 is it going to screw up the diagnostics of the car, or any consequenses on ride etc?

errrm, I think the standard tyre is a 235/40/18, so dont know where your 45s came from. The two standard sizes in the manual are:
normal summer tyres: 235/40/18 and winter tyres: 225/45/17 (17" would need different wheels of course !)

There is an excellent site for tyres info, referenced by many people on this site, at http://www.chris-longhurst.com/carbible ... bible.html

There are a couple of calculators on his site, which show that if you change from 45 to 40 aspect/profile tyres, you'll run 3.5% slower on your speedo (ie a couple of mph). Looking at it another way, you've actually been running about 3.5% faster than your speedo since the 45s are not standard !

His site also shows that both tyres can use the same rims without problems (assuming you have standard rims of course !); so it looks like you should go out and buy yourself some 40's, enjoy the better handling and a more accurate speedo as Audi intended ! You may notice a slightly firmer ride, but the difference in profile is not massive so the type of tyre you buy is likely to make just as big a contribution to the change in ride.

Mike

[BasilAudi]

Thanks Mike, I have checked out the link and am satisfied that I should be on 40's and have just ordered 4 Michelin PS2's from Costco at £170.95 each, including VAT and fitting. They will be fitted on Friday, so I hope the roads are dry as I fully intend to put them to the test! Lets hope I come across and M3 along the way!!!

Thanks again Mike

P.S My local Audi dealer has no idea why I have 45 's on instaed of 40's. Say no more!

[B6S4John]

P.S My local Audi dealer has no idea why I have 45 's on instaed of 40's. Say no more!

Your sure your not on 17" rimms 'aint you?????

[B6S4John]

P.S My local Audi dealer has no idea why I have 45 's on instaed of 40's. Say no more!

Your sure your not on 17" rimms 'aint you?????

[BasilAudi]

Got my new Michelin PS2's, 235/40/18 , £171.00ea at Costco and the difference over the Pirelli's is phenomenal!! They have more grip in the dry and the wet, but I just wonder if they will last as long, I guess we will see.

Thanks for your comments

[Merlot]

Are they just better than a worn set of Pirellis (which one) or would you say they are better than the Pirellis were when they had >5mm of tread on them?

[Pete.S]

but I just wonder if they will last as long

From experience, you should get roughly twice as many miles out of the Michelins Vs Pirellis

[BasilAudi]

Update on the Pirelli's - In my opinion they are better than worn Pirelli's as I was starting to notice the lack of grip from the pirelli's, they seemed to "warp" on high speed cornering. Either that or just "bounce" over a rough surface on sharp corners. I have much more confidence in the car in both the wet and the dry. This of course is only my opinion and I wouldn't hesitate to recommend the Michelins to anyone. After all, look what they are achieving in F1!!!!

[B6S4John]

I would have thought the biggest difference is because they are 40's and not 45's so it's not a fair comparison?