255's vs. 275's

[M-A8]

So, Gentleman, I have a fairly simple question to which I think I know the answer, but I'll ask anyway.

As per Richard's reply in this thread http://forum.a8parts.co.uk/showthrea...9508#post79508
...looks like I am running the wrong tyre size (width) on my wheels.

Currently I have 255/35 tyres on 20's but 9J's, instead of 8.5J's

I can extend my tyre life on a already lowered suspension (-15mm front & -10mm rear from the stock values across all suspension levels) by putting 275's with 35 profile.
Currently I buy a set each year doing no more than 5-6k miles a year I think, mainly because at this mileage inner tyre has no thread left whatsoever.
This year I may have to buy 2nd set in about couple of months.

So, other than extended tyre life, what else I will experience???
- worst acceleration?
- harder steering?
- more noise? (when compared to same manufacturer's 255's)
- slightly more comfortable ride because of extra 7mm of sidewall as per picture below?
- ''softer cornering'' as at the minute 255's on 9J's are nicely stretched and around the corners (with 40 PSI's) they just grip very well and are really hard especially in dynamic?
- mentioned already, extended life?

Your help in answering this silly questions will be very much appreciated

Thank you

PS. Wheel alignment done last week

[ainarssems]

I think the biggest differences will be look and price. Besides from that it looks like 255 is optimal width for 9" wide rim.

[PsYcHe]

255s definitely look narrow on 9J, some worse than others. The Falken 452s that I had looked like they had sent the wrong size tyre and the edges were bald with 4mm left in the middle, and the others looked just a little narrow but not too obvious.

275/30/20 was what I thought the 'official' size was, but /35 isn't much out and loads of both on fleabay.

[M-A8]

Thanks Richard

Has anyone got a chart with all the official sizes for each size and width on alloys??

Does it matter if new tyre's diameter is bigger by 14mm than the official one if all 4 on the car will be same same so not mixed sizes between the axles???

Cheers

[Lee S]

My car had the original tyres on it when I bought it and it came with the final edition diamond cut 20" split 7 spoke alloys which I believe are 9". They were all shod with Continental 275 / 35 ZR 20. This is also held out by the sticker on the inside of my fuel flap that details tyre pressures. I can get a photo of this tomorrow if you really want?

[PsYcHe]

As long as all 4 are the same, then the quattro system will be fine, though your speedo will be out a fraction.

[M-A8]

Lee, Richard, Thank You

Reason I'm asking is because there is a diameter difference between most of the OEM sizes.

Lets say stock is 255/45/18
If you use any of the following, 265/35/20 # 275/35/20 # 275/30/20 # 255/35/20, the actual diameter is between -7mm to +14mm from the diameter of the stock 18" wheel which has 255/45/18 tyre fitted

[PsYcHe]

Sounds like 275/35/20 is the way to go.

Change of diameter only affects speedo/trip counter by a little, so as long as all 4 are the same, then there's no issue.

[Lee S]

I would concur with that. The speedo difference would be small and as long as all 4 tyres start out the same, then, wear aside, you will be fine.

[M-A8]

Cheers guys, very much appreciated

Yeah, I wouldn't put different tyres on. I may actually see how much extra I can get from the fronts after tracking and then I will just put a new set as I always do.
I'm thinking about 265/35/20, but there isn't much choice in this size, so may have to go with 275s, but they look a bit weird, unless the ones I've seen on A8 were on 8.5J.
On the other hand 265s may still wearing quick on the inside so I may have no other choice than 275's
Thank you once again for all your input