Space saver spare wheel for S8?
 

Apologies for the sudden barrage of questions - I've had an S8 looked at by the RAC and it has thrown up an issue with the tyres, and also the spare.

The report tells me that the tyres on the car are shod with 265/35/R20 tyres, as they should be.

But the spare is said to be a 255/45/R18.

I thought running different tyre threads by 4mm or so across the same axle was supposed to play havoc with the Quattro diff. By my sums, the spare will 6mm shorter than a regular wheel.

Interestingly, my PDFs of the 2006 and 2008 brochures make no mention of the spare. But in the Mar 09 brochure, on page 8, it says that all A8s come with a full size spare, but then a footnote says that if you order 20” inch wheels you get a space saver spare. It doesn't mention the size of the space save though.

An amateur S8 review I have read on Pistonheads makes a point of saying that the spare is full size though.

Anyone care to look in their boot and tell me what they have?

TIA.

To be fair, apart from the wheels physically being such different sizes as a spare wheel it will work because the rolling radius is very similar as you will see from the attached, and that's what is important to quattro not throwing up any faults

http://forum.a8parts.co.uk/attachmen...1&d=1408218396

All D3 8s I've see sat either on 255/20 or 275/20

I've got 255/35/20 on 9J and as a spare 255/45/18 8.5J so they are identical

http://forum.a8parts.co.uk/attachmen...1&d=1408289872

Didn't realise you were running 255's on 9J wheels. I had that for a while and it destroys the shoulders (back on my 8.5J wheels now), that may also be a cause of your tyre wear as the tyres are wider at the wheel, flexing the main tread down a little resulting in heavier shoulder wear.

275/30/20 is the best option on 9J for tyre life.

Richard, I think you just solved my tyre wear issue. It increased after switching to 20s and going extra half inch on the width of the wheel.
Tyres atm don't look very stretched but they are definitely on the edge, so rim protector does nothing.

This actually makes sense and could extend the life as you said.
I was running 255s Dunlops on 8.5J 18" wheels (car already lowered) and I have to say that even if the inner tyre wear was still excessive, the rest of the thread was way more worn out that it is now where now inner side is almost bold, but rest of the tyre has plenty of life left.

Thanks Richard +++

D3 S8 tyre sizes (2006 model)
 

Hi Guys,

I read this rather late but investigated when I bought my winter tyres (18" rims).

The standard wheel for my car (d3, 2006 S8) is 20"*9", 10 spoke. The standard tyre is 265*35*20.

The factory fitted spare is 18"*8 with (fat) 5 spokes, sprayed gloss black with one of those horrible yellow stickers limiting you to 50 mph. The factory fitted tyre is 255*45*18. In my case, the wheel had never been removed from the wheel well (still shiny) and the tyre still had the rubber sprules sticking out, also unused.

When I bought my winter wheels, I bought 18"*7.5" also 10 spoke pattern match to the 20" originals. I fitted 235*50*18 winter tyres which are very similar in rolling radius (dunlop winter sport d3).

Hope that helps

Richardracer