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The obsolete Dunlop SP8000 tyres are roughly 8mm wider than the current generation of 225 section tyres. I know this because I laid both side by side on the table on the garden and measured them. (It defies me why the ladies aren't captivated by such behaviour.)

This suggests that current 245 sections, at 20mm wider than the current 225, would be 12mm wider than the original equipment Dunlops which were developed specifically for the car and is why modern 245 section tyres fitted to RS2s rub on the suspension and are to be avoided.

Using the internationally recognised unit of measurement, the current 225 section is one prised off beer bottle top narrower than the original equipment SP8000 245 section.

Depends on the 225. The new Goodyear asymmetrical has a marked outer rim protector. I could not see any difference in overall width. But then I did not go as far as the 'beer bottle top' method!

Good point, Alastair.

The 225 in this exacting comparison is a Pirelli P-Zero Rosso.

DickyC wrote:The obsolete Dunlop SP8000 tyres are roughly 8mm wider than the current generation of 225 section tyres. I know this because I laid both side by side on the table on the garden and measured them. (It defies me why the ladies aren't captivated by such behaviour.)

This suggests that current 245 sections, at 20mm wider than the current 225, would be 12mm wider than the original equipment Dunlops which were developed specifically for the car and is why modern 245 section tyres fitted to RS2s rub on the suspension and are to be avoided.

Now get back to the weeding
rs2315.

As a matter of fact, I went back to tending my tomatoes and chillies for this year's batch of ungentlemanly relish.

And you thought RS2s were hot...

DickyC wrote:The obsolete Dunlop SP8000 tyres are roughly 8mm wider than the current generation of 225 section tyres. I know this because I laid both side by side on the table on the garden and measured them. (It defies me why the ladies aren't captivated by such behaviour.)

This suggests that current 245 sections, at 20mm wider than the current 225, would be 12mm wider than the original equipment Dunlops which were developed specifically for the car and is why modern 245 section tyres fitted to RS2s rub on the suspension and are to be avoided.

Do you know what the rolling circumference difference is (taking into account tyre wear)

You had to wait until I put it back in the roof of the garage!

I'll fish it out and report back.

Try this calculator

http://www.kumho.com.au/tips_diameter.htm

Lloyd wrote:Try this calculator

http://www.kumho.com.au/tips_diameter.htm

Thanks for the link, but I understand tyre ratios and the whole point is that the dunlop 245/40 is not a 245/40 hence the question. Is it 40% of the actual width or the stated width, if so the rolling circumference could be less.

I'll check at the weekend - honest!

and the answer is ?

I mean it's been wet, what else could you possibly have had to do..... ah the relish !

The answer to The Tyre Question: the diameter of the original SP8000 245 17 and the Pirelli P-Zero Rosso 225 17 is, to all intents and purposes, indentical at 630mm-ish. The P-Zeros are fairly new and the SP8000 was the "keep the best one for a spare" with loads of tread. So no change in gearing between the old and new tyres. Phew.

The other answer is, this summer is having a terrible effect on my tomato and chilli crop. Ungentlemanly Relish 2008 is looking increasingly unlikely. Green tomato chutney with just a hint of chilli, anyone?

So, what was I doing at the weekend when I should have been in the roof of the garage struggling with an old tyre? You wouldn't believe me if I told you. You see, I had a call in July from a bloke I did some work for years ago. He wanted me to do just one more job...

Rallyejames has a different make of tyre but 225 and it appears to be a different width (noteably thinner) but at present we haven't done the bottle top test, to be done at the next meet.
Also I have no idea if his tomatos are ok, so the relish question is unanswerable at present, the slugs ate ours but haven't touched my tyres. Maybe they like the thinner profile?
I wish it would stop raining!
Cheers
T

Hi
Ive just measured the difference between my spare SP8000 (new) and the tyres on the car Dunlop sportmax 245/40. The sportmax is 5mm wider than the original tyres. I have had no problem with tyres rubbing. The tyres were fitted by the previous owner at the Audi main dealers in Paris Levallois.
I also have some spare wheels with Bridgestone Potenzas 245/40 - I shall measure them also when I've a minute. I think it is important to measure with the wheel off the car with the tyre on a rim to get true values.
Cheers
S