Originally posted by PeteH
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Alternate tyre sizes
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Originally posted by Drew View PostI thought the ride on 18s was good maybe you have worn shocks or broken springs or both?
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Originally posted by tens6 View PostI did think the same, whether there's something wrong suspension wise. I do have flexride(not sure if he does) so might make a difference. I have both the 18s and 20s but don't feel an awful lot harder amazingly.
Maybe something wrong with me, too. I find most modern cars are really crashy over tiny bumps - the kind pneumatic tyres were invented to absorb - because they don't have fat enough tyres.
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Originally posted by Alex421 View PostI thought it was 40s fitted to 20s. Well most I've looked at buying. I'd never have 35s would get destroyed up here.
With the gap round the arches on either 20s or 18s they would fit any of above sizes that's my point.
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Originally posted by Drew View Post245 width was found to be the magic number which is why they feature on a lot of manufacturers cars.
As you go up a rim by inch diameter you drop an aspect ratio by 5% magically the rolling circumference (the important bit) stays very close.
Works with reasonable accuracy from about 245 up to about 265. I wouldn't be surprised if 245 is most common just because it's the narrowest tyre that it works with.
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The aspect ratio is only relevant to the tyre not the wheel. The wheel is in inches. If you have a tyre that is 245/35 you have 88.75mm of tyre wall height. Times that by two because the tyre is there at the top and bottom of the wheel. Thats 171.5 mm. Now say thats on a 20 inch rim so 20x2.5 (to get it into cm) is 50. Times 10 is 500mm. Add that to 171.5 equals 671.5mm. Times that by Pi equals 2109.28mm rolling circumference.
Lets do 245/40 thats a total tyre height top and bottom of 196mm. But now you have to drop an inch on the rim to 19in or 475mm plus your tyre height equals 671mm. Times Pi 2108.28mm circumference.
The difference in circumference is just 1mm which as a percentage of the overall circumference is nowt. Theres a bigger difference between a new and worn tyre!
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