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gjm

Tyre width and profile, and rim width

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I have a set of 8J & 9Jx16 rims that I'd like to use. In order to maintain (closely) factory rolling diameter, I'd like to run a 245/50-16 tyre on the wider rear rims.

Looking at various pages it is suggested that this size tyre should be used on a rim from 7 to 8.5 inches wide. (Narrower than my rim :( .) 

A 245/45-16 is claimed to be typically fine on an 8 to 9.5" rim. As the profile height goes up, the recommended rim width for fitment comes down - a 245/70 should be fitted to a rim between 6.5 and 8" in width.

Back in the old days we used to calculate the optimum tyre width as being rim width (in inches) multiplied by 25, plus 'a little bit'. ;)  Hardly scientific, but it worked reasonably well. Modern tyre construction means there have been many changes; for example, the tyre pressure for a given car recommended by the car manufacturer back in 1985 may not be as relevant now as it was then - good modern tyres typically run at higher pressures.

The question is... Would I run into problems using a 245/50 tyre on a 9" rim? I could run a 255/50-16 (OK on a 9" rim according to the LVVTA, but still not OK according to several online calculators) but they are (literally) twice the price of a 245-wide tyre.

Having resolved this little conundrum, I need to consider what size to run on the front, too...

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On what car?

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1 minute ago, zero said:

On what car?

Shouldn't matter, but these are for the 500SE.

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The 9 inch style 350s on my car run a 275 width from the factory.

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14 minutes ago, Herbmiester said:

The 9 inch style 350s on my car run a 275 width from the factory.

I've come to the conclusion that retaining the rolling diameter is going to mean going to a wider tyre...

Why do they have to cost twice as much for a width increase of just 10mm? :cry:  Oh well - safety first. And I'm sure they'll look great.

Edited by gjm

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dont need to go to an odd size graham. just stick with a more common size

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