View single post by chris

Posted: Sat Aug 22nd, 2020 05:22 pm

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chris
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Joined: Thu Oct 5th, 2017

Location: Leigh On Sea

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That is all fine in theory, but in the real world there is also the flat patch where the tyre meets the road to take into account. So the actual rolling diameter is a little less - how much depends on the pressure and the load the tyre is carrying.

I guess for an unloaded Ranger on beefy tyres it doesn't matter but a heavy saloon on soft road tyres it can be quite a bit.

The way to work it out is to find a flat, level patch of road/car park and chalk a mark on tyre and road - move car forward 7 tyre revolutions till the tyre mark is on the road and mark the road again - measure the distance between the road marks in inches and divide by 22 to give the true rolling diameter.

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