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+--- Forum: Wheels & Tyres (https://www.japcarforum.com/forumdisplay.php?fid=152)
+--- Thread: tyre size help (/showthread.php?tid=8977)
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tyre size help - Stoney - 15-09-2019
jay_russell it's so crazy with tyre sizes,
the first 3 numbers are in mm ( 215)
the next 2 numbers are a % of the first
and the last 2 numbers are in inches
what a messand i work with this every day
It seems a bit crazy, but it does work! I it's simpler this way. Normal cars only ever run 35-65 sidewall ratings, in steps of 5. Rather than a random number of mm.
Off road tyres can be even more complicated, as they often revert back to imperial measurements, the mud pluggers on my Land Rover are referred to 33"!
tyre size help - sprinter2012 - 15-09-2019
jay_russell it's so crazy with tyre sizes,
the first 3 numbers are in mm ( 215)
the next 2 numbers are a % of the first
and the last 2 numbers are in inches
what a mess
I agree, especially as tyre widths are in mm and wheel widths are in inches!?
Plus for example, it means if I wanted to put wider tyres on the back of my car, the chances of getting the rolling radius the same would be very slim because the profile is a percentage not a measured distance. :Chair:
tyre size help - Stoney - 16-09-2019
sprinter2012 I agree, especially as tyre widths are in mm and wheel widths are in inches!?
Plus for example, it means if I wanted to put wider tyres on the back of my car, the chances of getting the rolling radius the same would be very slim because the profile is a percentage not a measured distance. :Chair:
You can work it out with a bit of calculation! The closest you can get, in terms of rolling circumference, to 225/40/18s, is 255/35/18 (0.2% difference) and that is why I am looking to fit 255/35s on the rear, and 225/40s on the front.