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[General] How to calculate overall rolling diameter

nathanVY

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Hey everyone, had a quick search and don't think this has been posted before.

Here's a formula for working our the overall rolling diameter of your wheel setup.
Most states let you increase by a maximum of 15mm.

You will need a scientific calc to do the sum, I just used this one


Fomula
((Tyre width x profile%) x 2) + (rim size x 25.4mm)


Eg: 205/65R15 – Standard 15" profile for a VS

((205 x 65%) x 2) + (15 x 25.4mm) = 647.5 mm


So to see if you're wheel/tyre combo is within legal limits, first calculate the standard wheel size overall, then use the same formula but input your desired wheel sizes.

So for 19s..

((235 x 35%) x 2) + (19 x 25.4mm) = 647.1 mm

Hope this helps someone... :)
 

MrNutter

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Your maths is right but I'm lazy & just use one of the online tyre calculators instead. The one at Ozexplorer.com (I think) is pretty good as it offers you direct comparisons to.
 

nathanVY

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Your maths is right but I'm lazy & just use one of the online tyre calculators instead. The one at Ozexplorer.com (I think) is pretty good as it offers you direct comparisons to.

Yes there are some online ones, please post the proper link to it. I couldn't find one and ending up using the calculator instead :p
 
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