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So my R32 has 18" wheels and the tyres are 40 profile

The R32 came with 205/55 R16

The rules as per QLD at least state

"The rim diameter may be varied from the standard size

but the overall diameter of the tyre must not vary by

more than +15mm or -26mm."

so if I have 245x40 R18

18 x 2.54 = 45.72 + 4cm = 49.72cm

and stock

16 x 2.54 = 40.64 + 5.5cm = 46.14cm

49.72 - 46.14 = 3.58cm or 35.8mm

am I doing something wrong or is my car currently not legal?

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agreed with Bubba, it is a percentage measurement.

using the calculator that Bakes supplied above - yes the difference is 22mm which according to those QLD laws is ILLEGAL for you.

however, if you were to fit 235/40/18 tyres on the same rim - the overall diameter increase would be 13.47mm = LEGAL :iluvff:

so moral of the story, fit 235/40/18s and you'll be all sweet :D

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https://www.sau.com.au/forums/topic/279124-is-my-car-legal/#findComment-4718721
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agreed with Bubba, it is a percentage measurement.

using the calculator that Bakes supplied above - yes the difference is 22mm which according to those QLD laws is ILLEGAL for you.

however, if you were to fit 235/40/18 tyres on the same rim - the overall diameter increase would be 13.47mm = LEGAL :thumbsup:

so moral of the story, fit 235/40/18s and you'll be all sweet :yes:

wow, thanks for that i just learnt something. so i'm 1/2 legal, just need to sort out the rears which are bald anyway.

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https://www.sau.com.au/forums/topic/279124-is-my-car-legal/#findComment-4721749
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