Thread: Rim and tyre size change

I am weighing up the pros and cons of dropping from my 20" rims to 18". This is allowable on my L322 RANGIE without upsetting the speedo. My thoughts are if I buy 5 18" rims and go to smaller diameter tyres will I save anything over the span of say two sets of tyres or would it take longer to come out financially in front? Jim

Factory 20s are 255/50R20, if you go to (factory size) 255/60R18 the difference in rolling diameter is 0.2mm.
You can go to 265/60R18 which are 12.2mm larger rolling diameter which keeps it legal. {different brands/models of tyres will be slightly different - your tyre shop will have the exact figures}

To remain legal overall rolling diameter (wheel and tyre) cannot be varied by more that -25 or +15mm from the factory set. I enquired about engineering certification of oversize tyres and was informed by the Vehicle Mod Division of QLD transport that it is NOT allowed, to the point that there is not even a ‘blue plate’ code in the system for tyre changes. So even if you find an engineer that tells us it is - he has no codes to put on the mod plate to certify the change.

The $ question would depend on how much you pay for the rims...