Hey all, I'm looking to buy some "new" wheels soon and I'm trying to figure out what the correct wheel / tyre sizes are for my car.
From my reading so far, everything indicates that I'm actually running my rolling diameter slightly too low.
It's a KF Xi so came with stock 16" alloys.
Right now it's got 235/45/17's on there.

What is the correct tyre / wheel size for it?
If I'm getting 18's, what would be the correct tyres for that size? (I'm basically decided that I want 18's)

Thanks,
Matt.

Hey all, I'm looking to buy some "new" wheels soon and I'm trying to figure out what the correct wheel / tyre sizes are for my car.
From my reading so far, everything indicates that I'm actually running my rolling diameter slightly too low.
It's a KF Xi so came with stock 16" alloys.
Right now it's got 235/45/17's on there.

What is the correct tyre / wheel size for it?
If I'm getting 18's, what would be the correct tyres for that size? (I'm basically decided that I want 18's)

Thanks,
Matt.

18's you will need a 235/40r18 to keep the correct wheel diameter so your speedo isnt out. I currently have 18's on my th and it came stock with a 16' wheel.

Verada KF Xi came with 215/60/16 tyres from the factory. Overall diameter = 664 mm. Your current tyres 235/45/17 have OD 644 mm which is 20 mm less than factory fitment (in Victoria you are allowed +/-15 mm difference, don't know about SA).

235/40/18 OD 645 mm, (-19mm)
225/45/18 OD 659 mm, (-5 mm)
235/45/18 OD 669 mm, (+5 mm)
245/40/18 OD 653 mm, (-11 mm)

Thanks guys that is extremely handy to know.

So... with a 20mm negative difference, I don't suppose anyone is good enough at maths to tell me the speed difference that makes at 60kph and 100kph?

I assume it would be relatively negligible.

Thanks again. :)

this site is your friend in this matter.
http://www.miata.net/garage/tirecalc.html
and its been posted 100's times b4.

this site is your friend in this matter.
http://www.miata.net/garage/tirecalc.html
and its been posted 100's times b4.

Ooooh, that one is pretty good.
Thanks.

My real problem was that I didn't know what the stock tyres were on the car. I knew they were 16s, but didn't know what rubber it shipped with.

Ta for all the info everyone.

We can't tell you what 18's to buy until you pick a rim, the numbers are based off the width of the rim.