Hi all,

Was given 235/40 Goodyear F1 becos there isn't a 225/45.. Tyre shop says wheel overall size identical for both.. Can't figure this out. Pick ur brain, can?

45% of 225 = 94mm
40% of 235 = 101.25mm

Difference = 7.25mm x 2 = 14.5mm (for total wheel diameter). . What makes them equal? (wild thought) Thicker tyre thread? Thanks..

King105

 

235s are smaller diameter, wider tread width. Makes about a 2% dif on your speedometer, no biggie. If it says 100, you're only doing ~98.

 

The 2 sizes are not identical. The diff is 2.2%. In real life, no prob living with it.

Cheers

 

the tire shop can be right in saying they might be the the same. why so? cause not all 225/45/18 tires are the same. take for instance the RE040 and AD07. AD07 is wider than the RE040 of the same size. so it could be that it might be the same after all. maybe you should have measured the diameter of the two tires and compared.

 

Here's a good link, tire calculator has been up there for years..

http://www.miata.net/garage/tirecalc.html

 

Hi all,

Indeed my suspicion.. Thanks for the advice!

King105