Ideal tyres for 18s on a 2005 WRX

[wilbo83]

Am I right in thinking that the ideal tyre size is 225/40?

[ScoobieWRX]

I'd say you could use 235 40's without rubbing issues but i suppose that depends on the offset of your wheels and if your car has been lowered. No probs on a bog standard car though with the right wheels.

[wilbo83]

Car is a 2005 WRX lowered on Prodrive springs. Wheels are Ultralite ATECs 18x7.5". Currently they have 215/35 tyres on (on my celica).

[rhinochopig]

wilbo83 said:

Car is a 2005 WRX lowered on Prodrive springs. Wheels are Ultralite ATECs 18x7.5". Currently they have 215/35 tyres on (on my celica).

235 is the widest tyre you can fit on a 7.5 rim. Standard fit is 225.

[wilbo83]

rhinochopig said:

235 is the widest tyre you can fit on a 7.5 rim. Standard fit is 225.

What about which profile to ensure rolling radius and speedo remain accurate?

[ScoobieWRX]

All speedos are set to read more mph than you're actually doing so running a larger diameter tyre that more closely matches what the speedo says is not a bad thing. Rather go very slightly over than further under or stay the same.

[dmitry]

Standard wheels are 215/45R17. 225/40R18 will be ~2mm more and 225/35R18 ~2mm less than overall diameter of standard ones which gives around 1.5% difference in speedometer readings either way.