215's vs. 225's

[Z/WRX]

I'm going to be needing new tires for my 06 WRX soon so I've been doing some searching here for tires that are recomended (plenty of info). What I noticed was that some people have gone to 225/45/17's instead of sticking with the stock 215/45/17's. Is this the best route to go? Also the speedo will read 1.4% to slow. I know to most people thats not a big issue but I'd like to keep it as accurate as possible. Just trying to find out how much of a difference in cornering there is between the two sizes or what the reasoning is behind going to 225's. Are the recomended tires not available in 215's? Thanks

[mosc]

well, it's an easy choice for 225s. Your rims are 7.0" wide so it should work fine.

Frankly, the stock 215/45/17s are a peculiar choice for Subaru. They use 25" tires on all other Imprezzas including the STi. Your "stock" tire height is really 25" even though the tires that come from the factory are .4" shorter. I think they just tried to keep it different than the STi while still wanting to shift it to 17" rims which lead to them putting on a rather weird tire size choice for 06-07.

It's worth noting that the 08 WRX returned to a 25" tire. It's only those 2 years that got 24.6" stock tires.

Can your rim support 225 wide? Well, it's 7.0" which is 177.8mm which means the tire is 26.5% wider than the rim. BFG I know says keep it 0-20% but most tuners do 25% routinely. Ideally you'd have a 7.5" or 8" rim on there to do 225 wide but if you're going to use a high performance tire with a stiff sidewall, 26.5% should be fine.

225/45/17 on a good high performance stiff tire is what 06-07 guys should go with. You might consider getting new rims though, your stockers are over 23lbs each unlike the other older WRXs (and all STis) so going something like a <18lb 17x7.5" rim would be a hefty 20 lb savings of unsprung weight.

[Z/WRX]

thanks for the info. Yeah, I've been considering getting some different wheels simply due to the weight savings. I didn't realize how much they weight until I started searching for tires and such. Now has it been confirmed that the 06/07 WRX uses a different speedo cog to make up for the tire size difference? I mean I see what you are saying as far as the other WRX's using the 25" tire and the STI except for the 06/07. I'm just wondering if Subaru bothered changing the speedo cog or not because if they didn't then going to the 225's wouldn't do anything except make the speedo read accurate. Again thanks for the info. I'll be looking into other wheels for now I guess and see where that leads me.

[mosc]

I don't know but I'd wager they did. 24.6" is 1.4% off which means when it says 60, you'd be going 59.1 if they had it calibrated for 25" tires. That's 140 more miles every 10,000 on your odo that should be there which is a decent chunk.

It's something I wondered when the 06 first came out but I never checked into it. Anyway, that's more of a tidbit than a requirement. 25" tires sure ain't going to hurt it any.