Im looking into putting 17's or 18's on my 03 wrx wagon, and wanted to know what size tires won't screw up my gearing, odometer, etc. Currently the car is bone stock. Thanks

 

What width are you wanting to go with? The stock tires have an od of 631.9mm, a 225/45/17 od is 634.3 (+2.4mm), a 225/40/18 is 637.2 (+5.3mm) and a 215/40/18 is 629.2 (-2.7mm). On a 225/45/17 tire the 225 is the width in mm, the 45 (profile) means 45% of the width which in this case is 45% of 225mm and the 17 is the wheel od in inches.

This is the way to figure out the od of a tire. (I will use a 225/45/17 as an example)

(1) multiply the width and the profile (225x.45=101.25mm)
(2) multiply x 2 (101.25x2=202.5mm)
(3) add the od of the rim (1"=25.4mm so 17x25.4=431.8) (202.5+431.8=634.3)

If the way I explained this is to confusing tell me what width tire you are going with and I will figure it out for you.

 

Awesome question and awesome answer!

Thanks

 

the easy way:
http://www.miata.net/garage/tirecalc.html

 

Thanks for the cool link.

 

The closest match to 205/55R16 is 215/45R17. That's the size tires used on the factory option 17" wheels (not STi). But 225/45R17 is really close too, so use that if you want.

 

no prob

 

Thanks a lot, great response MO REX. That gives me a good idea of what to look for. Would the 215/45r/17 fit better on 7in or 7.5in wide rims? Also does anyone know about rubbing issues for a 225 45 17 with a stock suspension set up"

 

Check the tire manufacturer's website, they should have minimum, optimum, and maximum rim width specs for each tire.

 

You could use either size wheel and not have issues. I'd get 7.5" if I could, but if the wheel you like best is 17x7 it will be fine. Prodrives and OZ SLs come to mind.

 

thank you

 

Look at the sticker on your driver door or door sill. Go with the optional size there, if listed. That's what subaru recommends.

 

Like Ban said both will work with the stock suspension but if you plan on lowering the car in the future you may rub with a 225 depending on the tire and offset of the wheel. Different tires have different physical widths so one manufacturers 215 may actually be the same physical width as another manufacturers 225.

My 02 sedan has 225/45/17 SO3's on wheels with a +48 mm offset, it is lowerd 1.2" (rear) with 1 degree of - camber and the tires rub the fenders when I push the car hard on sharp corners. If you had a similar setup in the future you would definately rub since wagons have less room in the rear fenders than sedans.

Hay Ban (or anyone who knows), if he does plan on lowering the car in the future do you think he would be better off with a 48 or 50 mm offset since he has a wagon? I would guess a +50 but I dont know much about wagons.

 

WRX usable tire sizes and diameters

15"
195/65-15 25.0
205/60-15 24.7

16"
205/55-16 24.9
225/50-16 24.9

17"
215/45-17 24.6
235/40-17 24.4
225/45-17 25.0

18"
215/40-18 24.7
225/40-18 25.1