[jsmsustudent]

-Are there any fitment or rubbing issues with putting a 245/45 on our stock bbs wheels. Does the extra weight of the rubber outweigh the benefits?

-Finally our cars speedo is a little off b/c of our 225/45 tires (jdm is 235/45). We are actually going slightly slower than what our speedo says. So if i put 245/45 tires on will the opposite happen. Will i actually be going a little faster than what my speedo says. The same is for the miles traveled and the odometer. 225/45 tires make our car think it is traveling more miles than it actually is.

[SonicBoom]

I've been looking for a definitive answer on this as well... It seems to me that 245/45/17's would be too tall and that 245/40's would be better. I forget which website(I think its tirerack.com) that has a calculator to see diameter's/width... 255/40's are actually the closest match but I'm thinking those'd rub for sure... Then the issue is further confused by manufacturer, Bridgestone 225/45's are wider than xxxx brand 225/45's..

[robertaflack]

so you're saying 255/40's are closer to stock than 245/40's?

[SonicBoom]

going by the tirerack calculator... yes... then again there's the difference by manufacturer I mentioned to throw a monkey wrench in the works!

[T3h_Clap]

255/40 17 RT615s fit on a MY05+ STi on stock wheels even when lowerd on STi Pinks.

how do i know?

there are alot of us who have done it.

and the amount of difference between running a 225/45 17 and a 245/45 17 is like 250 miles per every 10k miles IIRC.

[austinpike]

tire size calulator:
http://www.miata.net/garage/tirecalc.html

1) 245/45 or 255/40 will be fine on 05+. Plenty of people running them.

2) The speedo is so far off that it would take something in the neighborhood of a 245/50 to correct it. With a 245/45 you will still be slower than what it says. The odometer is not tied to the speedo and is more accurate. Non-stock tire size may affect the odo, but the difference is like +/- 1% either side of 235.

[jibSTir13]

i'm running 245/45/17 rt-615 on pinks and can confirm that they fit fine.

[T3h_Clap]

I assume you're running you stock wheels?

if not, size and offset would be appreciated to know what fits and what doesn't.

[STIBLITZ]

another good one is
http://www.1010tires.com/TireSizeCalculator.asp

you can see images of various tire size dimensions to give you a reference of how much/less a tire will be.

http://www.1010tires.com/WheelOffsetCalculator.asp

offset calculator, well its pretty obvious what it does. it only gives you a general idea of the changes. supsension settings will alter the outcome a bit (i.e changing to coilovers)

[T3h_Clap]

neither of these mention the change in section width with a different width wheel.

this is a significant change.

[STIBLITZ]

Originally Posted by T3h_Clap

neither of these mention the change in section width with a different width wheel.

this is a significant change.

correct

havent found a chart or anything that shows it.

sidenote:
re01r 245/40/17 weighs 27 pounds
re070 225/45/17 weighs 27 pounds

[T3h_Clap]

well the "basic" rule is 5mm increase or decrease for every .5" wheel width difference from "measured rim width"

mine is the only chart that i know of that takes it into account.

[VSGTS14]

if u want to know the diameter, look at thed tire manu. spec

all tires run diff sizes you n00bs

[lokutus1]

this is helpful info. i'm looking into new tires soon too. so, 245/45/17s and 255/40/17s will fit stock 05 rims and sti pinks. correct? no rubbing or fender rolling necessary? any opinions on which would be better for performance/grip?

[Rac10000]

I wouldn't put anything larger than a 235/45 on the stock or any 8" wide rim. Yes, a 245 or 255 will fit but it just doesnt make sence. There will be way too much sidewall felx. You want the sidewall to be flat, not boulge out towards the bottom.