Tires for my wheels
 

Would the recomended tire size for 18 by 7.5 ssr competitions
be 215/40, or would it be 225/40's? Would it be crazzy to stick
18 by 8's on my 02 WRX. What would you guys think the best
set up would be?




Imprezv Jenn

I have 225/40/ZR18's on my 18" wheels I also have 18x7.5

[QUOTE][i]Originally posted by 02BlackWRX [/i]
[B]I have 225/40/ZR18's on my 18" wheels I also have 18x7.5 [/B][/QUOTE]


Have you noticed any speedo alterations with this
set-up?

No i did not...atleast I dont think so...

There should be little or none in the alteration of the speed. All you need to do is find what the overal diameter of the tire is and make sure that it is close to the stock overall diameter. The closer the more accurate your speed reading and mileage count is.

according to both tirerack.com and tires.com 225/40/18 is the tire you should be using to keep the same overall diameter...

[QUOTE][i]Originally posted by 02BlackWRX [/i]
[B]according to both tirerack.com and tires.com 225/40/18 is the tire you should be using to keep the same overall diameter... [/B][/QUOTE]


But does the 225 have anything to do with
the overall diameter. I thought (I try not to do this to much
w/car related stuff) that the 40 was the profile of the
tire and this number is what changed the overall diameter.
That would make the 225 or 215 number the width wright?
This is how tires were explaned to me. If not correct then
please set me straight.



Imprezv Jenn

the first # may be larger, the the middle number is smaller and they even out...225/40/18 = the same diameter as 205/55/16 (or whatever the factory size is)....the 225/40/18 is a little bit wider, but it still has the same diameter and thats what counts when it comes to the speedometer...and the 40 is an aspect ratio and it has something to do with the width and percentages which I am not to familiar with so I won't go into it...the 225 is the width, you are correct about that.

Here, check this out. [url]http://www.miata.net/garage/tirecalc.html[/url] This will give you an estimated difference. To get the most accurate difference, you will have to check the specs on specific tires. A lot of tire manufacturers list how many revolutions per mile a tire turns. The RE-92's turn 830 revolutions per mile. You just need to figure out which tire you want and check the manufacturers website.