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Old 05-13-2006, 04:22 AM   #1
cinemaster
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Member#: 76127
Join Date: Nov 2004
Location: San Francisco, CA
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2005 WRX wgn 5spd
Obsidian Black Pearl

Default Can I put different width of rims on front and rear?

I've got rota 17x8.

Can I put 225/40/17 for front and 235/40/17 for rear on my wagon?
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Last edited by cinemaster; 05-13-2006 at 06:00 AM.
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Old 05-13-2006, 05:53 AM   #2
silentbob343
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The 40 isn't the height, but rather a ratio to the width.
I.e. the 225/40 has a 90mm tall sidewall or 3.54"
The 235/40 has a 94mm side wall or 3.7"

Good tool to help you see the difference in various tire sizes
http://www.miata.net/garage/tirecalcold.html

As you can see the circumference has changed. Now the 225s are going 837revs/mile to the 235s 827revs/mile. This difference will have to be sorted out via the center diff and depending on the size/amount of the difference this would not be good for it, i.e. overheat and cook the diff. The difference in your case is very small, but you should check with manual IIRC it states no more than a 1 or 2mm difference in which case you would be over. Is this a case of Subaru being over cautious and just trying to CYA.......

Food for thought; some tuners suggest using the same size tire, but using a wider rim on the front. This is what your thread title says, but you ask about tire in your post. A 255/35 would be closer to the 225/40 than the 235/40.


I'm no expert so take what I say with a grain of salt.

Last edited by silentbob343; 05-13-2006 at 07:48 AM.
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Old 05-13-2006, 06:06 AM   #3
seth_man
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well you shouldnt. with some quick math the 225 tire has a 24.08" height and the 235 tire has a 24.4" height. now i know somebody is going to say that within 3 or so % of each other is ok. you CAN put them on but it will cut the life of your center diff down an unknown amount. i would try to get tires that are the same height.

the math: section width = W, aspect ratio = A, rim size = R

((W*A)/25.4)*2+R = tire height

tire manufacturers will also have all their tires specs on their website so you can compare sizes.
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Old 05-13-2006, 10:38 AM   #4
waktasz
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The circumference has to be within 3%...not diameter.

His original question was about wheel widths, and there are people who have done that...but different tire sizes are baddd.
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Old 05-13-2006, 11:26 AM   #5
BIGSKYWRX
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09 GH B+

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You've also got the wrong relationship front and rear. With a AWD car you would generally want a wider combo up front, not rear (like a RWD)- ths will help dial out uneersteer.

The "easiest" way to accomplish this is to run the same tire front/rear- but run a wider rim up front say 8" front/7.5" rear- this gives you a little wider package up front (as a general rule section width increases ~ .2" per .5" of rim width increase).

You can run a different tire size combo, but you must be very cautious and get the heights very, very close (f/r)- proceed w/ caution w/ this endeavor.
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