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Discussion Starter · #1 ·
Sooo im thinking about buying 18x9.5 tsw bathursts because how concave they are (love concave rims) but i want the front rims to be less concave than the back and so im thinking of putting 18x9 in the front and 18x9.5 in the back. Is it okay to run different width rims? Im gonna be putting 255/40/18’s front and back
 

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First, I have no idea whether that combo would clear without rubbing. Maybe someone else could weigh in on that. To address your question, though, wider rims in the back would be fine from a safety point of view. Going with a wider rim with the same size tire stiffens the sidewall. So, in this case your rear tires would have less sidewall flex and alter the handling bias towards understeer. 255/40X18 size tires are approved on rims 8.5 to 10 inches wide, so you'd be ok there, too. That size is kind of tall, maybe consider 255/35X18? Going with staggered rim widths will make it so you couldn't rotate your tires without dismounting them, a major hassle.
On a side note, I've seen the popularity of upsizing from stock to 245/40X18. People seem to give the extra width credit for reduced tendency for wheel spin. Instead, I believe that is simply a result of the change in gear ratio as that size is proportionately larger in diameter as compared with stock.
 

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Discussion Starter · #3 ·
@NCST1 you say “its kind of tall” but isent 40/18 stock profile/wheel size. I didnt think the width of the tire changing would affect the overall diameter of the wheel. If it does can you elaborate please?
 

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@NCST1 you say “its kind of tall” but isent 40/18 stock profile/wheel size. I didnt think the width of the tire changing would affect the overall diameter of the wheel. If it does can you elaborate please?
235/40X18 has sidewall height 40% of 235, or 94mm. 255/40X18 has sidewall height 40% of 255, or 102mm. Difference of 8mm times 2 (top and bottom) and you get a difference in overall diameter of 16mm, more or less. 25.4mm = 1 inch. Doesn't seem like much but significant.
 

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Yeah what @NCST1 said. The "40" is only an aspect ratio, not all "40" series tires are the same sidewall height. You are taking 40% of 255 to get the sidewall height as opposed to stock which is 40% of 235.
 

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"On front-wheel drive cars, which already tend to understeer, putting a wider tire on the back is a detriment to handling. 90% of the braking, all of the power delivery, and most of the weight-bearing is being done by the smaller tires. The overworked front tires give up first when pushed, and the car wants to plow straight ahead, inspite of the steering input telling it to turn." - Ben Rooney
 

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Discussion Starter · #7 ·
Oh i see... thanks for the info and feedback guys do any of you know of an ST with 255/40/18 tires thats lowered im curious to know what additional things might have to be done to make it fit properly nd if its too much i might just go 245/40/18 which id assume can hold 9.5inch wide rim.
 
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