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Discussion Starter #1
Hello All,
Would a 245/60/15 on a 15x7 rim be the same exact diameter as the same tire on a 15x8.5 rim? I would think the tire on the 15x7 would be slightly taller. Am I right?
RTT:beer:
 

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VINTAGE MOTORHEAD
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I don't claim to be an expert on this subject, but I have run the same size racing slicks on different width rims. They always had the same overall diameter BUT, the narrower rim forces the sidewall "section" inward which does tend to round the tread. In other words, the tread area did not lay as flat on the narrower rim, rather it became convex. The center was higher than the edges. The tire will still roll the same distance. The wider the rim the flatter the tread will lay on the surface.
 

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i believe lockjaw is correct.you will change the look of the tire but the circumfrence will be the same
 

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Deputy Director Region 6 - 2013 Founders' Award Re
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In the smaller rims it make a difference I have made change on 15x7 to 15x8 & 15x 9 and it changes the diameter given all the same tire size, not a lot seams like its in the 1/8, 1/4 to 3/8 of an inch area, been a few years but I am certain. That's unladen weight measure.
 

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If you go to this link, you can input different tire sizes and wheel widths. It gives you the diameter as one of the output parameters.

http://www.rimsntires.com/specs.jsp
 

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Deputy Director, Region 3 PA (west)
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Changing wheel width on a street tire does change the diameter, but a very insignificant amount. I wrench on a Sprint Car, so measuring tire circumference is a very regular part of our chassis tuning. When I first swapped my front Rallys from 7" to 8" I measured them both ways. The difference in circumference was only about 5/8" IIRC, which would be around .200 in diameter. Not enough to worry about IMO.

Bill
 

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Discussion Starter #7
BillyJack
I am going to run a 14" slot mag on the front of my elky and interestingly enough, the wheels I have are 3.5 " BS and I can get away with running 245/60/14 on the front with no rub. I tired it to verify. So with a 15" slot mag on the back I want the front tires to look as tall as possible and I have both 14x7 and 14x8 rims to work with on the front. The 14x8 does make the rims stick out a little further in the wheel well however. So you are saying the 14x7 will be slightly taller??? RTT
 

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Deputy Director, Region 3 PA (west)
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BillyJack
The 14x8 does make the rims stick out a little further in the wheel well however. So you are saying the 14x7 will be slightly taller??? RTT
The difference in height is so slight it would never be noticeable. Personally, I prefer to use the widest wheel possible to optimize cornering.

Bill
 
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