255/70/17 to 305/70/17 - Jeep Wrangler Forum
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Old 09-29-2017, 08:16 PM
Thread Starter
Join Date: Aug 2008
Location: Central Va.
Posts: 58
255/70/17 to 305/70/17

Thinking of changing out stock wheels 17x81/2 and (255/70/17) tires to 17x9 wheels and 305/70/17 tires and was wondering what the effect on trans, axles and engine would be? No off roading, just local, and interstate on trips.
Thanks for the input!

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Old 09-30-2017, 04:41 AM   #2

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Join Date: Sep 2014
Location: Cheyenne, WY
Posts: 3,456
255 305 diff
Sidewall Height: 7.03'' 8.41'' 1.38''
Section Width: 10.04'' 12.01'' 1.97''
Tire Height: 31.06'' 33.82'' 2.76''
Tire Circum: 97.58'' 106.25'' 8.67''
Rev. / Mile: 649.31 596.33 -52.98

If your speedometer reads 65mph, you are going about 70.8 mph

RPMs 1:1 Auto OD Manual(6th) @65mph
255 2647 2197 2109
305 2475 2054 1973

A ~140 rpm change from stock should not mess with the ability of the Jeep to stay in OD if you have an auto.

You don't mention about any offset on the 17x9. Stock offset is 6.25. Since you are going 2" wider, you would need at a minimum 5.25 offset. This should keep in inside tire wall to suspension distance the as same as stock.

Trans shift points might be a lil off, and a ProCal ($170) would fix that.

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Old 09-30-2017, 12:44 PM
Thread Starter
Join Date: Aug 2008
Location: Central Va.
Posts: 58
Was thinking about the Trail Master TM220 rims, which have a backspacing of 4.75 and -6 offset, and 305/70/17 tires with a Rough Country 2 1/2 lift.
From what I've read from other posts, this setup is being run with no problems as far as rubbing or other problems. Just wanted some input on the driveline issues that might come up. Thanks
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