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Unread 06-01-2013, 06:06 PM   #1
ErikTheRad
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31" tires, 235/75 15 spare ok?

I'm buying a set of 31" A/T's for the Jeep, would like to keep one of the current 235/75 r15's for a rooftop spare instead of having to buy a 5th tire. I know ideally we should run the same size tires all around but would it be ok to use it as a limp-home emergency spare tire? Or will this screw up a front or rear differential? In some cases we're more than 150 miles from home, and at least 75 miles to the nearest tire shop.

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Unread 06-01-2013, 06:10 PM   #2
ErikTheRad
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As usual, I find conflicting information. As far as I can tell, with my 249 transfer case kept in full-time, I should be ok for a short while but get it changed asap. Should be ok to get it home. Does this sound accurate?
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Unread 06-01-2013, 06:21 PM   #3
cgcarpenter
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I do not know much about the 249 bit as I've heard hundreds of times here. Jut get the same size tire or AS CLOSE as possible or you will be in trouble.
I'm sure someone with a 249 will chime in and say the same
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Unread 06-01-2013, 06:21 PM   #4
jm8881
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It is not a good idea to drive on a mismatched tire for any amount of time, especially with an awd vehicle. Even on a fwd or rwd car you should make sure the drive wheels are the same size by swapping the flat tire with a good tire from the other end of the vehicle and putting the doughnut on the non drive wheels.
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Unread 06-01-2013, 06:24 PM   #5
BLarkin
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Ive got the 242, but from I've read here about the 249, you do NOT want to mix tire sizes, or even tire brands. Those TCs are extremely picky about tire height, and you will burn them up running different size tires. At the very least, scour your local CL for a good used 31, probably find one for $50 or less.
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Unread 06-01-2013, 07:01 PM   #6
PolkaPower
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No effing way. You will kill that 249 fast with an odd sized spare. Especially with the early 249's. All tires need to be the same and do not remove the front shaft and drive it. That will kill the VC too.
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Unread 06-01-2013, 07:05 PM   #7
dnuccio
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buy the 5th 31" tire. if you run the smaller tire for even a short time it will destroy the viscous coupler in the transfer case.
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Unread 06-01-2013, 07:30 PM   #8
JasonStebbins
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No. Unless you want to buy a new transfer case and front end.
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Unread 06-01-2013, 07:38 PM   #9
4x4andmetal
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I have a 249. One time I put a different sized tire on because I had a flat. I ended having to replace both differentials. I also only drove about 5 miles.
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Unread 06-01-2013, 11:40 PM   #10
Myusername1674
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From what I've heard thats a bad idea, I spent the extra money and got a 5th spare from what I've heard its pretty necessary.
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Unread 06-02-2013, 01:43 AM   #11
eagsc7
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So I shouldn't use the donut on my 33" tires either?

Only thing I've seen is that there was a Drivetrain issue with the 96 ZJs not working AT ALL with the doughnut spare. Course, There was a RECALL that's strangely ONLY for that year...
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Unread 06-02-2013, 04:54 AM   #12
PolkaPower
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With the 249 all tires must be the same size. That is the bottom line.

96-98 it's ok to remove the front shaft and it won't hurt the VC or roll. 93-95 it's not ok. The power split for 93-95 is 50/50 all the time. For 96-98 it's like 10/90 front to rear until the rear tires slip.
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Unread 06-02-2013, 05:19 AM   #13
Texas ZJ1
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Polka is correct. Using a smaller or mismatched spare is very, very bad. You will destroy a 249 and if you have a traction aid like a locker or limited slip with any other transfer case, you'll destroy it as well. Do not do that. Buy the matching spare.

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Unread 06-02-2013, 05:35 AM   #14
ErikTheRad
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Well I guess that answers that. No can do. And if the 249 is THAT picky, then I probably shouldn't even mismatch with a 31 of a different brand or one that's been worn down. Rats, more money.
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Unread 06-02-2013, 06:12 AM   #15
PolkaPower
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Quote:
Originally Posted by ErikTheRad View Post
Well I guess that answers that. No can do. And if the 249 is THAT picky, then I probably shouldn't even mismatch with a 31 of a different brand or one that's been worn down. Rats, more money.
That is correct
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