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  1. #1
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    Default Spare tire vs new tires

    Hi everyone - I just installed my 2000 XJ Sport with a 3" lift and upgraded from 15" to 16" Rubicon wheels and new P245/75R16 tires. Now, I'm looking for a spare tire and found a P245/70R16 off a 2000 XJ Classic. The difference between the two in the circumference is 1.86".

    I do not have a locker or a limited slip differential and what I would like to know is -- would this spare would cause any damage if I were to need it while trail riding (back down the mountain of course)? Would it need to be installed in the front?

    The difference in circumference tells me that it probably won't (along with some of the threads I've read) but I wanted to make sure by pinging it off you guys first.

    Thanks in advance!

  2. #2
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    prerunner1982 is offline Level: Uber Jeep Cherokee Trailer Queen
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    Default Re: Spare tire vs new tires

    If using 4wd I would not use a different sized tire. In 2wd on the front it should be fine.

    But when the tcase it trying to turn the front and rear axles at the same speed having 1 odd tire will cause all sorts of mis-matched rotational speed issues.
    Last edited by prerunner1982; 08-04-2011 at 06:47 PM. Reason: changed would to should..
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  3. #3
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    Default Re: Spare tire vs new tires

    NO! do NOT have a mis-sized spare i Fried my TCASE and front diff doing that.... always always try to keep all 5tires the same size... I only had my spare on (30'' rest were 31s) for only a day.....

  4. #4
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    Default Re: Spare tire vs new tires

    Quote Originally Posted by amorth View Post
    Hi everyone - I just installed my 2000 XJ Sport with a 3" lift and upgraded from 15" to 16" Rubicon wheels and new P245/75R16 tires. Now, I'm looking for a spare tire and found a P245/70R16 off a 2000 XJ Classic. The difference between the two in the circumference is 1.86".

    I do not have a locker or a limited slip differential and what I would like to know is -- would this spare would cause any damage if I were to need it while trail riding (back down the mountain of course)? Would it need to be installed in the front?

    The difference in circumference tells me that it probably won't (along with some of the threads I've read) but I wanted to make sure by pinging it off you guys first.

    Thanks in advance!
    Yeah I wouldn't have a different sized tire for anything but a spare, and that would be only if absolutely necessary. I would not run the spare in Part Time 4WD. Running it on the rear could cause problems if you have anything but open diffs. Also I wouldn't run it with the spare tire very long. Just long enough to get you where you can get the original tire repaired or replaced.

    I may be being overly cautious, but better that than having to replace a transfer case or carrier.

  5. #5
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    Default Re: Spare tire vs new tires

    We have not addressed what transfer case he has. Also, if you run that smaller tire off road on the front, it will make the rear try to push the front, which is heavier and will cause the rear to want to break loose. You would be surprised how much traction you will loose that way.
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  6. #6
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    Default Re: Spare tire vs new tires

    Thanks for your responses everyone - sounds like it's split down the middle on if it's good to drive it or not. Which now raises the question that if I were to go with a P245/75R16 on the spare (hopefully a good used one off of Craigslist), would it fit in the cargo area on the stock spare tire holder?

    4.3LXJ - to answer your question, I have a Command Trac transfer case if that helps any.

  7. #7
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    Default Re: Spare tire vs new tires

    Quote Originally Posted by amorth View Post
    Thanks for your responses everyone - sounds like it's split down the middle on if it's good to drive it or not. Which now raises the question that if I were to go with a P245/75R16 on the spare (hopefully a good used one off of Craigslist), would it fit in the cargo area on the stock spare tire holder?

    4.3LXJ - to answer your question, I have a Command Trac transfer case if that helps any.
    Yes it does. If you ran this different height spare in full time 4WD, your fluid coupling in the tcase would not like it. Which is why I asked. To me, this would be a 2WD option only.
    230 hp 4.3L Chevy
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    7.5" RE front and bastard pack rear on custom long arms
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    lockers
    And a bunch of other stuff

  8. #8
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    Default Re: Spare tire vs new tires

    If you have D35 on the rear, you probably have limited slip there too, different size will damage it.
    On the front - I wouldn't drive with different sizes.
    (I wouldn't on the rear too, since you are rear wheel drive by default)
    So, making it short, I wouldn't do so.
    When I replaced my tires, I replaced all 5 of them.
    Saar.

  9. #9
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    Default Re: Spare tire vs new tires

    You should be just fine using that tire as a spare only. That is the joy of open diffs. I had to limp my xj back to civilization once before using a 235/75 spare, and I run 33's.

  10. #10
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    Icon14 Re: Spare tire vs new tires

    Thanks so much for all your replies!! I received more here on this site than the others I posted on!!

    I have a Chrysler 8.25 in the rear.

    I think I'm just going to take the 16" rim with Goodyear tire on it and use it carefully - in the front only. I bought the rim and tire for 50 - I don't think I'll beat that anywhere.

  11. #11
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    Default Re: Spare tire vs new tires

    To be honest with as little difference in height as there is, it shouldn't matter if you use it on the front or rear

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