What size of spare do I need to use? - Page 2 - JeepForum.com

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post #16 of 25 Old 03-12-2009, 11:56 AM
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If you do not have a LSD or locker you can use a smaller diameter tire as a spare. Most compact spares are in fact narrower and less tall than the other tires (if they were the same size they wouldn't be compact spares). Just follow the same guidance given for them and you will be fine: try to limit to no more than 50 miles and don't exceed 45 mph.

Not optimal by any means but it will work.

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post #17 of 25 Old 03-12-2009, 12:23 PM
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I certainly understand that tires are not cheap but its nice to have the peace of mind when going off road that if you get a flat you can swap it out and not lose 4wd.... and face it... its a jeep the chances of getting a flat are a little higher... and chances of getting a flat in a 4wd situation probably even higher than that. As far as the tire carrier it can be temporarily made to handle a 33 till you get the funds back up
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post #18 of 25 Old 03-13-2009, 08:46 AM
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Since I never wheel alone there is always a full size spare available. In our tyipcal group 2 guys have winches, 1 guy has an on board welder, 2 with on board air, 3 with recovery straps and 4 guys with a 33" inch spare. If I needed it I could borrow their spare to get off the trail and then put my "compact spare" 30" to get home.
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post #19 of 25 Old 03-13-2009, 11:18 AM
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Originally Posted by scotch740 View Post
Running a smaller tire on one side will have your axle shafts spinning at different speeds. Thus your spider gears are going to be working over time till they go BOOM!
I don't think this is true. Spider gears can spin full speed all day long for 100,000 miles with no harm. That is how a front axle disconnect on all YJs, lots of XJs, and thousands of other 4wd vehicles work when they are running in 2wd. The driver's side axle shaft and side gear spins forwards and the side gear and stub axle shaft on the passenger side are spinning backwards full speed all the time. The spiders are therefore spinning full speed. This is what keeps the front drive shaft and ring and pinion from spinning, which is the whole purpose of the disconnect.

Bottom line is you won't hurt an open diff in the least by running different size tires. It would of course increase the wear on the clutch plates in a limited slip, but probably not much more than driving a comparable distance on a windy, twisty road. Probably shouldn't use 4wd unless absolutely necessary, and in the case if 4wd is absolutely necessary, you would probably have enough tire slippage to compensate. I have no idea about different size tires with an auto-locker. Seems like that might not be a good idea.

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post #20 of 25 Old 03-13-2009, 11:27 AM
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post #21 of 25 Old 03-13-2009, 11:39 AM
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i think the rule of thumb is 2 inch difference in diameter smaller or larger. that assumes you have open diffs. can't remember where i saw that so i can't back it up but i've had good success with it. i even used a 28 inch spare once from another jeep when i had 31's on and even though that is 3 inches different, it got me out of the woods and home without a problem.
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post #22 of 25 Old 03-13-2009, 01:17 PM
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Definitely do not have it in four wheel drive otherwise the smaller tire will spin faster than the vehicle is moving essentially creating a very long burn out.

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post #23 of 25 Old 03-15-2010, 06:54 PM
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Pulling up an old thread, but o well. Ive got a 285/75/16 as my winter tires. Would that be ok to use as a spare for 33x12.5x15?
And would it fit on my spare tire carrier?
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post #24 of 25 Old 03-15-2010, 07:14 PM
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I got a flat with 32"s and used the stock 30" to get home. 100 mile drive no problem. Now I've got 33"s and a 32" for a spare. So keep it close! full size is best, but do what you gotta do!
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post #25 of 25 Old 03-15-2010, 08:36 PM
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285-75-16 = 32.8" diameter x 11.2 wide, although I don't think many tires measure to the advertised size.

Since the thread is alive again,
Say with a new tire and a very used tire in the same size/different brand.

What about an Aussie?

What about a Truetrac LSD?

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