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Unread 12-22-2012, 04:41 PM   #1
Agent 000
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Can I Use A Smaller Spare With 31" Tires?

My 98 Classic is currently running on 31" BF Goodrich AT's. I have a matching full-size spare, but it is not mounted inside the vehicle (takes up the cargo area floor). My jeep also has a donut-spare mounted in it at the moment, in the factory location. I've been told that a 30x9.5 tire will fit on the factory spare mount with no modifications, but that a 31" will not fit, unless the mount is modified.

I want to run with a full sized spare, rather than a donut. Can I run with a 30x9.5 spare, or a 235/75 spare, as my rear axle is equipped with a Trac-Lok differential?

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Unread 12-22-2012, 06:19 PM   #2
sAe23
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Have you TRIED to mount the full size spare to the bracket?? I would guess that it might prevent the back seat from latching...

As for driving on a smaller size spare you could PROBABLY do it for short distances, but I don't know how the track-lok differential would be affected
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Unread 12-22-2012, 09:06 PM   #3
GetLifted
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Up to 32s should fit
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Unread 12-23-2012, 04:53 AM   #4
foggybottombob
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When I moved to 31s I had to mount my spare on a swing out tail gate. The other option is roof mount. You can use a smaller spare in 2WD but I would not do that in 4WD except for a short distance in an emergency.
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Unread 12-23-2012, 06:15 AM   #5
dav5942
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With our '98 running 31s we carried the factory spare mounted in side. With our current 33s we carrry a 33 spare on tailgate mount(Detours USA). Would NOT mount on roof as it will raise your center of gravity, etc.

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Unread 12-23-2012, 06:18 AM   #6
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On open differentials running a different size tire is perfectly fine - 2WD, 4WD or otherwise. If I had an auto locker or LSD I wouldn't do it though. OP, is your front open? Then just always plan that is where your spare goes and just requires two tire changes if you get a flat in the rear.
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Unread 12-23-2012, 09:16 AM   #7
Kevin108
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You can extend the seat latch bracket some to allow for a larger tire. If you have a compressor or OBA, take the tire down to single digit pressure and see if you can squish it down with the seat.
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Unread 12-23-2012, 10:12 AM   #8
djb383
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It's my understanding that with any type of traction enhanced diff equal tire diameter/tire pressure are very important, especially whenever driven on pavement. 31", 30X9.5 and 235/75 are 3 different diameters and could be tough on a traction enhanced diff when mixed opposite each other.
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Unread 12-23-2012, 11:12 AM   #9
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Your differntial will heat up when running different tire sizes- short period of time you are probably fine= extended no.

And I would not use 4wd with different sized tires.
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Unread 12-23-2012, 12:14 PM   #10
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I run 215 85R16 on my XJ. They are only supposed to be a 30'' but are juts as tall as most 32s.

I had to:
-Remove the plastic on the hatch
-Change the hook to the higher hole (the part where the ball and nut screw into)
-Remove the floor support that holds the smaller tire in place.

Right now, I have 225/75-15 ATs on it with a 215/75-15 spare.


When I first got the lift and tires, I only had 4 tires and the 215/75/15 tire as a spare. Eventually I bought a fifth.
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Unread 12-23-2012, 01:19 PM   #11
Bbasso
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It will fit, mine did. You'll need a longer hook and remove the bracket on the floor.
I bought a 'J' hook at Lowes for under $2.



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Unread 12-24-2012, 12:55 PM   #12
sAe23
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Quote:
Originally Posted by dav5942 View Post
With our '98 running 31s we carried the factory spare mounted in side. With our current 33s we carrry a 33 spare on tailgate mount(Detours USA). Would NOT mount on roof as it will raise your center of gravity, etc.

So then does a large spare tire on the bumper make you pop wheelies?
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Unread 12-24-2012, 06:30 PM   #13
DoctorTim
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i have a 33" tire just laying down in the cargo area. fits fine.
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Unread 12-24-2012, 09:10 PM   #14
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I ran a spare that was 31", but whell worn for about 20 miles... it really effected handling. With the missing tread, it was about 2" shorter. But I have open diffs. Ive also tried putting the tire up on the roof. 2 things about that. 1, In PA< unless it is secured to something that is not the sliding factory roof racks, it is not OK. Was told this by an inspection guy, something about those tiny pins not having the oomph to keep it in place in a collision.

2nd, it will effect your handling, it feels like if you were trying to run full tilt with a very , very heavy helmet. Or tryng to run with a sail mast... If you do not need your seat locked in all the way, you can get away with just mounting it in the factory location (I used a ratchet strap) and not letting the one side of the rear bench to latch. Pu t a cloth on it, as it will squeak against the hatch plastic.

(3rd crappy thing about the wheel on the roof... getting it down. IT sucks. Its heavy, and you will probably have to do it, when its raining or snowing, and you have to be somewhere and look half presentable. Oh, and if you guys with 96's and older think about this, that time you spend up there on the edge of the hatch? it will embed itself in your arms, and you will itch for a week. I know.)
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Unread 12-25-2012, 03:00 AM   #15
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You could build a trunk and bust out your back window and go with a truck mount..... gets a little drafty in the winter... buts its not so bad unless your a pu$$^
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