Using a 31" as spare when running 33"s

Hey guys, just want to get your opinion on this. I'm planning on buying a set of Goodyear MTRs sized 33x12.50x15, which have an overall diameter of 32.7.

Instead of buying a spare, I was wondering if I could use my current spare which is a Swamper SSR 31x10.50x15, which has an overall diameter of 31.5. With a difference of only .6 of an inch in radius, would there be any problem driving short distances with the smaller spare.

I was speaking with my brother and he said that if I ran the smaller tire up front, it wouldn't matter. I figured if I get a flat in the rear, I could put a full size in the rear and the spare in the front. Another remedy could be airing down the side opposite where the spare is. Also, with the full size tires wearing down, I figured it would eventually even out. Let me know what you guys think.

Thanks,
Raphael

 

[Alec]

If you have a limited slip or locker in the rear you'd have to run the uneven tires up front like he said. However, this will make the truck slightly unsafe as it will affect steering and handling.

Ok for very short distances, but IMO you should get a full-size. What if you get stuck on the trail with a flat 200 miles from home?

 

[Critical_Level2]

If you have the 4wdauto, 4hi, 4lo, switch then i do not think you can run smaller tires. On my 99 I can not have a smaller spare or my owners manual says It could make the 4wd act up.

 

[Rob_B]

with the 98 your front axle is alway's engaged, so it could mess up your front end running different sized tires. I wouldn't recommend it, I bet you could find a used 33 cheap.

 

[Doug]

As long as neither one of your axles is locked it won't matter. If you're locked in the rear you'll have to run the smaller diameter tire in the front. I have 35s and I have a 33" spare, I drove around for a week with my spare on the front till i got my new tire. as far as the auto 4wd is concerned one smaller tire shouldnt affect it.

 

[Robert]

Do the "brown wire mod" and put the smaller spare on your front if you have a limited slip or locker in the rear. If you have an open rear, then just doing the brown wire mod is all you need to do.

Incidentally, up through '97 Ford often times included a smaller spare, depending on tire the Explorer came with. My '97 4x4 with limited slip and 255 70R16 (30.5") tires came with a 215 70R15 spare tire (26.9") from Ford. In my Owner's Manual it even states that some vehicles may be equipped with a smaller, temporary use only spare. They did away with that starting in '98 and started saying that the use of a smaller sized spare may cause damage.

 

[GJarrett]

I did this once a couple of years ago in my '99, got a flat in the rear, moved a 33" from my front to the rear and replaced the front with the stock 31" spare tire. I went 250 miles from the Slabs in Texas back to Dallas with no problems from the open diffy front, even with 4auto. I did replace it once I got home, but it did work with no apparent ill effects.

 

[RPheezy]

Thanks for the responses fellas. I appreciate your expertise.

I want to put my 31" spare in the stock spare location instead of buying a 33" spare and have to put it on the roof or other location. I think I will just use the 31" spare. If I ever get a flat, I'm hoping that my 33's will probably have worn down to the same as my brand new 31" spare.