I recently bought a set of 31" tires and wheels from a wrecked F-150. My spare tire however is the stock size (29" ?). Would there be any problem if when I need the spare I use it along with the 31" for 100 mi or so until I could get my tire replaced?
My truck is a 96' F-150 2WD, open rear end, 2.74. Could having 2 different size tires in the back burn up the differential? I would think so on an LS, but I'm thinking it wouldn't matter for an open differential. Has anyone ever had to run with a combination like this for any period of time? Thanks.

 

Its certainly not a pleasant driving experience, but it shouldn't hurt too much as long as you limit the number of miles you're driving like that. You'd want to put the 29 on the back so that you don't have any steering issues. I imagine that over time it would cause the tires to wear unevenly, but not a huge concern as long as you get it fixed quickly.

I doubt you would have any differential problems under these conditions.

 

I've done this before.

Open diff and never engaging 4wd allows to you run a smaller (or larger) spare than your tires.

However, you'll find it irritating at best to steer with different sized tires on the front, so if you get a front flat, put a rear tire on the front and put the odd-sized spare on the rear. Just more work.

Or, get free towing with your insurance or AAA and bring a couple of cans of fix-a-flat (which is what I do - don't even carry a spare anymore).

 

I've always heard it's easier for the front suspension to deal with different size tires. I had a toyota once and the previous owner had retreads installed and I didn't know this and I was going down the interstate and there was pieces of tread comming off one of my front tires. It was weired every so often I would look in my mirror and I see something bouncing in the road so I pulled off at a rest stop and looked at my tires and I had a 4x6 inch patch of tread missing. I didn't know what was better for the spare so I called my mechanic and he said it would be better if it was on the front which it was. But the bad thing is my spare felt good enough so I put that on then let it down and it didn't have much air in it so I had to switch them back and drive to a station that had air then switch them back. Ever since then I check my spare quite often and I keep a gauge in the glovebox.

 

Maybe our difference in opinion on this has to do with what we drive Kista.

My 93 F350 crewcab *HATES* dissimilar tires in the front, as did my 4wd 81 F350 crewcab. Maybe it's a weight thing? More weight, more tire pressure, more intolerance of tire differences?

 

yeah I'm sure it depends greatly on the vehicle. The size of the retreads were 30x9.50 and the spare was a 235/75/15 so it wasn't that much of a difference. I just thought I'd share my experiance because it happed to me once. At least they're still giving us fullsize spares for trucks.

 

For the trucks I buy, they have to give a full size spare. Never seen an 8-lug donut .

 

yeah to be honest I've never seen a donut on a truck. I had an s10 2wd once and that even had a fullsize. I have 31x10.50 on mine and I'm thinking about getting another for a spare. Sometimes I do a lot of towing/hauling with mine and sure enough thats when something is going to happen (murphy's law). I do have new tires, bought them last dec. and I've only put 9k miles since then.

 

Check the junkyards for a decent spare, no need to spend much for a spare...