Is a full size spare worth it?

I recently upgraded to a larger size of tire (33" BFG T/A KO's). I still have a stock size spare. If I were to have a flat, I would only put the spare on to get me off the trail and/or to the nearest tire shop. Would running one tire of different size screw up my gearing, diffs, or anything like that?

 

yea it would screw up your trannny rotation ratio..... if you are into reall hard off-road or anything like that its worth the investment..

 

I would upgrade to full size spare . If you are on a budget I would find a used tire place that has your size or get a cheap brand spare in your size

 

Using 4x4 with mismatched tire sizes is ill advised.

 

Well unfortunately 33x10.5r15 is only made by BFG. I guess my next question is: Would there be any problems with using a spare on a 16" rim vs. all my other tires being on 15's? I know the tires would end up being the same diameter, but I imagine there'd be something of a weight difference...?

 

I'd think as long as the tire sizes match that you would be fine and that weight wouldnt be an issue especially if you arent going to be running the spare for very long until you got your other tire fixed.

 

I believe with a mismatched spare it's best to use it on the front and in 2wd for as short a distance as possible.

 

What about your normal passenger car with the small donut spare ? I don't think running down the highway in a sane manner (in 4x2 mode) will hurt anything such as gearing. I have big tires from the factory with a normal spare, there's no mention not to use the normal spare if I had to. Of course, you want to get it back to normal ASAP.

 

I guess it would make sense for it to work on the front in RWD... Just trying to doublecheck. As it turns out, they don't make 33x10.5r16 tires so I'd probably end up having to get a wheel and tire identical to the ones I've got on now. That's going to be like a $300 investment. On the other hand, that much could buy me a skidplate.

 

You really should try to match the diameter of the spare to the other tires as close as possible. you can get a skinnier tire on another size wheel. For example, you could get a 255/85/16 spare to closely match your 33-10.5-15. The diameter is almost the same and with a little trimming to the mount, it will tuck up under the bed nicely.

 

I've got 33's. And I'm not worried about it fitting under the bed, that's where I keep my onboard air. The spare's been living in my bed until I can get a rear bumper with a swingout.

 

sorry, that was a typo. The 255-85-16 is pretty much the same diameter as a 33.

 

Call your local tire shops or junkyards, 4WD shops, etc and ask if they have any used tires in the size you need. 33" might be hard to come-by, but you might get lucky. Tire shops usually have a used inventory to-be-trashed or recycled that you may be able to get one.

 

This ^^^^^

I don't see a problem with that. Weight is not as important a factor as tire height considering the temporary nature of spare tire usage (ie the doughnut spare on cars). BFG makes a 285/75/R16 that will get you very close (both height and width)to what you have now.

Not sure I agree, primarily based on most car manufacturers advice against putting the doughnut spare on the front. I would want the most balance up front for safe(er) steering.

 

This is one of those arguments that I've had with my Dad.
You can only run a tire of unequal diameters on wheels that are not driven by the powertrain. Just like previous post, it is ok to place a donut or small tire on the front axle if you are in two wheel or rear wheel drive, likewise you can mount donut on rear axle if you have a front wheel drive.
If you mount donut on driven wheel, your differential has to make up the difference in diameter, one tire turns 1 time on one side of differential, other tire turns 1.3 times over same distance. For a very short time your differential will slip, thinking you're turning, and allow the tires to turn at separate RPMs, but it will constantly be trying to force both tires to turn at same RPM. Something will give!! Usually it's the differential!

Last week a Subaru driver got a flat tire before work, 45 mile one way commute, went to discount to get repaired, discount couldn't repair tire, guy didn't want to buy all four new tires to replace the bad one( you must replace all four tires at same time on all wheel drive so as to avoid this issue), so discount mounted his donut on passenger rear wheel and guy took off late to work. About 20 miles into commute his rear differential starts on fire, takes 7 miles for other motorists to get his attention, lucky for him, he pulled over and car burned to the ground! Do you think you should run a full size spare? I think if its under 5 miles, might be ok, anything over that and I would think you could do serious damage.

 

If I put it on the front and only used RWD, it wouldn't mess up the front diff? I guess it wouldn't be engaged so shouldn't be a problem, right?

 

Nice sig, btw.

 

Exactly, no problems there with gearing or differentials.

 

Even if you had to use four wheel drive, you would probably be on a surface that would allow the tire to spin before hurting the differential.

 

Just buy a really cheap used tire for your spare. Doesn't have to be full tread or anything.

Matt