Spare tire size and fit.

My driving tires are 275/65R18 but spare is stock 265/70R16. If I have a flat and need to use the spare I am screwed...Can I replace the spare with (any brand) tire the same size on the stock rim as 275/65R16 and still fit under the truck?

 

people can fit 33s under the bed although bending the bracket may be necessary.

in @Hodakaguy build he took his hoist out, drilled two additional holes to move the bracket back by about 2 inches. this allowed him to hoist a 33 without even tugging on it to get it in position

 

You will be fine with the spare tire you have. Pretty much all cars have spares smaller than the normal tires (little donut tires). Also, your differential will be fine if you put it on the rear. Some people will move one of the full size fronts to the rear then put the spare on the front, but the differentials job is to spin the tires at different speeds. I would drive it slow, but it won't hurt it, especially in the short term. I wrecked mine offroad a few weeks ago, ended up driving it home on 245/75r16 on one side and 35x12.50r20 on the others

 

However, at one point I had a 285/75r16 under the bed. there are two little horns that you have to bend or cut off for it to fit, and the rear of the diff could hit the tire on compression.

 

I know the reasons, back diff and front steering.
Will stop by Discount Tire and check the prices. Since I never used the spare, will they give me something for it? Is the original that came with the PRO.
Looking for a like fit without any mods.

 

Some shops will deal, and some wont. The shop next to my place used to, but stopped literally 3 days before I got new shoes. Their argument that is a valid point is: 1 tire does us no good. If you changed out a full set, then yeah, we might have been able to do something. I showed up with 3 good ones, a wrecked 4th, and a mismatched spare. No dice.

Never hurts to ask though.

 

discount doesn't buy tires but I am sure you can find a local shop that will give you a little bit for it

 

May even be able to find one laying around in the same-ish size you may be able to swap straight across.