As most of you guys know,, I’m not the best mechanic in the world,, but I try to learn.
I had to get a new tire yesterday for the truck.. 275r75-16.. cost was 165 bucks for the tire and all the bells and whistles.
I went and checked out Walmart tires and saw some tires a bit cheaper… I can’t remember the exact same numbers but it was something like 265-r70-16…would it matter too much to have an odd sized tire on a pickup???
I need the spare tire replaced. Just need input.

If its 4wd, all 4 tires should be the same size, otherwise it is going to handle really poorly in 4wd. If its 2wd, you could get away with different sizes front and rear, but should be the same side to side.
If its auto 4wd, its going to really handle poorly, as the wheel speed (hub) is what is monitored by the computer, and you'll have different speeds with different tires.
Any change in tire size will also affect your speedometer.

Odd size tire can be hard on transfer case. If on rear it’s hard on diff. It’s worth having right size spare in case your stuck driving it for a while. Imo

https://tiresize.com/comparison/

I found some tires that were 10 or 12mm narrower but otherwise the same circumference as factory , same weight range, for my and my sons trucks both take the same tires we have f150s 2 years apart in age we both did all 4 tires as both are 4wd

we don't mud but we do snow and narrower tires tend to track better in snow not that they are very much narrower but it cut I think around 70 dollars a tire off off the factory width.

otherwise , what k snow said

Any tire that will hold air is better than none, but if you are buying a spare, get it the same circumference (height) as the others on the truck. If it is a different width, it is no big deal. In fact a lot of guys who have Jeeps, Broncos or other four wheel drive Suvs that have the spare mounted on a carrier on the back, when they put oversized tires on their rig, they will buy a spare that is the same circumference but narrower, to cut down on weight and space taken up on those carriers (some won't fit a wider tire).

Actual measured circumference between different brands/models of tires with the same official size designation can vary quite a bit, but they still should be close enough to run fine as a spare, just keep that in mind if you are pushing the boundaries of what will fit in the wheel well in your truck, or if you are trying to fit tire chains on it.

265 is your tire width in mm. 75 is the aspect ratio of sidewall height to width. The 16 should be where there R is. It's your rim diameter. And as others have posted you better make sure it's the same height.

If you think your feet are the same size, would you wear one shoe a size larger than the other?

My question is where are you finding truck tires for $165 let alone mounted?

I'm assuming they are not LT rated tires, but P rated tires.

Neal tire

You missed it lol.
I had 6 spares for the last GM.
All same size. I think there are
still couple rims left.
A side benefit of buying parts trucks.

Now looking for 79 or older.

I got some 10 ply for that price in Jan 2025 165 each mounted and balanced 4 of them came to 660 and change

I just put four new 10 ply tires on my diesel for 165 apiece a week ago. And those are 17s which are generally more expensive than 16s. That was from Walmart. They are the slowest place on earth but their tire prices are good. I've ordered tires online for years, the prices are way better, but places have gotten to charging so much for mounting and balancing that I have been going through Walmart the last year or two.