I have actually been through a bit of blow outs with tires.

i actually was wondering when purchasing a new tire, do you need to replace all 4 ?

or can i purchase a single same size and tread tire.

i'm on a budget and i hate to spend 4-500 dollars on just tires.

I have falken ziex tires 235 40 18 and i was wondering aside from the question above, if i was to put a spare on, would i blow out the differential? or is it safe since all the tire shops i have been to have said putting a different size and tread wear tire will blow out your diff.

 

Depends on how worn the other three tires are. If its the same tire and tread depth then one will be fine. However, you want to avoid having a tire thats taller on one side vs. another.

Matching Tires on Four-Wheel Drive and All-Wheel Drive Vehicles

Measuring Tire Tread Depth with a Coin

 

the 3 tires have uneven wear on the inner wheel wells. On the 4th tire which im looking into is evenly worn on both sides. Will i be experiencing any problems?

 

More than likely. Sounds like the remaining three need replaced due to the uneven wear.

 

The fear about tire sizing is way overblown. What having a tire that is slightly different in size does is induce a bit more wear on the differential. It doesn't "blow the differential".

 

Sounds like you need to get an alignment as the toe seems to be off with negative camber.