Replace Only 1 Tire? / Spare Tire Question

[chermo12]

Hi guys,

I recently blew out my rear passenger tire, which needs to be replaced.

1) Is it okay to replace 1 tire with a brand new one (exact same tire)? My current tires have about 6000km (3700miles) Still pretty good tread life. Will this have an affect on the rwd if one side has slightly different treadwear? New vs Used.

2) Also, I just realized the manual says to put the spare tire on the front wheels. However, roadside assistance installed it on the rear. Will this ruin anything?
(I'm not driving regularly. Only drove it 20min to the tire shop to check out my flat)

Update: My old tire has 8/32 and the new one is 10/32. Is the 2/32 difference good safe enough to run? If so, better to leave the new one on the rear or rotate to the front?

Thanks!

[churchx]

6K miles/light tire wear .. hmm, i'd probably would get just one. And put pair with one replaced on front. At 10+K miles or middle tire wear i'd replace pair, for grip to not differ much between sides.

Spare on front wheels? Sounds like it's not full size spare wheel like in AUDM, but space saver skinny spare wheel? Advise from manual is with reasoning to have as similar as possible wheels on cars where there is LSD diff, or it puts heavy load on it with different outer diameter wheels (even if slightly). Maybe roadside assistance didn't knew if your car has or hasn't LSD, or simply were lazy with doubled work with changing also with front wheels.
Hmm, on second thought, if you changed with space saver wheel (guessing from notion in manual of spare->front), then shouldn't you still have your blown tire? It was flat or really blew with significant damage to it? In first case, and if it seems repairable, i'd take it to the tire repair shop instead of buying one tire for replacement. Should be cheapest option, and no problems with different threads. But then again, if you called roadside assistance for putting on spare donut, then maybe your car is one with tire repair kit instead of space saver wheel or full size spare wheel, i've heard, many tire repair shops refuse to fix/deal with fixing tires 'repaired' with those kits.

[mav1178]

1) not a huge difference but you should rotate them more often to even out wear or just run them in the front.

2) don't run different sizes on the rear for anything other than emergency use. It puts unnecessary wear into the diff and can prematurely damage it. A friend blew up his stock diff at the track over the weekend from too much heat in back-to-back sessions, you'd probably be able to do the same with 15-20 minutes of driving with mismatched wheels in the rear.

-alex

[churchx]

By just 15-20 minutes? Didn't know it's that easy to damage even with slower/more careful driving within speed limits and distance driven of space saver tires. But then again this is my first car with LSD diff on it, so no first hand experience how badly/quickly mismatch can damage not open diff.

[NyC Zn6]

I would personally would purchase two new tires for the rear and keep the other as a spare.