[zax]

This is not a good idea.

It is not appropriate to replace a single tire on an AWD vehicle under any circumstance. If the goal is to just limp the car to a shop to have the tire immediately replaced, what's the value in a full-sized spare?

 

[zax]

I don't intend to leave the full size spare on the car. If I don't get the flat tire repaired or replaced I'm without a spare for the next incident. I prefer a full size spare because I drive long distances and don't need the hassle of the temporary spare restrictions when I'm ~100 miles from the nearest repair facility. I also don't need the hassle of changing two tires to fix one flat when the flat is on the front (see original post).

The full-size spare will carry the same restrictions.

You cannot operate the vehicle at full speed for any distance unless you like to replace differentials when they fail.

 

[zax]

From the user manual:

1.

2. (not equipped on MT WRX)

3. Specifically called out on STI, will also affect WRX to lesser extent:

4. Most importantly:

I appreciate and expect that you want to cross-check our work, but please understand that those of us who have been in this community the longest have accumulated a lot of knowledge on these platforms. Running one tire whose wear does not match the others will trigger a DCCD warning on the STI (don't ask me how I know this) and will damage the WRX's less advanced differential. If you absolutely insist on ignoring my warnings (and by extension Subaru's warnings), have the full-sized spare shaved to 50% tread depth to minimize potential mechanical distress.

 

[zax]

The warnings are contradictory. The temporary spare is already smaller than the full size tires. And you can't drive any car any appreciable distance and get identical wear on all four tires.

Good luck.

 

[zax]

If we do a 5 wheel tire rotation every 2000miles, all the tires should have roughly equal wear. Most people I know from my parent's generation & older have always done 5 wheel rotations & I've never heard of issues with 4x4 systems or LSDs.

A 5 wheel rotation would indeed resolve the concern with the added inconvenience factor.