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Discussion Starter · #1 ·
I'm not a fan of temporary spares. And the fact that on my 2021 WRX the temporary spare can only be used on the rear axle is an additional drawback. I'm looking at buying a fifth standard wheel and mounting a full size spare. The Owner's Manual indicates that a full size wheel and tire will fit in the spare tire compartment, but before I spend the money I would like to know if anyone can confirm this.
 

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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?
 

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Discussion Starter · #3 ·
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).
 

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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.
 

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From the user manual:

1.
Organism Font Number Circle Rectangle


2. (not equipped on MT WRX)
Font Screenshot Number Rectangle Document


3. Specifically called out on STI, will also affect WRX to lesser extent:
Rectangle Font Parallel Number Circle


4. Most importantly:
Font Symmetry Number Document Publication



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.
 
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Discussion Starter · #9 ·
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.
 

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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.
 

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but before I spend the money I would like to know if anyone can confirm this.
It is you who can definitely confirm this. Put a spare on any wheel, and attempt to put that wheel in the spare storage compartment. Then post whether it fits.
 

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I'm not a fan of temporary spares. And the fact that on my 2021 WRX the temporary spare can only be used on the rear axle is an additional drawback. I'm looking at buying a fifth standard wheel and mounting a full size spare. The Owner's Manual indicates that a full size wheel and tire will fit in the spare tire compartment, but before I spend the money I would like to know if anyone can confirm this.
It should be fairly easy to check. The diameter of the wheel well is large enough in almost all cars otherwise you wouldn't be able to carry the normal wheel when you install the spare. Measure tire width with a tape & check whether the well is deep enough. I don't remember whether 235/245 is actual width or a nominal size. You can also confirm diameter while you are there.

For the accord you can buy a pre-cut hard foam sheet that goes around the wheel well. You sacrifice less than 20mm of trunk height but you can get a full size spare & still keep the trunk carpet flat. If nothing is available for the WRX, you can cut it yourself. I think closed cell foam of 70A or harder should work.

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?
This is an interesting point. I understand the logic behind Subaru's recommendation but there's a strange underlying assumption that you have 4 wheels in use & an unused full size spare. 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.

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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.
 
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