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Why did Subaru give us a spare tire?

41K views 64 replies 22 participants last post by  gregroot198521 
#1 ·
From what I have read mix matching tire sizes and tread patterns can lead to some differential damage so with that being said why did Subaru put a spare tire in the back if using it could lead to some expensive repairs?
 
#2 ·
It may be able to get you out of a bad situation. You can't run them for extended periods of time, but to get you out of a jam they come in handy.
 
#3 ·
as long as the overall diameter of the spare is the same there wouldnt be any issues. plus your not supposed to drive on them long or at fast speeds anyway. width really wouldnt matter. I never looked at my spare but I think it should be the same diameter.
 
#4 ·
Right, the spare is designed to get you back to civilisation.

Once there you're supposed to fix the problem with the full sized wheel and re-fit the full size.

By the way, it's an excellent idea to check the pressure on the spare routinely. I actually inflate mine to the max limit so that even if time passes it'll have enough pressure to get me home.
 
#10 ·
You have obviously never driven through Pittsburgh....here you will see the dinky donut spares on cars for months as if it were an old fashioned fullsize spare.

I am not sure about the spare that came with my rex, but my old CRX had stamped on the spare tire something about under 50mph and 50 mile range.
 
#6 ·
Id never drive around on a spare on any car for a long period of time I just thought that I had read of issues of differential problems b/c all the tires were not properly matched and I figured the spare would fall into that category.
 
#7 ·
The spare is OK to use provided you have also continued using the mains fitted originally with the car. That is, if your original diameter is still present the spare is correct. If you have gone taller/shorter with aftermarket wheels though, the spare will no longer be correct. How incorrect it will be will of course vary.
 
#9 ·
I was actually wondering the same thing recently. Obviously you don't want to drive far on the spare, but I was wondering just how far you could go on a brand new spare with moderately worn tires on the other corners. I guess it is just important to get into the first tire shop possible, or get the car towed (flatbed of course) if you have AAA and time.
 
#18 ·
As a cruel joke.

Given my background and daily interactions, I imagine it being an upper management decision contrary to the expressed opinions of the drive-train engineers. Somewhere there is a Japanese engineer that smirks every time he sees a WRX drive by.

I carry a mini 12 v compressor, fix a flat, and a plug kit. If I can't fix it with that, I'll call a flat bed.
 
#19 ·
Easy. More differential fires = more money Subaru can charge for repairs!

Alright, enough with the conspiracy theories... the diameter of the stock donut should equal the diameter of the stock wheels. As long as there is no radial mismatch, the differential shouldn't be overworked.
 
#20 ·
Well...I ALWAYS call a flatbed. It's a free service included with my insurance payment, so I use it. Like Jeremy, I also carry a small 12v compressor just in case. I don't even carry my spare anymore.

edit: Aren't there stickers you can get that say to only tow with a flatbed? I remember seeing someone have them on their car, I just don't remember where you can get them.
 
#27 ·
Probably a dumb question but since this is my first AWD car I'd figure I would ask:

Say you get a flat and the tire isn't pluggable/fixable. Would I need to change out the other 3 tires with new ones?
 
#28 ·
Depends on the wear on each tire. You don't want to mix 3 very worn tires with a brand new tire. If you absolutely must, make sure that you are rotating the tires regularly.
 
#35 ·
Man you guys exaggerate. Jeez, if you get a flat, use the spare. You're differentials see more abuse every time you turn the wheel.


Speaking of donut spares, when we were young we installed 4 donuts with dirt bike knobbies on my friend's AWD Colt Vista wagon. Holy **** that thing was fun in the snow and dirt/grass hills when they were installed.
 
#37 ·
I used tirerack - ordered a single replacement through them and they shaved it.



I would have agreed until I saw that thread. IIRC three people who had open flames from their rear end on a donut. It is probably something random, and a small sample still, but it gives me pause to recommend to anyone to drive far on the donut. What I would recommend to others might be more conservative than what I might do though. Also most people probably only have 30psi left in their donuts if they have had it long.

The Colt thing sounds outrageously fun.
 
#41 ·
TR's boy should grow up to produce a TV series.

"SH** My Dad Did to Cars"
lol.

You'd be surprised how much water you can pour into a crankcase and the engine will still run.

You'd be surprised how much sand you can dump into the crankcase and the engine will still run.

Running a gas engine on diesel is fun, but only for a short time.

Running a diesel on gas is fun and LOUD, but only for a short time.

Pumping compressed air into a Civic engine while running will eventually burn a hole in the piston from the lean mixture.

Flipping a differential over in a RWD car will allow you to drive really fast in reverse. Just make sure you plug the vent tube.

You have no idea how much **** I've experimented with over the years. :)
 
#46 ·
Correct me if I am wrong but with the New Rex's aren't they open diff's, and the VDC does the traction transfer by means of the brakes?
 
#48 ·
So a spare on a corner isn't going cause the front or rear diff any damage, therefore the big concern would only be towing with anything other than a flatbed, unless your dumb enough to run around drifting and pulling the e-brake.
 
#50 ·
Yeah I knew the older models had a better setup in the sense of the LSD's but wanted to make sure guys with the newer models knew that the spare tire issue prob wouldn't apply to them so they didn't go out and buy a full size spare or trade their cars in becasuse if they got a flat it was going to cost them $3K after they drove home with the spare mounted. Like anything its give and take, they took our LSD's and gave us the ability to run a spare to get home without smoking the diff. I would still rather have the LSD to the VDC though, just my .02
 
#52 ·
Yeah, all functionality being equal, I'd rather replace brake pads than diffs, but it's hung in there just fine for the last 95k miles, and will probably outlast the transmission anyway.
 
#54 ·
thanks for all the replies everyone. Been awhile since Ive been on the site but plan to be more active now. One other question regarding this is that if someone were to get a flat and a spare was put on either front or rear would DCCD controller to transfer the TQ to the opposite end of where the spare is be recommended until you could get to a place to get it replaced or to limp you home? Or would adjusting the DCCD not matter in this situation?
 
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