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OB 2011 3.6R Limited with NAV
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Discussion Starter #1
I have full size spare tire in my OB trunk and I am going to Arizona from Canada next week towing a small camper in the winter.
So, I was thinking about leaving behind the donut spare tire.
However, it occurred to me that this donut tire might play some additional role in the overall safety of the car by design. I read about the crumple zones built in into the modern cars and I wonder whether the spare donut tire (with considerable amount of rubber on the steel rim) play any role in the overall safety of the car structure by its ability to absorb extra energy on impact?
Should I leave behind the donut spare tire?
Thanks.
 

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2012 Silver Outback Premium 2.5 CVT
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175 Posts
You would have to think not, as I wouldn't think they would want the car to become less safe after you got a flat. Right?
 

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2005 3.0 R n totaled
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7,529 Posts
As far as I know "no". More and more car manufacturers offer brand new cars without a spare tire - or, only as an option. They are all trying to cut down on weight and improve the mileage.
 

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2012 Outback 2.5i CVT
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468 Posts
As far as I know "no". More and more car manufacturers offer brand new cars without a spare tire - or, only as an option. They are all trying to cut down on weight and improve the mileage.
Yes but those cars are designed and crash tested without a spare tire in the trunk. In contrast, the Outback and any other vehicle with a spare tire would have been designed and tested with the spare on-board. I never really thought about this but jackw49 may be on to something. These tires are stored at bumper level and would likely be crushed during a rear end impact. That crushing requires energy which is good because that means it won't be available as kinetic energy to cause harm to the occupants. The more I think about this the more I have to think that not including the spare tire would change crash results.
 

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2005 3.0 R n totaled
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Yes but those cars are designed and crash tested without a spare tire in the trunk. In contrast, the Outback and any other vehicle with a spare tire would have been designed and tested with the spare on-board. I never really thought about this but jackw49 may be on to something. These tires are stored at bumper level and would likely be crushed during a rear end impact. That crushing requires energy which is good because that means it won't be available as kinetic energy to cause harm to the occupants. The more I think about this the more I have to think that not including the spare tire would change crash results.
How do you know how OB was crash tested? I kind of agree with you but being a trend to sell cars without spare tires nowadays, I would think Subaru crash tested them with and without spare tires. Also, if he is going to tow a small camper that would be an extra crash safety zone.
 

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2012 Outback 2.5i CVT
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468 Posts
How do you know how OB was crash tested? I kind of agree with you but being a trend to sell cars without spare tires nowadays, I would think Subaru crash tested them with and without spare tires. Also, if he is going to tow a small camper that would be an extra crash safety zone.
A coworker of mine worked for Chrysler conducting crash tests on cars until a couple years ago (he was laid off). They do the absolute minimum required by law and the car must only be in the configuration sold. If Subaru sells it with a spare tire under the truck that's how it is tested.
 

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2010 2.5i Outback, 2015 2.5i Legacy w/Eyesight
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These tires are stored at bumper level and would likely be crushed during a rear end impact. That crushing requires energy which is good because that means it won't be available as kinetic energy to cause harm to the occupants. The more I think about this the more I have to think that not including the spare tire would change crash results.
While it may change the results, I would hope it is a negligible if the engineers did their jobs right. Also remember that the tire is flexible, but the rim is not and after a certain amount of crumple it could be a rigid body in part of a crumple zone which is the opposite of what is desired there. I have not studied the crumple zones of my vehicle at any length apart from the knowledge that our engines are supposed to partially drop out of the way in the event of a front-end collision. Given that, I would think they would try to design the crumple zone so the spare tends to move a little up/down and out of the way as well rather than having full lateral travel as part of the crumple zone so that it is more-so removed as a variable.
 

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'08 Veracruz Limited
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I'd think it would be safer without the spare, especially if it's interior mounted. One less thing to be pushed/propelled forward into the passenger space. It is certainly not designed into the "crumple zone". If it were, it would be mounted a lot more securely than a bolt with a plastic wingnut to hold it down.

Under mounted spares are probably less of a concern, although their proximity to the fuel tank could mean that you're safer without a spare under the vehicle, too.
 

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03 H6 OBW & 06 WRX Sportwagon
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they have no idea if you're hauling dogs in the back or a 12 cylinder engine block either.

It isn't worth worrying about one way or the other. I suspect they test the cars in an 'as delivered' configuration for NHTSA but, so what? they have no idea how the car will be used and couldn't be expected to do extensive testing with any weird deviations from the 'as delivered' condition. With/without spare MAY be something they test - but, wouldn't most people put the flat in the wheel well? even if the cover didn't quite fit flat?

I wouldn't lose any sleep over it one way or the other.
 

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2013 Outback 2.5i Premium
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Yes but those cars are designed and crash tested without a spare tire in the trunk. In contrast, the Outback and any other vehicle with a spare tire would have been designed and tested with the spare on-board. I never really thought about this but jackw49 may be on to something. These tires are stored at bumper level and would likely be crushed during a rear end impact. That crushing requires energy which is good because that means it won't be available as kinetic energy to cause harm to the occupants. The more I think about this the more I have to think that not including the spare tire would change crash results.
I have my doubts about that. I know for fact that some European car manufacturers sell the identical vehicle (no technical or structural differences) in Europe without a spare tire, and with a spare tire in the US!
 

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2012 Outback 2.5i CVT
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I have my doubts about that. I know for fact that some European car manufacturers sell the identical vehicle (no technical or structural differences) in Europe without a spare tire, and with a spare tire in the US!
Crash tests are different in Europe and the US. If a manufacturer wants to sell a car in the US it must pass all crash tests required by the US government. That means if the car has a spare tire in the back when sold in the US it must be in the vehicle during the crash testing. I am not saying the car isn't just as capable with and without the spare tire in the back, it probably doesn't make a ton of difference. To be honest the tire is located low and likely just pushes down and out of the way as it's sitting on and bolted to a think sheet metal floor. All depends on angle, how the car is it, and what's around the tire. Too many unknowns to figure out if it makes a difference on the Outback.

To the OP, just don't worry about it and go on your trip. Enjoy.
 

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2011 OB 2.5i Prem CVT HK/AWP, Ruby Red Pearl
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I’ve done mechanical design prototyping and destructive testing. Any engineer worth his license would test worst case scenario, with user laying the flat on the floor deck (unfastened in the well), and getting rear ended. I’d expect no less from a $B company.
That spare well appears to slide/crumple under the gas tank in a (pre-determined std) crash.
 

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03 H6 OBW & 06 WRX Sportwagon
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given the trailer and perhaps the other load involved, I doubt leaving that donut spare behind will save enough $ in fuel to buy a combo meal at Subway.

Some people report being able to place a deflated full-size spare in the well on some soobs. But you must carry a 12V compressor or other means to properly inflate it in an emergency.
 

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OB 2011 3.6R Limited with NAV
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Discussion Starter #15
given the trailer and perhaps the other load involved, I doubt leaving that donut spare behind will save enough $ in fuel to buy a combo meal at Subway.

Some people report being able to place a deflated full-size spare in the well on some soobs. But you must carry a 12V compressor or other means to properly inflate it in an emergency.
My rationale is to regain the storage space as I carry full size spare in the trunk. The donuts spare well could be used for storing tools,extra oil and infrequently used items.

I like to keep my camper uncluttered and with daily necessities only and my car is the storage so idea of the spare tire well storage is appealing to me.
 

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If your towing a trailer the rear crumple zone is your trailer ;-)

I do recall reading some place a few years back that pretty much all auto makers factor in the spare tire as playing some level of crush zone energy absorbing effect.

From experience I would say if your filling every little nook and cranny including the spare tire well up with stuff - then adding a trailer - your probably pushing it on weight and not to mention if your hauling that sort of weight a fair distance you have a higher probability that a spare tire will be a good thing to have.

We have so much camping crap after years and years of collecting it there is some stuff that gets left home. If I were still doing the solo camping thing or heck if I and my Son were just going camping we could get away with a smaller car than the OB.
 

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OB 2011 3.6R Limited with NAV
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Discussion Starter #17
If your towing a trailer the rear crumple zone is your trailer ;-)

I do recall reading some place a few years back that pretty much all auto makers factor in the spare tire as playing some level of crush zone energy absorbing effect.

From experience I would say if your filling every little nook and cranny including the spare tire well up with stuff - then adding a trailer - your probably pushing it on weight and not to mention if your hauling that sort of weight a fair distance you have a higher probability that a spare tire will be a good thing to have.

We have so much camping crap after years and years of collecting it there is some stuff that gets left home. If I were still doing the solo camping thing or heck if I and my Son were just going camping we could get away with a smaller car than the OB.
I read somewhere on this forum that you need to have full size spare while towing. So I bought and carry one. Using the donut tire while towing is supposedly dangerous and very unwise. So I wonder whether to leave the donut tire behind as I will be towing. I do not have any problem with space at all (very minimalistic approach really in terms of stuff that I take for two months trips) and having tire well as a hidden storage is simply a nice way of optimizing and organizing space for such long trip.

Let's put my question this way: If I can't use the donut tire while towing my camper why to have it in the tire well?
Of course if the donut tire plays some role as part of the crumble zone as you imply (and I will drive a bit with just OB leaving my camper on the campgrounds) then I have to keep it in the well.
 

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I read somewhere on this forum that you need to have full size spare while towing. So I bought and carry one. Using the donut tire while towing is supposedly dangerous and very unwise. So I wonder whether to leave the donut tire behind as I will be towing. I do not have any problem with space at all (very minimalistic approach really in terms of stuff that I take for two months trips) and having tire well as a hidden storage is simply a nice way of optimizing and organizing space for such long trip.

Let's put my question this way: If I can't use the donut tire while towing my camper why to have it in the tire well?
Of course if the donut tire plays some role as part of the crumble zone as you imply (and I will drive a bit with just OB leaving my camper on the campgrounds) then I have to keep it in the well.
^ even with the full size spare for the car on a tire bracket mounted to the trailer - it makes no sense to leave the mini tire at home. Leave it in the trunk if you need it its there. No good reason to take it out of the car unless your doing Drag Strip nights at the local Drag strip which case your doing it with the wrong car to start with.. LOL


I suspect the reason for that suggestion is that the donut tire is not ideal for towing with if you were to use it. The tires have nothing to do with the towing capability of the car except when the donut is actually on the car with said trailer behind it.

Which either way if your on a long road trip the mini tire is only intended to be used to get to the nearest tire shop not to finish your trip on. Most people who drive long distances and on rough roads tend to pack a full size spare anyway trailer or no trailer. If you want more trunk space buy a cheap spare tire bracket and put your full size spare on the trailer which case you should have a full size spare tire for the trailer and full hub with bearings for the trailer also if your going to the effort to have a full size spare for the car.
 

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2020 Touring Onyx XT; 2014 Tribeca
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it's a better place than my 83 GL. The spare was sitting on top of the engine under the hood and was part of the crumple zone.
 

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2001 OB Limited 2.5 Auto
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It is taught in the autobody field that the spare tire is a part of the structure of the vehicle. One reason why the tire is "temporary only"
 
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