Compact Spare for Two Eco

The spare fills some of the void, but it will behave differently in a collision. The foam will be better at absorbing and dissipating the crash energy than a steel wheel designed to support a thousand pounds.

For the most likely, low speed impact, I don't think the change will mean much. The difference in cabin noise will be the bigger change. But I think people should consider all the angles before doing a mod.

 

Well, it wasn't convenient for their survival.

 

That would be "dynamat", not dynamite. The latter would make crash ratings much poorer. The dynamat will also help with minor shock absorption, ie - rattles. It's expensive, but it does work.
I suspect a full size wheel/tyre would not fit as the tyre is much larger than the compact spare the well is designed for. But it might fit if deflated. After all, the car does come with a compressor when there is no spare.

For crash "rating" or energy absorption, you do need to ensure the spare, compact or otherwise, is properly fastened down. I suspect to get the "factory" absorption, you would need the foam pieces the cars with a spare come with. Be sure you're sitting down when you ask the parts guy how much.

 

Here I thought I wasn't getting the joke.

Bet you could just make your own with some cardboard barriers and spray foam. maybe even make some nooks in it for the jack and what not.

 

From the photos in post #1, there is an anchor point to fasten the spare so I don't see much problem in securing the spare. Also, I don't see anything about the well that suggests that that full size tires would also sit properly within the well.

From post #13, the top of the foam is about 6" above the bottom of the well and 4" below door opening. My 15" 195/65's are about 8" wide inflated and loaded (about 8mm wider than the nominal 195mm so if the floor panel(s) are 1" thick but sit a bit below the opening, the tires should fit OK. I'm not sure of the actual inflated width of 17" 215's but they might be a bit too tight or might just fit if the floor panel is thin enough where it sits on the tire.

 

i can't wait to find out.

 

The spare itself is bolted to the floor, so the foam is just along for the ride I think. On the third gen the jack pieces and wrench clip and bunjee to a plastic piece, which acts like a big washer, is captured by that bolt component.

 

it's one thing to say the foam or spare was there for the crash test. it's another to show the crash test without them.

 

Did NOT catch on about that, just figured bisco had a reason.

 

never.

 

Hmm. I'm having second thought now before i commit myself to do this mod, safety and noise will be the top of my list. I'll stick with tire plug kit, air pump + AAA towing service for now.

 

Trollbait's comments about possible unintended consequences are well worth thinking about but that does not necessarily mean that there are significant problems that can't be mitigated while still retaining the benefits of a spare.

Discussing safety first.

• If the foam is discarded and a compact spare is installed (or left in place), the configuration will be similar to that in a Gen 3 and it would not be surprising if the degree of protection was similar to the Gen 3.
  • If a full size 195/65/15 spare replaces the compact spare, protection will probably be better due to the greater deflection and energy absorption provided by the larger volume tire at lower pressure.
• If foam is added around the spare (as in Gen 4's with compact spare), the effect of the foam may be better protection, may be worse protection or may depend on the nature of the impact.
• It seems to me that the main benefit in leaving the arrangement it as it is, is that it's presumably been tested for some defined protocols for some kinds of accidents. It's a lot less clear to me that it will lead to significantly better outcomes in all kinds of rear end accidents.
• The thought that my Gen 3 does not have the space under the rear floor filled with foam does not keep me awake at nights

Discussing sound.

• The foam will help reduce resonances in the sheetmetal surfaces it is in contact with.
• Unless it is mass loaded (heavy), I would expect that the foam will block relatively little of the sound passing through it and with the design priority that has been given to weight reduction, its not likely to be mass loaded.
• The foam will absorb some sound but it's presumably closed cell foam and closed cell foam is not particularly good for this purpose.
• Greater sound reduction can quite likely be obtained without sacrificing the spare or the potential storage space around it by lining the well and adjacent space with mass loaded vinyl or similar material. (e.g. Dynamat)

 

I'm sure the OP will agree to let us crash test his car if we ask nicely.

Personally, I wouldn't worry about safety when removing the foam. I'd even consider doing so if the car came with a spare for the extra space to store ice scrapers and windshield shades and such.

What the foam does for road noise may be very little beyond just filling up a hollow space. If the cargo floor is just coroplast, the foam may just be structural support fit. Together, they may be lighter than a floor/lid substantial enough to support cargo with an empty space beneath. They are more likely cheaper.

 

I think the main thing to acquire is that long bolt and washer that the models with temp spare have. Check that there's the threaded hole in the bottom of the temp spare well; it very likely is there.

 

Great work.

After looking at your install, I was wondering why in the world the models that come with the spare have the hatch floor two inches higher, than those without.

The screen shots of owners manual answer my question. It looks like that is so one could stow the roll-up tonneau cover (if your model had one) on top of the donut or fit a full size spare under there.

 

Had a flat on my CMax Energi this afternoon. Removed it to find this on the inside sidewall:





Tire goo ain't gonna' fix that! Glad I had purchased a spare.

 

Did anybody do this for Four Touring?!