In the quest of increasing the space in my front trunk to integrate an oil cooler, I came across this piece of information that I thought was worth sharing.

Mercedes has been using Vredestein Space Master 165-15 collapsible spares on their smaller models like the C230 and the SLK.

After looking at the pictures and comparing them to my 911 space saver on steel wheel, I think they are the exact same tires.

The difference is that it is mounted on a 4.5" alloy wheel, not 5.5" like the Porsche.

So, one though to gain trunk space would be to mount the space saver tire on a ~$100 4.5" Fachs from cip1. Lighter and narrower wheel, win win. The goal would still to have it laying flat for impact absorption, yet probably allowing a lower trunk floor and giving room for the front mounted cooler to vent out.

Now the challenge is finding a place that will want to remove the collapsible Space Master tire and mount it on the Fachs...

Below is the MBZ space saver wheel/tire.

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I believe that the spare needs to be inflated to help with impact absorption.

Removing a space saver tire is very very very..........hard.

Using a Boxster spare might be a good compromise. Narrow wheel, but inflated and correct bolt pattern. It would lower the frunk floor but still give you the crash protection.

I used one in my V8 914 but moved it to the rear trunk.


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Currently have both in hand, 911 5.5" steel rim with space saver and 986/996 skinny spare. I am studying my options as to ways fit a cooler in there yet minimize the body cutting.

Good point Mark that inflated would definitely help more the absorption.

McMark's U shape ducting with flat collapsible spare in between is probably the most elegant option as recently seen in PMB Coatchwerks' orange car, but clearly involving and cutting...

Trying to see what is the simplest way as my fabrication capabilities and my house garage operation are somewhat limited .

Thank you for sharing your thought...

I have a 944 turbo collapsible spare, same as a steel spare but it's aluminum rim.
I haven't seen McMarks U shape ducting, but I was thinking along the same lines. Just remember the area of the exit(s) should be 2X the area of the inlet.

Right! And i believe some later 911 also have alloy 15x5.5 with collapsible but not sure. Looking at the 4.5" Fachs, the offset makes the wheel center protrude a fair amount outward going against my goal of thinning the wheel...

So my current 3 options are:

1- 986/996 spare: 3.5",light, full diameter, inflated.
Below is a mockup with a Mesa style cooler with a fan on top. The trunk floor is lower that the stock one. To achieve that, I would need to cut a ~9x9" opening in the floor though... Inlet would be front plugs.

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2- 911 or alloy collapsible: 5.5", heavier than 986/996, small diameter, requires compressor.
Below is the mockup using a Mercedes Diesel oil cooler, the narrower one, which fits under the arched shelf. This doesn't require any body cutting, just remove front 5 plugs and 2 rear access ports.
As for area, 5 ports = 11.1 sq.in., and 2 outlet opening = 25.1 sq.in., so Ratio is good!
The trunk floor is pretty much at the same position as the stock setup or even a little lower or without angle.

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3- Fachs 4.5" with temporary donut (125/70-15): 4.5" anrrower than 5.5" (but center protruding), light, OD 22", inflated.
Unfortunately, I don't have the wheel setup to validate this option but I think either cooler configuration could be used but there probably wouldn't be any gain in trunk space vs. option2.

So, at the moment for more of a "bolt on" setup, I am leaning towards the collapsible option but I definetly need to either find an alloy collapsible spare, or find someone that can swap the tire, which as mentioned earlier, can be very difficult...

All of these options will require a custom trunk floor that would seal all around to create a plenum. Air path would be pretty turbulent compared to the beautiful work below but that would be my first step.

@Mark Henry :
This is McMark's setup!

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And this is the integration done in PMB's recent build

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When I blew up my space saver it was all lopsided. Tried to find a replacement tire with NO LUCK. Cut the tire off and I plan to mount a traditional tire to the wheel.

Remember, those space-saver tires are over 30 years old. They won't be there when you need them, they are just too old to function.

Go get a Boxster spare. If you have Boxster calipers, the 15 inch space saver spare won't fit anyway.

Right!, they are old.
That is where the Mercedes C230 ones become appealing but they need to be transferred...

I am using 16" Boxster inflated.

Do you have a front mounted oil cooler?

The 986/996 spare that I have is 17" (105/95-17)

and also the windshield washers!

No oil cooler.

On my bug and '67 bus I have 15" rims with T125/15 temporary spares, only thing is they barely stretch fit onto a 4-1/2" rim.
They do have fake 5-bolt Fuchs that are 4-1/2" made for the Bug crowd

That is the setup I had on my Bug 30 years ago!
The 4.5" fake Fuchs from cip1 is exactly what I had in mind with a 125/70-15 for my option 3. Specs for the 125/70-15 tire is for rims 4-4.5"
Picking up a free Honda donut spare today that will allow me to mock up.
My only disappointment in the bug 4.5" fake Fuchs is its offset which makes the center protrude out a lot, going against my goal of thinning down the spare, but this donut would have 22" diameter probably giving enough room for a front mounted cooler while being an inflated tire.

So am I, but no front oil cooler. Direct replacement bolt in and still maintains crash assistance of the original spare. Besides I have 200 mile towing with AAA, if really necessary.
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Beautiful setup

PMB Coachwerks:

http://www.914world.com/bbs2/index.php?sho...p;hl=Coachwerks

Alloy spacesaver mounted in the rear of the car,have 944 air compressor but may just inflate it,I was told it came from a 964 but haven't checked the part number yet.
These wheels are pretty solid and fairly heavy but certainly lighter than the steel version,I had no choice but use the alloy one as it clears my 944T calipers.
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I bought my space savers at different prices over the years. I have a couple of 15-inch ones and when I switched to 16 on my 6, I bought a Mercedes Benz spare in 16 and had the local guy remove it. I sent that one to Eric (PMB) to use for my six mounted on RSR finish on 16x6


Bob BClick to view attachment Click to view attachment