Replacement for factory Mini-spare tire (AKA Donut)

[DPDISXR4Ti]

The rubber on most of the original spare tires has reached the end of their useful life. Even if it looks okay, it's probably not and will likely shred if you actually have to use it one day. If you've already replaced the tire, great, you're all set. But a better alternative might be picking up a larger spare from a newer junked car that also has a 5x112 bolt pattern. I'm targeting a 16" wheel as I recently discovered that my recently completed rear brake upgrade won't clear the factory spare. Too bad, as I like the fact that it's Aluminum.

VW seemed like a good choice since the Passat has a 16" spare, but the center hub would need to be opened up from 57.1mm to 63.4mm. Mercedes seems to be the better choice since there are 16" spares and it owns a center hub size of 66.6mm so it will clear our 63.4mm hub. For a spare I won't bother getting a hub spacer - I'll just let the lugs do the temporary job of carrying the load. Speaking of the lugs, Mercedes does use 14mm, so the holes will be a little over-sized, but again, for a temporary spare the 12mm lug nuts will have ample contact.

So in short, 16" Mercedes spare is on my junkyard shopping list. The only question is whether it will fit in the cavity in the Scorpio trunk. Anyone tried this yet?

[Ed Lijewski]

A few months after coming out of a Home Depot I saw the right front tire on my '89 flat. I removed the spare and found it was low on air although several months earlier after I acquired the car I had added air to it after checking its pressure. Fortunately a gas station was adjacent to the HD with a coin-op tire inflator, however the station had no change for my dollar bill's so the 2-3 quarters in my pocket had to suffice. Unfortunately the pump did not have an air gauge and the crew in the repair bay said they didn't as well. I had one quarter left, but apprehensive about over inflating the little round bastard I did the poke/feel/bounce appraisal of it and judged it might be okay to make the return to home trip of 7-miles or so.

A few miles towards home I checked at a gas station with open repair bays if anyone could repair a flat (find the cause first, of course). I was lucky that the mechanic on duty wasn't busy and checked the tire out and found a nail it, plugged it the tradional way, filled it with air and mounted it on the car, all for $20.

Then he said before checking with a gauge the donut spare was underinflated. I told him my story about inflating it, and he asked me to guess its PSI which I thought might be 80 or 90. He said wrong, checked it to be 55/60-ish which was his estimate, then inflated it to 90 or whatever was recommended on the donut itself, and put it in the car's trunk.

I don't have great fear about using that spare again if necessary. It hasn't been exposed to heat, UV rays, or use other than described above.

Re 30 y/o rubber all being inches from the dump, note how supple and resilient the two intake hoses are; I'm in awe each time I remove them for access to maintenace or repair on some nearby area.

Just to blow your mind, the Michelin top line tires on my '89 were manufactured in March 1995. They have almost all of the original tread depth remaining and unscuffed sidewalls. The car was garaged a lot by the original owner. I've thought often maybe I should replace them, but after a few thousand miles of my ownership with only the nail in the tread that caused the slow leaking and then the flat described above I decided to roll with them further for now.

YMMV

[brokencase]

I keep a tire plug kit in my vehicles... Along with either a 12v air pump or a can of fix-a-flat.

I never had to use them on my vehicles, but I have used them on coworker's vehicles many times.

The Sprite is a special case. Wire wheels and inner tubes. The spare is the only option and I always top off the air in the spare before any long haul.

For a while the "EECIV Chief" was driving around on worn tires on his F-150. I must have plugged those tires about five times before he finally ante'd up an put on a new set of All Terrains!

[Ed Lijewski]

I always carry new/unopened cans of Fix-a-Flat in each car.

In my post above re the flat at Home Depot, I injected a shot if F-a-F into that tire a few days earlier. Then on finding the tire flat at HD I put the rest of the can, probably 4/5ths at least, into the tire. But, it all came out of the tire somewhere.

YMMV

[DPDISXR4Ti]

I've somehow got four of the factory spares - they worked great when painting the car to provide good access and easy rolling of the car in and out of the garage. One seems to be okay (tire might have been replaced), one slowly leaks around the rim and will only hold air for maybe two weeks, and the other two have pretty much self-destructed - one gradually, the other suddenly (bang!).

[DPDISXR4Ti]

I came home the other day with a mini-spare from a 2006 Mercedes C-class sedan. The bolt pattern matches and the center hub clears as expected. The problem is that the tire has a really tall 90-series profile. It might clear okay in the wheel-well - haven't even tried it yet - but it definitely doesn't fit into the spare wheel well in the trunk. All is not lost though, as I happened to have a 115/70R16 spare in my XR (Saab 9000 spare), and a test fit of that finds it just barely fitting.

So what you could do is replace the 125/90R16 tire on the Mercedes wheel with a 115/70R16 tire. I did a quick study and found several modern vehicles that could donate the requisite spare tire (only) which could then be mounted onto the Mercedes rim...

1999 - 2008 Saab 9-5
1999 - 2002 Saab 9-3
2012 - 2017 Chevrolet Sonic
2012 - 2017 Buick Verano
2011 - 2020 Chevrolet Cruze
2000 - 2005 Saturn L Series
2006 - 2011 Mazda 6
2004 - 2013 Mazda 3
2006 - 2015 Mazda MX5 Miata
2002 - 2006 Acura RSX

Edit footnote... Some of the above are actually 125/70R16 tires -specifically, the one from the Mazda 3. I figured for $10 I'd try it, and it definitely does NOT fit.

[DPDISXR4Ti]

Fits fine as is as long as you don't mind the fact that it doesn't fit into the spare wheel well. I'll probably grab another spare with a from the list above with a 115/70R16 tire and swap it onto this rim.

P1017215.JPG (1.09 MiB) Viewed 5833 times

[Bob Weir]

I often thought about the tire well & removing the floor supports, especially the forward one. This would allow using a full size spare.

[my8950]

Not on a Scorpio, but XR. Last year before Carlisle I was prepping to put everything but the kitchen sink in my car to make the journey, I checked the spares I had, all of which were about flat. When I put air, they all had a rim leak, due the where the bead of the tire mounts being rusted. I removed the tire and tried cleaning and painting the rim, no go...I ended up stuffing a full size as a spare just in case.

[brokencase]

Out of curiosity I took a peak at my spare yesterday. I had not gazed on it since I purchased the car in late 2015.

Looks original. Holding air no problem. No dry rot apparent. It only had 20 psi in it so I filled it up to 60psi.

I'm going to guess that the spare was used once before previously. It still has the mold protuberances on the sidewall, but only a few on the tread, as though it had been ridden on a very short distance.

BTW my8950 - The Scorpio spare rim is aluminum so rust on the bead is not an issue.

[DPDISXR4Ti]

Looks original. Holding air no problem. No dry rot apparent. It only had 20 psi in it so I filled it up to 60psi.

I had one like that. Looked totally fine, but low on pressure so I also topped it up. A few days later it looked like shredded wheat.

Just sharing my experience.

[Ed Lijewski]

Aluminum corrodes. So the inside wheel rim of a deflated spare in the dank wheel well clearly can corrode resulting in poor or failed bead sealing surface.

YMMV

[brokencase]

Looks original. Holding air no problem. No dry rot apparent. It only had 20 psi in it so I filled it up to 60psi.

I had one like that. Looked totally fine, but low on pressure so I also topped it up. A few days later it looked like shredded wheat.

Just sharing my experience.

So you're gonna force me to go check the tire again...I get it. Its a reasonable assumption.

Well I did check it and it still looks OK.

The phenom you describe happens quite often with bike tires... and they don't have to be old for it to happen. Bike sits over winter and then you go to inflate in the spring and you get all the little splits. It is not such a big deal on bike tires because they have inner tubes. Generally you can ride them until tread wears to carcass. But the littles splits do open up the chances of getting a flat.

Moral of the story is to keep pressure topped off.

[eaton53]

Aluminum corrodes. So the inside wheel rim of a deflated spare in the dank wheel well clearly can corrode resulting in poor or failed bead sealing surface.

YMMV

My '77 BMW 320is had this problem.
Guaranteed flat tire if it sat for an extended period during wintertime.
Had to have all of the perfectly good tires dismounted and the wheels cleaned up.

[andyofcolumbusmerkur]

It can be hard to find good rim sealant. I used that non-hardening permatex red gasket sealant on mower wheels and tires. Xtra-seal or Napa sealer bead sealer part number BK 7101204 is ok. I've seen the discount tire places using just dish soap. Not to mention an ancient air compressor with who knows how much water inside the tank. The best option would be something like Napa no rust rim repair part number BK 7100021. Then fill the tire with an air hose that has a water trap inline. Or even Nitrogen.