Compact spare for your Mopar

[471_Magnum]

Here is something I've been toying with on and off over the years.

For those that don't see the value of a functional spare tire, move along. You either don't drive your car much, or never venture to areas where roadside assistance and cell phone service is sparse. Or you just like living dangerously. That's cool. That's your choice. I'm not looking to debate that point here. If on the other hand, you do prefer to have a good spare in the trunk like I do, read on. You might find this interesting.

One of the challenges I've run into after installing aftermarket tires and wheels on my Mopars is having a spare tire that closely matches the rear diameters. This is critical if you have a sure grip differential and don't want to wear out the clutches in short order.

Just mounting the same size tire as the rears on a spare wheel doesn't work. Many of the popular sizes won't fit in the trunk, or function as a front tire. Truck space is at a premium in E-bodies, so even if they do fit, you're left with very little space for anything else. They also can be really freaking heavy, weighing about 60 lbs in some cases.
Another potential issue is brake clearance if you are running larger than stock brakes.

Two of the most popular rear tire sizes are 255-60-15 and 275-60-15 with diameters of 27 and 28 inches respectively. Those are relatively tall tires, and their widths make it impossible for them to fit under the package tray in the trunk storage location.

So the challenge is finding a narrower tire with a similar diameter. There really isn't much out there. Some 70 series tires come close, but the cost of a new tire and hassle of cleaning up a crusty wheel got me looking for other options. That led me to start looking at late model compact/temporary use spares.

While most "donuts" are way too scrawny, a lot of SUVs are now coming equipped with a 155-90-16 as a spare. These measure out just shy of 27 inches in diameter. Perfect relative to the 255, and probably as close as you're going to get to the 275.

The bigger challenge is finding a wheel for it. All of the tires I've found in this size come on a wheel with a ton of positive offset which just won't work. Jeep Cherokees are a good source for the tire (note that some have a 125-90-16), and have the correct bolt pattern, but the wheel has about 3 inches of offset and it contacts the brake drum preventing the wheel from seating on the drum face in some cases. I've actually used one of these spares with wheel spacers, but it's not a very elegant solution. 
Searching for another 16-inch spare with the correct bolt pattern and less offset I found the spares used in Ford Crown Vic, Mercury Marquis and Lincoln Town Car. The later model years of these come with a 16x4 steel or 16x4.5 aluminum spare. These appear to have less than an inch of offset. Tire size is scrawny at 145-80-16 (25 inches), but it's the wheel I'm after. The Town Car is your source for the aluminum, which is what I chose to test.

Anyone who as ever tried to install an OEM Ford wheel on a Mopar knows that the center register is too small in most cases. These spares are no exception. A few minutes with a die grinder takes care of the issue though. Only a couple thousandths need be removed, so I took my time and test fitted frequently.

After getting the wheel to bolt up, I made a trip to my local used tire store with both the Lincoln TC spare and Jeep Cherokee spare. For $10, I had the tire from the latter mounted to the wheel of the former.

What it yields is a compact spare perfect for a Sure Grip equipped Mopar. The aluminum wheel looks pretty trick. The whole thing weighs under 40 lbs, which is a modest ten pound savings over at typical conventional spare. I definitely wish I would have had one of these for the space savings in the trunk of my Challenger on the Power Tour a couple years ago. I'd like to have tested it over the 13 inch Cobra brakes on the Cuda I use to have.

While this spare might a solution to a number of problems, there is one it won't solve. If your 275-60-15 goes flat, after you install your spare, you still have to figure out where to carry that flat tire. It's not going to fit in your spare tire storage location.

I've probably got $70 invested in this exercise. Both the wheels came off Ebay, but a trip to the local salvage yard may have yielded both for less than what I paid.
The Ford "Panther" series cars are the only ones I've found with the needed wheel size, offset and bolt pattern. I think there maybe some obscure Mustang or Thunderbird spares as well.

There are a lot more sources for the tires: Jeep Cherokee's, Honda Pilots, GM S-series pick-ups, and some GM SUVs. I'm sure there are others. Small to midsize SUVs seem to be the best source.

Posted are some pictures showing the examples and results. Standard disclaimers apply. This has only been tested on my 72 Road Runner with factory discs and drums.

[471_Magnum]

More pics...

[Just 6T9 CHGR]

Nice write up & detective work Jim

[bull]

I just looked at the overall diameters of some smaller tires I wanted to match up with 295s in back. 295-50-15 is 26.61" in diameter and 245-60-15 is 26.57" in diameter. Put a 245-60-15 spare in the trunk.

[471_Magnum]

Just hitting the diameter is only part of the equation. I can tell you a 235-70-15 will not fit under the package tray of a 69 Charger without airing it down a bit. Too fat. I'd think a 245 wouldn't fit. Other B-bodies probably have a little more space. E-body guys ought to love this thing.

The other benefits to consider are weight, cost, and brake clearance.

It's at least a 10 lb weight savings, although most of us probably aren't that weight conscious, especially over the rear axle.

It's relatively cheap. You probably can't even get a new conventional tire for 70 bucks. No hassling with cleaning up crusty old steel wheels either.

I'd like to test it on some aftermarket big brake conversions, but obviously it will fit over many brakes that a 14 or 15 inch wheel won't clear.

[jaak]

I have a 2001 S-10 pick up, and it has a 155-90-16 temporary spare on it. In fact the reason I know, I had to use it for the first time the other day since I bought the truck new 11 years ago. So later model S-series pick ups is another source for the tire.

Jason

[thedodgeboys]

I'm packing a late model mustang spare tire in my trunk. They come in a 17 inch wheel for a little more clearance for those running big brakes and are 27 inches tall.

Don't forget to get the late model jack they pack neatly inside the spare tire and work pretty good. I would never use a bumper jack 

But I like that aluminum wheel you posted  

One addition make sure you bring along the correct lug nuts  (open ended) my closed ended ones bottom out on the stud before contacting the wheel. Also the cone shape could be differant than your aftermarket nuts.

Thanks.

[471_Magnum]

I considered the Mustang spares, but they are t155-70-17. That's 25.5", not 27".

The effective roll out on the compact spares is actually less than they might appear if you measure them free hand. The tread really flattens under load.

Good point about the lug nuts.

I always carry a small bottle jack, but a scissor jack would be a batter option in some situations.

[myk]

Don't forget to get the late model jack they pack neatly inside the spare tire and work pretty good. I would never use a bumper jack  

Lol, for years I never understood that a bumper jack was how you jacked up a car "back-in-the-day."  When someone finally explained it I was always saying, "why in God's name would you want to push a car up by it's bumper?!"  

You know what?  I remember throwing out my OEM bumper jack because I didn't know what the hell it was when I first bought the car!  

[471_Magnum]

Had the rear apart tonight swapping gears. Took the opportunity to bolt up the spare for a photo op.

Note the front of the car is on jack stands, so then rear ride height is a little higher than normal.

As it sits on the car, the spare looks just a bit taller than the 255-60-15 it replaced.

[myk]

Thanks for doing the research.  It may not be pretty but it's compact and gets you home!

[472 R/T SE]

The tread really flattens under load.

So how much diameter do you figure when the tires' are compressed?  How close do you need to be for the  Sure Grip?

I've also tossed around carrying an e body space saver.  Question about that.  Are there different height sizes for space saver spares for 14" & 15"?  If not, I guess the factory must not have been too worried about it so why should I?
I have about $1k in a new Sure Grip Power Lok chunk. 

[thedodgeboys]

My question is how many miles can one go safely on 2 differant tire sizes on the rear before damageing the sure grip?

They can't be so weak that 10 or 20 miles to a tire store would kill one,

[Rolling_Thunder]

no real way to say -  think of it as driving with your clutch misadjusted and slipping...     the faster and further you drive the more it wears....    I would say you will immediately start wearing the clutches in the diff...    at what point it causes major issues is anyone's guess.

[471_Magnum]

Just going around a turn wears the clutches. Running one tire low on air pressure wears the clutches.

Key is to minimize the wear. We're talking about 1% difference in roll out instead of 10% or more. As R_T states, what that translates to in terms of LSD life is anyone's guess.

[Neal_J]

GREAT post.  Thanks!~

[1970Moparmann]

Wow, great thread!

[Big Sugar]

Thats a great idea !  Good work. Thanks for sharing, 2karma points for you.


Ron

[bill440rt]

Excellent write up! 
Definitely something to consider as I only have a standard 14" spare in my trunk, it would never fit with the big Wilwood brakes that are on the car.

[Nacho-RT74]

While most “donuts” are way too scrawny, a lot of SUVs are now coming equipped with a 155-90-16 as a spare. These measure out just shy of 27 inches in diameter. Perfect relative to the 255, and probably as close as you’re going to get to the 275.

I have found Calibers and Compass carrying these ones. Being Mopar, bolt pattern should fit, right ? just wondering about the backspace now

[471_Magnum]

I have found Calibers and Compass carrying these ones. Being Mopar, bolt pattern should fit, right ? just wondering about the backspace now

Bolt pattern.... maybe. Back space.... no way.

Grab one for the tire, anyway, then go find a Town Car, or Crown Vic for the wheel.