Right now I have a space-saver tire for a spare as recommended in the CMC build manual. It is mounted on a 4.5" wheel.
It is 125/70. I don't like that the tire is narrower than the wheel.
Does anyone know if a 155/80 tire would fit as a spare? The diameter would more closely match my regular 175/70 tires.
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I brought two new 135 x 15's mounted on 4.5 chrome 4 bolt VW rims to Carlisle and no one wanted them...great spares ! To answer your question it probably will but you may need to replace the battery with a low profile one to get the tire low enough to shut the hood aka bonnet.
I have the larger gas tank and have thought of cutting the battery box about 2" up from bottom and then lowering it 2-3" to recess the battery further in the nose.
I have a tiny little battery. My current spare rests on the tank and the edge of the battery recess.
I use a 145R15 spare in my trunk (at least that is what I think it says in my picture)...
Looks like Alan's 155 tire would be 1" taller sidewall and 1.6" diameter) and a 155 would be 1.5" taller and +3 in diameter. Using Miata tire size calculator. Suspect you'd want to use an early 4" wheel vs the later 4.5 stock wheel (if height of tire laying down was a issue). If a 155 fits then the tire your running would fit - assuming I used aspect ratio of tires - (most VW tires were 80 stock if not marked).
Tire Size Comparison
Specification Sidewall Radius Diameter Circumference Revs/Mile Difference 125/70-15 3.4in 10.9in 21.9in 68.8in 921 0.0% 135/80-15 4.3in 11.8in 23.5in 73.8in 858 7.4%
155/80-15 4.9in 12.4in 24.8in 77.8in 814 13.1% 165/80-15 5.2in 12.7in 25.4in 79.8in 794 16.0
175/70-15 4.8in 12.3in 24.6in 77.4in 818 12.6
The 175 tire I am running is slightly smaller diameter than the 155 but it is about .79" wider (higher laying down). Because it is higher, I don't think we can say the 175 would fit if the 155 fits.
I already have a 4.5" wheel.
Maybe I will put the 125 in and move it back toward the tank 1.5" so it is centered where the 155 would be. Then check height would be available.
Michael McKelvey posted:Right now I have a space-saver tire for a spare as recommended in the CMC build manual. It is mounted on a 4.5" wheel.
It is 125/70. I don't like that the tire is narrower than the wheel.
Does anyone know if a 155/80 tire would fit as a spare? The diameter would more closely match my regular 175/70 tires.
Michael - My FiberFab(CMC) spare is the same size but I remove it from the trunk for long trips because I need the space for my wife’s wardrobe and a few of my clothes 😂 Anyway, my spare on those trips is AAA, fortunately I haven’t needed it yet!
@IndianBob by same size do you mean 155/80?
Actually, by “same size” as recommended by CMC, I mean a “temporary spare tire.” I guess it’s not the same size as you wrote about. Mine is a Goodyear T115/70D15. But it still takes up too much room for my traveling space needs. So, my wife has so many clothes we also have the suitcase on top of the rear deck rack!😊
I feel you Bob. My wife has a garment bag in the trunk, trunk on the luggage rack, and a duffel in the back seat. I put all my stuff in a garment bag and lay it in the trunk as well.
My only "spare tire" is the one around my middle...... 
Recommend a spare no smaller than the smallest tire that will take its place in the event of a flat. Unless you plan to abandon your flat tire (and wheel) on the shoulder.
135 x 15 on a 4.5 rim fits from the edge of the battery and rests on the tank...i have a piece of carpet between the tire and the gas tank
I figure I could always chuck the flat tire/wheel behind the front seats (in a car with space behind the seats, so this probably doesn't apply to a Spyder) if it won't fit back where I got the spare. I'll make space for a few miles. It doesn't have to live there forever-- it just to go somewhere.
I've got a 3" wide AL drag wheel and a space-save spare. It's pretty ridiculous, but it'd work in a pinch.
Any affect on the diff if a smaller diameter tire spare replaces a rear tire gone flat ?
If you have an open differential, no. IF you have a LSD, perhaps. Either way, I'd get the tire fixed ASAP. This is not meant to be a forever thing. This gets me to the next exit if there's a bad problem.
David Stroud posted:Any affect on the diff if a smaller diameter tire spare replaces a rear tire gone flat ?
Stan Galat posted:If you have an open differential, no. IF you have a LSD, perhaps. Either way, I'd get the tire fixed ASAP. This is not meant to be a forever thing. This gets me to the next exit if there's a bad problem.
As Stan said, a smaller, emergency spare (or space saver) spare with an open differiential will work. You don't want to be driving it this way a long time (the space saver won't take the cornering loads the full size tire on the other side will) so get the tire fixed right away- that's kind of a given. An LSD is designed to have the same size tire on each side; I would think you wouldn't want to run it for even a short time with different diameter tires. The friction plates would be continually moving at different speeds, creating heat. What to do- I'll ask my friend Bruce next time I see him...
@Stan Galat also said- "I've got a 3" wide AL drag wheel and a space-save spare. It's pretty ridiculous, but it'd work in a pinch."
Remember guys, it's for emergencies only; hopefully you never have to use it.
Maybe you would be able to move a front tire to the back and put the space saver on the front.
Michael McKelvey posted:Maybe you would be able to move a front tire to the back and put the space saver on the front.
That's exactly what we did when we bought the Speedster in Boise, Idaho. Tires looked good on purchase but one blew after 300 miles and one more 75 miles later. Spent the long weekend in Spanish Fork and with the good graces of the Big O Tire shop and their loaner we got to learn about the local culture and got up to Park City and Sundance too. They've sure got some weird liquor laws up there though.
I was unsure about possible issues with slightly different diameter tires on the rear end hence my earlier question.
Alan Merklin posted:135 x 15 on a 4.5 rim fits from the edge of the battery and rests on the tank...i have a piece of carpet between the tire and the gas tank
I had a tire/rim of that size in the Speedster for long trips and had a flat aluminum plate standing up aft of the battery tall enough to hold the spare from coming forward but no direct tie down on the spare. Bad move. 100 miles from Carlisle one year we stopped for lunch and came out to start the car and zero happened. Like a dead battery. I looked under the hood and the spare had moved forward somehow enough to dislodge the positive battery cable from the battery post. A quick fix but I felt pretty stupid / careless. Fasten your spare down somehow.
