I've always wondered why space savers always come with warnings not to drive on them more than 50mph or further than 50 miles. I mean, what technical reason.
I never saw anyone driving around on four of them but I bet it would be good for mpg. If not handling.
Outside diameter of the tire is often different, which is definitely bad for the differential.
Really, though, the main reason it says not to drive them far is that they are not designed for general purpose driving. They are narrow, low profile, high pressure, low capacity, with tread that is not designed for great traction or long life. They were designed to be inexpensive, lightweight, and compact; and to get those qualities, they compromised other abilities.
I'd like to use a couple for my boat trailer, which was homemade (by someone else) and carries very little weight on currently huge tires, too high for easy loading of the boat. I can't seem to figure out my bolt circle correctly; I though I measured and calculated it perfectly but the wheel I bought didn't fit right.
There's a bit of a minefield in bolt circles in that there's 3 sizes that are very close, the old imperial 5x4.5 inch, then there's also 114.5mm and 115m, and then it depends how they are meant to fit on. There's hubcentric wheels which fit close to the hub and the stud holes tend to be a little oversize and you can use flat lugnuts, then there's the stud centric ones where there's lots of clearance around the hub, but the stud holes fit closer and are dished and you need conical bottomed lug nuts to center them properly.
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice
I'm unaware of any distance limitation on these temporary tires. There is a speed limitation to limit the possibilities of weird handling characteristics and grip during turns creating accidents, but I've never seen total distance limits.
Oh, there is the expected 'replace as soon as possible with a real tire' advice, but the temporary spare can be thrown into the trunk for the next use.
These aren't good mpg tires. I did some roll-down distances tests with a set of four while preparing for the 2005 Tour de Sol event. Four 185-60-14 Michelins at their max of 32 psi coasted further from a standstill on a slope than did 4 T-105-70-15 Continentals at 60 psi. Needless to say I kept one for a spare and left the other temp tires home.
I have heard that the "doughnut" tires as I have heard them referred to should only be traveled on 50 miles at no more than 50 MPH. this may be an urban myth or just something that has been passed down and been added to as it has been passed down.
one idea (just an idea) maybe it is a limited trip amount. maybe it can't take the heat of traveling that fast for that long. I do agree that it is strange to have a range limit on a tire and I wouldn't throw the tire away after only 50 miles. it makes more sense if it were limited in a single trip how far it can go.
at the same time, I can't recall ever seeing it on the tire anywhere where it said the range limit so maybe it is just urban myth. it does say max speed and temporary tire.
crap...now I gotta check my spare.
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It's a pretty tough situation. The axle is a front axle from a RWD vehicle of some sort, but I can't identify it.
I thought it was 5x4.5, but I got a compact spare from a vehicle with that size at a junkyard (for a highway robbery price of $60, because I lost a wheel on the highway 100 miles from home and they were about to close) and it didn't fit right. I had already done the bolt circle measurements/research beforehand or else I would have had to try to bring the other wheel and Cinderella it.
I got lucky with the hub, anyway; the wheel fit that properly, IIRC.
Here it is with the wobbly wheel:
Here's a pic of the axle:
And here's where insult was added to injury. No, wait, injury was added to injury...
I was driving home from a "Man's weekend" getaway when the wheel fell off on the highway. I drove up and down the shoulders for a half hour trying to find it and then gave up. I found a junkyard that was open and got screwed buying that compact spare, then bought some bolts and lug nuts. I got down to it and the nuts didn't fit the bolts, and two trips later I finally had what I needed. I mounted it and the bolts didn't line up even though I had brought a piece of cardboard on which I drew a template and compared to the wheel...
I got it home driving backroads slowly with the wheel all wobbly at like 1:00 am. I parked on the back lawn and left it to deal with the next day. So, I woke up and went out to park it properly, and as I was backing up I jacknifed and broke the tongue too.