Space saver wheels
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. |
I don't know this as fact but I have always heard that they are too skinny and can't take the Gs in turning at high speeds.
my metro has 155mm wide tires on it. I think the spare was 105. big difference in footprint. not a lot of rubber on the road. |
Isn't it related to their size?
They are of a very different diameter than the regular tire, so having odd sizes must destroy the differential on the car. Using smaller diameter tires means higher engine RPMs for a given speed, so why would you expect better MPGs unless you tweak the gear ratios? |
in my metro my regular tires were 12" rims where the spare was a 13". I think the spare was actually larger in overall diameter.
the spare is smaller on larger vehicles and this may just be something weird that chevy did on the metro. |
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. :( |
I would think that you could get some pretty small trailer tires that would fit it. you did say it was home-made which may throw a monkey wrence in my idea.
check out sumittracing.com or jcwhitney.com that is where I get most of my car junk |
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.
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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. |
Er...pardon the threadjacking...
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: https://lh5.ggpht.com/_oNsRR_T1Qx0/R-...8/IMG_0516.JPG Here's a pic of the axle: https://lh3.ggpht.com/_oNsRR_T1Qx0/R-...8/IMG_0518.JPG And here's where insult was added to injury. No, wait, injury was added to injury... https://lh3.ggpht.com/_oNsRR_T1Qx0/R-...8/IMG_0511.JPG 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. :( |
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just a thought, you could replace the entire axle. that way you would know what it was. maybe talk to a junk yard before you pull the axle as far as pricing and tell them you want to do it cheap and what you are using it for. they may hook you up. we have these places around here U-PULL-IT and they are reasonable but as the name states. you have to pull whatever it is off of the vehicle so it may take the better part of a day.
as for the tongue, can't you weld it back? I know, that isn't the point. |
Yeah, I was thinking of just replacing the whole axle with a proper trailer axle. That would cure every one of my problems. I figure I could get a totally rusted out trailer with a reasonable axle for near nothing.
Another option would be a junkyard car axle, the rear axle from an older FWD car might do the job (I remember the axle on my '97 Grand Am went all the way across with a simple beam). Most (maybe all) junkyards around here are full-service only (they call themselves "used auto parts" businesses) and won't allow you to pull your parts or even walk into the junkyard area. Anyway, if I got one, I would then know what compact spares to get! I can't weld it because I'm neither equipped nor trained for welding. Some day I will get appropriate equipment. Any recommendations for a shoestring budget welding setup? (I know, not likely.) |
before I even say this, it is very BUBBA-engineering but...
you could go to lowes and get some metal straps, drill some holes in both pieces and bolt it back together. using locktite on the bolts so they don't come undone. maybe even paint it so it doesn't rust again. that is instead of getting a small welder. given the tongue weight of that traier (just by the looks) you may not have any problems just strapping it together. I would use several straps though and as heavy duty as I could buy. *edit* another consideration for an axle is maybe a small car that was rear wheel drive like a chevette or something. gears shouldn't matter, you will have your solid axle and the small tires you want. just a thought. |
:D I wasn't going to admit it, but yes, splicing it with additional metal was the most likely solution I was going to use. I have some nice angle iron that would be perfect. The tongue, and the whole trailer completely loaded, is very light indeed; I lift the tongue by hand, and I can even lift either rear corner by hand. Those huge tires actually cause the whole thing to float without the boat, motor, and two batteries on it (with the batteries in the rear). That's another reason I want less tire, so it doesn't float.
Good point about the RWD axle working also. It ought to be easier to find that a beam rear axle from a FWD. Oh, one additional addtional thought on bolt circle: Considering that it came with SUV tires on it, I took that as confirmation of my bolt circle measurement and vehicle match. |
When I bought a set of (5) VX rims for my '91 Civic, I took a closer look at the factory spare. It had the same height and weight as my factory steelies. So even if you could ride on four "space savers", you might get better FE with a lighter wheel/tire combination.
Bill |
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You should be able to figure out the bolt pattern by measuring center to center of two holes that are side by side and then check 2 holes on a diagonal center to center, then just find a wheel with the same dimensions. |
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i certainly drive more than most, but i can't give a tech reason supporting undersized spare's limitations. instead allow me to site a common sense observation:
i've see an uncountable amount of vehicles abandoned with a small blown spare ON THE CAR. it's pretty simple...use the spare (undersized or not) to get where you're going, then repair/replace the original and put the spare back in the trunk! |
upon seeing the frame I exclaimed "MODEL A FORD" what you have there is a modified front axle from an OLD car that has been cut and welded together to be narrower than original. I would recommend replacing it with something with a standard pattern and call it a day. and the tongue have a buddy who welds for a hobby/living do it that job would take 5 minutes and you'd be set.
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