Recently I got a flat tire and had to drive home on the interstate on my spare tire. My owner’s manual (yes, I actually consulted it) said not to exceed 50 mph on the temporary spare. Wild man that I am, I set my cruise control at about 55 or 56 and drove home with no problems (with other vehicles whizzing past me and Sammy Hagar running through my head). (Note: traffic was light enough that I wasn’t obstructing anybody; other cars could easily go around me.)
So, in exceeding the recommended speed limit by about 5 mph, was I living on the edge? Or was I being unduly cautious? What’s the real safe speed to drive on a temporary spare—does the owner’s manual need to be followed to the letter, or is it overly conservative?
Saw a car show years back. They did some testing w/ the donut, actually 4 donuts. IIRC they drove 80+ mph, they also noticed greater acceleration (0-60 time) w/ the donut. Their conclusion was just drive. YMMV
Also some cars can’t have the dunut on the drive wheels due to different diameters of the L and R wheels. Then to change a tire to a donut on a drive wheel you must 1st take off a non-drive wheel, replace that w/ the donut, then take the tire you just took off and use that as the spare. Suberus have a way for the owner to temperally disengage the rear wheels from the drive system (usually a fuse has to be added, makin gthe car FWD instead of AWD) to allow for tire size mismatch.
Donut test: notice braking and handling weren’t tested, nor were a variety of cars tested. Wet traction? Heavy bumps?
Sure, you can probably squeeze out a few more MPH here and there, but the limit is one that allows you to drive an interstate speed and get home without pushing the envelope.
I believe that space saver tires are just another sign of the Apocalypse.
A solid rubber tire does not shed the heat of road friction so well as a pneumatic tire. This can cause them to spontaneously disintegrate if they are used at freeway speeds for prolonged periods. I wish the highway patrol would be more aggressive about drivers who endanger others by operating their vehicles on freeways with solid core tires. They are a menace to society.
So is the spelling “donut” now standard, accepted, or preferred? To me, I read it as “don-ut,” so have to backtrack anytime I see it after I figure out the context. I believe it comes from “Dunkin Donuts,” but accepting that as the spelling seems like seeing a restaurant called “Kuntry Kitchen” and then using “kuntry” in general writing.
Actually, Zenster, in my experience, space saver (or “donut”) tires are pneumatic. They typically are pressurized to a higher pressure than ordinary tires (50 psig?). However, they do indeed have less rubber for heat dissipation, and a car’s handling is surely impaired. I agree that they are a menace.
I say this in particular as someone who frequently goes off-road, and has had to change several flat tires this summer due to construction debris. Thank goodness that SUVs generally still come with full-service spares. (And before I get jumped, I drive what is now considered a mid-size SUV–I have no need or want for one of those behemoths.)
CurtC, I thought that both spellings were acceptable.
Never heard them called “donuts” before. The spare tire should have a speed rating listed on the side wall. Read it, not what’s in your manual (because it can differ). Exceeding the speed rating on the tire may not cause it to blow (or have a bad case of tread seperation) but the tire company also isn’t liable if you are doing stupid things with your tires.
My spare is a full size 17" but is much thinner (my regular tires are 215 mm wide, the spare is a 180?-ish.
BTW, a spare is going to get you better accelleration due to it’s smaller diameter. Street cars that drag race (at a track) regularly swap their larger road tires for smaller drag tires.
Yes, it’s okay to drive a mid-size SUV. Nothing against the law. Search the subject and free up a month of time to catch up.
Back to the spare tires: for all those SUVs out there without donuts of the non-dunkin(g) variety, should the full size spare be rotated through the regular tire rotation or should it hang on for life as a full size rarely used spare?
According to the manual for my tires, if you have a full spare, it should be rotated using the 5-tire rotation method. I figure it’s probably better to “air out” the tire than let is rot on the tire holder (or wherever).
Only if you have HP to spare, as in the case of a streetrod. In this case traction is a limiting factor. Having 4 donuts you have less traction but you have less rotational inertia and a smaller tire effectivly changes your gear ratio, this adds to acceleration. In a mideratly powered car the last 2 seem to outweight the 1st one.
Also corering and braking were tested, IIRC cornering was a little less but much better then everyone expected, braking distances were longer.
I’ve had to help my friend change a tire with one of those mini-dealies. You notice immediately that the tire is smaller. In fact, being the odd-tire out, it leaves the vehicle slightly tilted. The all-four-mini-tires demo mentioned above would probably have been safer, as the car would be balanced. With only one, braking, steering and acceleration forces aren’t symmetrical anymore. If I were writing the manual, it’s this effect I’d be more concerned about - the spare has signifigantly affected the handling of the car, and I wouldn’t want to leave the impression that the owner still has a precision performance vehicle.
I’ll add an anecdotal point of evidence:
About 4 years ago, a group of guys (myself included), decided to drive to a college football game that was about 300 miles away. After the game, we head home, get about 50 miles out of town, and get a flat. Plop on the spare donut/doughnut head down the road hoping to find a service station. Being that it’s approaching midnight on a Saturday night in rural Missouri, we obviously can’t find one. Since we’re too broke to afford a hotel room for the night, we drove all the way home, 50mph, on the dougnut/donut. Something on the order of 220 miles.
I don’t think I’ve ever even seen one of these things in Australia. All the cars I’ve ever owned or driven (including 2000+ models) have a regular wheel as the spare.
FWIW, a while back I had a blowout on I-4 somewhere between Orlando and Daytona. I replaced it with a spare and drove about 150 miles to Tampa, at about 85-90 mph. And then I still kept it on for about a week. Couldnt afford a new one right away, being in high school and all.
They hold up pretty well.
I worked with a fellow who had been a fleet mechanic for a bakery. One of his parts suppliers was a man who drove endless miles on a company car. The company did not buy his tires. He had the whole car shod in temporary spares. Why? The ride was rough, but he could buy the temps for ten dollars each. Every 1000 miles or so, he’d put a on a new set, and throw away the old ones. Besides, he got a mileage allowance, and the temps, being smaller, racked up more miles.
Yes, actually it is OK. But rather than further hijack this thread, please see here.
Also, AskNott, that’s the stupidest, most unsafe thing I’ve heard all day. Heaven help the guy if he blows out a tire on the freeway and plows into the schoolbus in the next lane…
Also to further on AskNots post, Autozone sells something like 30,000 miles ‘Maypop’ tires for as low as $30 each. I’m sure he could get the smallest diameter if he wants to increase milage, but in tire cost savings alone it’s 1/10 the price.
