Car people - What specifically can happen to a car being driven on a flat-to-the-rim tire?

Perks

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Hi!

I'm reading up on it now, but there's mostly a lot of vague warning telling us that it's bad to drive on a flat tire. (And I'm talking about a tire flat to the rim, not just low.) They say it can cause "damage" and "instability" but I'm looking for something a little more specific than that.

If one of the rear tires was flat to the rim and the driver kept going, aggressively, what might we expect to happen to the car? Can it get a few miles? Might the wheel itself break?

And why do I always worry that I'm courting the Fates to give me firsthand knowledge of the stuff I need to know for my stories?

: )


Any knowledge or anecdotes are appreciated!
 

Bacchus

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I suppose the answer would be, like lots of things, it depends... mainly on the wheel material, the speed, and the road surface.

An alloy wheel on concrete or asphalt roads would deteriorate much more quickly than a steel wheel. I have seen a driver - presumably drunk - go past with a shredded tyre and the bare steel sparking on the concrete road. An alloy wheel wouldn't do that but would wear more quickly, it may crack if driven very aggressively.

Either type of wheel would make quite a racket on a made road, but could be driven for quite a long time, on an unmade road the vehicle could go on almost indefinitely but it would be a very uncomfortable ride and the handling of the vehicle would be fairly erratic with ruts and cracks tearing at the steering.

Trains manage very long distances without tyres...
 

Bufty

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I assume there's no spare wheel.

The tyre would rip to shreds, the road surface would suffer, the steering would be extremely awkward and I suspect eventually the axil and hub would complain a lot. Speed would be impossible, I wouldn't drive far in such a vehicle at all unless maybe crawl a couple of hundred yards if I knew there was a gas station ahead..

A lot would also depend on the size of the vehicle. I'm assuming a normal small four wheel car. How four-wheel-drive would be affected I haven't a clue.
 
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WeaselFire

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Watch the various high-speed car chase videos out of the Los Angeles area. :)

I drove 32 miles on the shoulder on a flat tire/rim and made it to a garage with no wheel damage. Took forever, hard to steer and I expected to have to buy a new rim and tire. Just got a retread tire for $20 installed, went to Sears the next day for new tires. Don't drive without a spare, without road service or AAA and before cell phones existed on roads with no traffic. :)

What do you need for your story? From little damage to flames and explosions is all plausible.

Jeff
 

Felix

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Fun story... I'll spare you. :)

What they said ^.

As a driver, you'd notice a lag, a bit of a decrease in speed. You'd have to give it a little more gas to get it to go. Wobble. Like driving through peanut butter. The bead seal on the tire would give way and the flapping rubber compound would escape and be left behind.

Depending on a billion variables, I can tell you that it might take your brain a moment to realize what was happening. On a typical road... Sparks, yes. Depending on the type of wheel - steelies will do this - you will leave a hell of a rut in the road. Depending on how much the road people care, it'll still be there a decade later. ;)

The sound. Thunk. Flap flap flap flap. Grind. Grrrrind.
 

Perks

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I assume there's no spare wheel.
There's likely a spare wheel, just no way she'd stop under the circumstances, if she could help it.

Which leads me to ...

What do you need for your story? From little damage to flames and explosions is all plausible.

I need the car to be disabled within five or six miles.

I'm thinking the tricky steering will betray her as she trying to keep up some speed. (Someone is following her.) She could smack a curb and maybe break the wheel.
 
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Perks

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Ha! We did have a delamination at highway speeds when I was nine. I'd forgotten about it until you just described the flap, flap, flap. We thought a helicopter was landing on the roof of the car because of the noise and that it was bouncing so wildly. We stopped immediately, so I don't know what would have happened if she kept trying to go.
Fun story... I'll spare you. :)

What they said ^.

As a driver, you'd notice a lag, a bit of a decrease in speed. You'd have to give it a little more gas to get it to go. Wobble. Like driving through peanut butter. The bead seal on the tire would give way and the flapping rubber compound would escape and be left behind.

Depending on a billion variables, I can tell you that it might take your brain a moment to realize what was happening. On a typical road... Sparks, yes. Depending on the type of wheel - steelies will do this - you will leave a hell of a rut in the road. Depending on how much the road people care, it'll still be there a decade later. ;)

The sound. Thunk. Flap flap flap flap. Grind. Grrrrind.
 

Old Hack

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The car pulls hard towards the side where the flat is.

Front tyre flat makes it much harder to control than a back tyre flat.

There'll be a lot of flapping noise as the tyre shreds. And then, once you're driving on the wheel rim, a lot of grating noises and sparks. The wheel rim will quickly deform and you'll have reduced speed, reduced control. Steering will be very heavy and erratic. The car will dip down on one quarter but as you steer, depending on the speed and the wheel concerned, it'll level off and dip again as you turn.

Control would be the biggest issue, I think. There would be a lack of speed. And it would be hard to get away without being noticed.
 

MDSchafer

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Hi!

I'm reading up on it now, but there's mostly a lot of vague warning telling us that it's bad to drive on a flat tire. (And I'm talking about a tire flat to the rim, not just low.) They say it can cause "damage" and "instability" but I'm looking for something a little more specific than that.

I will laugh and point.
 

cmhbob

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On a larger vehicle like an SUV or full-sized van, you'd likely run into stability issues, especially with a back tire going bad. Stability like possibly rolling it.
 

Bren McDonnall

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Front tire will cause sloppy steering and much reduced traction. Kind of like driving on ice. Over the short term, the tire will disintegrate. Depending on how this happens, you could get part of the belt fouling in the suspension and causing considerable body damage as things start tearing apart. You're also going to lose ground clearance, so obstacles in the roadway that would normally not be a problem could catch the frame or suspension and stop you.

Eventually (the one time I had to do this, it took about 30 miles of mountain road) the tire will be pretty much gone and you'll be rolling on a pair of steel rims-- at least until they flatten out. This will cause quite a bit of heat, so look for your brakes to start getting mushy, or possibly seizing if the rotor warps (this is era specific, so if the story is a period piece in the '70's, for instance, you'd have different brake issues because of the different types of brakes used back then). 1 brake locks up and if you aren't ready for it, or don't know what to do about it, you stand a good chance of spinning the car.

Due to the lack of shock absorption the tire would have provided, you might lose some lugs (those threaded bits you use to connect the wheel to the suspension) You lose the wheel and you're driving on the drum/rotor, and THAT'S a party. Even less ground clearance, if any at all, and driving on a part that's not designed to hold weight. You could easily end up with seized calipers (the bits that slow and stop the rotor. They work like rim brakes on a bike) or a warped drum (older cars) Rougher, harder roads will make this happen quicker.

Rear tires. If you don't have positraction, where both wheels are supplied with power equally, generally what happens is that power is applied to the wheel experiencing the least resistance. That would be the one with the flat once the bead breaks and the rim is spinning freely inside the tire, or when the tire falls off. This means you probably aren't going anywhere. In this case, you'd almost be better off if the brake did lock up. At that point, you'd be dragging that wheel, and the noise you wouldn't believe, but at least the other wheel would now be providing traction (I actually serviced a car where the woman who owned it dragged a frozen brake until her brand new tire exploded, changed to the spare, and dragged THAT one until it exploded. I cannot imagine how she didn't hear that squeal.)

If you DO have positraction/limited slip, both wheels provide power regardless of drag. You'll get some slew as the tire flops around on the rim. This could break things like brake lines or body work. Very hard on the chrome. You'll be getting lots of stress inside the differential, but in the time frame you're dealing with, it won't be an issue.

Finally, with any sort of flat running at high speed, you're going to see extreme heat. The least you can expect is to see globs of melted rubber slinging everywhere. At worst, the tire will catch fire. At that point, brake fluid starts to expand, and that's flammable too. You've also got fuel lines running along the frame on most cars, and you do not want open flames (and rubber burns hot) around those, as many of them are only steel until they bridge the gap between frame and engine. Then there's a rubber(ish) section that melts under intense heat. The smoke is pretty noxious as well, and might be a greater hazard than the flat itself.
 
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cornflake

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Depends on the rim too -- some rims are quite sturdy little suckers. I've driven on back flats for decent stretches with no damage to the rim or anything else save scratches and minor dings on the thing. Front flats will impede your ability to steer much more -- a blown tire, more than a progressive flat, is scary at speed and very hard to control. I've still not done damage, heh. Have her in a cheap thing/cheap rims.
 
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DrDoc

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Just for the record, carbon fiber rims, as those made by HiPer Technology (where I used to work) will go for miles on a flat. One of our sponsored riders was on a 25 mile over-the-mountain cross country race and three miles into the race his front right tire went flat. The driver knew he could no longer win the race, but he also knew he could not afford a 0 points award for a Did Not Finish (DNF in race terms), so he went on to get the few points he could just to finish. The tire chewed up completely and was thrown off eventually. The rim took the punishment and , as a steering rim on the front, performed to get him where he needed to go. He finished the last 22 miles and crossed the line. After the race the driver, impressed with the rim, put another tire on it and the rim held air pressure but leaked slowly.

If the vehicle is at high speed the tire may not go flat once it is punctured. Centrifugal forces will keep the airless tire expanded. If the tire delaminates (meaning the layers of the tire simply separate) there could be catastrophic consequences, but imho, less so for a rear tire.

Good luck with your story.

DrDoc
 
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Twick

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There's a Mythbusters episode that addresses this, comparing running on a flat tire to various substitutes. In general, if you were desperate, you could go for a considerable time on a flat, although as mentioned above steering and traction would suck.

I had a "detached belt" at speed on a highway and simply moved onto the shoulder then proceeded at low speed to the next exit where it could be dealt with. I felt car damage was less worrisome than trying to change a tire alone at night on an extremely busy highway. It turns out none occurred anyway.
 

neandermagnon

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I actually did that. I drove 2 stories down a multi-storey carpark and all the way up the hill where I worked before I realised the tyre was flat.

I thought there was something wrong with the engine as it felt very sluggish to drive. I was getting annoyed thinking I'd have to take it to the garage and that there was something wrong with the engine. I only stopped driving because another driver was flashing their lights at me and pointing at my car in an ominous way. When I realised that the tire was flat I was surprised it'd got as far as it had. It was completely flat to the rim flat. It had driven that way uphill too. The hill where I work is very steep; I normally have to drive up it in 2nd gear because it's a 20mph limit and it's too steep to drive uphill in 3rd gear at 20mph. My car has a small engine so doesn't usually do that well with hills. But it managed that hill even with a completely flat tyre.

The guy at the garage said that the tire was utterly ripped to shreds and thankfully there was no damage to the wheel itself, because if there had been it would've cost a lot more to replace the entire wheel. I only had to replace the tyre.
 

WeaselFire

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I need the car to be disabled within five or six miles.

Right front tire goes, rim digs in, wears off quickly and pulls her into a soft shoulder where it gets stuck and can't be moved. Heroine meets grizzly fate at the hands of the one-eyed hatchet murderer... :)

Jeff