someone called in this question to the library reference desk where I work:
How fast would a fully loaded semi trailer have to go for the tires to catch fire?
:dubious:
does anyone have an idea where I might start with this? (outside of getting a Ph.D in physics, of course) Should I call the person back and tell him that there places where he can get help with his drinking problem?
thanks,
MS
[330k PDF] Here’s a fairly comprehensive article from Goodyear on the subject. Note that a tyre is far more likely to burst before it actually catches fire from overheating.
I think they are really talking about brakes over heating on a downhill run.
A truck tire will separate and blow out from heat before it catches fire, this usually
occurs w/ recaps or tires that are under inflated. Overheating from excessive brake
use can cause a fire and this, while not common, does happen occasionally.
Thanks for all of the replies so far. As some of you have said, this question ends up being more about brakes than actual speed. (see below) I would imagine that a semi trailer would have go very, very fast on a level surface for tires to catch fire. One of my colleagues said the entire semi would probably break up due to the stress of wind resistance before the tires would catch fire.
I talked further with this person and apparently someone he knows saw a semi trailer careening down a rocky mountain highway. The driver managed to get the vehicle off the main highway onto one of those emergency braking lanes. By the time he got the rig stopped, the tires were on fire.
MS
As the shoes/drum overheat they “fade”, or lose their ability to provide friction and
slow the vehicle. Experienced drivers will gear down before they begin a steep
descent to avoid missing a gear and finding themselves freewheeling w/o the engine to
aid in slowing. A fully loaded 18 wheeler will accelerate very rapidly on a
downgrade, unless it was caught at relatively slow speed, the brakes would be
insufficient to stop it. That’s the primary reason for those truck escape ramps.
As an aside, modern trucks, w/ air brakes, are designed so that losing air pressure
causes the brakes to be applied, rather than losing brake function. You sometimes
see long sets of skid marks on the highway. These are often caused by a truck that
has had a sudden loss of air pressure, another good reason for not tailgating, or
“drafting” a truck.
Well, during The Siege of Tyre in 1111-12 the Franks made a siege of the city but lost when the siege towers and battering rams burst into flames, but that was due to the Greek fire, no record that Zahir al-Din used semis…
I saw one on fire in the previously described manner. It was only going 40ish down a long mountain descent in the Rockies.
At the Bonneville Salt Flats, where there’s an annual pursuit of speed records, the front parts of semi-trailer trucks go faster than a fully loaded one could go, and their tires don’t catch fire.
And there’s the problem – the faulty assumption that only speed could have caused said fire.
Well, if you have coloured tyres, they can be damaged if you park your motor-car too close to the kerb, or people kick things into the road from the pavement.
Truck driver here – I have never heard of a tire catching on fire due to speed.
However A wheel catching on fire from an overheated brake does happen. It can be caused by improper braking on a long downgrade or a brake dragging (IE partially applied all the time).
As was already mentioned above, when a truck looses air pressure the brakes apply. In some situations it is possible for an air leak to cause one or more brakes to drag and if this goes on to long it could overheat and start a fire.
Well, of course those hot dogs couldn’t flatten tyre, but neither could Nebuchadnezzar in 586-73 BC, and the Babylonians were certainly familiar with the legend of Semiramis, which one supposes influenced their choice of siege gear.
Dried out bearings on mobile homes can get so hot as to light off a tire or even melt and shear off an axle.
If the tires have been filled with propane … Nice big boom…
Why would anyone fill tires with propane? Or am I being whooshed here?
I have seen 2 semi trailers with the smoke coming out of a tires, each caused by the same thing. The smoke was coming out of the brake assembly after the driver went 20 miles with a brake locked up in one wheel. It’s not as noticable in a semi and trailer, as your car. They find out a brake is locked up the first stop, but it’s to late by then. The assembly can heat to the point of welding all into a unturnable wheel, or it can send sparks onto the highway and other parts of the trailer.
You probably won’t see it on a truck, but those “fix-a-flat in a can” products use propane as the inflator. Tire shops hate them, because it makes their jobs very hazardous.
That was almost certainly a brake fire. Drivers who aren’t accustomed to mountain driving and ignore the wrning signs to use low gears in going down mountain grades have this problem from time to time.
And back in the 60’s when most mobile homes were small and used propane in small bottles for heat and cooking, most yards had lots of bottles around and you were always carrying them around so it made sense to just put an air chuck on a line that would hook to a propane bottle. Not done much anymore but it used to be.
Also the 'fix-a-flat as posted above.