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Today I was riding with my road bike when I suddenly hit a patch of hot asphalt. The day before the one side of the road was already filled with a hard first load, so I didn't think much of riding along there again. Also there was traffic on the other side, so I didn't think about going to the left. After maybe 50 meters I felt that there was a sluggish kind of noise and there was steam rising from the ground.

The wheels looked fine as I checked them after the ride, but may they have suffered some substantial damage (security risk)?

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Do you mean freshly put down asphalt? –  freiheit Apr 24 '13 at 20:46
    
The worst part is cleaning all the asphalt and grit off your frame later. –  alex Apr 24 '13 at 23:29
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People clean their bikes??? –  Daniel R Hicks Apr 25 '13 at 1:24
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@DanielRHicks My trainer told us to clean them once a week! nuts! –  robthewolf Apr 25 '13 at 11:32
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@robthewolf wax on wax off? –  James Bradbury Apr 26 '13 at 11:30
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5 Answers 5

up vote 9 down vote accepted

I don't think so - I've ridden over 1/4 mile stretches of freshly poured asphalt with no apparent damage to my tires.

The asphalt is around 300 degrees F when it leaves the plant, but it will have cooled to 200 degrees or less by the time it's open to traffic (water will stand on the surface without boiling, so it's definitely below 212F)

Further, unless you're stopped, your tire has a very short contact period with the hot road. A typical road bike tire has a circumference of around 80 inches, and at 5mph, it will be rotating at about 1 revolution per second. If your contact patch is 2 inches long, that means each part of the tire is in contact with the hot road for only 2/80 = 25 milliseconds before having almost a second to cool off in the airflow. 25 milliseconds is about 1/10th the duration of a typical blink of the eye. Or, to look at it another way, each part of the tread only spends about 2.5% of the time in contact with the pavement and 97.5% of the time exposed to air.

The hot asphalt definitely has more "give" than cooled asphalt, so it will feel a bit spongy under your tires, but that's not because your tires are melting.

I'd be a little more worried about the fresh oils on the surface of the asphalt, the oil might degrade your tires if in contact for a long time, and it's super slippery if you hit a wet patch or ride over an iron plate before the oil wears off the tire's surface.

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It's amazing how much "give" asphalt has, even weeks after it's put down. –  Daniel R Hicks Apr 25 '13 at 15:55
    
Very nice explanation! Also note the air temperature above the asphalt if you're riding on overinflated tires –  CSᵠ May 25 '13 at 7:43
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Hot asphalt can be in the neighborhood of 200F, and contains some fairly volatile oils. It's probably safe to ride a few hundred feet on the stuff, but I'd avoid anything longer, especially with lightweight tires.

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I don't think the heat will damage your tires much but there is another problem that I experienced a few times. On hot patches of asphalt (either newly placed, or just on a hot day in full sunlight) your wheels can pick up a bit of sticky asphalt. This asphalt patch in turn picks up small pieces of debris from the road and that is where the trouble starts.

Sharp rocks or pieces of glass stuck in one place on the riding surface of your tire will slowly bore their way through the outer tube and into the inner tube causing a hard to fix flat. Removing sticky asphalt from your tires is difficult when you are on the road though unless you carry paint solvents with you. What I usually do is scrape as much of the asphalt off and then press some fine sand or dirt that I checked for sharper bits on the patch. Usually the sand/asphalt mixture wears off quickly without lasting damage.

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Racing slicks are delicate depending on your brand/quality, but I wouldn't throw them up against any type of weird surface or material. When in doubt, walk it out.

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I would be much more worried about something like the famous Beloki crash in the TdF ten years ago.

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And what caused him to crash? All that video shows is a bit of impromptu cyclocross during the TdF. –  whatsisname May 1 '13 at 17:07
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From Wikipedia: "He lost control of his bicycle after he locked his rear brake and the rear tyre came off the wheel on a patch of tarmac that was softened by the sun, sending his rear wheel skidding first in one direction and then the other." –  amcnabb May 1 '13 at 21:07
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