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Hydroplaning
When an automobile is driven fast on wet roads, especially if it has worn-out tires, a cushion of water can build up under the tires, preventing the rubber from contacting the road. This is very scary and dangerous, because it leads to a total loss of traction.
Fortunately for cyclists, this cannot happen to a bicycle; they don't go fast enough, nor have a large enough contact patch, nor do the tires run at a low enough pressure to make hydroplaning possible.
Even with automobiles, actual hydroplaning is very rare. It is a much more real problem for aircraft landing on wet runways. The aviation industry has studied this problem very carefully, and has come up with a general guideline as to when hydroplaning is a risk. The formula used in the aviation industry is:
Speed (in knots) = 9 X the square root of the tire pressure (in psi.)
Here's a table calculated from this formula:
| Tire Pressure | Speed Miles per hour |
Speed Kilometers per hour | |
|---|---|---|---|
| P.S.I. | Bars | ||
| 120 | 8.3 | 113 | 183 |
| 100 | 6.9 | 104 | 167 |
| 80 | 5.5 | 93 | 149 |
| 60 | 4.1 | 80 | 129 |
| 40 | 2.8 | 66 | 105 |
An ill-founded fear of hydroplaning often leads people to buy bicycle tires with inefficient tread patterns, when they would be better off with slicks.
