Many years ago, during my Air force pilot training, we were told that any tire will hydroplane at a speed equal to nine times the square root of the tire pressure. For the typical passenger tire, that works out to the low 50's MPH. From personal experience, I have found this to be pretty much on the money. The amount of water on the road is also a factor.


Robert Schrader
Wentzville, Mo.
'05 Roadster