I've just read an article (Honest John, Telegraph Motoring) that states that "a wheel will aquaplane at a speed approximating to nine times the square root of the tyre pressure".Running at 18 psi in my locost this works out at 39 mph. Does anyone out there know if it really is as simple as this formula (presumably, when using the formula all other conditions (tread, etc) must be ideal) or is there more to it.
My first car was a citroen AX and it would aquaplane at 0 MPH. Seriously, there wasn't a speed at which the front wheels would lock up on a wet road. In the dry it was great. The steering was full of feel and it was quick for its engine size but in the wet...
Of course it's not... a wheel doesn't aquaplane at all, a tyre does.
Seriously though - it depends on the tread depth, design, road surface etc etc... if it were really that simple tyre companies wouldn't spend
millions designing new treads...
IMHO
Steve
why would it be related purely to tyre pressure?
I appreciate that tread and road quality affect aquaplaning, but assuming these are as good as possible is it really as simple as that formula?
he did say 'approximatly'
quote:
Originally posted by blakep82
he did say 'approximatly'
That is apparently a general guideline that the aviation industry made from their studies according to http://www.sheldonbrown.com/tires.html
I'm sure it works at a very approximate level as the contact patch reduces as tyre pressure increases, so the tyre has less water to move and the
contact patch is exterting more force per unit area to move that water.
surely the weight of the car would be very important in this sort of equation?
I would gues that by tyre pressure he meant the Wieght on that wheel devided by the tyre contact area in sguare inches.
it would be a VERY rough approximation that. Other factors that would be crucial would surely be the amount of standing water, width of tyre and weight of car. There are loads of lesser variables but those above would have a significant effect on the result.
Yes 9rootp is the aquaplane speed but its in knots - nautical miles per hour - so you've actually got about 44mph!
Doesn't that assume a standard design of tyre in aviation or something?
I can run low profile wider tyres on the car at higher pressure and have a lower aquaplaning speed. that doesn't fit the formula.
When aquaplaning, the front of the tyre's contact patch is lifted up off the road by the water. The faster you go, the more tyre is lifted up. If you have wide tyres, the contact pactch is short but wide, if you have narrow tyres, the contact patch is narrow but long, for the same tryre pressure and vehicle weight. aquaplaning is widely said to be worse on wide tyres than narrow ones.