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Tire contact patch size / aquaplanning

MvM

Legendary Member
Joined
12 February 2002
Messages
3,021
Location
Rotterdam, Netherlands
There was a long thread here on how the size of the tire-patch would be the same regardless of tire size if tire-pressure was the same.
Concerning this, I have a question.

If tire-pressure and tire-patch are the same, ground-pressure is also the same. However, everbody always tells me that with wider tires you will start aquaplanning more quickly. In my opinion that doesn't make sense. If the contact-patch is the same size (but different in shape) the amount of water to be displaced by the tire is also the same so aquaplanning should occur at the same speed. At the same time there is always talk about how much more grip you get on a dry surface when using wider tires. Same goes for F1-cars. These weigh very little compared with a normal sedan yet use extremely wide tires which should give them a very low ground-pressure. So why then the large tires if larger doesn't give you more grip. I must be missing something here.
 
The amount of water on the pavement that needs to be displaced is greater with a wider tire. A tire that has 205 mm treadwidth is going to cut a swath of pavement with that width, and displace however much water is on that 205 mm wide strip of pavement. A tire that has 245 mm treadwidth is going to displace 20 percent more water than a tire that has 205 mm treadwidth, because the amount of water on a strip 245 mm wide will be 20 percent higher than the narrower strip.

In other words, the amount of water to be displaced depends on the width of the contact patch, not on the area of the contact patch.
 
IMO treadpattern is more important than tire width and possibly even air pressure in the rain. I noticed significantly less hydroplaning with Kumho 712's which have a wide center channel than with Yokohama Ao22's
which don't.
 
Tread depth is very important, too. In the rain, the OEM Yokohama A022H is awesome when it has full tread depth, but frightening when it wears down close to the treadwear indicator bars.
 
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