WNo that is an oversimplification and would only be true if there were no treads on the tire..

The idea of with larger tires giving more traction, is that you have more surface area in contact with the road surface. Yes you have a lower force per square inch but a larger surface area. But in theory with a properly designed tire your coefficient of static friction is higher (which is related to the surface area). And ultimately the physic equation says that the amount of lateral force required to start a skid is directly related to that coefficient. The idea of different tread patterns and all weather tires is a tradeoff of that tread (as well as the rubber characteristics) and how it affects different performance characteristics.

Which is what you want to keep from breaking loose and skidding.. If this wasn't true we would want narrow tires on the drive wheels to give us better traction, but of course skinny tires on the back end are easier to spin and do a burnout as we've all seen..

What makes it work is that the treads are designed to channel the water away just in front of where the tire surface touches the road, and when successful it keeps you operating under the static coefficient of friction and thus tire width which helps determine that coeff of fric is still helping you..

This works up until the point there is too much water and the tread pattern can't do it's job, and then water gets between the tire and the surface then you instantly have a lower coeffecient of friction because the water acts as a lubricant. And then as soon as you start skidding it gets worse because now you have a dynamic coefficent of friction which is much lower. At this point you are screwed.. and the dynamic coefficent of friction is influenced by other things and while skidding maybe a larger surface area isn't better (i.e. it's like having a bigger ski on ice)..

Also know that the ability to channel water away through the tread is also related to speed.. So if you slow down a little it allows it to work properly. Thus when you father told you to slow down in the rain, he was right since it allows the tires to work better..

Bottom line, all else being equal and with a good tire design, wide tires should better.

But don't confuse a little water on the surface of the road as always resulting in hydroplaning, up until you have standing water in combination with high speed the tire will work.. And if nothing else slowing down make it work better. If this weren't the case every time it rained every car on the road would be in a ditch.... So bottom line as road conditions deteriorate in a down pour or poor road drainage, slow down...

A digression, but of special interest to rear-engine cars, especially 2 WD P-Cars.. we have this unique characteristic with the aft weight in the car.. So when cornering at very high speed just as the rear tires just begin to break loose, it is from the physics perspective we are right at the balance/equilibrium point when the friction holding the tires on the ground (coeff of friction * weight over the rear tires) is equal to the lateral side load during cornering. Where a little more lateral force would cause the tail to start wagging.. It it is just at that point when the normal driver reaction is to let up on the throttle, which shifts the weight balance of the car from the rear towards the front of the car.. And the result of doing that instantly reduces the weight over the rear tire. And then based on the physics equation, (Wt * Coeff of friction) that frictional force between the tire and the ground is reduced, so the lateral force takes over and in most cases you end up with the back of the car in front of you.. Not directly related to hydroplaning issue, but it relates to the importance of coeff of friction and the weight on each tire.. And also why in a rear engine car, you never lift the throttle on a curve when the tail is just breaking loose... which for most drivers is counter-intuitive..

 

very nice explanation and appreciated. I have Algebra and quadratic equations, complex numbers, etc this qtr in school and see how it actually might apply in the real world somehow now. All I know is when I change the tires for the winter, the summers have these giant water funneling canyons running through them and while driving, they cut through the standing water vastly better than my Audi S5. I was actually worried to drive the Audi with oem summer tires in the rain as it slid all over the place, compared to the 991 which has stayed planted and sure in my experience. Anyway. Thanks

 

nicoli, saw our comment on the pzero's........how many miles are you getting on them (if you have replaced). I'm at 8k on mine and they look like maybe get to 12k. The chip seal roads here don't help.

 

Has Porsche gave Michelin's Super Sports their N rating yet? If not I wouldn't put them on my Porsche.

 

Thinking about Toyo Proxies T1-R's

 

Can't say for sure as I've swapped for two winters and driven all winter long on the Michelin Alpin 4 tires.. The oem summer pirellis are in great shape though according to Elliot and I expect them to last quite a bit longer...

(via 6SpeedOnline iOS)

 

They are great in the rain. I have driven them on the track at high speed in the rain. One word of caution; the temperature. I did it while it was warm. The combo of 35 degrees and rain may make them a little trickery.

Marc