Contact patch: the PORSCHE 918

[TURBO2GO]

If you guys haven't read the test of the Porsche 918 in Car and Driver, you should. It's filled with fascinating stuff. The car ran 0-60 in a record 2.2 seconds. Within one revolution of its tire, or in 7 feet, it reaches 16 MPH. It ran the 1/4 mile in an unreal 9.8 seconds.

And some other interesting stuff:

"The massive 325/30/21 Michelin PSC2 tire is 29 inches tall, two inches taller than the 911 turbo S. INCREASING OVERALL DIAMETER INCREASES THE CONTACT PATCH". Pretty much what Billy had said regarding the benefits of a jump to a larger diameter front and rear setup, and counter to the "contact patch is dependent on weight and pressure" argument.... which I've learned after a ton of research, is not true in real world conditions because of several reasons.

 

[JoseJA1979]

Love this car! Especially the exhaust setup!

 

[docjohn]

A good question is what are the tire pressures.

 

[stuntman]

Articles are often wrong on technical comments. It's still somewhat true that contact patch is dictated mostly by your tire pressures, the weight of the vehicle, and the tire construction and changing the diameter and width only changes the shape. However, going larger in diameter and width allows you to run slightly less tire pressure which helps to increase the contact patch. Either way changes shouldn't necessarily be made until you have a problem then change things to fix them. Not for the sake of changing things.

For me, the larger diameter means more tire mass, which means longer (slightly) tire life, higher top speed, and more tire volume to resist tires from overheating on track.

 

[RYU]

I just want bigger wheels to look cool. It's like putting 215 tires on a 10" wide wheel. That's cool man.

 

[angus]

You guys are hilarious, I do totally agree that not all the tech in a lot of articles is correct.

The wider/taller/shorter/fatter argument has raged for years and I bet if aesthetics were not such a huge issue as they are - we'd have purely functional tire and wheel fitments that more closely resemble F1 cars… or maybe 18th century wagons?

 

[stuntman]

Diameter increases are also driven by the need for larger brakes which is driven by heavier and faster cars, which is driven by better safety standards and the need for more power.

 

[TURBO2GO]

One article I read also said having a wider patch exposes the tire to a smaller fraction of the sidewall needing to compress as it hits the road. That tiny difference in the amount of sidewall being compressed, times many revolutions, becomes significant in terms of heat generation. The tiny wires in the sidewall continously flexing up amd down generates lots of heat. Even on a similar sized contact patch, the wider tire is running cooler. That allows for different rubber formulations.

 

[davidf]

I just cannot imagine 0-60 in 2.2. Oh man that must be awesome.

 

[Dhalsim]

I think it looks great in person too. So much want...............

 

[TURBO2GO]

I just cannot imagine 0-60 in 2.2. Oh man that must be awesome.

It's insane. I didn't think that was even possible.

 

[Juice]

Best Porsche ever. In every way.

 

[davidf]

That's is so sexy I just went out and threw rocks at my car.:redface:

I think it looks great in person too. So much want...............

 

[scammy]

^lol

 

[warrenw]

The 3rd 918 sold on North America was right here in Edmonton AB CANADA
$1.1M

https://www.youtube.com/watch?v=AZ17GTpd3bk&list=UU0U7zARrm9f8nTNQ4QVmSPw

 

[davidf]

I'm shocked Jerry Seinfeld hasn't taken possession of one of the first ones.

 

[djp5]

Contact patch depends very much on things like weight and pressure. But it's not simply just one or two things. This is why there are jobs for tire engineers.