Heavier car can be faster and brake shorter?

[madoka]

Reading about the 2014 GT-R and came across this:

He assures us that the 2014 GT-R’s 545 horsepower; its claimed 3825-pound curb weight (our long-term, 2013 GT-R tipped the scales at 3887 pounds); and sticky, run-flat 20-inch rubber will help the car rocket from 0-60 mph in 2.7 seconds (our long-termer hit 2.8), corner at up to 2.8 g, and stop from 60-to-0 mph in less than 100 feet, even in the wet! He says that any changes to this ideal “power-weight-tire footprint ratio” would lead to slower times and less stability.

“For example, if we were to lighten the GT-R by 200 pounds, its 0-60 mph sprint time would fall from 2.7 seconds to around 3.3 seconds. And its stopping distance (from 60 to zero) would stretch from 99 feet to around 115 feet,” explains Mizuno. “The ratio we have now is the ideal one. Only this time, our modifications make it an even better car to drive!” stresses the man who answers directly to CEO Carlos Ghosn.

http://www.motortrend.com/roadtests...apanese_spec_drive/viewall.html#ixzz2DNViukw5

 

[Howard]

What a terribly written article.

 

[KentState]

Guess what they are saying is that the car has a healthy footprint due to the weight. I'm sure the extra drag causes impacts top end speed and fuel economy.

 

[rommelrommel]

Clearly his English is not perfect. I find it dubious that dropping 200 pounds would hurt the acceleration and braking like that unless he's chopping weight by removing items that actually make the car perform better.

 

[Ferzerp]

I can't really figure out a way that this could be possible unless they just mean that all the weight they can save, they have, and any more weight reduction would have to come from mechanical bits that make the car perform as it does.

 

[Howard]

Maybe a larger tire patch helps? In that case he should just drop the tire pressure.

 

[KentState]

Maybe a larger tire patch helps? In that case he should just drop the tire pressure.

That's exactly what he means. Dropping tire pressure might not be ideal or widening the tire either.

 

[wirednuts]

well hes right in that there is a certain point where you have more power then youre able to transfer to the ground so weight becomes a non issue and if you can add a little to get more friction then it can potentially make you faster.

 

[Howard]

That's exactly what he means. Dropping tire pressure might not be ideal or widening the tire either.

But increasing the weight will affect the size of the tire patch exactly the same way. The pressure inside the tire is always the same and that is your coefficient between weight vs patch size.

Widening the tire doesn't change the area of the tire patch.

 

[LTC8K6]

Reminds me of the Ice Road Truckers wanting heavier loads so they could get up icy hills...

 

[thomsbrain]

Somebody give that PR guy a promotion.

 

[disappoint]

Would be funny if someone reviewing the car stripped 200 lbs off and proved him wrong.

 

[rommelrommel]

Hell, try it empty vs full tank, there's about 130 lbs right there. You'd find the other 70 lbs somewhere pretty easily, probably enough non-essential interior stuff to pull.

 

[exdeath]

Tire physics lesson:

friction != adhesion.

Too many people focus on normal forces, surface area, etc, and apply 3rd grade physics formulas for rolling friction when in reality friction is not how a tire works at this level. It's much more complicated than that.

Does a wider puck on an air hockey table gain additional friction? No.

Does a wider velcro strip require more force to separate? Yes.

Tires + asphalt are to be treated more like velcro in terms of the physics behind them.

 

[Howard]

Tire physics lesson:

friction != adhesion.

Too many people focus on normal forces, surface area, etc, and apply 3rd grade physics formulas for rolling friction when in reality friction is not how a tire works at this level. It's much more complicated than that.

Does a wider puck on an air hockey table gain additional friction? No.

Does a wider velcro strip require more force to separate? Yes.

Tires + asphalt are to be treated more like velcro in terms of the physics behind them.

Why?

 

[Apex]

Why?

Because tires are soft, and deform to the asphalt.

 

[exdeath]

Heat, microwelding, abrasion, material transfer, etc.

 

[RedRooster]

2.8 cornering g's? Wow, makes you question the rest of the numbers too. That can't be possible.

 

[Ferzerp]

I'm still sticking with my "we've removed all the possible weight to remove" view because the other claim is ridiculous.

 

[Throckmorton]

Maybe weight distribution would be worse.

 

[JCH13]

Maybe weight distribution would be worse.

Reducing weight, assuming functionality is maintained, can only improve performance. Even if it changes weight distribution. Changing weight distribution will change the car's balance if suspension changes aren't made though.

I cannot fathom their wild claims that 200lb difference will change performance so much... a tank of fuel is most of that weight difference... a fat passenger would more than make up for it. That would mean that if a 350lb guy drove the car he would be 0.6s faster 0-60 than if I drove it. That's insane. There's something they're not telling us or that they're grossly oversimplifying.

 

[Apex]

2.8 cornering g's? Wow, makes you question the rest of the numbers too. That can't be possible.

The cornering g number is useless without some sort of standard. With a slow, tight enough turn, virtually any car can pull multiple g's cornering for a momentary measurement. For a wide, fast steady-state cornering measurement, 2.8g is impossible for a street car.

 

[Jumpem]

I trust what he says. Wake me up when Lamborghini, Ferrari, and Porsche catch up.

 

[rommelrommel]

I trust what he says. Wake me up when Lamborghini, Ferrari, and Porsche catch up.

Really the GT2 RS is all over the GT-R lap times. I suspect that the Enzo could be if someone was willing to beat the hell out of one lap after lap after lap like they do to get these times. The 918 has supposedly put down a 7:12.

 

[Jumpem]

Really the GT2 RS is all over the GT-R lap times. I suspect that the Enzo could be if someone was willing to beat the hell out of one lap after lap after lap like they do to get these times. The 918 has supposedly put down a 7:12.

They can't out accelerate it. 0-60 is all that concerns me in sports cars. It's the best indicator of on the road performance.