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Old 26th April 2014, 08:49 AM   #9 (permalink)
Little Nismo
Little Nismo is A Pickled Cabbage
GTR.co.uk seasoned Member
 
Join Date: May 2002
Location: Hamilton New Zealand
Cars owned: Nissan Skyline R33 GTR, 402kw @ 1.75bar
Posts: 110
Quote:
Originally Posted by borat52 View Post
Don't confuse downforce with weight.

Essentially its basic physics - the heavier a car the more momentum momentum = mass x velocity which means you have to apply more force to accelerate the car and more force to decelerate the car.

Friction = mu (co efficient if friction which is a constant for a given surface pair) x R where R is essentially mass.

What does all of this mean? If you want to turn a heavy car then it has lots of momentum which means you need proportionally more friction (equates to more tyre and brake wear) and if you want to accelerate a heavy car then you need proportionally more power.

An F1 car uses downforce to create more R (reaction) while maintaining low weight so it gets the best of both worlds - more friction and less momentum.


The GTR is heavy and it copes, at the expense or brakes and tyres. If it were 500kg lighter with all other things equal it would be a lot quicker.
And don't you confuse weight and mass. Downforce effectively increases the weight of the vehicle. For any given downforce the less the mass of the car the better. But if you have a total of 1800kg from mass alone or 1300kgs mass and 500kg from downforce doesn't that, mean that 1800kgs still has to turn the corner or be accelerated? It still requires the same traction.

If you have ever driven a powerful Ute you would wish for some more weight in the rear; zero traction. It seems to me there is a cross over point where you have too much power for the mass of the vehicle given the traction it can produce from the wheels selection... Clearly a weightless car will not perform well.

The point then is that datsun are saying that the optimum is 400kg per corner for at GtT car of the dimensions and wheel selection of the gtr.

Otherwise why does the gtr perform so well? What's their secret it's heavier and less powerful than a number of other vehicles but yet quicker? Is it all lower gearing and 4wd? I doubt it.
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