DO LONGITUDINAL G'S AND LATERAL G'S BALANCE?
02-04-2006, 01:20 PM
#16
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I am not totally sure about this but tires with contact patches that are longer than they are wide will tend to pull more G's fore/aft. This is due to the distance available for contact patch deformation prior to the entire contact patch beginning to slide.
I think you got off the topic somewhat by subtracting out the aero drag Gs. Johan's original post did not make this distinction. As you correctly pointed out, a fair amount of the decel G is available without using any of tire's capability.
To answer Johan's question, I would guess that if his data is accurate, then he has a chassis problem that hurts him under braking, and not so much in cornering. If he has a giant front sway bar, he may be able to get cornering balance (and therefore good grip) by using a giant rear bar or giant rear springs. Under braking the giant front bar will always cause lockup (or ABS) due to the individual front wheels being unable to follow bumps correctly.
I wouldn't use the term 'overloaded' to describe tires. I think you have to consider the static weight on a tire to be the baseline, and weight transfer adds or subtracts a percentage of this baseline. Obviously the more weight transfer the worse the grip from the pair of tires, so minimizing 'overloading' is no more important than 'underloading'.
I agree that it is strange that the best grip comes from the smallest pair of tires. This is only true because engine power is so limited. With a good enough engine, the best G will be accelerating, since the weight transfer helps you in this case (RWD).
If the track was > the wheelbase, the car would turn better than it braked for sure.
Every car I have had data on has done better under braking than cornering. For this to be true, you have to ignore any corner with banking. Otherwise it is not a fair comparison. Most corners have some banking, so this is not always easy.
Chris Cervelli
Premier Motorsports
I think you got off the topic somewhat by subtracting out the aero drag Gs. Johan's original post did not make this distinction. As you correctly pointed out, a fair amount of the decel G is available without using any of tire's capability.
To answer Johan's question, I would guess that if his data is accurate, then he has a chassis problem that hurts him under braking, and not so much in cornering. If he has a giant front sway bar, he may be able to get cornering balance (and therefore good grip) by using a giant rear bar or giant rear springs. Under braking the giant front bar will always cause lockup (or ABS) due to the individual front wheels being unable to follow bumps correctly.
I wouldn't use the term 'overloaded' to describe tires. I think you have to consider the static weight on a tire to be the baseline, and weight transfer adds or subtracts a percentage of this baseline. Obviously the more weight transfer the worse the grip from the pair of tires, so minimizing 'overloading' is no more important than 'underloading'.
I agree that it is strange that the best grip comes from the smallest pair of tires. This is only true because engine power is so limited. With a good enough engine, the best G will be accelerating, since the weight transfer helps you in this case (RWD).
If the track was > the wheelbase, the car would turn better than it braked for sure.
Every car I have had data on has done better under braking than cornering. For this to be true, you have to ignore any corner with banking. Otherwise it is not a fair comparison. Most corners have some banking, so this is not always easy.
Chris Cervelli
Premier Motorsports
