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Automotive brakes work on the principle using friction to convert kinetic energy into heat energy. The formula for friction has no area component, it is strictly applied force (in this case the hydraulic force applied by the calipers to the pads) multiplied by the coefficient of friction between the brake pad and the cast iron rotor surface.
Dragsters use super wide and soft tires not to maximize the the friction between the tire and the road surface, but to maximize the tire area for the shearing force of the soft tire rubber. Shear force calculations have an area component, and it is this shear which leaves the black tire rubber on the roadway.
It may be possible that the coefficient of friction between the rotor and pad is ever so slightly reduced due to the cross-drilling, but the cross-drilling provides escape paths for rain water and the gasses generated by pad wear, and also promote additional brake cooling by rejecting heat faster. Eliminating these three real problems (water, gasses, excess heat) more than compensates for any theoretical reduction in the friction coefficient.
Larger rotors allows the pads to be located further from the axis of rotation resulting in additional braking efficiencies, similar to using a longer breaker bar to remove a rusted nut.
I agree that cross-drilling provides little benefit for regular highway driving, but I still like the looks of drilled and/or slotted rotors. And yes, if you haven't guessed already, I run cross-drilled Zimmermanns on my 2000 9-5 lpt.
posted by 68.40.14...
_______________________________________
Saabs owned:
2008 9-5 Aero Sedan, sold at 227K miles
2006 9-3SC 2.0T - Wife's daily driver
2000 Viggen Convertible - Sold May, 2022
1964 Quantum IV Formula Car - Retirement project
2000 9-5lpt Sedan, sold at 318K miles
Posts in this Thread:
- rotors... Does it matter what kind I use?, Hoffa, Wed, 3 Jan 2007 08:56:43
- Be cheap, dtech, Wed, 3 Jan 2007 11:47:50
- Yes!, Noel, Wed, 3 Jan 2007 11:18:39
- trade offs, bobc , Wed, 3 Jan 2007 11:12:27
- Re: rotors... Does it matter what kind I use?, wooglin , Wed, 3 Jan 2007 10:56:22
- Re: rotors... Does it matter what kind I use?, paul o., Wed, 3 Jan 2007 09:14:47
- Stick with a name brand for a good reason...., MI-Roger , Wed, 3 Jan 2007 09:11:07
- They stop the car. Don't bargain hunt too hard., BrianG, Wed, 3 Jan 2007 09:07:58
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