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Old 11-29-2010, 01:37 PM   #257
Scooby Guru
Member#: 141373
Join Date: Feb 2007
Chapter/Region: E. Canada
Location: Quebec, QC
2008 2.5i-hatch -
now with a HID retrofit


Originally Posted by Cartmans 03_Wagon View Post
Ummm so good arument if we are debating based on opinion, but where are the facts? Controlled stopping tests on same car with different brakes? Braking under hard track driving vs. street driving, wet and dry braking, and on and on.

You're stickies seem to be opinion and severely lacking in the evidence department, I would be more inclined to read what you say if it wasn't just opinion after opinion with nothing besides your (1 person's) experience.
Physics are not an opinion, unfortunately. To stop the car you need to decelerate it. Since we're not equipped with parachutes or reverse thrusters, the only way it's happening (short of drag) is through surface friction. The only points of contact in between the car and the road is the tire. The force applied at the contact point is equal to mass x acceleration vector. The static friction coefficient will then be the ONLY parameter at this point which will yield the moment (or the peak deceleration value) at which you will lock your tires. Want to decrease your stopping distance? Change the said coefficient - brake on a surface with more grip, or get tires with more grip.

One thing that people forget is that stock cars are designed to be able to sustain a single threshold breaking event from their top speed to zero under full legal load. Period. (and I wouldn't be suprised if there was an additional margin for downhill cases too) You can lock the tires / engage the ABS of ANY stock car on the best hyperpaved street on this continent - which implies that the brakes have sufficient power and that the limiting factor is the tire/surface grip. Brakes are also designed so as to provide sufficient thermal dissipation for the aforementioned braking event.

Fading, overheating, boiling, thermal dissipation, and all of the issues people raised on here - they all are outside of the original post, as they deal with repetitive braking with intervals which do not allow sufficient cooling - and cooling here is the ONLY issue. On the first U-turn or twistie in a canyon, stock brakes will be perfectly sufficient regardless if it's a 165hp NA or a 700whp STi (corrected for the vehicle's weight an speed from which it is decelerating). On the 10th turn, temperature effects will chime in - but NOT a lack of intitial "breaking power".

Also, a MAJOR source of naive confusion is the brake response vs pedal depression. It is the same as with the DBW system on newer imprezas. Remapping your DBW map will NOT make your car accelerate faster, it will make it "feel quicker" due to a more pronounced initial response to partial gas pedal brush. Similarly, revamping your brakes will make it "feel stop better" because the initial grip will be stronger.

Originally Posted by Scooby207 View Post
great thread... can't argue with physics
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