Yesterday evening, I had to come to a complete stop from 80 ina as short of a distance as I could. I have a 98 civic cx hatch. What suprised me was that the brakes seem to lock up from about 40 all the way down to 0. I have stock brakes with 185 all season tires on vx wheels. (I know I will need a bigger wheel than 13") I was eventually planning on upgrading my brakes, but if these brakes lock up at such a high speed, is there any point to the upgrade? Won't I just lock up at an even higher speed, if everything were to remain constant?

 

Brakes don't lock up because of speed. Speed has NOTHING to do with the brakes locking or not. Nothing.

It's all about the pedal pressure.

They lock up because of how you drive. Learn what threshold braking is and try it out.

You have a fixed amount of deceleration you can apply, based on your brake size, the contact patch of your tires, the weight of your car, the stickyness of your tires and of the road, and your speed at any given point during your decelleration. The trick is to learn what that maximum amount of decelleration is at every point (it looks like a curve that gets higher as speed lowers for normal brakes and tires) and adjust your pedal pressure accordingly.

To stop really really fast from 80, you're going to need to modify not only your wheels, tires and brakes, but your suspension too. And, of course, your driving style.

 

for a good answer.

Does maximum decelleration occur at the point where you can apply the most pressure without causing lockup? How does one go about teaching themselves where this threshold occurs? Changing one piece of the equation will improve the situaction correct? Say with sticky but not nessasary wider tires, or better brake pads, assuming you readjust your own brake sensibilites to take advantage up the brake system changes?

 

The best way to learn about high performance driving is to spend a day at a race school. Skip Barber and Bob Bondurant and the NASA days and things are expensive, but spending $500-1500 on you will make your car a lot faster than spending $500-1500 on the car after a certain point. It'll also make you a safer driver on the street if you use some common sense.

As for the technical stuff...

Where your max decel happens depends on how you're measuring it. Suffice it to say that max decel will happen when the tire is slowed as much as possible in it's rotation without causing it to slide. Definind decel by % tire RPM change or G load or any number of things tweaks the position of this over the course of stopping distance, but you'll slow down the most when the tires are still stuck, but barely. Thus threshold braking, ie, at the threshold of skidding.

Improving one part of the equation will indeed improve the whole situation. Stickier tires allow you to use more pedal pressure to stop, because the tires can hold onto the road better and absorb more of the friction effect of the brake bads before skidding comes in. Wider tires will do the same thing. Bigger brakes on stock sized tires increase the pad area, and allow for shorter stops without lockup too (more feel, more finesse, etc). Suspension tweaks can help keep the car balanced and the braking distribution more even (in terms of weight on the corners) and improve stopping distance too.

-dave