noobie brake questions

[chmercer]

im looking to replace my pads and rotors in the near future, and i have a few general questions about braking systems. From what i understand, the only point of a larger caliper and rotor is to more evenly spread heat, to keep the unit cooler, reducing brake fade under heavy use. So i think i have that part pretty well under control. but I am kindof confused about brake pads.

Every car ive ever driven was able to lock up its brakes if i jam the pedal at a reasonable speed. Locking the wheels is the most stopping a brake system can ever hope to do. Now maybe if i was driving a bronco with 42" mud tires and rear drums, the brakes would have a hard time locking the wheels. but thats apples and oranges. back on topic now.

how does changing brake pad compounds reduce (or increase) stopping distance? Wouldnt the stopping distance invariabley be the same if you always threshold braked? can somone please explain this?

thanks!

[Grant@tirerack]

I think you already answered the question. If you can lock up the brakes on your car, going to a bigger brake system or better pads/rotors is not going to make it stop in a shorter distance. It will allow you to control the braking a little better but there is another key to the solution. The next step is to get tires with better traction. That makes the most sense.

You can only brake at the limit of your tires.

For track use or autocross where you put a lot more demand on the brake system, better pads, rotors, and larger rotors, and calipers may make sense. For most street cars and daily drivers, it's overkill. They look great and can create more brake torque but without the tires, they are like a $5000.00 paint job on a YUGO (nice but not doing anything to improve the situation).

[chmercer]

so the bar graph i saw at autozone that said the more expensive brake pads made your car have a shorter stopping distance was just bogus marketing?

the only way to decrease stopping distance (assuming your brakes are strong enough to lock your wheels) would be stickier tires and weight reduction, correct?

[chmercer]

oh also, anyone know what these little slots are for in the rotors?

[SmithSR]

Yet another venting design, used in racing. 100% overkill for road cars.Chmercer, the other issue about brake pads could be compound of the pads themselves. Similar, but different, to a soft tire/hard tire issue.

You can get pads that are marketed as quieter(ceramic), organic, or semi-metallic pads that are harder, take longer to enter operating range, hold heat better, and offer premium brake force(maximum pad/rotor adhesion) when up to temp, and other high end/exotic racing compounds. Brake pads work best in a given heat range. If you get metallic brake pads, you'll notice in town and morning braking feels terrible, but after you've heated the pads well, braking performance improves. All at a premium hit to your wallet, because performance pads(even in OEM spec) cost more, and of course tend to wear faster. Once you enter the realm of performance tires/brakes, the cost only goes up, so research as much as possible to find the right pad for you.

So, you can get what is marketed as a better performing pad, just like you can get a grippier tire, but cost goes up and so does replacement intervals. Cool pic BTW

[Dori Dori]

I have my doubts that those slots are for cooling. I'd bet they are there for deglazing purposes. Could be wrong though.

[SmithSR]

Well, since glazing is one result of overheating, yes. Venting brake material and heat to the inner vanes of the rotor, then to the atmosphere, similar to a regular cross drilled configuration.

Venting comes in many shapes and sizes. drilled, slots, notched...

[Dori Dori]

I don't know, the more I think about it, the more I am leaning towards those notches being there to possibly measure how much rotor is left (being that they are composite and can wear like a pad). Then again, I know almost nothing about composite rotors and again could be completely off.

[chmercer]

dori i think you are right, being that the notches are of varying depth.