The Truth About Brakes

[Karlo]

The Truth About Brakes by Dennis Cook

See pdf file below

[cordycord]

I used to make aluminum brake rotor hats for Corvettes. We used aluminum hats mated to Porsche rotors to take the place of the 'Vette units. Porsche is one of the few companies that make their own rotors. They are unique as when they forge the rotors, they also forge in the "drill holes" in order to prevent stress at those points. Otherwise, drilled rotors are losing popularity to slotted.

Some things I've learned about brakes:

a) make sure that there's enough clearance between your caliper and the wheel. Usually 1/4" is good. You can go to as small as 1/8", but this room is needed for flex, road debris, and even wheel installation.

b) Pick you pads based on where you'll be driving. The best Hawk racing pads are useless and stupid on a car that's not on the track. The same goes for a street pad that gets serious track use. The results for both may be unwelcome. :(

c) Russell Speed Bleeders are GREAT.

d) Some road cars require replacement sensors when you change the brakes, and sometimes require a computer reset. Check when ordering.

e) When replacing banjo bolts, be careful to check the thread length and hole placement in relationship to the brake line hole. If you're also replacing the brake lines, you may have end fittings that are thinner than OEM, preventing the proper flow of fluid. Misalignment, not good. It's always good to replace the crush washers and to torque to manufacturer specs.

f) Those cool, light weight colorful aluminum banjos just don't give me the peace of mind of a steel fitting.

[Macdaddy]

Not sure what cross the author bears. He has some valid points I agree with, but some I don't. For example, on the matter of drilled vs slotted vs. std, I think there is a total lack of facts across the entire internet. Nothing but opinion, one opinion is as invalid as another.

He makes the point that drilled holes cause cracking. Well, certain pad materials cause cracking in non-drilled rotors. I don't think a small crack starting from a drilled hole is evidence of structural failure. I've held a 17" diameter truck disk brake in my hands where one entire braking face was worn off, but the rest was still in one piece.

A year or two ago I saw this in NASA tech briefs. There was an article about a technical paper Simulation of Heat Generation in Analyzing Thermoelastic Instability in Disk Brakes by Eltoukhy, Asfour and Almakky of the University of Miami. Among other things, they did a computer study of standard, perforated (drilled) and notched (slotted) brake rotors. Not sure of all the conditions but I suspect as it is a computer simulation they skipped outgassing and air circulation and wheel envelope issues, but they had interesting conclusions. They found the standard, drilled and slotted rotors all had the same maximum temperature. No cooling effects at all. However, they did find that the drilled or slotted rotors had " better results as far as the temperature distribution and the heat flux as compared to the standard" {quoted from NASA tech briefs July 2007}. LOL what that means to me is they should last longer! - less hot spotting.

So I'd like to see more analysis and dynamometer testing behind these "do this" or "don't do this" opinions. When some can say "we ran this series of tests on drilled and non-drilled rotors, and the results were......" I'll listen.