Stopping Brake Myths in Their Tracks

1. All Brake Pads are Created Equal.

One of the greatest myths out there is that you won't use the full potential of your brakes because of your driving style. As we all know, life happens, and the one time you need to use the full potential of your brake system, the performance isn't going to be measured in dollars and cents, but in inches and feet.

2. The more lube, the less noise.

Blasting a set of pads with lubricant or caliper slides with lubricant, no matter how expensive they are will not solve a noise issue for an extended period of time. Because lubricant can melt or flash off; worse yet can find its way over the pads making your car "judder" when you brake and increase stopping distance.

When your brakes are over-lubricated, they have a nasty habit of attracting dirt and debris, so as it hardens it becomes as soft as concrete, and if that build up happens to find its way onto the caliper body, you will have to get the caliper replaced because the rubber boot on the caliper is going to be damaged.

3. Rotors Warp.

Rotors do not warp, it was a theory that came out in the 70s to try to wrap a couple different phenomenom in clothing that the layman can understand. These are Brake Torque Variation (BTV) and Disc Thickness Variation (DTV).

BTV is a variation of torque across the face of the rotor. Normally this is caused by uneven deposits of friction material across the face of the rotor, which causes the brakes to slip and grab alternately.

DTV is the second part of this equation. DTV is calculated by measuring the thickness of the rotor in several different places, the subtracting the thinnest measurement from the thickest measurement.

As the thickness variations of the rotor pass through the caliper the piston will move in and out that causes the pulsation that you are feeling. Most vehicles are designed with DTV tolerances of 17 microns or less (about the width of a human hair). Normally if the difference is 15 microns or more in DTV, then you will get that pulsating feedback through your brake pedal.

3. All Rotors are the same.

How many times have I written this already? How many times will I write this in the future? Vehicles are designed from the tires up, just because the rotor from your 2008 Colorado 1WT fits on your 2010 Silverado LS does not mean that is the right rotor for your vehicle. The wrong rotor also will develop a run-out or BTV and DTV. Low price/low quality rotors may have compromises in structure or metallurgy that make sense to the wallet in the short term, but will affect performance long-term.

4. New Rotors need to be machined.

Re-read that third sentence in the section above, vehicles are designed from the tires up. When rotors come out of the box, they are supposed to be finished to specifications and ready to install.

There should be no reason to give them a clean-up cut. If they do need one, then it better be the suggestion of the vehicle manufacturer. Normally when you machine new rotors, you shorten the life of the rotors, but also may leave a rougher finish on the rotors that leads to BTV and DTV.

5. Shims are not required.

Alright, say it with me. Vehicles are designed from the tires up!!! If you get nothing else out of what I write about in this blog, you will gain an appreciation of the design work that goes into an individual model of a vehicle.

Shims are an important component of the brake system, not only to create a boundry layer to prevent vibration from being transferred to the caliper and knuckle, but also allow heat to be shunted off instead of being transferred to the piston. Because of the important role that shims play in todays vehicles they should always be replaced along with your brake pads.

6. You work on all brakes the same.

Just because it looks the same doesn't mean it is the same. You may miss something as simple as a torque specification for a caliper bracket to being as complex as disarming the ABS before pulling the brakes apart. You should always have access to current repair information if you are going to do it yourself, if not then make sure your repair shop has the most current information. That way you are not coming back to get something fixed that should have been done correctly the first time.

7. Dial indicators and calipers do not exist.

This is akin to saying the internet does not exist. There are shops out there that will make this claim or claim they are unnecessary or too costly. It really doesn't matter what the excuse is for not having the tools, if the shop doesn't have the tools to measure the rotor, then turn your car around and get it to a shop that has the proper tools to test your vehicle and repair it.