Please don't ask us to do it wrong. *Updated*
We have had customers come in wanting us to do what we call a pad slap. A pad slap is when you just put new brake pads on and do nothing to resurface the rotor surface. When I get asked to do a pad slap I always hear my Automotive Tech School instructor’s voice in my head saying “Never, never, never put new pads on an old rotor surface!” While a pad slap is, in theory, cheap and fast, you are doing your car and yourself wrong.
A used rotor surface has a mirror like finish that you won’t see on a new rotor. When you put new pads on an old glazed rotor you are messing with the friction coefficient that is designed to stop the car in all situations.Sometimes customers come in and their brake pads look great as far as thickness, but they are saying that they have a vibration when braking, especially on the highway. What has happened is the brake rotor over time has been exposed to excessive heat and cold, which causes the rotor to warp and they are feeling this as a shake/vibration when braking. Rotors must either be replaced or machined when pads are replaced.
We first measure the old rotors to make sure there is enough material to be machined (cut) off so that the rotor does not go below the minimum thickness specification. At Jammin J Automotive we have a Procut On Car Brake Lathe, which will do what is called Machine Matching of the brake rotors. The Procut Machine machines the rotor while still on the vehicle and literally matches it to the wheel bearing and hub; the result is a beautiful new braking surface which is balanced to the vehicles rotating parts associated with that wheel’s braking system which equals safe and very smooth braking. When we purchased the machine we were told by the technician that even new rotors should be machined and we thought he was crazy. After measuring and testing new rotors over the course of several weeks, we were shocked at how many needed resurfacing (all of them!) to correct for inconsistencies in the rotor’s surface and now we Machine Match all new and existing brake rotors to ensure the best braking performance possible on every brake service we perform. To view what this process actually looks like, click here to view a video.
Here are some pictures of a customer's rotors who wanted just pads only, showing both sides of the rotor. While the side of the rotor that was visible through the wheel doesn’t look so bad, the back side clearly has extensive rust and very severe grooves that are just too deep to machine out of the rotor.
Please be wary of ads that speak of brake repair based upon how inexpensive it is. When it comes to brakes, they are the #1 safety system on a car and we will not cut corners just to save a buck. Brakes that are done correctly are safer, last longer, and cost less over the long haul. It is always important to use the proper quality of braking system parts that are recommended for your specific vehicle’s needs. Here at Jammin’ J Automotive, we do brakes right or we don’t do them! Our goal is to keep our customers on the road in a safe vehicle with the best possible braking equipment.