How and when to replace brake rotors
All cars truck and SUV have brake rotors, usually four of them and they are quite expensive. When the time comes to replace brake rotors here is how to know if you really do need to replace brake rotors or if you can skim them at a much lower cost and get more miles out of them. First rotors are a disposable items and will need replacing anywhere from 15,000 to 70,000 miles into their use depending on your driving style and the type of brake pads used.
Some brake pads are much more aggressive than others. A sign of a fairly aggressive pad is one which makes a lot of dust. Tests have shown that over 90% of brake dust is actually Fe or iron material coming from your rotors so a less aggressive pad will wear rotors less and also produce less dust. Some rotor wear must happen for the rotor to self clean and function properly, no wear at all usually will result on rotor black spotting where with a self cleaning pad, the rotor surfaces get mildly scrubbed us as you drive the car to keep them smooth and keep them true. Before you replace brake rotors look at these photos which will guide you on whether you need to replace brake rotors or you can salvage them.
Before you replace brake rotors look at these photos which will guide you on whether you need to replace brake rotors or you can salvage them.
This is a typical cross drilled rotor and what it will look like after about 40-50,000 miles commonly fitted to Jaguar, Mercedes and Audi cars. The drill holes do not cover the entire rotor surface and thus different surface areas exist across the rotor and some areas will wear faster than others. leaving behind nasty ribs. If you see ribs like this on your rotors take them to an on car brake lathe (not a bench lathe) provider which you can find on these links: Pro Cut Lathe.
UK Pro Cut Lathe Centres: http://www.skimmydiscs.co.uk/index.php
USA Pro Cut Lathe Centers: http://www.procutusa.com/zipfind.aspx
If fitting new brake pads, the time to bed the pads in will be significant due to the ribs which prevent the pads from seating properly, bed in times can take 1000 miles more than normal and brakes will be poor and noisy during this time. A skim from the rotor surface of 0.005 inches on an on car brake lathe will solve the problem.
The next photo is a partially worn OEM style rotor that still has life left in it. You should measure or have your garage measure using a micrometer (not a vernier) across the centre of the rotor and if the rotor is still above its minimum thickness, you may not need to replace brake rotors but they can be skimmed and used for more miles.
To find out if your rotor is below minimum thickness call a technical department of any brake supplier and ask them, they should have this listed in their handbooks and if not email this company, they are very helpful firstname.lastname@example.org. As a very rough guide if the lip on the outside edges of the rotor is less than one sixteenth of an inch or one millimetre there is a chance the rotors still have life in them.