Brake rotors operate by using brake pad friction to slow the automobile. In the old days they were thick and can be resurfaced several times but nowadays they're not so thick and are sometimes made out of composite materials. Your Volvo XC90 brake rotors can show some early warning signs of failure that you can immediately remedy if you know what to look for.
Check the dashboard for a brake warning indicator light as trouble codes may appear via the dashboard in cases of brake failure. If there are any unusual sounds coming from the brakes under normal driving conditions, it is possible that your brake rotors have become worn or they overheated. These sounds are most noticeable during very slow stops.
When you feel a vibration in the brake pedal-and the faster you travel the more violent it pulses-you might be dealing with a warped brake rotor. A badly warped brake rotor should be replaced if they are of the composite style. However, if they are of the thicker, more old-fashioned cast-iron variety, they can be resurfaced.
The brake caliper should also be inspected as it holds the brake fluid that exerts pressure on the pads to grip the rotor. A faulty caliper will make the brake fluid leak, and this leak can contaminate the rotors, causing slippage, glazing, and burning.
Brake rotors should have a smooth, clean, and shiny surface, so any sign of striations or grooves in their surface is a red flag. Brake rotors that have worn past to their rivets or have worn past factory specification limits should be replaced immediately.
Brake rotors have to be resistant to heat fade during high-speed braking and repeated stops. How long rotors last is directly related to the heat generated by the vehicle and the efficiency of getting rid of it. City driving generates more heat; it also provides less cooling airflow, thereby wearing out the rotors faster.
Rotor systems should be resistant to water and problems associated with running through puddles. They also adjust for wearing pads and require no manual adjustment.