FAQs—Pontiac Brake Disc
- Why do some brake shops require brake disc/rotor turning when they change the brake pads?
Rotors are usually turned during pad replacement to ensure proper surface finish for the break-in of the pads and for improved braking performance. Even with new brake pads, braking power and efficiency may still suffer if the rotors are no longer in great condition. The new pads may produce more friction on old rotors, and this can lead to a braking issue or poor braking power. Hence, some shops turn or replace rotors/discs when changing pads to prevent a brake problem. If they only change the brake pads and not the discs, the customer may need to come back soon for another brake system defect.
- I’ve experienced some pulsation when stepping on the brakes. I checked the rotors/discs and found out that there’s uneven wear. What causes uneven wear on the rotors/discs?
Uneven wear on the rotors/brake discs may be blamed on excessive runout or hard spots. If the lug nuts aren’t torqued evenly, this may result in the distortion of the discs. Aside from this, the distortion may also be brought about by accumulated dirt or rust in between the hub and the rotor. Differences in the thickness of the rotor can result from uneven rotor wear, which may cause pulsation in the brake pedal.
- How can you prevent excessive runout on the rotors/discs? Is there anything that can be done to reduce runout?
To reduce runout, the rotor’s position on the hub can be re-indexed. To do this, you have to remove the rotor from the hub. The rotor hat and face of the hub must be cleaned using a brush. As you mount the rotor on the hub, the rotor must be moved from the previous position. Moving it over 1 or 2 bolt holes is usually good enough. Runout should be gauged using a dial indicator. Make some adjustments as needed until you get the least runout or until it falls within the factory specs. If runout is still beyond the limit, a correction plate may be set in between the rotor and hub flange.
- I had my Pontiac brake disc checked, and it turned out that there are hard spots on the rotor. The mechanic said that the disc should be replaced instead of resurfaced. Can’t resurfacing fix the uneven wear caused by hard spots?
Resurfacing the rotor/disc can be done to fix uneven wear. Runout problems can be fixed by this. However, hard spots are best fixed by replacing the rotor. Even if the disc is already resurfaced, hard spots may emerge after a few thousand miles since changes in the rotor go beyond the surface. You can’t fix hard spots simply by trimming or shaving off the top—this will just be a temporary fix.
- As I changed the pads, I found some cracks on the discs. Do I have to replace the rotors as well?
Minor cracking on the surface is actually quite normal. Surface cracking is caused by heat and wear. If the cracks are over an inch, the rotors should be replaced. Deep cracks may cause rotor failure, resulting in a compromised braking system.
- When should the rotors be resurfaced? How would I know if resurfacing should be done on the brake discs?
If there are scores, rough spots, and a wavy disc surface, it may be time to resurface the rotors. Resurfacing is recommended by some manufactures if the grooves are over 1.5mm in depth and if thickness variation is over 0.025 mm. Runout that goes beyond the specs and severe corrosion on the face of the rotor are also good reasons to have the rotor resurfaced.
- How would I know if the discs should be replaced instead of turned?
Brake discs/rotors should be turned only a couple of times, within the manufacturer’s specifications. The discs can’t get too thin. Otherwise, they will crack and get damaged badly. To find the measurement for minimum thickness, you can check the discs or the service manual. This information is usually stamped on the disc. It would also be better to just replace the discs if the grooves or cracks are already deep.