I replaced the front brake pads and rotors on a 99 Bonneville about a year ago. The outside pad on the passenger side has worn completely out and has ruined the rotor. The inside pad on the same side looks fresh. Everything on the driver’s side looks good. What the heck happened? I am not an expert but I have replaced many of these GM brakes and have never seen this result. Thanks for any input.
Either the caliper is sticking or the pads are sliding on a corroded surface and not moving freely.
The caliper pin is sticking. They should be lubed every time the brake pads are replaced. They may need new seals.
Thanks for responding, but how do I figure out which possibility is the culprit?
Its the pins. Do you have ABS? There is a way to check but the technique depends on the answer.
Thanks! If ABS is = to Anti lock Braking System, the answer is yes.
With ABS, you have to remove the brake hose from the caliper. Then pry the inside pad back into the caliper. You can do this with a big screwdriver. Yes it will probably damage the pad and nick the rotor, but those are going to be replaced anyway. Now with a good gap between the inner pad and the rotor, grab the back of the caliper and pull it toward you.
You will feel a large resistance before the caliper suddenly moves. After that it may move back and forth freely, but it will stick again if the pins aren’t removed and greased with a synthetic or silicone grease. Considering the age of your vehicle, you probably need new seals for the pins.
The pins are sometimes called bushings BTW, but most mechanics call them pins. You should also replace the hardware kit on the caliper.
If this is the original caliper, you might be better off with new calipers and new brake hoses. They would be 17 year old now, time for a change.
Thanks Keith. I have owned the vehicle for many years and would believe the calipers are the originals. So you would believe that if I replace the calipers, rotors, and pads on both sides, the brakes will be back in good condition?
Only if you also take care of the hardware (pins, etc). If the new calipers can’t slide properly, they’ll simply stick and destroy the next set of pads and rotors.
Gotcha. Many Thanks!
I second everything Keith said. I had to change my rear rotors a year or two ago for the same problem. And, like you, mine were the originals.
Asymmetrical wear is a dead giveaway to sticking caliper slides. At 17 years old, change the calipers.
I agree, the caliper is not moving freely like it should. Good idea to replace both calipers along with new rotors and pads. Then you’ll have both sides done, all new. Can’t guarantee your brake problems will be solved, but you should be well on your way to like-new front brakes. When you purchase your new calipers, ask if there’s someone experienced there who could show you what exactly needs to be lubed, and that you have the required brake lube product. New rotors usually come with an anti-rust coating which must be removed before installing the rotors, otherwise it will clog and ruin your new pads. Brake cleaner works well, but many people just wash them thoroughly in soap and hot water.