Little did I know when I started to rebuild my brakes, front, and back, that new brakes would squeal. More interesting is that there are multiple articles and entries on forums such as the MG Experience documenting this topic.
A couple of weeks ago I completed my brake job front and back including a complete clean-up and painting of the hubs and backing plates.
This was the first time I ever worked on brakes, and it was a learning experience and at the end, I was proud of the job I had just completed. I got in the car to test the brakes and upon my return I had a smile from ear to ear. The car stopped straight and fast and the brakes exceeded my expectations.
Then a week later, just before our club’s Spring Tune-up Day, I went to fill up with gas and when coming to a stop at the corner of my street, the brakes let out this horrible squeal. Quite embarrassing, since everyone is already looking at the car, because its an MGB and that’s what people do.
I immediately went online to find out what could possibly be going on with my new brakes. I, of course, felt that I must have done something wrong.
At the Spring Tune-Up I asked a few members, and they too have intermittent squeals from their brakes. I searched MG Experience and found many people with the same phenomena. I spoke to experts who have worked on these cars since the seventies. They all had different solutions that may or may not work. They all agreed the squeal was harmonic vibration of the pads against the metal caliper. So, I decided to try the Brake Quiet silicone solution, removed the pads, and applied the solution to the back and sides of the pads. I went out for a drive and there was no squeal for the first ten minutes and the squeal returned.
I then removed the pads again and noticed that the pistons were not evenly pressing on the pads. In fact, the bottom part of the pads seemed to have little or no contact with the pistons at all. This led me down the road to a search on piston directions since, after examining the pistons, I noticed they each had a section that was recessed and would not apply pressure to the pads.
I found an old diagram about MG calipers and pistons and realized that the new calipers from Moss have the pistons installed in the calipers incorrectly.
If you look at the picture of my pads, you will notice how the piston circle extends past the back of the pads. The circle is not on the middle of the pad. According to the diagram, it makes sense that the recessed area of the piston is facing back towards the hub, applying equal pressure from the pistons to the pads.
I therefore removed my calipers from the hub and placed them on a stool, still connected to the brake line. I blocked the middle of the calipers with a tool and pumped the brakes to have the calipers extend outwards without them falling out.
I then used a rubber bottle top opener to grab the pistons and turn them so that the recessed area is in accordance with the above sketch, facing to the back. Using the rubber ensured that I did not damage the surface of the pistons.
After both pistons were aligned properly, I started to reassemble the pads. This time I used Permatex silicone ceramic brake lubricant on the back and sides of the pads.
Finally, when putting on the clips, I used two clips squeezed together instead of one. I question the tolerances on the caliper machining, so the extra clips apply slightly more tension to the pads.
Once assembled I took her out for a drive. Stop, start, and stop again. There was no squeal. I resisted the temptation to do my garage happy dance until a week later when I put on another 200 miles and the brakes are as silent as can and should be.
I can’t say definitively what exactly fixed the squeal, but I think it is the pistons in the right position and the silicone ceramic brake lubricant. But I also, think the double clips may play a supporting role.
All I know for certain is that the brakes work perfectly and do not squeal.
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John Leeman said:
Great that you’ve been so thorough and that you’ve not just accepted the attitude that it’s new out of the box so it must be OK! Often it isn’t nowadays unfortunately. Happy motoring. John.