Gimme a brake… Lockeed Caliper overhaul (Part 2)

As mentioned before the Lockheed calipers I took of Mildred (my 1973 MGB GT) are in a really bad condition. After getting the pistons out and taking them apart I spent a good amount of time cleaning them with a wirewheel. The old brake fluid turned into some form of goo which I got out of the channels with the help of some pipe cleaners. The surface for the top seal is quite pitted but the bore that the piston run in still looks ok. It took almost two hours before I came to the conclusion that only glass-blasting will result in the surface finish I want.

As preperation for this, I reinstalled the old top piston seals from Maggie’s (my 1967 GT) capilers along with the old pistons. This will protect the insight bore from blasting. As I also don’t want the mating surfaces of the two caliper halves to be damaged by blasting. I reassembled them including a piece of the old brake hose – sealed off with a screw. Hopefully that will keep out most of the debrie from blasting.

Time to focus on Maggie’s original Lockheed calipers. The reason why I replaced them with aftermarket ones was that I had uneven pad wear on the Mintex M1144 that were installed by Frontline Developments back in 2018. While I am not 100% sure I think that one of the contributing factors for this was that the “C-section” you typically see on the pistons was completely gone. Additionally the surface of the bore – especially the ridge between the two piston seals was quite dirty. I had those calipers blasted and powdercoated last year already.

A two inch / 5cm clear-strip-disc attachment for the power drill helped cleaning the inside surface. I used a edge of the cutter and the tip for a small screw driver to clean rust and dirt for the channels for the seals. Plenty of brake cleaner and pipe cleaner where used to clean the channels. New bolts, seals and stainless steel pistons came from Moss earlier this week. With all parts cleaned and on the bench the assembly was the easiest and quickst part of the job. I carefully installed the top seal (the one with the groove inside) with the metal retainer. A fews with a rubber mallet follow by some gentle hits on a piece of flat bar. They need to be flush with the caliper surface. As I was unsure if any of the grease I have is compatible with DOT4 brake fluid – I dipped the seals in the same. The inside of the calipers and the pistons where also smeared with DOT4 this is enough lubrication to get the seated easily.

The two caliper halves got a new seal between them and the new bolts got a few drops of heat resistance Loctite 648 before I gave them 50NM (37.5 ft-lbs) – a valve I found on MGEXP in a screenshot of the Brake Survival Kit instructions from Lockheed. I wanted to test if the pistons move easily and put a bit of flatbar between the pistons but prevent that they fully come up. Then I applied a bit of air and repeated the process a few times. Initially one side would pop out faster than the other. But after 4 or 5 times they both moved almost identitcal and I could press them back down with my fingers easily.Last I tested the fitment of the EBC Greenstuff pads in the freshly rebuild calipers. As you can see in the picture – the side of the pads aligns perfectly with the round groove inside the calipers. This is what Peter Sanderson pointed out in his video and I believe he is spot-on with this observation.

Job ‘s a good ‘un I think. Next I need to swap the calipers on Maggie and I will find out next week if this setup finally elimates the break squeal.