Advice on Lockheed brake caliper and upgrades

Hi everyone,

I have a 1973 Combat Commando that I rebuilt from a crashed parts bike a few years ago. I did a complete rebuild from the frame up, and it's been running smoothly.

The bike came with a Brembo master cylinder, original disc, and Norton Lockheed caliper. I rebuilt the caliper with new seals and pistons, and replaced the seals in the master cylinder.

Everything was working fine until this year when I discovered the brake wasn't functioning at all. The master cylinder was empty, but I couldn't find any evidence of leaks.

I tried bleeding the system using the brake lever, then with a syringe to push fluid up to the master cylinder and vice versa. I had some success, but a few days later, it seemed to be full of air again.

I'm really puzzled by this, so I'm considering my next steps. Here are some ideas:

- Remove the caliper, check if the pistons are the correct type with the step on the back, and ensure all internal passages are clear. Try refilling with brake fluid before fitting.
- Rebuilding the master cylinder, making sure all holes are clear.
- Check the brake line for blockages, and possibly replace it.

Another option is to upgrade my brake system. I could get a new master cylinder, but I need one with a brake light switch. I'm not sure which one would be suitable.

I'm also thinking about getting one of the replica Girling calipers. Do these work better than the original Lockheed caliper, and are they easier to bleed?

Any advice on how to get my brakes working again would be greatly appreciated. Also, thoughts on whether it's worthwhile to upgrade the master cylinder and caliper would be very helpful.

Thanks!

gunnag said:

Do these work better than the original Lockheed caliper, and are they easier to bleed?

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Their advantage is the increase in mass and the larger surface area of the pads, so they can absorb more braking down long hills before overheating and greater friction. But the piston size also is adverse to getting to the sweet spot of 27:1 ratio so you need a 12.7mm or 12mm Master cylinder piston size rather than the 13mm, but that is a minor issue. I have one fitted but to be honest the greater improvement was from a stainless braided line than the caliper.

The brake fluid must have gone somewhere, you need to find the leak, either air in, or fluid out, or both. How old are the brake pipes? and the brake fluid? The rubber lines should be replaced every few years and the hard bundy tubes checked for blockages. Just expecting a better brake by swapping the Norton Lockheed caliper for a replica Girling wont do much at all, The pad area is greater but the piston diameter is smaller so one cancels out the other.

gunnag said:

Any advice on how to get my brakes working again would be greatly appreciated. Also, thoughts on whether it's worthwhile to upgrade the master cylinder and caliper would be very helpful.

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A pocket may have formed in the brake hose, into which the oil is pumped. Replace the rubber part of your brake line and test again.

- Knut

There is a product which is sold in car parts shops which is known as 'rubber grease' It is used to seal and lubricate the pistons in brake calipers. Otherwise the rubber cup in the master cylinder might be faulty, but you should be able to detect the leak. The guys who do brake services for cars are worth talking to. They fit new liners into master cylinders.

Or, so perished they expand with each brake pump, but are no longer elastic enough to return to shape. Started happening on my old Honda. Brake fluid was reducing, but no leak. When I replaced I went with braided lines with a black outer. Look original.

Thanks for the ideas, the rubber brake pipe is at least 10 years old, so I'm going to replace it with a stainless braided one.

I will have a look at the caliper, when I originally rebuilt the caliper used stainless steel pistons from Andover Norton, I dont remember where the seals came from or whether I used brake grease, so I will rebuild using brake grease.

Will report back when done.

I would suggest putting a larger brake and sleeving the MC to 13mm. I did and the improvement is exponentially better. I think there's a guy on this site, Madass, who sells a kit. Mine was made from a bracket, AP caliper clone, and floating rotor all sourced from different places. New hoses fabricated at local shop. They're rubber but brake is fine with good feel.

Gun,
I purchased the complete kit from Don Pender (Madass) about 4 years ago and am very pleased.Bolts right on along with the brake switch included.Myself I think it is reasonably priced and works great.You have many options and it all depends on which way you want to go.
Mike

It may be that the piston rubber cup in the master, that seals and forces fluid into the system when you pull lever, is not doing its job sealing the cylinder and fluid is byassing it and not being forced into the circuit. That can explain why you get a firm lever then later not.
So my suggestion is to start with a master cylinder rebuild
Dennis

Thanks for that advice I'm not sure what diameter the MC has, but it is a Brembo MC with an adjustable lever, maybe already 13mm. Yes a rebuild would be a good idea, so thats on the list of tasks.

The brake line has a banjo fitting at the MC end and the other end connects into the standard bundy tube. For the new brake line, I'm thinking of connecting directly in to the caliper, seems like a better solution to me.