Rebuild a Norton Commando Disc Brake Caliper

| 2/19/2014 2:43:00 PM

Old versus new: A 1974 Norton Commando 850 disc brake caliper stripped bare with old parts on left, new on right. 
Old versus new: A 1974 Norton Commando 850 disc brake caliper stripped bare with old parts on left, new on right. 

Although some people today criticize the front disc brake fitted to the Norton Commando starting in 1972 (earlier models used a twin-leading-shoe drum) for a lack of bite, they were highly regarded when new and considered superior to the drum brake setup.

It's important to remember that 40-plus years of development has resulted in performance levels in 2014 undreamed of in 1972. Former Norton employee and now Barber Museum restoration expert Brian Slark notes that when Norton introduced its disc brake, "Britain still had streets paved with cobblestones and wood blocks sprinkled with tramcar lines everywhere, and the last thing you wanted was to send a rider skidding down the road when he squeezed the front brake."

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That doesn't mean the Norton disc brake was without issues, however. Similar to many bikes, disc brake model Commandos were originally equipped with chrome-plated iron pistons. The problem is that over time — and especially if moisture gets into the system or the brake fluid gets contaminated — the chrome on the iron pits and flakes, wrecking the caliper seal. Further, the steel caliper piston plug fitted to the Norton caliper tends to seize to the caliper body. The cover is screwed in tight using a "peg spanner" and the pegs — or holes — in the cover are often damaged during removal.

Stainless steel, however, won't flake, and it's extremely resistant to corrosion and pitting. That makes it a perfect material for replacement caliper pistons, something the aftermarket has long recognized. Norton didn't specify stainless steel pistons, most likely because they would have been more expensive.

For this How-To, we rebuilt the front brake caliper on a 1974 Norton Commando 850. Our caliper pistons were corroded, with the chrome surface scuffed and pitted, so along with new caliper piston seals we installed new stainless steel caliper pistons and a new stainless steel caliper piston plug. We sourced our stainless steel pistons and plug from Job Cycle, along with a rebuild kit containing new caliper seals and plug seal, and a new stainless steel bleeder screw. Total cost was $146, not including brake fluid. The brake pads had been recently replaced, so we reused ours. Budget another $30 or so if you need new pads.

You’ll need a “peg spanner” to remove the outer caliper piston plug. 
You'll need a "peg spanner" to remove the outer caliper piston plug. To learn how to make your own cheaply and easily, click here.

7/30/2019 3:01:23 PM

How about something on bleeding the rear brakes? I never have much luck with it. Front no problem. Maybe there's a trick to it I don't know about?

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