OEM brake caliper rebuild caution

MexicoMike · Jul 28, 2017

I recently had one of the pistons seize in my OEM Norton/Lockheed caliper. The bike had been unused for a while and some moisture in the system caused that. I decided to rebuild the caliper using the Commando Specialties kit, consisting of new pistons, a new cover plate, seals, and disc pads.

I immediately discovered that the new pistons would not fit into the OEM caliper bores. I thought perhaps the bores had become out-of-round over the years but further futzing around revealed that the a new piston would start into the bore if placed "face down" but would only insert approximately 1/2" in before completely jamming. When I tried to install the piston "face up," as the inner piston has to be, it would not insert at all. So, I cleaned up the OEM pistons, installed them with new seals, and reassembled the caliper. The brakes now work perfectly.

I sent an email to Commando Specialties explaining what happened and asking if I could return the pistons but never received any response. I expected SOME sort of reply, even if it was to say they would not take them back. I was actually more concerned that they be aware of a possible problem with their pistons than I was about getting a refund. I have quite a few "new" Norton parts from various suppliers that either don't fit at all or require considerable "adjustment" to fit correctly so having "Norton" parts that don't work is nothing new!

But I wanted folks to be aware of the possibility. FWIW, there's probably no real reason an original piston needs to be replaced. They can easily be cleaned up and I'm not sure why I decided to buy the complete kit when all I really needed was the three O-ring seals! I guess it was one of those "Seemed like a good idea at the time" things.

jaydee75 · Jul 28, 2017

It sounds like you were trying to put the piston in upside down?
Jaydee

concours · Jul 28, 2017

MexicoMike said:
I recently had one of the pistons seize in my OEM Norton/Lockheed caliper. The bike had been unused for a while and some moisture in the system caused that. I decided to rebuild the caliper using the Commando Specialties kit, consisting of new pistons, a new cover plate, seals, and disc pads.

I immediately discovered that the new pistons would not fit into the OEM caliper bores. I thought perhaps the bores had become out-of-round over the years but further futzing around revealed that the a new piston would start into the bore if placed "face down" but would only insert approximately 1/2" in before completely jamming. When I tried to install the piston "face up," as the inner piston has to be, it would not insert at all. So, I cleaned up the OEM pistons, installed them with new seals, and reassembled the caliper. The brakes now work perfectly.

I sent an email to Commando Specialties explaining what happened and asking if I could return the pistons but never received any response. I expected SOME sort of reply, even if it was to say they would not take them back. I was actually more concerned that they be aware of a possible problem with their pistons than I was about getting a refund. I have quite a few "new" Norton parts from various suppliers that either don't fit at all or require considerable "adjustment" to fit correctly so having "Norton" parts that don't work is nothing new!

But I wanted folks to be aware of the possibility. FWIW, there's probably no real reason an original piston needs to be replaced. They can easily be cleaned up and I'm not sure why I decided to buy the complete kit when all I really needed was the three O-ring seals! I guess it was one of those "Seemed like a good idea at the time" things.

Were you drawn in by the siren song of "Staaaaaaiiiiinless"?
Just kidding. My original chrome plated ones cleaned up ok, but there was some pitting (no leaks). I imagine others could be far worse.

Numbers, we're going to need measurements & pics.

Onder · Jul 28, 2017

First, did you telephone? Just curious a lot of places are slow on email.
Secondly, if I remember correctly, the OEM pistons are plated. It seems to
me that small rust spots can ruin the seals and if you buff them and reuse
the rust will return . Perhaps in dry climates this isnt a concern.
I went to SS for this reason.

MexicoMike · Jul 28, 2017

As far as "upside-down - Both pistons have to drop all the way into the bores. The inner piston has to face "outward"," the outer piston has to face inward. IOW, if you have the caliper on the bench with the bore opening facing upward, the first piston has to be installed with the "flat" (which presses against the brake pad) facing upward, and the 2nd piston has to be installed with the flat facing downward. The problem was that the new pistons appear to have a very slight taper which caused them to jam. The OEM pistons re-installed with no problem at all.

I didn't pay any attention to whether the new pistons are SS when I ordered the kit. I didnt take any pics at the time I was doing the work; obviously I should have. I'll mic the new pistons to see if I can detect any taper but since they would insert about 1/2" face down and not at all face up (caliper on bench, bore opening facing upward), it seems to me there HAS to be some taper...

NO, I didn't telephone - I guess I should do that...

MexicoMike · Jul 28, 2017

Here's the micrometer measurement of the piston. There is a slight difference in diameter...apparently enough to cause the problem. 1.752 and 1.754 And yes, - SS

cliffa · Jul 28, 2017

MexicoMike said:
FWIW, there's probably no real reason an original piston needs to be replaced.

With respect Mike, that's a bit of a sweeping statement. The chrome was peeling off mine, and had I cleaned and refitted the pistons the new seals would have been damaged and leaking in no time. To be honest even if they weren't peeling I would have replaced them anyway. This is not an accessory we are talking about, but a device which makes the difference between life or death. Maybe not yours, but somebody who happens to step out into the road in front of you.

It's very worrying that suppliers seem to be churning out sub standard brake components ( see my recent post about brake discs). You were lucky that the pistons were machined too large, can you imagine if they were too small ?

Unfortunately you can start to see the reason behind quality standards like "Type approval", "DOT" and "T.U.V." etc.

Cheers,

cliffa.

JimNH · Jul 29, 2017

I had a problem with something I bought from Commando Specialties, I've forgotten now what it was, but I do remember that they were very accommodating and made it right.

Let them know about your apparently oversized pistons; they don't want unhappy customers as word of mouth spreads fast.

MexicoMike · Jul 29, 2017

Cliffa - you are right, of course. I have had a couple of Commandos and hadn't seen a piston with delaminated chrome but obviously, that would be a problem as opposed to just needing some clean up of the piston or the bore.

MexicoMike · Jul 29, 2017

It was called to my attention via a private message that I posted incorrectly in my explanation on fitting the pistons. Although I did it correctly on the bike I was "thinking in reverse" when I posted. I said that the "FLAT" of the piston goes against the brake pad, but that is, of course, incorrect. Sorry for whatever brain-dislocation occurred and any confusion it may have caused. AGAIN, the flats go toward the OUTSIDE of the caliper, NOT toward the pads.

I was so concerned that I may have actually installed them backwards, that after receiving the PM, I went out to the bike, removed the caliper and disassembled it to be sure it was right! I also tried AGAIN to get the SS pistons to fit with no joy!

Re those pistons - Old Britts shows 3 different pistons available, all of them are 1.748" or less diameter compared with the 1.752+ diameter of the Commando Specialties. Ironically, the order for the pistons was probably the first Commando parts order I have made since 2006 that WASN"T from Old Britts!

The diameter of the OB pistons matches the ID of the OEM pistons that are in the bike.

ashman · Jul 29, 2017

Maybe the machine that made the new pistons weren't running true at the time, a good machinest should have picked that up.

How many people change their brake fluid every 2 years, not many by the sound of it as thats one of the reasons that mositure gets in their brake systems, over time the fluid boils from hard use or just goes past its use by date and how many cars are on the road that have never had their brake fluid change in their life time of use, scary just thinking about it.

Ashley

BrianK · Aug 1, 2017

Here in Boston (our climate is frequently damp, etc.), I found biennial brake fluid changes not frequent enough to prevent problems. I now do annually. No problems now.

OEM brake caliper rebuild caution

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