Commando caliper dismantle

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dynodave

dynodave

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For those who have trouble dismantleing the Norton/Lockheed caliper, these few words might help...
Note the three passage drillings.
One entrance port for the brake fluid going into the outer piston bore.
Second drilling to connect the front bore to the bleeder passage.
Third drilling from the Bleeder down to the rear piston bore, while also completing the interconnect between the outer to inner bore.


Commando caliper dismantle


Make sure that a #31 drill (smaller than 1/8"? will pass down all 3 drillings ( especially troublesome is the rear one.
Failure to insure all 3 are clear has caused the caliper to split, at around 2500PSI when attempting to use the hydraulic extraction method . The bleeder passage to rear piston was jam full of water based DOT3 aluminum corrosion.
The passage was cleared and a port for the hydraulic fitting was drill and /tapped to complete the hydraulic piston removal.
The pressure in the outer piston pressing on the 1/4" steel plate and the blockage in the passage prevented rear piston movement. BANG


Commando caliper dismantle

To remind you that pneumatic pressure is dangerous for piston removal, but can succeed when there are no major hang ups.
Heavy duty hydraulic has never failed when the passages are cleared.
 
Torontonian said:
Wow. I have a good clear used one if you need it. A little JB weld should fix that explosion up and good to go !
Click to expand...
Thanks for the offer of a caliper. I'm confident I have close to enough for the 16 or so commando kits (basket cases) I have.
However, I do seem to have more difficult disassembly cases than most. It seems I get almost half that are in the difficult catagory and need the heavy duty method.
Even removing the outer cap, I often need my "killer" pin wrench and have to sometimes POUND it hard with the air impact to get it out.
The pix of the split above has been my only failure...
 
dynodave said:
Thanks for the offer of a caliper. I'm confident I have close to enough for the 16 or so commando kits (basket cases) I have.
However, I do seem to have more difficult disassembly cases than most. It seems I get almost half that are in the difficult catagory and need the heavy duty method.
Even removing the outer cap, I often need my "killer" pin wrench and have to sometimes POUND it hard with the air impact to get it out.
The pix of the split above has been my only failure...
Click to expand...
Dave thanks for this info The piston I have is not flat like a normal piston but is definitely significantly concave I was thinking of drilling a hole and tapping it but it looks like it is back against the inside wall of the caliper
 
heat or penetrating oil or acetone/ ATF
If you can slap it on a board to make it come out, than it was an eazy peazy one...

If you follow the procedure
clear the 3 passages
use a grease gun with grease, oil or even water and it "will" move the rear piston
It has never failed except as above thread that split the caliper @2500psi
Only brazing a 1/8 npt to 3/8-24 fitting is the prep work needed
air blow is a joke at around 150-175 when upward to a 1000 psi is sometimes needed, though that is a very hard case
 
I'm in the process of rebuilding the calipers off of my Mklll, so really glad you posted this Dave, as an aside note I'm blown away by how heavy the calipers are Anyway thx again. Cj
 
would it help to heat the caliper to make piston removal easier? What would be the limit?
I've noticed that the rear cavity is reluctant to fill. It can be done with some coaxing and making sure there is space between piston and caliper. Has anyone drilled a vent on the foreward part of the rear cavity?
 
seattle##gs said:
would it help to heat the caliper to make piston removal easier? What would be the limit?
I've noticed that the rear cavity is reluctant to fill. It can be done with some coaxing and making sure there is space between piston and caliper. Has anyone drilled a vent on the foreward part of the rear cavity?
Click to expand...
first effort is blow air if it works fine you lucked out. If not then you have a hard case and I go right to war,
I wouldn't waste my time dragging out the torchs,
Drill and tap- wouldn't waste my time
1500 psi (normal car pressure on hard braking) will make any air behind the piston shrink to the size of a small grain of sand or less. The piston back space WILL fill with fluid water or grease.
Buy a long lever grease gun at a yard sale or at the car parts place NOT a pistol grip type. I have 7 of them and one has a 3000psi gauge "T"ed in the HP hose. That's how I know it split at about 2500psi. Braze together a 1/8 npt fitting to 3/8-24 brake fitting
 
dynodave said:
first effort is blow air if it works fine you lucked out. If not then you have a hard case and I go right to war,
I wouldn't waste my time dragging out the torchs,
Drill and tap- wouldn't waste my time
1500 psi (normal car pressure on hard braking) will make any air behind the piston shrink to the size of a small grain of sand or less. The piston back space WILL fill with fluid water or grease.
Buy a long lever grease gun at a yard sale or at the car parts place NOT a pistol grip type. I have 7 of them and one has a 3000psi gauge "T"ed in the HP hose. That's how I know it split at about 2500psi. Braze together a 1/8 npt fitting to 3/8-24 brake fitting
Click to expand...
Aggressive approach but I'm sure it works. I go at it gentler at first , by soaking in penetrant oil , making sure all passages are clear, toasting up everything with a heat gun , then oven mitt smacking down hard on a piece of soft wood like a 2 X 4. Get that rusty old piston out and fit stainless ones with new seals. The outer cap with 2 pins should hit the bin too and be replaced with stainless.
 
Or maybe just Paypal Don Pender for a replacement front brake setup, which is what I did after mucking about with the Lockheed setup for Waaaaay too long. I love the look of the stock setup but...
 
Unless the caliper has been stored long term in a swamp (not seized) it might be easier to remove the caliper from the fork, restrain the outer piston then use the master cylinder to pump the Inner piston outward.
The Outer piston is fairly straight forward having easy access via the threaded plug removed.

The potential problem using air is it is compressible so when a piston leaves the bore it can still accelerate (stored energy of compressed air)
Hydraulic forced out that energy is dispersed with minimal danger being non compressible.

That does not apply if you elect to use outside hydraulic force sending the pressure gauge needle where no man (or Woman) should go for their own longevity.
 
Scout63 said:
Or maybe just Paypal Don Pender for a replacement front brake setup, which is what I did after mucking about with the Lockheed setup for Waaaaay too long. I love the look of the stock setup but...
Click to expand...
Yeah it's all about money. Great upgrade. If you value your life and others'.
 
Not to many people know the pressure that can be generated by simple grease gun, operator beware as fluid injection into limbs can be fatal as well as exploding bits of plant and equipment striking people, best to know what you are doing rather than finding out through experiment resulting in death or loss of limbs.
Hand operated grease guns can generate 3000 to 10000 psi, depending on the area you are applying this too the resultant force can be unbelievable.
There are many scary stories and evidence of what has happened with fluid injection and exploding pieces from over pressurization.
Best be aware of the risks stay safe.

burgs
 
Time Warp said:
The potential problem using air is it is compressible so when a piston leaves the bore it can still accelerate (stored energy of compressed air)
Hydraulic forced out that energy is dispersed with minimal danger being non compressible.
Click to expand...
Correct, when I was looking at ways to find air leaks in my hot water central heating system I found that using air pressure to increase the pressure is a no no but hydraulic pressure is allowed. I bought a small water tank with a plunger and forced extra water into the system and found at 2 bar of pressure 2 small leaks cured by tightening the couplings. I then released the pressure back into the tank and the tank just filled back up safely.
 
Burgs said:
Not to many people know the pressure that can be generated by simple grease gun, operator beware as fluid injection into limbs can be fatal as well as exploding bits of plant and equipment striking people, best to know what you are doing rather than finding out through experiment resulting in death or loss of limbs.
Hand operated grease guns can generate 3000 to 10000 psi, depending on the area you are applying this too the resultant force can be unbelievable.
There are many scary stories and evidence of what has happened with fluid injection and exploding pieces from over pressurization.
Best be aware of the risks stay safe.

burgs
Click to expand...
A trucker died when we were in Mexico . He was inflating a big tire at a gas station . It exploded.
 
I routinely push brake pistons out using compressed air if the caliper is already off the bike. A piece of wood placed between the pistons stops anything travelling more than half an inch, and a rag over the top keeps any fluid spray under control.
That said, seized Commando calipers are uniquely difficult to strip down regardless of method used, and I've drilled and tapped the inner piston to extract with 100% success so far.
 
dynodave said:
Thanks for the offer of a caliper. I'm confident I have close to enough for the 16 or so commando kits (basket cases) I have.
However, I do seem to have more difficult disassembly cases than most. It seems I get almost half that are in the difficult catagory and need the heavy duty method.
Even removing the outer cap, I often need my "killer" pin wrench and have to sometimes POUND it hard with the air impact to get it out.
The pix of the split above has been my only failure...
Click to expand...
I've had some really difficult ones but they all came apart doing what married men cannot/should not do - boiled caliper in the kitchen. I boil them submerged in plain water for about 30 minutes and then bang them on a piece of wood. The really difficult ones take 2-3 rounds of that.

Commando caliper dismantle
 
I use a propane camp stove for that purpose...cost me $10 in a yard sale almost new. I bought an adaptor on ebay so I could use a large BBQ size propane source rather than the expensive small cans.
 
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