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dynodaveWed Jun-11-14 07:42 PM
Member since Mar 18th 2009
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"commando aluminum brake calipers"


  

          

If you are trying to revive an old commando caliper, I have a tip for you.
#1
Be sure you clean the passage from the bleeder down to the rear piston with a number 31 drill bit. The bore is actually 1/8" but since the bottom is probably mashed a bit from the bleeder then you're better to use a #31. Check the front drilling also....
WHY?
As you may know the grease gun brake piston extraction is incredibly powerful. I have never failed (until now) to get both pistons removed without using the butchery that is promoted on other forums.
In this case I easily got the outer piston free. Then the inner one was not moving with my pistol grip grease gun. So I went to the long lever one for more leverage and cranked away until... crack... I split the caliper in two.
Autopsy... The passage to the inner piston was totally clogged with yellow aluminum corrosion and it was thick, dense and required a fair bit of effort to remove it. The clog seemed to be enough to hold off the effort of the long handled grease gun which may be making a few thousand PSI.
#2
The above incident was the result of a guys caliper being damaged by a defective steel tube that crushed and deformed the bottom of the inlet. At first I though the new pistons and new seal were not doing their job, but upon closer inspection it WAS leaking out the 3/8-24 inlet port. removing the line and close inspection of both pieces showed the story...both were messed up and deformed. The bubble flare was bad and it would not seat on the bottom of the drilling.
Be sure to inspect the steel line and caliper inlet port real good before attempting any rebuild.

  

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NortonGuyThu Jun-12-14 07:55 AM
Member since Mar 18th 2009
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#1. "RE: commando aluminum brake calipers"
In response to Reply # 0


  

          

Thanks Dave.

NortonGuy
Board Founder

  

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dynodaveWed Jun-25-14 05:19 PM
Member since Mar 18th 2009
706 posts
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#2. "RE: commando aluminum brake calipers UPDATE"
In response to Reply # 0


  

          

I drilled and tapped the busted rear caliper for 1/8 NPT. I then installed the grease gun with a 3000psi gauge inline. Expecting the worst I thought it might be a real hard push to get the piston out. In reality it came out easily due to the cleaned passage and never approached 100PSI to get the rear piston out.
That demonstrates the strength of the clogging action in the 1/8" passage very well such that I could split the caliper and not move the rear piston at all.

  

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NortonGuyWed Jun-25-14 05:33 PM
Member since Mar 18th 2009
143 posts
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#3. "RE: commando aluminum brake calipers UPDATE"
In response to Reply # 2


  

          

I am glad you had it easier than you thought.
Good idea with the grease gun. I will keep that in mind.

NortonGuy
Board Founder

  

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