Discussion in 'The Garage' started by CrabbyCustoms, Jan 7, 2020.
That's a good idea, I will try it.
Watch out. The piston will shoot out with quite a lot force. There are threads here about the process. Looks like everything is cleaning up nicely.
+1.Ive removed a piston with compressed air, and I can really recommend it unless you have an empty field you can point it towards. That piston missed every bike in my garage, but managed to hit about a dozen other things...never found it.
A rag, spray lube and a bicycle tire pump has not failed me yet. Easy does it
Wrap it up in some rags before you put the air to it.
don't use air, it ain't safe. when the piston flies out you have made an air cannon.
What I do is swap the bleed nipple for a grease nipple and pump the piston out with a grease gun.
Note that shop air is ~120 psi max where an el-cheapo lever action grease gun exceeds 1,000 psi
and grease don't have stored energy to act as a propellant.
When I was a wee lad, our shop teacher showed us how to make an air cannon. He then demonstrated the correct method of wrapping the caliper in shop rags. In 50+ yrs I've never launched one.
did your Guru have a fix for when 120psi shop air pressure wouldn't shift it? Besides a 1,000+ psi grease gun, that is?
I have used air with a c-clamp to keep the piston from flying out.
Nope, if the air didn't move it, grease gun was step 2.
I would try the air method, I found you need to get it moving a little first with the air, then back in with a C clamp, keep working at it, when it moves a little more, then heavey on the air. But yes keep the C clamp in, maybe try the rag wrapping, I put something heavier over top while it was laying on the floor. It will be a projectile without some form of precaution, that's for sure.
Thanks to everyone for chiming in. I started with air but it was too stuck so moved on to the grease gun and it worked perfectly.
I cleaned the caliper and stripped the paint, the inside of the caliper has a bit of corrosion but I'm assuming it's still good to use. The piston has a fair amount of pitting and i'm assuming I need a new piston.
You assume correctly Crabby! And congratulations on your success! Hopefully the cylinder inside the caliper can be salvaged with a simple honing. If it takes too much, the new piston may not seal. It'll be good as new before you know it!
Hmmm maybe I need to consider buying a new caliper? since I was buying the piston, rebuild kit and rubber boot anyways, for $40 more I can just get the whole caliper. Probably not worth the risk. Thanks!
I didn't intend to convince you to spend more than you have to. But, years ago, I had a truck that started leaking out the bottom of the steering box. I asked my mechanic to quote me to rebuild it with a new seal. A whole new steering box was another $40-50.00. I'll give you three guesses what I chose to do (and the first two don't count!). The ability to turn (and stop!) is important, so chose wisely!
Absolutely! easy decision. I just wish I hadn't spent the whole day restoring it!
Since the seal is inside the caliper and not on the piston, a little pitting in the cylinder won't hurt anything.... quiet a bit of pitting is acceptable actually. It's the piston that won't tolerate much pitting, as the seal slides against it. I'd stick with the housing you have... if it were me.
Thanks Jim! Well there ya go Crabby! $40.00 to spend elsewhere!
thing is, there's two of them. Seals, that is.
The square O-ring on the piston and the seal ring in the cylinder.
Each one needs a reasonably good surface to run against.
OTOH, it's amazing how well a less than perfect surface will work.
Me, I'd use it too but I'd check it really well before I road tested it.
Dunno Fred... all 3 of mine had just the square one in the caliper and a dust seal and snap ring on the outside. None of 'em had a groove on the piston for a seal.
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