Caliper seal frustration.......

JOHNO23 · Jul 10, 2020

I’m replacing the seals in my rear caliper, std Norton brake caliper. I’ve successfully done the inner seal and fitted the new stainless piston. However when I fit the seal for the outer piston and then attempt to fit the piston it fouls on the seal slightly, I have already buggered two seals

the piston slides in the bore beautifully but then catches on the seal when I slowly push the piston down the bore. Any idea what I’m doing wrong or how to prevent it.

Bernhard · Jul 10, 2020

JOHNO23 said:
I’m replacing the seals in my rear caliper, std Norton brake caliper. I’ve successfully done the inner seal and fitted the new stainless piston. However when I fit the seal for the outer piston and then attempt to fit the piston it fouls on the seal slightly, I have already buggered two seals the piston slides in the bore beautifully but then catches on the seal when I slowly push the piston down the bore. Any idea what I’m doing wrong or how to prevent it.

Have you cleaned the seal grove the whole way round?
I find it beneficial to put some caliper grease in the grove before assembling and gently push it into the grove with the round handle of a screwdriver.

L.A.B. · Jul 10, 2020

JOHNO23 said:
I have already buggered two seals the piston slides in the bore beautifully but then catches on the seal when I slowly push the piston down the bore. Any idea what I’m doing wrong or how to prevent it.

Try inserting the piston first, then fit the seal and push the piston back out through the seal.
That way at least you should see if the piston is catching the seal at any point and if necessary use a blunt tool to ease the piston through the seal.

EstuaryBoy · Jul 10, 2020

I believe buggering seals may be frowned upon in the UK.... Canada?..... maybe?

(Unless you're an MP, of course)

milfordite · Jul 10, 2020

I'm with LAB, that's how I do it.

Bernhard · Jul 10, 2020

EstuaryBoy said:
I believe buggering seals may be frowned upon in the UK.... Canada?..... maybe?
(Unless you're an MP, of course)

I like the way some people's mind works, but I'm not sure about you

CanukNortonNut · Jul 10, 2020

I bought some S/S pistons long ago from the "Beard" These had sharp chamfered edges on the inboard side of the piston rather than a radius edge. I ruined too many seal kits trying to use this product that I bought from him. Carefully inspect that part of the piston.

EstuaryBoy · Jul 10, 2020

Bernhard said:
I like the way some people's mind works, but I'm not sure about you

I was a fully paid up member of the RSPCA for many years, Bernhard. They rejected my suggestion for a marketing slogan, though: 'Protecting Dumb Animals From Even Dumber Animals'
(Apologies to OP here, and Canadians, of course...)

olympus · Jul 10, 2020

EstuaryBoy said:
I was a fully paid up member of the RSPCA for many years, Bernhard. They rejected my suggestion for a marketing slogan, though: 'Protecting Dumb Animals From Even Dumber Animals'
(Apologies to OP here, and Canadians, of course...)

dobba99 · Jul 10, 2020

Round off the end of the piston using fine emery tape then polish on a buffing wheel. A lot of aftermarket stainless pistons have the wrong surface finish. They might look pretty, but they give the impression that there is still air in the system as they aren't moving through the seal properly.

CanukNortonNut · Jul 10, 2020

I agree. I used a lathe to radius the edges. But back when I bought it in the 80's, I was just a newbie.

olympus · Jul 10, 2020

dobba99 said:
Round off the end of the piston using fine emery tape then polish on a buffing wheel. A lot of aftermarket stainless pistons have the wrong surface finish. They might look pretty, but they give the impression that there is still air in the system as they aren't moving through the seal properly.

On the AP caliper i fitted whenever you went to the bike after a few hours and pulled th front brake lever it almost came into the bars, repeated bleeding produced no air..
It was only observing the brake pads that you your see them coming away from the disc a good 25thou...it was then I realised it was the new seal pulling the Pistons away
After I cable tied the lever to the bar overnight, it cured the problem and has never reoccurred

JOHNO23 · Jul 10, 2020

Ok! Job done........( no seals were harmed in the repair of this caliper

)
I got hold of some good caliper grease and using wet and dry just took the sharp edge off the lip where the seal went........all good now thanks Everyone ................problem I have now is I couldn’t select neutral on the gearbox

so the bloody outer cover will be coming off !........

concours · Jul 10, 2020

Todays excitement: $1200 EACH SEAL (there were 4) and none after that in North America.

Betcherass I stoned the chamfers smooooooth first.

CanukNortonNut · Jul 10, 2020

$1200 EACH SEAL (there were 4) what is it for? A Elon Musk Space X Rocket?
Nothing for a 45 year old Norton.

edgefinder · Jul 10, 2020

At that price it must be German like for a Maho. Thats for your chuck not the turret right?

concours · Jul 10, 2020

edgefinder said:
At that price it must be German like for a Maho. Thats for your chuck not the turret right?

Japanese engineers beating the Germans at their own game of complexity.

Unclamp cylinder on a side milling head on a twin spindle, live tool turret 9 axis turning center.

Caliper seal frustration.......

JOHNO23

Bernhard

L.A.B.

Moderator

EstuaryBoy

milfordite

Bernhard

CanukNortonNut

EstuaryBoy

olympus

dobba99

CanukNortonNut

olympus

JOHNO23

concours

CanukNortonNut

edgefinder

concours

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