classic car forum header
Classic cars forum & vehicle restoration.
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
How To Register     Posting Photographs     Privacy Policy     F/book facebook.com/oldclassiccar

Restoring hydraulic calipers
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> Mechanical Restoration
Author Message
rcx822



Joined: 31 Dec 2010
Posts: 112

PostPosted: Tue Dec 29, 2015 11:48 am    Post subject: Restoring hydraulic calipers Reply with quote

Hey!

I'm soon going to undertake the overhaul of a rusty pair of brake calipers. I don't know how they look inside yet. New rubber seals are available to buy.

The calipers are aluminium with steel pistons plated in chrome.

Is it safe to make my own pistons on a lathe?

Is it usually just the pistons that corrode and need replacing? Is there a chance that the cylinders are also degraded? And if so is it safe to "sleeve" them?

I have to say that sleeving is beyond my skills and beyond the machinery that I have access to, but I do have a couple of machine shops that can do that kind of job, I just wanted to know if this is a normal route to take.
Back to top
View user's profile Send private message
ukdave2002



Joined: 23 Nov 2007
Posts: 3491
Location: South Cheshire

PostPosted: Tue Dec 29, 2015 12:01 pm    Post subject: Reply with quote

Hi

The answer is yes to both questions, neither sleeving the cylinders of turning pistons is difficult, but bare in mind this is a critical component so needs to be done properly.

I have sleeved a member of older cylinders, the sleeve needs to be an interference fit, but not so tight that the original cylinder is over stressed, so a minimal interference fit combined with the appropriate loctite adhesive ( they make one for the job) will Be fine.

You also have the ability to use materials other than plain or plated steel, so can improve corrosion resistance.

There are folk who will snear at cylinder liners, but done properly it's perfectly acceptable.

Cheers

Dave
Back to top
View user's profile Send private message Visit poster's website
goneps



Joined: 18 Jun 2013
Posts: 601
Location: Auckland, New Zealand

PostPosted: Tue Dec 29, 2015 10:04 pm    Post subject: Reply with quote

If the original pistons are chromed then it will be hard chrome, not ordinary decorative chrome, so if you make new pistons you'll need to find an industrial plating shop that can do the job properly.

Richard
Back to top
View user's profile Send private message
rcx822



Joined: 31 Dec 2010
Posts: 112

PostPosted: Wed Dec 30, 2015 6:33 am    Post subject: Reply with quote

Do we know why the pistons are chromed and not made of stainless? Google says that aftermarket pistons are sometimes available in stainless. Maybe it's pure money saving?
Back to top
View user's profile Send private message
goneps



Joined: 18 Jun 2013
Posts: 601
Location: Auckland, New Zealand

PostPosted: Wed Dec 30, 2015 7:20 am    Post subject: Reply with quote

Among the less attractive qualities of stainless steel is its tendency to work harden and become brittle. This is why s/s bolts should never be used in critical or stressed applications. The metal is greatly over-rated by those who don't understand the pitfalls. Special grades are used when necessary, of course, but at special prices.

It's an excellent material for sleeving pitted brake cylinders, as Dave has suggested, but in my view unsuitable for other brake applications. The question is this: why take the risk?

Richard
Back to top
View user's profile Send private message
rcx822



Joined: 31 Dec 2010
Posts: 112

PostPosted: Wed Dec 30, 2015 7:27 am    Post subject: Reply with quote

Ok. Though if the pistons must be chromed steel then it's not worth making them compared to cost of buying. Pistons are still available for my application.
Back to top
View user's profile Send private message
47Jag



Joined: 26 Jun 2008
Posts: 1470
Location: Bothwell, Scotland

PostPosted: Wed Dec 30, 2015 12:44 pm    Post subject: Reply with quote

The original pistons are made from sintered steel (powdered) and then plated because the sintered steel is porous. This is one of the reason that they seize in the calipers. The plating breaks down and the brake fluid then swells the piston. Why they are made that way??? I've no idea

Art
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    Classic cars forum & vehicle restoration. Forum Index -> Mechanical Restoration All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
Forum T&C


php BB powered © php BB Grp.