Section : General

General Vitesse messages

Caliper pistons

Posted By : Steven Povey, 12-Sep-2006, 07:56pm

Hi All,

After a long layup (15 years plus) i got round to checking the calipers yesterday,although the brakes work and were not binding one piston on each side was stuck,pressing the pedal with one pad in freed them up but when i lift the boot you can see rust spots and pitting on the pistons,
Should i strip it and clean pistons and fit new seals or forget it and get new ones.They were rebuilt with new seals and silicone fluid before the layup.
Cheers
Steve

Followups :

Caliper pistons

Posted By : Jason Green, 12-Sep-2006, 08:45pm

Is cost an issue? It is for me but only to the extent that I'd never consider a new part where a simple renewing of seals and clean up is required. Having said that, I replace everything that I can get to when doing a job, often nuts and bolts (always new nylocs).

I have recently done my seals and took the trouble to clean and paint the entire caliper. The bleed nipples were in v. good condition so I didn't replace them but would have done if I'd had any doubt; I tested them before ordering the seal kit.

You may need a gentle rub with some 800-1000 corn wet & dry in the bores and around the piston to clean them properly.

It is a simple and rewarding job.
Caliper pistons

Posted By : Mark Palmer, 12-Sep-2006, 09:04pm

Ultimately, the best option to buy news ones, which you can get from ebay. I had this problem, and decided to strip them down instead. I was fitting vented discs anyway so, needed to do this. I simply got new seals and used fine wet and dry to rub the outer the surface of the pistons smooth. I then smeared red rubber grease onto them, the new seals, and in the pots, before pushing them home. Alternatively, you can smear a small amount of engine oil there instead. Mine have worked a treat.
- Caliper pistons
  
  Posted By : Chris Taylor, 12-Sep-2006, 09:27pm
  
  If they were rebuilt shortly before the layup, I'd just polish off any obvious rust, and see if there is any sign of leakage under heavy use. A new set of seals would be a good idea, (principally because they may have hardened up with no use) but you are most unlikely to have any brake failure with pistons as you describe. I'm pretty sure that many older cars on the road have calipers with mild pitting (or worse) on the pistons without giving any cause for concern.
  Although as usual the "proof of the pudding" applies, I thought you should NEVER use ordinary grease or oil on brake seals? Makes them swell or something, which is why you have to use special red brake grease on hydraulic components.
  - Caliper pistons
    
    Posted By : Mark Palmer, 12-Sep-2006, 09:58pm
    
    The engine oil advice came to me through a telecon I had with Tony Lindsay Deane about a month ago. I was talking to him about some work on my engine and discussed the work I was doing on the calipers too. He stated that you don't really need the red rubber grease, and that the racing guys tend to use a liberal amount of oil instead.
    - Caliper pistons
      
      Posted By : Ian Osprey, 13-Sep-2006, 08:10am
      
      You only have to look at your engine mounts to see what engine oils do to rubber!
      Unless you KNOW that your seals are not the same type of material as those, steer well clear of engine oil in the hydraulics.
      I wonder if the racing guys are using fully synthetic oils rather than normal mineral oil, and/or silicone seals rather than rubber?
      - Caliper pistons
        
        Posted By : Piero Franchi, 13-Sep-2006, 09:11am
        
        Unless you race, why are you listenint to these guys anyway.
        there needs are differant to yours.
        Oil and rubber dont mix as said.
        read your manual, you cant go far wrong.
        also you could always but stainless pistons and never have the worry of rust.
        Piero
        
        Caliper pistons
        
        Posted By : Dan Owen, 13-Sep-2006, 12:18pm
        
        Watch out for chromed iron pistons, when these get old the chrome plating can flake off (they rust inside the caliper due to water absorbed in the brake fluid). These flakes of chrome can actually "cut" the seals causing brake failure. Never seen it myself but I did know a guy a few years ago who had a lucky escape.
        
        Caliper pistons
        
        Posted By : Chris Taylor, 13-Sep-2006, 06:41pm
        
        I think people tend to think of our racing guys as more technically knowledgeable. I'd certainly expect TLD to know what he's talking about. Interesting point about synthetic oil, but, like you say, I see no advantage of using engine oil over red grease (apart from being easier to get hold of) and so will steer clear.
        Not quite true that stainless pistons mean no corrosion because the caliper bores can corrode, although it IS the case that pistons seem to suffer more. Regular changes of fluid (every couple of years) should minimise corrosion, and braided hoses may reduce water uptake of the fluid as most of it enters via the brake hoses.
Caliper pistons

Posted By : Mike Strutt, 13-Sep-2006, 02:50pm

Steve
If you are going to fit new ones look at the pistons on http://www.revingtontr.com/ they have some nice
157685SS PISTON16PB STAINLESS
TR6 late. Stainless steel piston. they also have some for the 16p caliper.
I bought some but will fit them later in the year, they look splendid!
No rust!

Mike
- Caliper pistons
  
  Posted By : Dan Owen, 14-Sep-2006, 12:04pm
  
  If anyone's having trouble getting hold of red rubber grease, check out Frost- I got a big tub off them very cheaply compared to what I've paid in the past for tiny little tubes of the stuff.
  - Caliper pistons
    
    Posted By : Ian Osprey, 14-Sep-2006, 03:14pm
    
    Chears Dan! I've been looking fot this stuff for ages