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kwl0525

Brake caliper question - Phenolic or metal pistons?

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I need to replace the rear calipers on my 2003 Monaco Cayman; at least one is starting to stick.  They are BOSCH with the casting number 4153222.  I've found replacements at NAPA, which reference my BOSCH casting number, but they have 2 versions.  One version uses metal pistons and the other uses Phenolic (plastic) pistons.  Their description states "OC Phenolic Piston". 

Has anyone used Phenolic Piston before or have experience with them?    Metal rusts and sticks over time, so I'm not sure which route to take here.

Thoughts?

 

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kwl0525,  You mentioned that the one option is Phenolic, that is a very rigid plastic, more pron to cracking and with the possibility of high temps when descending a steep grade could heat things up and a dragging brake  pad would do the same .  Plastic and steel have totally different expansion cofficiants - that would tend to skew me towards the metal pistons, but I have never used calipers with Phenolic  pistons. 

I fear the caliper pins hanging up more then any other part of the caliper !  If the coach sets for extended periods - they need more attention then the pistons.

Rich. 

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It is my understanding that the Bosch brake recall was for brakes with the Phenolic pistons.  If brake fluid was not changed as it should be, the pistons absorbed water and failed to retract.

I am not suggesting which ones to get-- might give a call to Bosch, tell them your application (include miles per year, how often you change brake fluid, whether you are in dry/humid areas) and get THEIR advice.

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Steel Pistons in my system never rusted. Oshkosh/ John Deere chassis with four wheel disc brakes.Flushed the brake fluid and replaced it with fresh annually. Would need moisture in the system to enable rust. Brake fluiid is hygroscopic. We  traveled the mountains of Colorado so I took no chances.  Reccommend the old fashioned steel. Monarch, Wolf Creek, and other famous passes with just common sense and a well maintained brake system. Now I am fortunate enough to have air brakes and an exhaust brake. 

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