Brake caliper piston install

[Pablo M]

More questions!

Nothing is ever easy, is it? 

With a lack of reasonably priced options for a left caliper I decided to rebuild mine. Took it apart, cleaned it, took 0000 steel wool to piston and barrel and all seems good. 
I’m trying to get pistons back in and can’t get them to seat all the way down. Got them most of the way and just can’t move them further. 
My process, let me know if I messed this up please:

-use new brake fluid to lube inner seal and install. 
-install rubber boot on piston.

-apply very thin layer of grease to inner seal and piston. 
-slide piston into barrel, careful to get it seated and square as it goes in. First half went in pretty straightforward and how I would have expected. Then gets very difficult. 
-then used old pad to push against trying to get them in further.  
 

Caliper is off the car and brake lines loosely connected. I bolted up caliper thinking I’d gain leverage but nope. 
 

Whats wrong with my process? Pistons are still 1/8”-3/16” out from where they need to be. 
 

 

[gracer]

First off don't ever use petrolium in the brake system.  I use a little silicone grease to lube the piston rings.  You have to push the pistons firmly into the caliper.  It takes quite a bit of pressure.

[Pablo M]

13 minutes ago, gracer said:

First off don't ever use petrolium in the brake system.  I use a little silicone grease to lube the piston rings.  You have to push the pistons firmly into the caliper.  It takes quite a bit of pressure.

I used high temp red grease. I’ll have to clean it again and try a second time. 
I guess I’m too weak and fatigued from working on the car two weeks straight lol. 
thanks. 

[tzei]

Brake lube/grease for piston & seal. 

[bergie33]

You could also use a big "C" clamp to help seat it. 

[dlacey]

rubber grease

[Mikesmalaga72]

A special hydraulic paste lube will aid in reinstalling the caliper pistons without swelling the seals as the petroleum does.

Chances are the seals are ruined Buy another set and reattempt. Do not force the pistons to prevent denting/scraping bores. They should be able to insert straight down with 2 thumbs pressure.

 

Hard to find but try here: 

Lubricating fat mount brake brake caliper piston lubricant

CALIFORNIA-MOTORCYCLES.COM

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Grease Lubricant Assembly Pump and Pistons Brake Clamp Master Cylinder And Brake Caliper Piston Lubricant 180 g versilube g322

 

 

 

 

 

Edited January 4, 2023 by Mikesmalaga72

[TobyB]

That stuff is not easy to find- thanks for linky!  I'm almost out of the 

PBR (Australian for brake, mate) tube I bought in 2001.

 

And +1 for c- clamp, altho if it goes in that far, usually just a chunk of wood

to spread the force out a bit works just fine.

 

t

 

[stephers]

Brake fluid to lube the seals and a BF water pump pliers to squeeze the piston in

 

Thanks, Rick

[tech71]

29 minutes ago, TobyB said:

That stuff is not easy to find- thanks for linky! 

Also available on Ebay, best hurry only 9 left

180G ATE Brake Cylinder ASSEMBLY PASTE BRAKE RUBBER GREASE LUBE BREMSZYLINDER

WWW.EBAY.COM

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Find many great new & used options and get the best deals for 180G ATE Brake Cylinder ASSEMBLY PASTE BRAKE RUBBER GREASE LUBE BREMSZYLINDER at the best online prices at eBay! Free shipping for many products!

I have always used Dow Corning 4 with no ill effects

[Son of Marty]

sil-glyde is a brake grease easy to find for under 10 buckson e bay for a tube that will do 30-40 pistons 

 

[Pablo M]

3 hours ago, tech71 said:

Also available on Ebay, best hurry only 9 left

180G ATE Brake Cylinder ASSEMBLY PASTE BRAKE RUBBER GREASE LUBE BREMSZYLINDER

WWW.EBAY.COM

---

Find many great new & used options and get the best deals for 180G ATE Brake Cylinder ASSEMBLY PASTE BRAKE RUBBER GREASE LUBE BREMSZYLINDER at the best online prices at eBay! Free shipping for many products!

I have always used Dow Corning 4 with no ill effects

That’s great but won’t arrive for a few weeks. Can’t wait that long. What can I Sue that’s readily available, either a few days or actually locally. What other options are there?

[tech71]

Sil glide should be available at any decent auto parts store, hardware store for around $10

Edited January 4, 2023 by tech71

[stephers]

Brake fluid         

[dlacey]

Use

1 hour ago, Pablo M said:

What other options are there?

Any silicone based grease (vacuum grease, dielectric grease, etc) or anything miscible with brake fluid - e.g. castor oil (medicinal/cosmetic grade) is one of the ingredients of traditional brake grease and will work fine.

 

Don't use brake fluid, as the fluid trapped above the seal and below the dust cover will corrode the caliper bore.