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Brake Piston Finish #4657564
02/06/18 01:04 AM
02/06/18 01:04 AM
Joined: Oct 2017
Posts: 312
California
vavavroom Offline OP
vavavroom  Offline OP
Joined: Oct 2017
Posts: 312
California
When cleaning and refinishing aluminum brake pistons, what grit is appropriate to achieve the final finish? I am currently debating this topic with someone. Is a polished finish or a 2000 grit finish ideal? Another party said "Just use an abrasive green pad." All this really doesn't matter if aluminum brake pistons are usually anodized. Are they?

Re: Brake Piston Finish [Re: vavavroom] #4657586
02/06/18 05:29 AM
02/06/18 05:29 AM
Joined: Mar 2004
Posts: 21,123
Upstate NY
Donald Offline
Donald  Offline
Joined: Mar 2004
Posts: 21,123
Upstate NY
I thought it was chrome plated steel. Not aluminum. It should be fine to clean off the crud, but if its rusty that means the chrome plating is compromised and time for a new piston. Unless the piston is mirror smooth it will eventually damage the seal and cause a leak.

Last edited by Donald; 02/06/18 05:41 AM.

2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Brake Piston Finish [Re: vavavroom] #4657631
02/06/18 07:01 AM
02/06/18 07:01 AM
Joined: Oct 2012
Posts: 4,825
Taiwan
Ducked Offline
Ducked  Offline
Joined: Oct 2012
Posts: 4,825
Taiwan
I used aluminium foil on mine, which appeared to be steel. I use foil for most metal cleanup and finishing jobs.




Re: Brake Piston Finish [Re: vavavroom] #4657692
02/06/18 08:05 AM
02/06/18 08:05 AM
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
CHrome plated pistons on the ATE calipers on the BMW. Elbow grease for the gunk. Any pits were smoothed out with a fine file. Calipers respond well to taking apart, cleaned and lubed with Sil-Glyde and re-assembled using original parts


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: Brake Piston Finish [Re: vavavroom] #4659362
02/07/18 06:17 PM
02/07/18 06:17 PM
Joined: Oct 2017
Posts: 312
California
vavavroom Offline OP
vavavroom  Offline OP
Joined: Oct 2017
Posts: 312
California
Let me rephrase my original question.

1. How smooth a finish do brand-new brake pistons have? Mirror-smooth, semi-matte (maybe 2,000 grit) or more textured finish (maybe abrasive green pad)? The images I find online vary from not quite a mirror finish to semi-matte, and that mirrors my experience with the handful of not-new brake pistons I have seen.

2. Are aluminum brake pistons always hard-anodized?

Re: Brake Piston Finish [Re: vavavroom] #4660950
02/09/18 12:37 PM
02/09/18 12:37 PM
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
You mostly don't want the pistons to corrode. The pistons don't contact the bores, the seal does. It is at the outer end of the piston. I have only encountered chrome plated pistons from 30+ yr old calipers.Cleaned up they're shiny Now-a-days I heard the pistons are plastic.


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: Brake Piston Finish [Re: andyd] #4669151
02/17/18 09:42 PM
02/17/18 09:42 PM
Joined: Oct 2017
Posts: 312
California
vavavroom Offline OP
vavavroom  Offline OP
Joined: Oct 2017
Posts: 312
California
Originally Posted By: andyd
The pistons don't contact the bores, the seal does.


Do you understand that piston smoothness affects seal wear?

Re: Brake Piston Finish [Re: vavavroom] #4669936
02/18/18 03:49 PM
02/18/18 03:49 PM
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
Originally Posted By: vavavroom
Originally Posted By: andyd
The pistons don't contact the bores, the seal does.


Do you understand that piston smoothness affects seal wear?
Not really, the seal in the ATE caliper is on the piston, like a ring. Being chrome plated, I buff them until I can see my reflection. Does this meet your smoothness spec? grin2


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2
Re: Brake Piston Finish [Re: vavavroom] #4671856
02/20/18 12:08 PM
02/20/18 12:08 PM
Joined: Dec 2006
Posts: 494
Phladelphia
NYSteve Online content
NYSteve  Online Content
Joined: Dec 2006
Posts: 494
Phladelphia
To pick everyone's brain here - I have a Toyota 4Runner that is notorious for seized pistons. This is due to the calipers being cast iron and the pistons being steel.

Is there any coating that would be prevent seized brake pistons like the hard chrome mentioned above?

Re: Brake Piston Finish [Re: vavavroom] #4672106
02/20/18 04:05 PM
02/20/18 04:05 PM
Joined: Jan 2016
Posts: 338
Cheshire, England
barryh Offline
barryh  Offline
Joined: Jan 2016
Posts: 338
Cheshire, England
I lubricate the pistons before assembly using red rubber grease or silicon grease. Besides preventing corrosion it helps the seal retract the piston preventing brake drag.


Barry

1979 BMW R45 (Triple QX 5W40)
2009 Mercedes C180K (Shell Helix Ultra 5W40)
Re: Brake Piston Finish [Re: vavavroom] #4673974
02/21/18 11:26 PM
02/21/18 11:26 PM
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
andyd Offline
andyd  Offline
Joined: Sep 2004
Posts: 7,829
Marshfield , MA
I use Sil-Glyde with great success. On my BMWs taking apart the calipers is a maintenance item. I don't think it is mentioned in the manuals, but in MA and because the cars sat, sticky calipers happened. I'm still using the tube my son bought me 10 yrs ago


'16 Camry LE STP synth 0w20 and STP filter. the Fridge

1994 Ranger ,the Rat, 5w30 dino, STP filter

'16 Camry SE, Valvoline HM 0w20 and OEM filter
Thick oil is better grin2

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