Poll

Which pistons do you prefer?

SS
5 (25%)
Phenolic
15 (75%)

Total Members Voted: 18

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Offline joren

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SS vs Phenolic?
« on: April 22, 2011, 05:52:48 PM »
I bet this is come up before, but I couldn't seem to find it. Are Phenolic, or SS break pistons better to run on a little cb550? My current ones have some pretty major pitting, and I'm not about to pay honda $115 for something I can get made of better(?) material.
I saw some reference to SS and rubber not meshing, but as far as I can tell, the seal seems to be some sort of metal, maybe I need to pull it out and try to figure out what it is. 

Anyways, just thought I'd try to get some info from people who have ran either of them. They seem to be priced about the same, waiting to hear back from this keven dude to see if he still makes the phenolic ones.

-Joren
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Offline KRONUS0100

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Re: SS vs Phenolic?
« Reply #1 on: April 22, 2011, 06:38:13 PM »
buddy of mine turned my new pistons out of aluminum at machine he works for.  cb750F.
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Offline Kevin400F

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Re: SS vs Phenolic?
« Reply #2 on: April 22, 2011, 07:36:57 PM »
Hi Joren.  E-mail sent with pic and details.

Kevin
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Offline Steve_K

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Re: SS vs Phenolic?
« Reply #3 on: April 23, 2011, 06:16:39 AM »
I made mine out of SS because I could.  Took some time for me to polish the OD to suit me.  I would buy the Phenolic piston if I could not make a SS one myself.
Steve
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Steve_K

76 CB 550, 73CB750, 86 GSX-R750, 16 Slingshot
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Offline hondaface75

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Re: SS vs Phenolic?
« Reply #4 on: April 23, 2011, 07:04:03 AM »
This might be stupid, but whats the difference? Is phenolic a metal? Ive never heard of it before, or is it a type of design?
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Offline Kevin400F

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Re: SS vs Phenolic?
« Reply #5 on: April 23, 2011, 07:29:15 AM »
The phenolic material is non-metallic.  It is a compression-molded thermosetting composite resin material, dimensionally stable, capable of exposure to 800 degrees F during short excursions.  Many modern cars / trucks use phenolic pistons as OEM equipment.
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Offline hondaface75

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Re: SS vs Phenolic?
« Reply #6 on: April 23, 2011, 07:37:25 AM »
Thanks!  Ya learn somethin new everyday!
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Offline Duke McDukiedook

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Re: SS vs Phenolic?
« Reply #7 on: April 23, 2011, 01:11:15 PM »
Phenolic all the way.
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Offline steam-powered man

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Re: SS vs Phenolic?
« Reply #8 on: April 23, 2011, 01:21:28 PM »
ditto on the phenolic.  perfect fit and finish, no corrosion, last your lifetime. 
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Offline ddanz27

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Re: SS vs Phenolic?
« Reply #9 on: April 23, 2011, 02:49:35 PM »
Plus one for phenolic. Its a better buy too!
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Offline ColinMc

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Re: SS vs Phenolic?
« Reply #10 on: April 23, 2011, 03:08:33 PM »
Where can you get phenolic for any honda? I've only ever found stainless...
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Offline Hannibal Smith

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Re: SS vs Phenolic?
« Reply #11 on: April 24, 2011, 10:14:29 AM »
Before everybody goes nuts for "Phenolic" pistons, a history/engineering class might be in order.

The "Phenolic" piston is the offspring of the "Phenolic" puck or insert of yesteryear.

"Phenolic" is an insulator, and was used to combat the severe heat generated by heavy racecars. The old fashined method was to fab steel pistons with a relief or allocation for a "Phenolic" disc that would be in contact with the brakepad. This would insulate a portion of the heat from effecting the brake fluid temps- all this "Phenolic" was for, was to combat "fluid boil" and the like.

"Phenolic" is a totally generic term, and to an engineer, the word by itself means virtually nothing. In my shop alone, I have 4 different grades, each with a purpose.

We have peanut horsepower bikes, so the use of "Phenolic" gives you no real advantage. "Phenolic" is considerably cheaper than stainless steel typically, and it machines way faster.

Typical "Phenolic" heat figures are 260-275F and maybe intermittent to 780-800F (but only for certain types).

Run "Phenolic" if you like, I prefer good ol' stainless steel for a 70's bike. Modern stuff? A whole 'nother thread.
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Offline Kevin400F

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Re: SS vs Phenolic?
« Reply #12 on: April 24, 2011, 10:26:15 AM »
The phenolic brake pistons we're talking about on here are based on factory-new phenolic brake pistons from a late-model Lincoln LS sedan application.  The OD of the piston (sealing surface) is not altered in any way; the Lincoln brake pistons are simply cut down to the correct overall length to fit the CB350F/CB400F/CB550 caliper, with a chamfer added to the bore to clear the "raised dome" on the back side of the OEM Honda brake pad.  Rest assured this is not some sort of "generic" phenolic material......it is a high-performance brake piston of the correct diameter.

That being said, I see no real reason why stainless wouldn't work OK as well.
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Offline Hannibal Smith

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Re: SS vs Phenolic?
« Reply #13 on: April 24, 2011, 10:38:47 AM »
Quote from: Kevin400F on April 24, 2011, 10:26:15 AM
The phenolic brake pistons we're talking about on here are based on factory-new phenolic brake pistons from a late-model Lincoln LS sedan application.  The OD of the piston (sealing surface) is not altered in any way; the Lincoln brake pistons are simply cut down to the correct overall length to fit the CB350F/CB400F/CB550 caliper, with a chamfer added to the bore to clear the "raised dome" on the back side of the OEM Honda brake pad.  Rest assured this is not some sort of "generic" phenolic material......it is a high-performance brake piston of the correct diameter.

That being said, I see no real reason why stainless wouldn't work OK as well.


Ok- That is a factory thermal formed unit that is modified. Your piston is "good to go"!
I was going to say something about fabricating one from round stock, and how that would be sketchy (to say the least)-
Those factory units are 100% fine and durable, and "Phenolic" is truly a generic term when we are talking about that type. I still prefer stainless for 70's bike applications, but you guys/gals had me scared for a minute!
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Offline Doctorlumen

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Re: SS vs Phenolic?
« Reply #14 on: April 24, 2011, 10:51:28 AM »
I run a phenolic piston in my bike and love it. A lot cheaper (mine was $35) than stock. And lighter too!
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