Topic: caliper piston seal (help)

[spill]

I'm considering applying CRC synthetic brake caliper grease to the caliper piston outer wall and piston seal before assembling. It reads 600 degrees as the max of the temp range. Any experience with this black MOLY, PTFE, and graphite goo?

[TwoTired]

You have to be careful of the "specsmanship" of the product.  The writer's job is to make the product appealing to the widest amount of purchasers, often hiding important characteristics.

For example, if the product stops lubricating at 600 degrees, they can put that on the label.
But, that same product can phase change from a gel to a liquid at 300 degrees.  It still lubricates. It won't stay in place unless held captive by seals.  They didn't lie to you.  They just didn't tell you the whole story.

Does the product combine with water?  Can it be washed away by water?  Some petroleum based products can.  "Synthetic" can still mean it behaves as an oil or grease and be derived from a petroleum product.  This product's specs:
 "Water Washout       <5%"
...looks pretty good.  But, if the film thickness loses 5% each time it gets watered, when will you know it is time to be renewed in order to maintain protection?  The Dow Corning pure silicone grease will never, ever combine with water.

Where used on the SOHC4 caliper is behind and right next to the friction surface.  It needs to be a water repellent to keep water away from the metal surfaces where water can ingress.  This design has no seals and relies on the silicone grease (such and the Dow corning product) to do all the water repellent, and stay in place when hot, so as not to contaminate the friction pads and disc.

Another property of greases is its "creepage" characteristic.  Some of the grease may always stay in gel form, but some percentage of it can liquify and run or creep away from the gel binder in the grease base.  This won't help your friction pads stop the bike.

Have I tested the product to which you prefer?  No. 

The specs that worry me.
"Base Type       Polyalphaolephin & Pentaerythritol Esters w/ fumed silica"
Silica is the thickener.  At what point do the lubes separate from the silica?

"Working Temp       -40 to 600°F intermittent"
Intermittent?  So how long will it take for 600 degrees (or less) to phase change the product?

"Drop Point       >600°F"
The drop point is where the ENTIRE mass of grease becomes liquid.
Unfortunately, it can still be partially liquid at a lower temperature, unless they add a phase change spec.

"Oil Separation       <10%"
Note it is non zero.  So, I wold assume there can be some creepage/weepage/running onto your brake pads in the SOHC4 design.


Personally, I'll stick to the proven Dow corning product for this application in SOHC4 calipers.  It is also what Honda specified, btw.

Cheers,

[spill]

Thanks Lloyd. 

So, I hate to waste the CRC synthetic grease.  Two of the reasons I bought the bike in the first place was to, one, restore an unused vehicle; and two, to reduce my consumption of petroleum. Do you know how much petroleum it takes to manufacture a new vehicle (that's a question for another thread)?

O.K., I admit, I bought it because I love to ride and I love the asthetics of the 70s CBs.

Where (on the bike) can I use this black goo?  How would it perform in less, stressful, for lack of a better adjective, situations?  How about the rear axle [not that I already didn't apply it during assembly today . . . *crossing fingers* . . .]?

[TwoTired]

Some materials are special purpose, limited application usage.

I still have two tubes of Syl-glide I bought (ruined the brake pads), before I got the proper Dow Corning stuff.
Syl-glide cost me a set of brake pads and doing the job twice.

[OldSchool_IsCool]

At the risk of a set of pads and doing the job again,  Is this stuff worth a look?

http://www.permatex.com/products/Automotive/lubricants/specialty_lubricants/Permatex_Ceramic_Extreme_Brake_Parts_Lubricant.htm

Sayz there is no drop point.

[TwoTired]

At the risk of a set of pads and doing the job again,  Is this stuff worth a look?

http://www.permatex.com/products/Automotive/lubricants/specialty_lubricants/Permatex_Ceramic_Extreme_Brake_Parts_Lubricant.htm

Sayz there is no drop point.

Says there is no drop point per ASTM d2265 test.  Which specifies a limit of 625 degrees F.  Remember the drop point is where the entire test sample phase changes from gel to liquid. There is an orifice at the bottom of test vessel where they watch for the first drip.
I hate it when MFGs hide information, in this case the limit of the test.  It make the product sound better without any quantification.

Anyway, the product does look promising.  The only thing missing is a spec about creepage/weepage/running.  At whatever temperature.  Syl glyde does that at room temp, as do many other greases that are used primarily for lubrication.

The SOHC4 caliper doesn't need lubrication qualities where it is used.  It is used as an atmospheric and elements barrier on the exposed metal surfaces.  It has to stay put, and not allow any part of it to wander at any temperature that the caliper experiences in operation or storage.

Cheers,

[OldSchool_IsCool]

Buttered the caliper, piston and pad back with Permatex Extreme.  It has the consistency of thick tooth paste.  Will report back by next tune up if it has stayed put.  Sooner if it doesn't stay where it
s supposed to.

[TwoTired]

Try not to follow other vehicles too closely.


 

[OldSchool_IsCool]

Try not to follow other vehicles too closely.


 

Lloyd,

I highly value your opinion.  I will be the first in line if you ever write a book on the care and feeding of the middle fours.  If you think this product really isn't worth a shot or if you think my application technique is unsafe, do my dependents a favor and let me know.

[TwoTired]

I did a test in an ordinary gas fired oven in my kitchen.
 Put a small sample in an oven with a thermometer.  Set it to 250 F, and observed it through the little window while the temp rises.  After temp stabilization, I bumped it up 50 F increments, until I eventually got to the 500F limit of my oven.

I know the Dow Corning silicone was unaffected by heat to the limits of my oven (just like their product data sheet indicates).  It remained a gel glob on a little aluminum foil fashioned into a cup.  (Syl-Glide did not.  It partially puddled at 300F and vaporized at about 350F)

I did the oven test AFTER I ruined a set of brake pads with the auto parts store counterman's recommendation that Syl-Glide was the right choice for this (SOHC4 Caliper) application.
To this day I am convinced that he was willing to say anything that created a sales slip.

Having that experience, I would not test a new product and my safety on my bike without an off bike test to see if it meets the boasts of the salesman/marketeers.
If I WERE to test it on the bike. I would find a safe place to do 5-10 full braking stops in a row from high speed, to heat up disk and caliper, then examine the caliper and pad for lube leakage/weepage/creapage.

It's your call, though.

[OldSchool_IsCool]

Thanks Lloyd, your approach makes much more sense then my head long jump into a live test.