Topic: Front brake pad seems angled, not retracting ('74 CB750K)

[robvangulik]

ah gotcha.  so was i mistaken to apply brake fluid to the sides of the piston before inserting?

No, simple brakefluid is exactly what Honda (and all other manufacturers) advises to use for inserting the brakepiston in the bore.
Said O-ring will wipe the fluid off, which can easily be removed by rinsing with water, and after drying with a cloth or blowdrying with compressed air you can indeed protect the exposed end of the piston like Twotired wrote. To be honest, i just leave it as is, as the brakepads wear the piston will expose itself     more and more and i don't intend to remove the caliper every month to grease it again.
Just last weekend i cleaned the rear brake caliper of my CBR because it started to hang up, and the last time i did that was over a year and 10k km ago, and all i really had to clean (as usual) was the groove for the O-ring!

[evinrude7]

ah gotcha.  so was i mistaken to apply brake fluid to the sides of the piston before inserting?

No, simple brakefluid is exactly what Honda (and all other manufacturers) advises to use for inserting the brakepiston in the bore.
Said O-ring will wipe the fluid off, which can easily be removed by rinsing with water, and after drying with a cloth or blowdrying with compressed air you can indeed protect the exposed end of the piston like Twotired wrote. To be honest, i just leave it as is, as the brakepads wear the piston will expose itself     more and more and i don't intend to remove the caliper every month to grease it again.
Just last weekend i cleaned the rear brake caliper of my CBR because it started to hang up, and the last time i did that was over a year and 10k km ago, and all i really had to clean (as usual) was the groove for the O-ring!

word

[TwoTired]

To be honest, i just leave it as is, as the brakepads wear the piston will expose itself     more and more and i don't intend to remove the caliper every month to grease it again.

Never have to regrease if you use enough of the silicone grease to keep the water out.  I never have, since 1980 or so.  If you are still using a metallic piston instead of phenolic, it won't corrode anymore.  The 550 Honda manual instructs to use silicone grease.

The worst pitted pistons I've seen, were those assembled only with brake fluid.  Rain, humdity, and washing allow water to get in there unless you protect the surfaces with the silicone grease.

The first caliper I overhauled was on my 74 CB550 I bought in 75.  It had not been touched since Honda assembled it and the piston was still fine.  Scooped out lots of new-to-me silicone grease, which sent me on the hunt for replacement grease.  Dow Corning High Vacuum grease looked the same as what I scooped out and had the specifications to withstand high heat without flowing out.

I already stated why I use the assembly lube and the reasons are still valid.  But, don't whine about needing to replace parts in a few years if you ignore and wind up with pistons too pitted to retract properly.

Cut corners and you'll pay eventually, or you will foist the problem onto an unsuspecting buyer.

Do as you wish.  I've done all I can.  But, people will only hear what they want to hear.

[evinrude7]

To be honest, i just leave it as is, as the brakepads wear the piston will expose itself     more and more and i don't intend to remove the caliper every month to grease it again.

Never have to regrease if you use enough of the silicone grease to keep the water out.  I never have, since 1980 or so.  If you are still using a metallic piston instead of phenolic, it won't corrode anymore.  The 550 Honda manual instructs to use silicone grease.

The worst pitted pistons I've seen, were those assembled only with brake fluid.  Rain, humdity, and washing allow water to get in there unless you protect the surfaces with the silicone grease.

The first caliper I overhauled was on my 74 CB550 I bought in 75.  It had not been touched since Honda assembled it and the piston was still fine.  Scooped out lots of new-to-me silicone grease, which sent me on the hunt for replacement grease.  Dow Corning High Vacuum grease looked the same as what I scooped out and had the specifications to withstand high heat without flowing out.

I already stated why I use the assembly lube and the reasons are still valid.  But, don't whine about needing to replace parts in a few years if you ignore and wind up with pistons too pitted to retract properly.

Cut corners and you'll pay eventually, or you will foist the problem onto an unsuspecting buyer.

Do as you wish.  I've done all I can.  But, people will only hear what they want to hear.

to silicone or not to silicone?  that is the question.  so put it on after the piston goes in? 

[TwoTired]

I put a thin coating on the inside of the caliper on the air side of the caliper seal.  I also, put a thin coat on the piston where the seal doesn't ride.  I put a thicker coat on the piston where it meets the top of the bore.  You can do this as the piston goes into the bore after the other end has gone past the seal.

All the exposed unpainted aluminum bits of the caliper get a very thin coat of the Dow Corning pure silicone grease.  I put it on the steel backing of the brake pads, too.  They don't rust.

It's kind of used as a paint to keep atmospheric contaminants from attacking the bare metal.

[PeWe]

I used silicone grease on the piston(s) after reading the CB750 shop manual. It leaked a lot! First time ever. Both calipers did (I have dual brakes at front). It was NEW pistons and seals. One caliper was new too. Almost new DSS aftermarket MC.
I read the manual again and saw it different, grease on top of piston where the pad has contact. I use a dollop of copper paste there.

Never more silicone grease on piston side lubricating the seal on my bike.

After that good working brakes I use  very often and rather hard since the curves are thrown into my face much quicker lately. I guess it is due to some modifation Mike Rieck has helped me with.

[strynboen]

i use ATE grease for caliper piston its made for lube the piston sides..but dont put it at the end..so it komes in the brake fluid..just use the rekomendet grease and it Works fine..

[TwoTired]

i use ATE grease for caliper piston its made for lube the piston sides..but dont put it at the end..so it komes in the brake fluid..just use the rekomendet grease and it Works fine..

I was curious about ATE grease, so I did some internet fishing for specifications.  I didn't find any. 
This grease is not popular or readily available here in the states.  I can't tell if it is petroleum based, silicone, or what it is formulated from.

The pictures I found show it in use on brake parts that have a dust/rain boot.  Most modern brake systems have this component. (The SOHC4 doesn't).

The silicone for our calipers is there in place of the dust/water boot, and serves that function.

A separate dust boot would not only shield from contaminant ingress, but outflow onto the brake pads causing lubrication of the friction components.
I feel confident that the silicone specified, won't heat flow out to the friction pads. (-40 to +400 degrees F)

Have you done a heat flow test for the ATE grease?  Know what it is made of?  Have a spec sheet?

Cheers,

[strynboen]

its a very old tube from my Volvo 140 and 240 years..25 years ago..volvo used girling and ATE brake systems..so it are a automobil type grease for resambel of calibers internal parts..its looks silicone..and is not grease..vill not get melted or drip(i use very littel..just a finger tip on the piston..

yes sohc calibers is not vater teight..as the car types..but i have run for 5 years. on sohc.and have absolut no problems..so dont think it absorbst vater..

it are named bremszylinder-paste( ?  -dot 5,1)..germany made by ATE..
it vorks for me..but it can be pure luck..a data link on the produkt vill help us all..it can be the right stuff..for sohc...or just an other silicone grase...

[TwoTired]

Maybe you could ship your tube to needy caliper rebuilders?

Just joking...  Looks like it's been rattling around in a tool box for a couple decades.   

I found this slightly clearer picture on Amazon UK. 
https://www.amazon.co.uk/ATE-03-9902-0501-2-03990205012-Cylinder-Lubricant/dp/B004RAVYDG

Description doesn't say what it is made of.  Dang.  But, says it happily co-exists with brake fluid.  Would rather see a manufacturer's spec sheet, though.

Maybe you can test a bit of it, by smearing on a metal surface to see if it will repel water and not mix/wash off with it?  If it passes that test, and won't heat flow in a hot oven, looks like a decent alternative to the Dow Corning product.

Cheers,

[strynboen]

yes i gladly make some heat- damp- vater..tests..vill try to mix a bit up vith vater to if it mix es up..or splits..

have you any idea of that dot 5,1..cant read hvat it does or not can be used....normaly dot 3-4-are the norm..

edit ...i just faund this googling....its good for dot 3-4-5,1 fluid systems..so perfekt for sohc

[Yoshimitsuu]

Heat did the trick! One of the o rings is missing though. I know genuine Honda is 10 x 1.7mm but could I get away with a 10 x 1.8mm? Theyre way cheaper and can be had locally but if it's not recommended I'll do what I have to.

[Phinn]

Yeah, it's fine. Those o-rings (on the top and bottom of the pivot pin) are barely functional anyway, and are there just to slow down the accumulation of gunk in there, which happens anyway because the assembly is constantly showered with road grime. If the pin goes back in with the slightly larger o-rings you have, then you're good. Regardless of the o-rings, be prepared to periodically remove the swingarm from the pin to clean and lube.

[Yoshimitsuu]

Alright, so I know Halloween has past but I bring more questions to bring this thread back from the dead (ha ha). Most recently I was lubed and bought new O rings for the caliper pin and reinstalled everything.

The problem I've run into now:

- Front brake is still sticking at the caliper. I initially thought it was the front pad that was causing this but it seems to be retracting as it should (I can see it move to and fro with the caliper bolts loosened a hair).

-  The swingarm pad doesn't seem to adjust much (if at all) and is right against the rotor even with the adjustment screw backed off almost completely. The only way I can fit a 0.006 feeler in there is by loosening the caliper bolts a tiny bit (which is definitley a bad idea)

I have heard people sanding a few mm off of the friction face of the pads. Should I do this? If so, what grit and how many mm should I remove?

I'm at a loss here. I've tried almost everything else. I'm getting good pressure and feel from the MC and checked that hole for a clog. Also, the seal is replaced and the crevice is good.

[Phinn]

One of the sets of pads I bought came with a rear fixed pad that was too thick when new. If it binds the rotor when the swingarm movement is maxed out, it’s too thick. A few dozen strokes on sandpaper should reduce it a few millimeters and get it to work properly.

There’s no need to sand down the pad on the caliper side. Just push it back in all the way before starting the adjustment procedure.

[TwoTired]

Push/ retract the caliper.  Don't squeeze the lever. Set the .006 clearance on the stationary pad to rotor with the arm adjuster, lock it down.

The front wheel should spin easily.  Squeeze the lever, the wheel should not spin.  Release the lever, the wheel should again spin freely.

If it is still stiff to turn, open the bleeder valve, to check for pressure build up, and full release.

report back.

Cheers,

[Yoshimitsuu]

TwoTired and Phinn, your advice did the trick! I set everything before engaging the lever and all went smoothly. The front wheel spins even better now than I remember it spinning when I brought the bike home. Already have an appointment to get her registered tomorrow Trying to squeeze a bit of riding practice in before the season ends. Thanks again all!