Topic: Brake caliper piston

[longshanks]

I need to know if I can put a slightly taller caliper piston in my '72 CB450 caliper from a CX500 or GL1000. The specs on the 450 are 38mm wide by 34mm tall. The specs on a CX500 and GL1000, etc. are 38mm wide by 35mm tall. So we're talking about a 1mm difference here. Can anyone attest to this working?

Check out this link for more:
http://www.wingovations.com/#/additional-stainless-steel-bra/4548886954

[Powderman]

There shouldn't be any problem running either piston as long as you have the extra mm spacing before the pads start to drag. 1mm probably won't be an issue at all.

[bryanj]

The CX and GL are machined at the top of the piston for a dust boot that the 450 does not have and if you push the piston all the way in this hits the seal, so yes you can use it BUT NOT WITH NEW PADS!! Dave Silver sells a stainless patten piston cheaper than the original

[Powderman]

Bryan brings up a good point I didn't foresee. The groove for the dust seal may be too far in to seat the piston all the way and may interfere with the piston seal. You'll need to seat the CX or GL piston all the way to see if it does. The caliper housing may be thinner on the CX&GL and may not be a problem. You can push the old piston to full seat and measure how much sticks out and transfer that measurement to the new piston to see.

[Bru-tom]

The SS piston is a no-no in my books, with an moisture, the galvanic properties of alli and SS with cause a reaction, almost like a "battery". it will eat your caliper housing which isnt too practical for our older bikes. Brake fluid attracts water so sealing and shielding the SS piston will be very important if utilized.

[strynboen]

yes speciel on this primitive types vith no sealing..the ss get in kontakt with vater and aluminium..and starts to korode the aliminium...om sealed calipers it vork fine..i have some ss bolts on my cbx 1000..they eate holes in the calibers

[Bru-tom]

you need to use copper slip when using SS bolts in alli. It serves as a "neutralizer" between the two types of metal. 
Be sure to use it

[strynboen]

i have used normal grease(farming type)...think that kobber can make the galvanic proces worse..alu ..kobber.. salty water.. then you have a battery/accu running in your brake..its just my teori

[Bru-tom]

nope, copper slip will not cause it to get worse, it is the best to use for that application

[SohRon]

you need to use copper slip when using SS bolts in alli. It serves as a "neutralizer" between the two types of metal. 
Be sure to use it

Copper is an absolute no-no for stainless and aluminum... probably one of the worst things you can do to your calipers or cases. Use a zinc or aluminum anti-seize (I'm assuming that's what you mean by "slip") on your bolts for proper protection of the bolts and cases. Copper can be used in high-temp areas like the plugs and exhaust mounting bolts, but not much of anywhere else.

Copper eats aluminum for breakfast, lunch and dinner!

[RAFster122s]

I don't know what CX or GL pistons you have been dealing with but the CX and GL calipers I have dealt with (single piston caliper from '78 CX500 and a dual piston caliper from an '81-82 GL500I) have not had any groove in them. The caliper body has had dual square section seals but not the piston itself. So, time to ensure what you are dealing with is the same.

David

[dusterdude]

Run dot 5 and you dont have water issues

[Bru-tom]

you need to use copper slip when using SS bolts in alli. It serves as a "neutralizer" between the two types of metal. 
Be sure to use it

Copper is an absolute no-no for stainless and aluminum... probably one of the worst things you can do to your calipers or cases. Use a zinc or aluminum anti-seize (I'm assuming that's what you mean by "slip") on your bolts for proper protection of the bolts and cases. Copper can be used in high-temp areas like the plugs and exhaust mounting bolts, but not much of anywhere else.

Copper eats aluminum for breakfast, lunch and dinner!

ok, im really confused now...i read many times that copper slip is a must, maybe i misread it and supposed to use an anti-seize. but here me out here....

galvanic corrosion occurs when two dissimilar materials are mated together, correct? now, copper is a great conductor of electricity third to Silver and gold... now, seeing that copper is a great conductor, and adding it between two dissimilar metals, wouldn't it help to alleviate the "difference" in potential of the two different metals and make them "one"? its main purpose, like any other grease type substance is to keep moisture out, which is the number one cause of corrosion in the first place.

secondly, i think using aluminium slip is defeating the object of separating the two metals? to alleviate the differences in potential? arent you causing a better difference in material by doing that?

[SohRon]

you need to use copper slip when using SS bolts in alli. It serves as a "neutralizer" between the two types of metal. 
Be sure to use it

Copper is an absolute no-no for stainless and aluminum... probably one of the worst things you can do to your calipers or cases. Use a zinc or aluminum anti-seize (I'm assuming that's what you mean by "slip") on your bolts for proper protection of the bolts and cases. Copper can be used in high-temp areas like the plugs and exhaust mounting bolts, but not much of anywhere else.

Copper eats aluminum for breakfast, lunch and dinner!

ok, im really confused now...i read many times that copper slip is a must, maybe i misread it and supposed to use an anti-seize. but here me out here....

galvanic corrosion occurs when two dissimilar materials are mated together, correct? now, copper is a great conductor of electricity third to Silver and gold... now, seeing that copper is a great conductor, and adding it between two dissimilar metals, wouldn't it help to alleviate the "difference" in potential of the two different metals and make them "one"? its main purpose, like any other grease type substance is to keep moisture out, which is the number one cause of corrosion in the first place.

secondly, i think using aluminium slip is defeating the object of separating the two metals? to alleviate the differences in potential? arent you causing a better difference in material by doing that?

Not really into hijacking a thread. Read this; it should answer your questions: http://forums.sohc4.net/index.php?topic=94686.msg1086683#msg1086683

Don't use copper anti-seize on your bike except at the exhaust bolts or spark plugs.

[longshanks]

so SS is a no go?

[trueblue]

so SS is a no go?

I don't see why everyone is #$%*ing about SS pistons.  Stainless steel is essentially steel with Chromium mixed with it.  The standard pistons were Steel coated with Chromium.  Metallurgically there is 5/8Th's of sweet #$%* all difference, except the standards can corrode and pit if the chrome plate gets damaged.  I've used SS pistons in alloy calipers on a boat trailer that is regularly submerged in salt water for years and have never had any issues with the SS pistons eating the alloy of the calipers.  I highly doubt that the SS pistons would cause an issue on one of these bikes.

[dusterdude]

Actually ss wont cause a problem at all,chevrolet used ss in corvette calipers for years,they might still do

[Powderman]

I don't know what CX or GL pistons you have been dealing with but the CX and GL calipers I have dealt with (single piston caliper from '78 CX500 and a dual piston caliper from an '81-82 GL500I) have not had any groove in them. The caliper body has had dual square section seals but not the piston itself. So, time to ensure what you are dealing with is the same.

David

I think you are mistaken. The outer groove in the caliper bore is for the dust boot that also goes into the piston groove outside the bore. Every caliper rebuild kit I have seen for those calipers only have one piston seal in them, not 2.
And that is for all these models:
CX500   1979 thru 1981  all models

CB900C  1981

GL1000  1979 thru 1981  all models

CBX   1979 thru 1981

Your GL500I uses a 30mm piston so it doesn't apply to this situation.

[bryanj]

Without being rude I know I am right as i am running a GL 1000 piston in my 500 four with old pads

[Powderman]

Not to be rude, but you are right about what" How does what you are running in a 500 relate to the issue at hand with the 450? Are the calipers the same?

[bryanj]

Same part number piston, same fork legs