Zinc Plating Caliper Bores?

[Sam 78 GS750]

Anybody done it? Think it's a good idea? Mine were a bit rusted, but a good soak in Metal Rescue took care of that. No pitting though...the plating did its job and oxidized so the metal underneath was spared. There are some bare spots now where the original plating is gone.

I'm thinking I can mask off everything but the bores and re-plate using my zinc plating setup. Has anyone done the same and can give me a thumbs up? Can anyone think of reasons why it would be a bad idea or potentially unsafe? Should I just put new seals, etc in and use as-is (and just keep fresh brake fluid in instead of sitting with the same fluid for 10 years?)

I know I can get them re-sleeved or roll the dice on another used set that may be just as bad or worse. Don't wanna go aftermarket or mess with upgrades from other bikes...

[Sam 78 GS750]

Some photos of what I'm working with...

20180308_085039 by samL9, on Flickr

20180308_085107 by samL9, on Flickr

20180308_085137 by samL9, on Flickr

20180308_085203 by samL9, on Flickr

[Nessism]

Zinc plating is for steel. The caliper bodies are aluminum so you can not zinc them. Anodize would work. I suspect the bore was anodized when the bodies were made but I'm not positive.

The bore condition is not important really though other than maybe the seal groove. The piston doesn't touch the bore at all other than as a guide. The seal does all the work. Deep pitting behind the seal such that a continuous path is available from inside to outside would be a deal breaker for the caliper. Otherwise just clean the groove and any visible corrosion and install a new OEM (not K&L) seal and you should be good to go.

[Sam 78 GS750]

Good to know. I ddn't realize they were Aluminum. I thought they were steel because of the color of the rust. Reddish brown vs whitish color like I would expect from Al oxidation.

That answers that question.

Think I'll clean em, paint em, throw new seals in and call it a day.

[chuck hahn]

Clean the groove for the piston seal with a dermal and small wire wheel attachment. Inspect and clean the well out with a shot of carb spray or brake cleaner..then some air to dry it. Rebuild.

[Steve]

Good to know. I ddn't realize they were Aluminum. I thought they were steel because of the color of the rust. Reddish brown vs whitish color like I would expect from Al oxidation.

The "rust" in your system is due to moisture that has collected in the brake fluid. The steel that donated the rust is probably the banjo bolts that hold the hoses to the master cylinder and calipers.

As Nessism said, the condition of the bores does not matter. Brake fluid is the only stuff that touches the bores.

.

[Sam 78 GS750]

Thanks guys. This makes me a bit more comfortable about the condition of my calipers. I don't like to mess around when it comes to brakes. Makes sense about the rust coming from the banjo bolts, Steve. They were in pretty rough shape and are being replaced. This is probably a whole other can of worms, but since I'm starting with a fresh dry system, I'm thinking about using DOT-5 to avoid moisture in the lines...

[Sam 78 GS750]

This is probably a whole other can of worms, but since I'm starting with a fresh dry system, I'm thinking about using DOT-5 to avoid moisture in the lines...

Never mind... Just read a bunch of stuff about DOT5 that may or may not be true. Not worth the bother to find out first hand. I'll just flush the brake system and change my fluid every couple of years.

[Steve]

..., I'm thinking about using DOT-5 to avoid moisture in the lines...

Never mind... Just read a bunch of stuff about DOT5 that may or may not be true. Not worth the bother to find out first hand. I'll just flush the brake system and change my fluid every couple of years.

Not sure what all you have read, but there are many myths along with the truths about DOT5.

First of all, you need to have components that are compatible with the silicon-based fluid. Not sure if GS components are. Next, it's best to start with ALL NEW parts, as DOT3 (and 4) don't play well with DOT5, and the few drops that will be trapped in the nooks and crannies WILL find their way out.

One of the "advantages" of DOT5 is that it does not absorb moisture. Yes, it's true, but that creates some other problems. Not so much in our bikes, but in a car, where you have a longer line going to the rear wheels, the line might dip a bit to go under a crossmember or something. Water is heavier than brake fluid, and any moisture in the fluid will gather at that low spot. All that water will sit there all the time, possibly wreaking havoc on the brake line. Might be hard to flush out, too. With DOT3 and DOT4 (and DOT5.1), the water will be absorbed by and distributed throughout all the brake fluid, making it easier to drain the water and flush the system.

Many more points to be considered, but these should suffice.

.

[Sam 78 GS750]

Water is heavier than brake fluid, and any moisture in the fluid will gather at that low spot. All that water will sit there all the time, possibly wreaking havoc on the brake line. Might be hard to flush out, too. With DOT3 and DOT4 (and DOT5.1), the water will be absorbed by and distributed throughout all the brake fluid, making it easier to drain the water and flush the system.

Many more points to be considered, but these should suffice.

.

This was one of the main points that concerned me, and made me reconsider. "Doesn't absorb water" sounded good, but I didn't think about that aspect of it. Water sitting in a spot sounds worse than a little moisture in the fluid. The whole reason I was thinking about DOT5 was to avoid corrosion...
I also read that DOT5 is harder to bleed, because more (and smaller) air bubbles get trapped throughout the system. I hate bleeding brake lines, so that was that.