coating for brake calipers?

[briandneville]

I'm about to re-assemble the brakes after having calipers painted a nice and shiny gold to match the rims of my '83, and am looking at products that can be applied to prevent corrosion caused by contact with brake fluid.  There are a few products on the internet that claim to be corrosion inhibiting and safe to apply to paint, but since I have no spare parts to test this on, I'm wondering if anyone has any recommendations.

Thanks!

[WGuaire]

Have you considered clear coat?

[fret not]

If you want your caliper to be pretty powder coat it.  Generally paint will not withstand brake fluid,unless possibly it is a baked on coating.  The paint on the original master cylinder is pretty tough, and mostly withstands the brake fluid, but if allowed to soak in the fluid even that original 'paint' will soften.  Your other possibility is just be very careful with the brake fluid.

[kevin g]

I think I learned that DOT4 brake fluid less harsh on paint than DOT3.  I may be imagining this so YMMV.

[fiat-doctor]

I would check with your painter for his recommendation as far as a clear coat.

DOT 4 is silicone based and won't harm paint but is known to cause "mushy" brake lever feel.

I would just be careful with bleeding, and wash with water afterwards.  It's not like the exterior of the caliper is exposed to brake fluid.

[fret not]

DOT 5 is the silicone based fluid (will not absorb water), DOT 3 & 4 are glycol based and will absorb water.

[fiat-doctor]

Oops, you're right... forgot about 5, confused with 4

[briandneville]

Thank you all.  Maybe I should jsut douse them with brake fluid and get it over with

Trying to get feedback from the painter.  Either way I will be careful.

Does anyone have thoughts about gravity filling the lines from the top vs. injection from the bottom?  Gravity sure seems like it would be a lot easier, if it works.  I was talking to a friend about using a pump to bleed from the bottom.  Any thoughts on that?

 

[fret not]

When relying on gravity you have fluid viscosity and surface tension to contend with inside the brake lines, which can trap air bubbles.  So, if you push fluid up from the caliper you get no trapped bubbles.  Either method will work but if using only gravity the process will likely take a much longer time to complete.  When pushing fluid up from the caliper the job is done much sooner.  No air bubbles allowed.

[Prophet Of Doom]

I'm with Fret.  Do it from the bottom.
The procedure in Haynes is only suitable for a fluid change, not good when your calipers and lines are empty.

I use a 75ml syringe, and push gently to avoid a fountain at the master cylinder.

All my parts are powder coated, which holds up well.  Still needs to have spills washed off with warm soapy water.

[kevin g]

I recently did my rebuilt system going from the top.  I start with a MityVac pulling fluid down from the reservoir and finish with the conventional squeeze the brake lever and open the bleed valve.

One problem with the MityVac is that air bleeds in around the threads of the bleed nipple so it is not easy to tell where the air is coming from.  When fluid is pushed up from the caliper wouldn't some of it leak around the bleed nipple threads?  If air can sneak in around the threads when applying vacuum why wouldn't fluid sneak around the threads under pressure?

[jefferson]

An easy way to get those bubbbles moving up is to rap on the brake line with a wrench. It will break them loose and move them up to the master cyl. where they can be burped out.

[WGuaire]

I go bottom with a pumper. If I need to do a bleed, I use a Motion Pro tool. I bought a little air compressor brake bleeder. I haven’t used it yet.

[MikeScoot]

Another, low tech, way is to fill a long line with brake fluid, connect it (tightly) to the caliper nipple and then tightly wind the line around a bottle (or similar). This forces fluid through the calipers and up the hose at a rate dictated by your winding speed.
Can be a bit messy filling the line, but works a treat!

[lexx790]

My calipers had a Chromate Conversion Coating then gloss black HT caliper paint.
Has lasted 10 years with no paint flaking off, but recently the brakes jam a bit when moving the bike backwards.

[jefferson]

My bikes brakes did that also when pushing it backwards. Kind of a pain moving it around and never did look into it heavily as they worked good going forwards which was the most important aspect.