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Just got my calipers back from the powder coater. They did them glossy black and they look nice. I purchased rebuild kits and am getting ready to put together. There is a little paint "over-spray" in some areas, I'm not sure if I should be concerned? See pictures below. Some is near the piston bores... There is nothing inside the bore at all, but look at the over spray. Thru also painted the round holes where the little o-ring goes... Do I need to try and get any of this paint off?
Absolutely, The powder coaters really should have masked off the mating surfaces and the O-ring seal mount. looks like lots of fun getting it off. Powder coat is NOT paint.
The presence of the coating material on these surfaces is problematic for a variety of reasons.
First, glycol brake fluid will eat paint. This will contaminate your system.
Second, assuming you opt for silicone fluid and avoid the aforementioned issue, the design is such that when the bolts holding the caliper halves together are torqued, the clamping force is applied uniformly across the mating surfaces while providing for a specific amount of deformation of the o-ring. If the coating was uniformly applied across the whole of the contact surfaces this would not not necessarily be a concern. However, it is unlikely that the coating is indeed uniform. This could result in excessive deformation of the o-ring, leading to leaks. Worst case would be the piston bores would not be on the same plane as the mating surfaces would not be parallel.
Regarding the coating on the seal lands (the tops of the bores), the presence of the material will not allow the seals to seat properly, allowing dust and moisture to get behind the seal and contaminate the bore, the piston and the piston seal. Also, the amount of material may prevent the seals from being installed at all.
Best to remove all the coating from those surfaces.
What a shame..
try brass brush on wheel..walnut shell blast...something that will not deform the machined mating surface...
start to see if you can gently scrape if powder,,then brush..
Go to Lowes, get a fire extinguisher (if you don't already have one in working area), a gallon or 2 of acetone, and a well made plastic soaking bin.
Soak each caliper half until all coating has been dissolved.
Use compressed air to clean out each fluid passage.
Powder coating is not bullet proof...
I can't imagine that the painted area where the O-ring fits would be a problem, unless the O-ring just won't fit well with the additional paint. That is not a 'working' joint; it just stays there and seals off brake fluid from leaking out. If the powder coat used is not attacked by brake fluid, leave it alone.
If you have powder coat in threaded holes in the part, you should 'chase' those threads with a thread tap to clear out the paint. Otherwise, you will have difficulty getting the bolts inserted..AND if you can install them, they could loosen with any wear/fretting of the bolt threads against the paint (instead of the mating threads).
Thanks all. I was thinking of the brass brush/wheel on a dremel or a drill. Do you think a steel brush would be too aggressive if the brass doesn't work?
Thanks all. I was thinking of the brass brush/wheel on a dremel or a drill. Do you think a steel brush would be too aggressive if the brass doesn't work?
sand your o ring area with power sander to cut off MOST of the coating without going nuts..you can use fne paper as you get close which will remove the coating and polish the metal.
the seal area for piston less concerning as long as seals fit..imo...
From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
Use a small steel brush and a razor blade. Brake caliper iron is pretty tough stuff and is not easily damaged by aforementioned tools. Don't overthink this.
What I did on my calipers is cut out a piece of sandpaper the diameter of the o-ring bore (maybe a few hundreds larger), then glued it to a piece of wood dowel that was the diameter of the bore. Put in a drill with some WD-40 and it gave a very nice machine-turned finish to the 0-ring area. I started with 220 grit and finished with 400 I believe. In your case with the powder coating you probably need to start with something more course like 100 grit. Then go to a finer wet/try paper when you reach metal. I did both caliper sides on mine. The reason being that o-rings would seal better on a surface with smoother concentric machined surface.
Good advice above inside, but i would remove all the coating from the mating surfaces as well..
forthe same reason there is no coating where a wheel mounts to a car..( except steel)
OK. I spent a little time with the dremel. First a little steel brush, then a brass brush. The brass one is cone shaped so it kinda fits in the o-ring hole nicely. What do you think of this? Side I didn't do... Side I did do...
Does this look good enough?
The dremel is working at taking the paint off the large flat surfaces. However, I'm having a little trouble getting it out of the o-ring hole. Here are pictures of 2 of them. Do you think I need to keep working on it, or is this good enough? If I need to get more out, any suggestions on how to do it?
Caliper paint question
