Rear caliper drag (rebuilt, new ss piston, seals etc): axle alignment?

[DiverRay]

You may be able to fine a hone tool at the auto parts store. A lot of the "imports" use the smaller bore and someone may have the hone for it.

[DEEBS11]

It can't be silica. It has to be aluminum oxide or you will ruin the bore.

https://www.ebay.com/itm/234292184532

[gtem]

Ah, that's the exact one! No idea why I couldn't find that myself.

So last night I went through both the caliper and M/C again, recleaned the caliper seal groove even more, polished the caliper bore a bit with 1000 grit, checked the spooge hole on the M/C, bolted it all back together and rebled using all the tips/techniques I've now learned (one I've had good luck with is pumping the piston out a good ways then driving the piston back into the bore with a screw type caliper tool, you can see the bubbles come up into the reservoir). A test ride had the rear rear rotor merely warm, and the rotor warpage was much less of an issue. Pedal was still a bit mushy at this point, but after the test ride I just bled it a bit more and now the pedal feel is nice and actually the rear wheel is freer yet. I can spin it a full rotation by hand (grab it and get it spinning then let it go), rolling it around the garage it feels much better. One thing I have been noticing is that a bit of brake fluid will end up in the M/C dust seal, and that when pumping the M/C you can tell a bit of "suction" forms on the dust seal. So I'm not out of the woods yet, I do need to properly hone that M/C bore and hope that finally makes a proper reliable seal.

[gtem]

A further update: after sitting in the garage a few days, the caliper has gotten tighter again. I'm fairly certain it's down to that misbehaving (leaking) master cylinder. I've got the correct style ball hone on order, fingers crossed I can clean up the bore on one of my two master cylinders. Buying them used off ebay is a bit of a fool's errand I'm learning, they seem to *all* have some pitting in the bores.

I also worry about about whether the new seals on the rebuild kits are getting damaged with all this being disassembled then reassembled, or dragging on substandard surfaces... is it at all possible to buy just the two rubber seals rather than $30 rebuild kits with the metal piston, spring, etc?