Dumb front brake question

[wolf_walker78]

On my 79, did a brake refresh a year or so and very few miles ago using an aftermarket master cylinder and new pistons and seals in the calipers, seemed okay what little it's been ridden. Put new pads and stainless lines on it few months ago and a test ride to bed the pads it seemed fine. Took it out the other day and could barely push the thing, jacked it up and the front wheel couldn't be turned by hand, opening bleeders changed nothing but loosening the left caliper mount bolts did.
Sticking caliper, cool. Pulled them both, disassembled and cleaned thoroughly including the seal groove, pistons looks way better than they should for it's age so I assume I replaced them, did a very light hone of the cylinders and it all looked fine to me. I've done this junk on cars since I was a kid, looks like mostly same-same. Anyway, back together, bled fine, good lever, it's freezing again so haven't ridden it but the wheel is pretty stiff. I can turn it with one hand but it's certainly not moving after I stop turning it. Is that normal for these or are the pistons not retracting correctly? It's not a hydraulic issue so it's got to be the seal one way or another, unless a stiff wheel is normal? I know "stiff" is pretty ambiguous. If it was a car I wouldn't think too much of it to be honest but I figured I'd ask. It might clear up after riding, or not.

[gltriker]

I might be able to give you a little assistance with this conundrum.
I sorely wish now I had taken pictures to present why my '75 GL1000 front brakes were acting exactly the same.

The front caliper assembly is mounted onto its cast aluminum bracket with 2 hex socket screws that thread into their respective caliper slider pin. At the female threaded end of the slider pin that contacts the aluminum bracket, there are flats machined on either side that index against a flat edge on the mounting bracket to prevent the slider pin from rotating when the hex socket screws are being tightened.
I went round and round trying to figure out why, after replacing the original 1975 brake hoses, rebuilding both calipers, and the front master cyinder- all 3 several times each .

Finally, I discovered one of the slider pins had rotated just enough while tightening its hex socket screw that the slider pin and aluminum bracket complementing anti-rotation flats were no longer aligned and that slider pin flat edge had left a slightly elevated imprint on the aluminum bracket.
anyways...
Take both aluminum caliper mounting brackets off their respective fork lowers and inspect their slider pin anti-rotation flat edges.

[wolf_walker78]

Thanks Cliff, I made that exact mistake the first time I had these apart
I lubed the pins and made sure they seated to the caliper mating point correctly this time.

[wolf_walker78]

Pulled the calipers back off this evening. With either one removed the wheel rotates more like what I'd expect, though granted my expectation is not based off any bike experience. I did notice a little metal folded over on one of the caliper mounting surfaces from some previous owner doing exactly what Cliff said and not having the pin aligned correctly. I cleaned that up and replaced one bolt I suspect was bent slightly in the same occurrence. Made no difference in what it takes to rotate the wheel. I opened the bleeder on each caliper with it detached and the piston pushed back in by hand, I gently operated the lever and observed the piston pulsing out and in very slightly just as I'd expect.

In the absence of a point of reference for how much drag is too much, I'm stumped. The only other thing I know to do is order fresh seal kits and do some dremel brush in the seal channel and try em again. If it ever quits raining and/or being 30 degrees again I'll test ride it first and see how they settle in.

[robin1731]

See post #8.

viewtopic.php?p=386314&hilit=installing ... er#p386314

[wolf_walker78]

My service manual does not mention any of that. Where can I find it?



I did give a quick look and the disks seem to be fairly well centered, certainly aren't rubbing.

[wolf_walker78]

Seal kits in monday, in theory.

Did take a brief test ride, front brake feels strong but it's still pretty stiff when spinning up in the air.
The rear is about half as stiff, it feels like the front if you remove one (either) caliper lol...

I dunno, I'll rebuild the calipers again and see what it does. Seems like a lot of opportunity for small alignment error up there with the forks and wheel and caliper carrier position. It's not impossible the pads will wear in over time either I guess. I don't think I've done front brakes on a bike that weren't either drums or my dirtbikes single disk almost 30 years ago.

I also learned a new thing in the course of google'ing around about such. I was taught to just lube the piston and seal with brake fluid (which isn't a very good lubricant) but there exist a "red rubber grease" that is specifically safe for rubber and not harmful if it mixes with brake fluid. At least one of the major brake manufacturers has a part number for and recommends it. I ordered a little tub of it.
I notice the Honda service manual says "Lubricate the piston with a medium grade high temperature silicone grease before assembly" which they spec for the slide pins as well which is interesting.
Was the brake fluid originally silicone based in these? Far as I know glycol and silicone don't play nice together?

[robin1731]

Was the brake fluid originally silicone based in these?

No

[Sidecar Bob]

I've used silicone grease on brake pistons for decades and it hasn't caused any problems that I've noticed.

[wolf_walker78]

I've used silicone grease on brake pistons for decades and it hasn't caused any problems that I've noticed.

You aren't the only one from what I see. I have a hard time believing Honda would suggest something that wrong so I suspect it's just fine.

[Sidecar Bob]

FWIW, I learned it from a Suzuki manual so Honda aren't the only ones.

[Shadowjack]

I don't think that silicone fluid is bad for the glycol, it's that it just doesn't mix. The miniscule amount of silicone grease on the surface of the seal is not going to affect anything.

[wolf_walker78]

Whelp, this is annoying.

When this first happened, the first thing I did was crack both bleeders to see if it was a residual pressure issue, it wasn't.
At least not then. Today when pulling the caliper to re-re rebuild them, I pulled both the lines, little fluid drippled out, and I noticed the wheel was suddenly free spinning. Great.
I re-re-rebuilt the calipers anyway since I had the seals handy, bled em, same result.

I ordered (another) master cylinder. I may pull this one apart since it has no use on it and clean fluid and see if I can just clean it up. Or I might just wait for the replacement to show up. Annoying that nobody has anything one can get quickly.

Least I know the calipers are fine now. Several times over.

[Sidecar Bob]

Check the master cylinder's relief hole.

[wolf_walker78]

That's what I assume it is, it's as spotless inside the reservoir as the day it was installed so it's some crud inside it.