Caliper Honing

[Guest]

Wondering if anyone has honed brake calipers? I have them apart from 80 750E, they are not pitted but have some discoloration in the bore. I would like to salvage them if possible, pistons look really good.....

[posplayr]

Wondering if anyone has honed brake calipers? I have them apart from 80 750E, they are not pitted but have some discoloration in the bore. I would like to salvage them if possible, pistons look really good.....

I take some 800 grit wet dry sand paper and clean the bores up use some wd-40 to keep it wet and then clean well.

used 1500-2000 grit on cam caps/saddles

I take the chromed pistons over to the buffing wheel with some Roche and get them real spiffy.

Don't let them fly across the room though.

[jwhelan65]

I take some 800 grit wet dry sand paper and clean the bores up use some wd-40 to keep it wet and then clean well.

used 1500-2000 grit on cam caps/saddles

I take the chromed pistons over to the buffing wheel with some Roche and get them real spiffy.

Don't let them fly across the room though.

thanks Jim

I started to use 400 on them , I think they will be ok with new boots and seals. Just wondering if there were some kind of fancy hoing device.

[Adler]

thanks Jim

I started to use 400 on them , I think they will be ok with new boots and seals. Just wondering if there were some kind of fancy hoing device.

Oh there certainly are fancy hoing devices!!!

[posplayr]

thanks Jim

I started to use 400 on them , I think they will be ok with new boots and seals. Just wondering if there were some kind of fancy hoing device.

If you already hit it with 400, I would go back over them with something a little smoother

[Dogma]

Mechanically speaking, the bores only need to be smooth enough for the pistons to slide freely. They don't need to be anywhere near polished. They can even have pits and gouges as long as the bore is mostly good. Just get all of the brake fluid residue out and test the piston action by hand. The pistons need to be smooth because they are a sealing surface. As long as the machining under the chrome is good, the pistons should be OK. The seal groove also needs to smooth over some contiguous surface around the OD (deepest part). Pits in the groove are permissible if they leave enough good material for the seal to, um, seal.

[posplayr]

Mechanically speaking, the bores only need to be smooth enough for the pistons to slide freely. They don't need to be anywhere near polished. They can even have pits and gouges as long as the bore is mostly good. Just get all of the brake fluid residue out and test the piston action by hand. The pistons need to be smooth because they are a sealing surface. As long as the machining under the chrome is good, the pistons should be OK. The seal groove also needs to smooth over some contiguous surface around the OD (deepest part). Pits in the groove are permissible if they leave enough good material for the seal to, um, seal.

It is still a rubber seal running over metal, it needs to be pretty smooth . I would still go for nothing less than 800.

[Dogma]

It is still a rubber seal running over metal, it needs to be pretty smooth . I would still go for nothing less than 800.

I'm not really following you here. The piston should be good from the manufacturer or as long as the chrome is intact in the sealing area. More polishing (without launching) won't hurt. The bore never interacts with the seal, so I guess that's not what you're referring to.

[jwhelan65]

I'm not really following you here. The piston should be good from the manufacturer or as long as the chrome is intact in the sealing area. More polishing (without launching) won't hurt. The bore never interacts with the seal, so I guess that's not what you're referring to.

I undrstand, the piston actually floats in the bore. The seal acts as a seal and a spacer so really the condition of the bore is not as crucial as the condition of the piston. Worse case as long as there are no serious rust pitting in the bore, replacing the dust boots , seals and pistons should work.

[posplayr]

I'm not really following you here. The piston should be good from the manufacturer or as long as the chrome is intact in the sealing area. More polishing (without launching) won't hurt. The bore never interacts with the seal, so I guess that's not what you're referring to.

Yea sorry, it is the static seal in the bore sliding against the polished piston.

Still no reason to rough up the bores.

I was having a Mojito ; it is Fiesta

http://www.thedailysound.com/080510FIESTAFIRST

[Nessism]

Dogma is correct, smoothing the bore does nothing. Just make sure the groove area is clean and smooth. The pistons need to be smooth too. I don't polish but rather use a gray (fine) scotchbrite on the pistons if there is any crud.

[posplayr]

Dogma is correct, smoothing the bore does nothing. Just make sure the groove area is clean and smooth. The pistons need to be smooth too. I don't polish but rather use a gray (fine) scotchbrite on the pistons if there is any crud.

Ed,
You should try buffing the chrome, it works real well on fork stanchions as well. And from what I have heard the more polished the surface is the less likely rust is to form.
Jim

[almarconi]

I thought nothing rusts in California.

[posplayr]

I thought nothing rusts in California.

It surely does at the Beach , we got this big thing called the Pacific.... it is pretty salty