State of these brakes

[Vaderham]

Hey all,

Well, after being told to focus on safety in my last thread (Yeap, fair advice), I moved the brake rebuild up the list.

More bad viewing, I'm afraid. I'm wondering if you guys think that the caliper bore here is beyond help?

I'll be replacing the pistons, seals etc, but I'm not sure about the amount of corrosion going on in the caliper themselves. Appreciate any advice.

I didn't clean these at all. This is literally right after pulling the pistons. Also, these are all the same caliper. The other one is in slightly better shape.

Photo 1: https://ibb.co/HG03Xp8
Photo 2: https://ibb.co/Zf23yMT
Photo 3: https://ibb.co/2PKDFQJ

[OddDuck]

From what I can see, the caliper bore looks fine. Unless you've got obvious wear and abrasion down the bore, there shouldn't be a problem. The bits I'd worry about would be the seal groove and the slider pins and sleeves.

[sidecar bob]

They're virtually brand new compared to some of the stuff I rebuild.
Dig the seal out with a small screwdriver & use scribers to remove all the alloy corrosion in the seal groove, particularly right in the very corners of the groove, don't worry about scratching the groove, you can't harm it.
Clean up the corrosion outboard of the seal with 300 grit wet & dry paper, the piston is the sealing surface, so no worries there.
Buff the piston on a rotary wire buff until mint, then wash everything in hot water with laundry powder, including seals.
Run your fingernails around the seals to remove any attached alloy corrosion, they are very tough, so get right in there.
Rinse everything in fresh hot water & blow everything dry with compressed air.
Fill the seal grooves with Bosch blue rubber grease, & refit the seals to displace the grease, not worrying at all about the effects of a little bit of rubber grease mixing with brake fluid.
Smear the excess grease around the piston bore.
Lightly grease the caliper piston & slide it in.
Grease the slider pins & bushes with rubber grease also.
Wire buff the bleed screw thread & clean out the hole & rubber grease the thread. Regular grease is better for threads, but not around brake fluid.
Bolt it back on the bike, rubber grease the banjo bolt thread & bleed it up.
No new parts, best brakes ever & all done in half an hour.
That method was good enough for this guys bike & who knows, if you do it, you too may be able to do 200kmh victory wheelies.;)

[F5 Dave]

It's the dust seals that get the most wear. If they are deformed they can pull the piston back further. They should be straight with no obvious odd wear.

[SaferRides]

Is Bosch blue better than Castrol red rubber grease?

[Premature Accelerato]

Sidecar Bob, I assume you mean that he should buff the gungy side of the piston and not the surfaces that make contact with the seals?

[sidecar bob]

Sidecar Bob, I assume you mean that he should buff the gungy side of the piston and not the surfaces that make contact with the seals?

Buff the seal surface, the outside of the barrel.
That's the bit that really matters.
I always do it in a longditudal direction, the same way as the piston moves, it just feels right.
It's solid stainless, you won't damage it, only remove the shyte.
I will go into bleeding them when you're ready. It's far easier than most people insist on making it.

[sidecar bob]

Is Bosch blue better than Castrol red rubber grease?

I actually prefer red for brakes that are going together for ever, like road car brakes, that stuff will be great for a road bike.
The blue stuff doesn't stay in lumps & tends to be better for race brakes.
But really, as long as its automotive rubber grease, go hard.

[Vaderham]

Buff the seal surface, the outside of the barrel.
That's the bit that really matters.
I always do it in a longditudal direction, the same way as the piston moves, it just feels right.
It's solid stainless, you won't damage it, only remove the shyte.
I will go into bleeding them when you're ready. It's far easier than most people insist on making it.

Righto. That KS so much for the advice butguys. Ican manage fishing out the seal and ensuring the seal groove is...groovy, and can easily sand that exterior lip.

I don't have a buffing wheel however. I've seen at least one video online of someone taking super fine sandpaper to the exterior of the Piston (in a longitudinal fashion as prescribed). How likely is that to cause high speed death do you think?

I'll post some pics of the pistons when I get home tonight.

[sidecar bob]

Righto. That KS so much for the advice butguys. Ican manage fishing out the seal and ensuring the seal groove is...groovy, and can easily sand that exterior lip.

I don't have a buffing wheel however. I've seen at least one video online of someone taking super fine sandpaper to the exterior of the Piston (in a longitudinal fashion as prescribed). How likely is that to cause high speed death do you think?

I'll post some pics of the pistons when I get home tonight.

I serviced a pair of calipers at Taupo circuit without a buff last weekend & used wd40 & a scotchbrite on the Pistons, or use 800 plus wet & dry paper.
People spank their monkeys over brakes & safety.
Get right in there & don't be shy.
Nobody has ever been hurt from my methods, used commercially & for race use over decades.

[pete376403]

Your original post said you are replacing the pistons, If so why bother cleaning up the old ones? Are you referring to the plastic inserts that go inside the steel pistons?

[Vaderham]

Your original post said you are replacing the pistons, If so why bother cleaning up the old ones? Are you referring to the plastic inserts that go inside the steel pistons?

Sidecar Bob mentioned using the pistons again after buffing. Maybe I have that wrong? Definitely ok with getting some new pistons if y'all reckon it's the go.

[sidecar bob]

Sidecar Bob mentioned using the pistons again after buffing. Maybe I have that wrong? Definitely ok with getting some new pistons if y'all reckon it's the go.

Buff them up. If there are pits in the seal zone then get new ones.
If they come up smooth then why would you buy new ones? They don't wear out, they just get shyte attatched to them.
They're usually made of stainless, so unlikely to have holes rotted in them.

[Vaderham]

Hmm, I reckon I might need to get new pistons.

Photos:
https://photos.app.goo.gl/7BV1RfvXNnvdmpgk8
https://photos.app.goo.gl/71shNBo22QFXtUPy7
https://photos.app.goo.gl/eK4Hr4eowbEiWRSD6

[sidecar bob]

Hmm, I reckon I might need to get new pistons.



Hmm yeah.
I don't think those ones are stainless.
You won't know if they are any good until you give them a scrub up.
If there's pits in the outer barrel surface on the main body, and I think there will be, then that would be a smart move.

[F5 Dave]

Buff them up. If there are pits in the seal zone then get new ones.
If they come up smooth then why would you buy new ones? They don't wear out, they just get shyte attatched to them.
They're usually made of stainless, so unlikely to have holes rotted in them.

Um, what??

No, regularly they are plated steel. I'd they are gold coloured they won't be stainless. I'd prescribe autosol and super careful scotchbrite but at a point it's replace.

[pete376403]

https://www.ebay.com/itm/YAMAHA-XJ650-XV750-XSXV920-XJ1100-VIRAGO-FRONT-BRAKE-CALIPER-PISTON-AND-SEAL-KIT/291731922416?hash=item43ec93ddf0:g:oWYAAOSw8RJXBrN 7

[Vaderham]

https://www.ebay.com/itm/YAMAHA-XJ650-XV750-XSXV920-XJ1100-VIRAGO-FRONT-BRAKE-CALIPER-PISTON-AND-SEAL-KIT/291731922416?hash=item43ec93ddf0:g:oWYAAOSw8RJXBrN 7

That's a pretty sharp price, cheers for the link!

I think I'm just gonna splash out and get new parts.