Campy H11 Bleed Problem

[gorkypl]

Mine does not leak at master cylinder, but there is no reason why one piston would touch rotor sooner than the other in a properly functioning system. If you center your rotor using the method you describe, it would go out of center when the brake pads wear. So while it might work for some time, there is still something wrong with this.

Also, the lever would feel 'mushy' if there is a lot of air inside, but you would not detect smaller air bubbles with this method. They might manifest for example by uneven pads movement.

[roadchallenge]

Mine does not leak at master cylinder, but there is no reason why one piston would touch rotor sooner than the other in a properly functioning system. If you center your rotor using the method you describe, it would go out of center when the brake pads wear. So while it might work for some time, there is still something wrong with this.

Also, the lever would feel 'mushy' if there is a lot of air inside, but you would not detect smaller air bubbles with this method. They might manifest for example by uneven pads movement.

3 things at play here:

1. Rubber seals on pistons that drag on caliper surface when they being pushed.
2. No way to regulate equal amount of fluid going on each side of piston to move them same distance.
3. Magnetic retraction of pistons.

Unless each piston is manufactured with perfect magnet weight/power and perfect rubber seal contact patch with caliper, there is no way to make sure by design that each poston travels exact amount during initial press, so you have to guide it a bit with tricks like paper etc. its been 1 year for me and it adjust for brake pad wear just fine. All it really does is to make sure there is just right amount oil on each side of piston inside caliper.

P.S.

Pads from 12 speed come with a spring spreader for pads, they probably realized they get too many lazy pistons.

[AJS914]

Wow, that part actually says "campy"! That might be a first.

[gorkypl]

3 things at play here:

1. Rubber seals on pistons that drag on caliper surface when they being pushed.
2. No way to regulate equal amount of fluid going on each side of piston to move them same distance.
3. Magnetic retraction of pistons.

Unless each piston is manufactured with perfect magnet weight/power and perfect rubber seal contact patch with caliper, there is no way to make sure by design that each poston travels exact amount during initial press, so you have to guide it a bit with tricks like paper etc. its been 1 year for me and it adjust for brake pad wear just fine. All it really does is to make sure there is just right amount oil on each side of piston inside caliper.

Nah, it does not work like this, unfortunately.
1. There is a drag, of course, but it is more or less even for both pistons. Or should be. Minor differences do not matter, as the pressure of hydraulic fluid is high.
2. This is not true. According to Pascal's law, if there is no air in the system, the pressure of fluid acting on both pistons is equal.
3. Magnetic forces are used only to hold the pads to the pistons. They have nothing to do with the retraction (this is done purely by seals).

I agree that it probably can work, but if there is a need for tricks to compensate uneven pad movement, then I'd say something is wrong with the system.

And these new pads look wonderful, but they were not included yet in April when I ordered 12s Record.

[raisinberry777]

Wow, that part actually says "campy"! That might be a first.

Some smaller parts do - the inline cable adjuster that comes with 2015+ levers has 'Campy' on it.

[roadchallenge]

3 things at play here:

1. Rubber seals on pistons that drag on caliper surface when they being pushed.
2. No way to regulate equal amount of fluid going on each side of piston to move them same distance.
3. Magnetic retraction of pistons.

Unless each piston is manufactured with perfect magnet weight/power and perfect rubber seal contact patch with caliper, there is no way to make sure by design that each poston travels exact amount during initial press, so you have to guide it a bit with tricks like paper etc. its been 1 year for me and it adjust for brake pad wear just fine. All it really does is to make sure there is just right amount oil on each side of piston inside caliper.

Nah, it does not work like this, unfortunately.
1. There is a drag, of course, but it is more or less even for both pistons. Or should be. Minor differences do not matter, as the pressure of hydraulic fluid is high.
2. This is not true. According to Pascal's law, if there is no air in the system, the pressure of fluid acting on both pistons is equal.
3. Magnetic forces are used only to hold the pads to the pistons. They have nothing to do with the retraction (this is done purely by seals).

I agree that it probably can work, but if there is a need for tricks to compensate uneven pad movement, then I'd say something is wrong with the system.

And these new pads look wonderful, but they were not included yet in April when I ordered 12s Record.

https://www.campagnolo.com/US/en/CampyW ... ke_project if you search for “magnetic” on this page it explains how they originally thought magnetic spring will be robust, pads magnetic is separate feature.

Excerpt from campy site:
“The design of the brake incorporates a magnetic spring on the pistons which eliminates the need for mechanical springs between the pads and guarantees a faster return as well.”

Pascals law for pressure is affected by symmetry of opposing forces, I was referring to initial press of lever, as soon as pads start moving closer to rotor if one pad has slightly more drag (slightli wider rubber seal) then it will move shorter distance for same pressure, and other pad will move further, as soon as you done pressing lever and system pressurized the volume of oil on each side of piston is dictated by how far piston was able to travel. Frankly its silly they recommend in their video, to squeeze then bolt down caliper, they were relying too much on their magnetic force to even out piston travel ...

You should hear F1 engineers rant about hydro braking and trying to de-air fluids, their fluid boils after 1 tap of brake pedal during cornering and rotors are red hot, while hydro is great, its far from perfect, but as a product on market, I would say, it qualifies to exist due to benefits.

The new pads come with SR 12 EPS. Backward compatible. Will def buy them with new slick cables.

[gorkypl]

https://www.campagnolo.com/US/en/CampyW ... ke_project if you search for “magnetic” on this page it explains how they originally thought magnetic spring will be robust, pads magnetic is separate feature.

Excerpt from campy site:
“The design of the brake incorporates a magnetic spring on the pistons which eliminates the need for mechanical springs between the pads and guarantees a faster return as well.”

To be honest I cannot see where a 'magnetic spring' could be used *inside* the piston.
Again - there is no 'return spring' inside the brake caliper. The piston return relies solely upon the elasticity of the rubber seal. And the only 'magnetic spring' that is there, is the magnet that is used to hold the pads close to the pistons - which they now found insufficient in some cases and supply classic metal spring too.

Take a look at this video - it's not Campy-specific, but it shows everything in a clear way:
https://www.youtube.com/watch?v=vQXFFgRButo

Pascals law for pressure is affected by symmetry of opposing forces, I was referring to initial press of lever, as soon as pads start moving closer to rotor if one pad has slightly more drag (slightli wider rubber seal) then it will move shorter distance for same pressure, and other pad will move further, as soon as you done pressing lever and system pressurized the volume of oil on each side of piston is dictated by how far piston was able to travel.

This is exactly what should not happen. The drag forces should be equal enough so they do not cause significant differences in piston movement. And the pressure of fluid behind each piston is still the same - it is a connected system, not two separate hydraulic circuits.

You should hear F1 engineers rant about hydro braking and trying to de-air fluids, their fluid boils after 1 tap of brake pedal during cornering and rotors are red hot, while hydro is great, its far from perfect, but as a product on market, I would say, it qualifies to exist due to benefits.

It's a totally different application. Different pressures, different temperatures, different fluids.
Hydraulic brakes do work in bikes. Be it Shimano, SRAM or Campagnolo.
Campagnolo brakes in my bike do not work correctly. That's all

The new pads come with SR 12 EPS. Backward compatible. Will def buy them with new slick cables.

True!

[roadchallenge]

Well i hope campy does not just lie.

Same fluid in F1, usually dot-4 230C boiling point. Then after each race it absorbs too much moisture, and boiling point is sub 75C so they have to rebleed. So for cycling this is a year interval.

I guess point i’m trying to make is, there is no way to get rid of air completely it will be there it will degrade brakes feel over long period. What set you back is Campy instruction video that just hit or miss. Once you figure out how to mess with campy setup in reproducible manner it works great, but its royal pain. Works for me now and I get to swap wheels with no rub.

[gorkypl]

Well i hope campy does not just lie.

Nah, I do not think they do.
Still, I think there might have been some misunderstanding, translation issues or the person writing the advertisement text had not understod the 'magnetic' thing thoroughly enough.

Same fluid in F1, usually dot-4 230C boiling point. Then after each race it absorbs too much moisture, and boiling point is sub 75C so they have to rebleed. So for cycling this is a year interval.

Campy (and Shimano) do not use DOT-4, but mineral oil. SRAM uses DOT-4. DOT-4 absorbs moisture (as you said) and it is more difficult to eliminate air from it. It has other advantages, but according to Shimano and Campy these are not really relevant in such a small system like bike brakes. Of course SRAM states otherwise

I guess point i’m trying to make is, there is no way to get rid of air completely it will be there it will degrade brakes feel over long period. What set you back is Campy instruction video that just hit or miss. Once you figure out how to mess with campy setup in reproducible manner it works great, but its royal pain. Works for me now and I get to swap wheels with no rub.

Yeah, this is probably the main point - I believe there must be a way to properly bleed the system. But I agree, my experience is so far limited to this one - and unsuccessful - try.

I called the only Campagnolo Pro Shop in Poland, and the head mechanic said it basically should work as on the video, without any tricks. I'd still be happy to hear from @graeme_f_k though...

[roadchallenge]

Ah I see, didn’t know, thought mineral oil is practically same thing as dot-4.

Yeah every shop I talked to says exact same thing about video, but if i follow vid its just air coming in 24/7 from somewhere, one shop even said they updating their rotors so they stay more true, hopefully its true by the time i’m ready to get 12sp. I hope you figure it out, I just accepted the fact that I might have air in the system and pistons are all lazy lol, as long as it doesn't rub and lever is firm i’m good.

[gorkypl]

Yeah, I will let you know once I have this sorted...

The guy from Campy Pro Shop said I can come next week if I won't solve it on my own, but not sure if there is anything else that can be done. I am very curious...
A friend of mine, who is a former MTB bike mechanic, told me that Magura never had a reputation of being exceptionally good when it comes to manufacturing process - precision, alignment etc. On the other hand, maybe it's us doing sth wrong...

All this looks like some teething problems - rotors not being exactly true (at least mine are not), this retaining spring being added later on (the new pads look wonderful though), and these bleeding problems...

On the other hand, I really like the way that these brakes work - much more than Shimano. Never used SRAM for longer, but I hope the issues will be sorted out, as the system is definitely worth it.

[roadchallenge]

Yeah campy disc brake feel and adjustment is just best, I think also shifter shape helps alot, shame its hard to bleed.

Yeah let me know how pro shop thing goes.

[corky]

Disc brakes for road bikes ....what an immature design. You wash your bike and ‘contaminate’ your brakes?.......phhht. Does this happen with motorbikes? Cars? MTBs.?

They rely on the deformation of squared edged rubber seals to retract pistons after the brake lever has been released. Which is why the gap between the pad and rotor has to be so slender, which leads to rub.......

[roadchallenge]

Disc brakes for road bikes ....what an immature design. You wash your bike and ‘contaminate’ your brakes?.......phhht. Does this happen with motorbikes? Cars? MTBs.?

They rely on the deformation of squared edged rubber seals to retract pistons after the brake lever has been released. Which is why the gap between the pad and rotor has to be so slender, which leads to rub.......

Well if I sprint on a car and rock it side to side, probably disc-brakes will rub lol. If I put like 300mm cast iron cranks on moto gp, and side load it, I think I can get rotor to rub. But then these vehicles come at $10k a year maintenance price + monthly payments that drive many into debt, I would say discs on bicycles are just fine for what average customers can afford

I’m assuming gaps can be designed to be “more bigger” but then you have to overcompensate for travel at the shifter with additional engineering, so you might end up with $800 per shifter instead of $400.

[gorkypl]

So I have a small update on this.

I think it's indeed impossible to bleed the brakes using the Campy procedure. Every time I pump the brake lever while pulling the bottom syringe, the air bubbles appear in the bottom hose - I think the air might be coming through the master cylider bladder or the caliper o-ring.
However, I spent the whole evening, bleeding using procedures for Hope, Avid and Sram brakes, also unscrewing the caliper and gently tapping and rotating it to eliminate any trapped air. I think I made it to a point where there is no air in the system.

However, the pistons still move in a very uneven way - the one on the side whithout brake hose is much slower.
So I thought I'd take a look at the rear caliper, which was not touched by me at all since being bled by Campagnolo Pro Shop. And guess what - it is even worse. One piston almost does not advance, while the other one (the one on the side with hose) moves easily.

Of course I exercised the 'sticky' one multiple times, cleaned it thoroughly, lubricated with oil - no effect. Even removed the piston completely (by pumping it totally out of the caliper) to clean it. Still it does not move even closely to the other one.

I think I might start a separate topic on this, as quick googling shoeed it's not a Campagnolo-specific problem. However, I have to admit I'm already so tired of this, that I almost start to regret removing fully functional Ultegra Di2 and putting Campagnolo Record on this bike. It is definitely more beautiful, but the amount of troubles almost kill the joy.