I think I figured out the extra brake lever travel

[Tufbusa]

IG, Spend your time figuring out HOW it works instead of WHY it works and you'll be WAY ahead!

 

[IG.]

change the piston seals and leave the Einstein part to Einstein problem will be solved

So, basically you don't know why. Rebuilding the caliper is sort of obvious. That's what I am trying to avoid.

 

[IG.]

IG, Spend your time figuring out HOW it works instead of WHY it works and you'll be WAY ahead!

That approach doesn't work for me - Going through life without understanding why things work a certain way. Not sure how I will be ahead, and what I will be ahead of.

So, no one seems to know. At the first opportunity, I will try to relube the pistons without taking them out of the caliper completely, and push them back and forth a couple of times. We'll see what happens.

 

[Tufbusa]

That approach doesn't work for me - Going through life without understanding why things work a certain way. Not sure how I will be ahead, and what I will be ahead of.

It's the ONLY way it works. You are getting your cart before your horse. You must first learn how it works before you can learn why it works.

 

[IG.]

It's the ONLY way it works. You are getting your cart before your horse. You must first learn how it works before you can learn why it works.

Tuf,

I already know how it works. It's not that complicated. So, can we move to the "why" part? It's a simple question: why the calipers are being pulled back more as the pads wear off? It's puzzling to me, and I don't see a straight answer.

 

[Tufbusa]

If you know how it works then tell me how the pads are released from the disk when you let go of the lever? What takes place that makes that happen?

As the pads wear out and get thinner, the pistons are being pushed further out taking along more brake fluid from the reservoir, and the vacuum inside the reservoir gets stronger and stronger.

It appears you don't understand how it works?

 

[IG.]

If you know how it works then tell me how the pads are released from the disk when you let go of the lever? What takes place that makes that happen?

As the pads wear out and get thinner, the pistons are being pushed further out taking along more brake fluid from the reservoir, and the vacuum inside the reservoir gets stronger and stronger.

It appears you don't understand how it works?

Tuf,

You are confusing two things hear - a) how it works and b) my attempt to hypothesize regarding the piston pullback.

You clarified a few posts ago that there are vents in the reservoir even though you didn't elaborate much where the vents were. So, I removed the cap and finally found the vents. After that, I clearly admitted that my hypothesis was wrong, and I moved to the next hypothesis - binding pistons.

In 'how it works" part, as the lever is released the disc pushes the pads which in turn push back the pistons a tiny distance so that the pads are staying very close and barely touching the discs - just enough distance to release the pressure.

With so many posts wasted, why don't you simply explain how it works if I am incorrect, and then please explain why the lever needs to be squeezed more as the pads wear off.

I am trying to figure things out, and an occasional incomplete piece of information causes more confustion on my part than helps.

Some people are OK with just the notion that "this is how it's done, and I don't care why". I need to know it all, can't help it. It may appear I am stuck on a certain subject, but I am not. The more I see an incomplete or inconsistent explanation, the more I want to know why.

Cheers,

 

[Tufbusa]

Tuf,

You are confusing two things hear - a) how it works and b) my attempt to hypothesize regarding the piston pullback.

You clarified a few posts ago that there are vents in the reservoir even though you didn't elaborate much where the vents were. So, I removed the cap and finally found the vents. After that, I clearly admitted that my hypothesis was wrong, and I moved to the next hypothesis - binding pistons.

In 'how it works" part, as the lever is released the disc pushes the pads which in turn push back the pistons a tiny distance so that the pads are staying very close and barely touching the discs - just enough distance to release the pressure.

With so many posts wasted, why don't you simply explain how it works if I am incorrect, and then please explain why the lever needs to be squeezed more as the pads wear off.

I am trying to figure things out, and an occasional incomplete piece of information causes more confustion on my part than helps.

Some people are OK with just the notion that "this is how it's done, and I don't care why". I need to know it all, can't help it. It may appear I am stuck on a certain subject, but I am not. The more I see an incomplete or inconsistent explanation, the more I want to know why.

Cheers,

I'm out the door at the moment but I'll explain how it works and why it takes more lever as the pads wear later!

 

[IG.]

Great! Thanks.

 

[Tufbusa]

The pistons or pucks in your brake calipers are pushed out by pressure created at the master cyclinder. When you release the lever the pressure is reduced to nutural. The pucks are still in their pressurized position but relaxed at this point. They don't retract. If they did you would loose your feel.

What takes place is the seal around the puck called a "Quad Ring" expands and contracts with each brake application. As the quad ring contracts it retracts the pucks just enough to allow the rotor to move again.

This part I am assuming: As the pads wear the pistons/pucks are pushed farther out and the quad ring stretches a bit more. When the pressure is relieved the quad ring retracts the puck more than it did when pads were fresh and new forcing the master cylinder to push a bit more oil into the caliper in order to move the pucks the extra distance. Although the distance is tiny the master cylinder moves very little oil during a single stroke. The result is moving the lever slightly farther in order to move the pads to the rotor.

 

[IG.]

Tuf,

Thanks for the explanation. The contraction of the inner seal and the outer dust seal, what you call a "quad ring", was my last suspect. I also don't think it is as much the inner seal (which has a direct contact with the brake fluid) as much as the dust seal which has little lubrication and gets bone dry.

I had no patience, and did try what I said I would try - specifically to combat both conditions - binding pistons and the piston retracting issue: I moved each piston out about 1/4" or so, lubed with brake fluid, and pushed it back. Did this a couple of times to every piston. It made a noticeable difference - after that I could move every piston back with my fingers, although some pistons improved greatly, while others only moderately.

The unfortunate drawback of my approach was that in one of the pistons the binding with the dust seal was so good that when pushing the piston out it dragged a portion of the dust seal with it to the outside. I though it was some speck of dirt, but then realized it was part of the rubber dust seal. So for that particular piston I had to pop it out completely, re-seat the dust seal, push back the piston, and re-bleed to get rid of the air. That piston now moves very well. However, in retrospect this entire approach is a bit too painful. So, I am not going to touch another caliper, but rather order a new set of seals and rebuild both calipers during the winter time.

Regarding the retraction of the pistons, I still had a couple of tight ones. So, when I reinstalled everything and bled the system, I noticed the extra travel of the lever. Suspecting what you described as an excessive retraction, I tried to combat it by squeezing the lever extra hard and holding it squezzed for a few seconds, hoping the rubber seals would release the binding pistons, and would not retract back as much. It did work. The extra lever travel disappeared. Feel free to try and see if that makes a difference on your bike.

Well, in conclusion I have to say that I neglected my calipers all this time, and probably it would be a good idea to take them off the bike every winter and clean them well.

I ordered today a set of speed bleeders from ebay, so bleeding would be a piece of cake.

 

[Tufbusa]

Speed bleeders make the job easy!

 

[Strife]

Was it here that I read about someone tied their brake lever to bring back the stiffness in it or something like that?

 

[Tufbusa]

I compress and ziptie my brake lever often when I transport the bike. It is a tool used to shake those stuborn air bubbles to the top. It does help to firm up the lever by expelling air from the system.

 

[kromdom]

Was it here that I read about someone tied their brake lever to bring back the stiffness in it or something like that?

A buddy of mine helped with my switch to GALFER lines and he suggested that I zip tie the levers overnight to "purge" out any residual air bubbles