Calling all hydraulic brake road bike users

[Richard A Thackeray]

You're wrong on all 5 counts

I've only been using them on a road-bike for a few weeks now

On arrival, & initial riding/testing, in the dry I found them no better than the bedded in (but not worn to any extent) Ultegra on my Gran Fondo
Any dry difference could be down to the fatter tyres on the CGR ('28') opposed to the '23' on the GF

In the wet, though, compared to the Tiagra, on my (2013) 'blue winter' Ribble, they're a lot better
Granted, there is still a very slight delay, as any water is swept off the disc
One factor that is seemingly forgotten, is the clearance issue, in the case of a buckled rim, from a pothole - there's no rubbing on brakes (or the need to use the cam to give clearance - and reduce brake efficiency)

 

[Yellow Saddle]

I've only been using them on a road-bike for a few weeks now

On arrival, & initial riding/testing, in the dry I found them no better than the bedded in (but not worn to any extent) Ultegra on my Gran Fondo
Any dry difference could be down to the fatter tyres on the CGR ('28') opposed to the '23' on the GF

In the wet, though, compared to the Tiagra, on my (2013) 'blue winter' Ribble, they're a lot better
Granted, there is still a very slight delay, as any water is swept off the disc
One factor that is seemingly forgotten, is the clearance issue, in the case of a buckled rim, from a pothole - there's no rubbing on brakes (or the need to use the cam to give clearance - and reduce brake efficiency)

The width of your tyres make no difference to braking.

Clearance is the issue with disc brakes. 50% of the complaints are clearance related, the other 50% noise.

 

[Yellow Saddle]

I wish I could be arsed.

Don't be. Live with the mystery for the rest of your life. I always thought figuring out small little things which puzzle us are one of the joys of life. But then again, some people think small things amuse small minds.

 

[Oldfentiger]

With a hydraulic braking system, are they not designed to operate with (theoretically) no clearance. As the pads and disc wear, then the hydraulic system allows more fluid into the master cylinder via the reservoir, which then allows more fluid into the slave cylinder to allow the pads to compensate for wear.
As sometimes happens with me, I could be sprouting total bollox.

 

[Kbrook]

With a hydraulic braking system, are they not designed to operate with (theoretically) no clearance. As the pads and disc wear, then the hydraulic system allows more fluid into the master cylinder via the reservoir, which then allows more fluid into the slave cylinder to allow the pads to compensate for wear.
As sometimes happens with me, I could be sprouting total bollox.

There must be some clearance but that distance should always be the same, no matter what the pad wear, is my understanding. Just wish that clearance was a tad more

 

[Oldfentiger]

There must be some clearance but that distance should always be the same, no matter what the pad wear, is my understanding. Just wish that clearance was a tad more

How would this clearance be established? Is there some clever witchcraft which allows a tiny bit of fluid to escape back out of the slave cylinder to create this clearance?
I would add that I have no experience of hydraulic disks on bicycles, as mine are cable operated. I've ridden motorcycles for many years, and if the pads weren't constantly rubbing slightly then there was something wrong. In fact if you experienced a "head shake" it was best practice to give the lever a pump to get the pads next to the disc again.

 

[Yellow Saddle]

How would this clearance be established? Is there some clever witchcraft which allows a tiny bit of fluid to escape back out of the slave cylinder to create this clearance?
I would add that I have no experience of hydraulic disks on bicycles, as mine are cable operated. I've ridden motorcycles for many years, and if the pads weren't constantly rubbing slightly then there was something wrong. In fact if you experienced a "head shake" it was best practice to give the lever a pump to get the pads next to the disc again.

Clearance is established through flexible piston seals. The piston doesn't actually slide in and out of these square seals because the movement is very small and the frictional force to move the pistons is larger than the seal's resistance to flex. In other words, the pistons "pout" towards the discs and "pucker" back. However, once the seals are caked with dirt or have become hard with age, they no longer flex easily. That's when the piston advances fully and stays there, constantly rubbing.

 

[Oldfentiger]

Clearance is established through flexible piston seals. The piston doesn't actually slide in and out of these square seals because the movement is very small and the frictional force to move the pistons is larger than the seal's resistance to flex. In other words, the pistons "pout" towards the discs and "pucker" back. However, once the seals are caked with dirt or have become hard with age, they no longer flex easily. That's when the piston advances fully and stays there, constantly rubbing.

Thank you. Makes sense to me

 

[Cycleops]

Clearance is established through flexible piston seals. The piston doesn't actually slide in and out of these square seals because the movement is very small and the frictional force to move the pistons is larger than the seal's resistance to flex. In other words, the pistons "pout" towards the discs and "pucker" back. However, once the seals are caked with dirt or have become hard with age, they no longer flex easily. That's when the piston advances fully and stays there, constantly rubbing.

Thanks, I've never seen 'pout' and 'pucker' seen to describe disc braking before, I thought those terms were only descriptive of people on Facebook.

 

[Kbrook]

I've just been out after a bit more fettling. I managed to get some fluid out of the reservoir by opening the bleed screw and pushing the pistons back. Not sure whether it was my imagination but that seemed to create a bit more clearance.
On the ride today I used by back brake more than I usually do in combination with the front, I also dragged the front brake less using on and off braking more. No noise. Not sure whether it was the removal of a bit of fluid or the different riding style that helped. Also I didn't go down any major descents. Oh and the noise of the wind helped! So is it sorted, who knows, I must learn to be less fussy about noises in future as well.
Thanks yellow saddle and everyone else who posted, I can now worry about something else.

 

[Juanito]

After several steps (1, adjust front wheel; 2, adjust front wheel again; 3, use 400 grit to sand both sides of rim & brake pads) my Magura hydraulic front brake no longer squawks after sample ride. It might still squawk after a more extended biketour....! Please consult my website/FB page for details. --"Juanito"

 

[Juanito]

I currently pedal a Doublevision, acquired 17 years ago at Tandems Ltd (BirminghamAL-USA); owners Susan & Jack assisted me in the navigation of my first 'bent. My intention was that my daughter would be stoker (I was captain), my son could pedal his own, and we were going to biketour from Victoria to Tijuana on the PCH. HOWEVER, it was not to be....!
Whilst I have a tremendous amount of experience, it can sometimes be too much to expect of novices. In a sense, I'm glad because both my children are now full-functioning adults who enjoy occasional pedals--not having been burned out an early age?!
Anyway, I spend much of my biketouring nowadays on the "International Ft. Hancock-Las Cruces I-10 Bicycle Bypass" best access to our "Hidden Gem of the World, Crossroads of North America, anchored by El Paso, Cd. Juarez & Las Cruces!" You will be most welcome pedal here!

 

[Globalti]

After several steps (1, adjust front wheel; 2, adjust front wheel again; 3, use 400 grit to sand both sides of rim & brake pads) my Magura hydraulic front brake no longer squawks after sample ride. It might still squawk after a more extended biketour....! Please consult my website/FB page for details. --"Juanito"

Squawking and juddering as you roll to a stop means the brake is contaminated with oil or brake fluid.

 

[Richard A Thackeray]

The CGR's front disc has worked slightly loose

At first I assume that the rocking with the front brake, on full, was a loose headset, but no
With fingers on the fork/head-tube, there's no play

However, rocking the bike, & looking at the front, I noticed that the disc was moving
Maybe only a mm or so, I'll try to borrow a tube of blue Loctite at work, tomorrow (if I take my Torx keys, I can do it in the morning, & it should be set after maybe 5 -6 hours

 

[Yellow Saddle]

The CGR's front disc has worked slightly loose

At first I assume that the rocking with the front brake, on full, was a loose headset, but no
With fingers on the fork/head-tube, there's no play

However, rocking the bike, & looking at the front, I noticed that the disc was moving
Maybe only a mm or so, I'll try to borrow a tube of blue Loctite at work, tomorrow (if I take my Torx keys, I can do it in the morning, & it should be set after maybe 5 -6 hours

They often do that but I don't know how easy yours moves and whether it is loose or just as most of them are. The holes in the disc and screw diameter are not exactly the same, so there is play there. The only thing that prevents easy play is a bit of pressure from the screw head on the disc.

Tightening the bolts don't really solve the issue and I'll be very surprised if it is that which causes the juddering you described. But, lets hear what happens after your operation. Even centre bolt discs have a bit of play. This doesn't matter because in use discs only resist force from one side and once the lash is taken up, it's all good, until next time you pull the brake and pull the bike backwards.