Magura rim brake question

[whisperdancer]

Sorry to post this question here, but in some way we all are retrobikers, so I think the probability of someone knowing this is greater on this forum.

All of a sudden, after I loosened and put back to normal the pad wear adjuster of my hs33 brakes, one of the pads was always against the rim.
After half a day trying to adjust the brakes and after a good clean on the outside, one of the master cylinders doesn't fully retract. If I press it by hand, the other side moves a bit towards the rim and I can feel some movement on the lever also.

These were never serviced since I put them new 6 years ago (I don't know for how long the store had them on the shelve).

Is this normal? Would servicing them solve this?

Thank you in advance.

[w2zero]

<<All of a sudden, after I loosened and put back to normal the pad wear adjuster of my hs33 brakes, one of the pads was always against the rim.
After half a day trying to adjust the brakes and after a good clean on the outside, one of the master cylinders doesn't fully retract. If I press it by hand, the other side moves a bit towards the rim and I can feel some movement on the lever also.>>

The master cylinder is in the brake lever.  The rim brake cylinders are slaves. 

You have many adjustments that can be made with those brakes so there are many ways to have them get out of adjustment too.  The levers have two adjustments made with a two millimeter allen key.  One for putting the pads closer to the rim and another adjust the distance from the lever to the handlebar grip.

The slave cylinders can be adjusted for angle, and distance from the rim with the 4mm hex key.   The upper adjustment swivels the slave cylinder  and clamp in/out via a splined "L" shaped arm that rests against the fork, swing arm or seat stay & transfers the braking force to the fork/seat stay/swing arm.  The lower adjustment at the clamp allows the slave cylinder to be moved towards the rim or away as well as angling the cylinder/brake pad around since it has the capability of swivelling, plus it can move the cylinder/pad towards or away from the axle centerline.

Let me know if that makes any sense to you.

[Tel]

Hi Whisperdacer,
To me it sounds as if you may have goten some sort of muck in the piston and cylinder its become stiffer on one side, I have had this problem myself as I didn't clean the piston before resetting it when I fitted new pads, I found if I took of the pads and carefully squeezed the lever so as to expose some of the piston and gave it a scrub with something non abrasive then squeeze the lever and help the piston in and out a few times it became free again and in balance with the other slave.
Hope this is of some use to you mate, Tel.

[whisperdancer]

Thank you for your replies.

w2zero: you are right: the master cylinder is in the lever (as in motorcycles). I got confused when reading about maguras and never thought of it while typing.
I think you are refering to the new maguras. I have the old raceline fluorescent green. Adjusting them is not easy on the supports, and the lever is the old style with the big TPA red adjuster.

Tel: I already cleaned them with a toothbrush and soap in warm water. I pressed the lever all the way, pressed one of the slave cylinders to get the other one fully out and cleaned it. Finally I used a rag to remove anything left. Did this in the two cylinders.
You can see in the photos both cylinders, and one of them (left one) doesn't go all the way in. in fact, they will never both fully retract: pressing into one makes the other one come out.

It almost fells the system isn't completely filled with oil.

EDIT: these photos made me see one of the supports wasn't parallel to the fork. It's already corrected.

[Colin]

Have you tried pushing both slave cylinders in at the same time?
If there is any air in the system, maybe this will move it back up the line?
Never had this problem myself in 6+ years of using HS11's on my XP-X..............

[whisperdancer]

Yes. I just can't. They equalize themselves and won't go any further.

[Spokes]

"pressing into one makes the other one come out." This is normal and should happen as its s sealed circuit. Have you checked the back of the pad for an obstruction? If they are new, check that they are both the same shape and its not a manufacturing fault. If you have cleaned them as Colin says , a common fault on cars and motor bikes is that when the pads are worn so the piston has been pushed out of the slave for a long time grime/sediment builds up behind the piston. Try "gently" pushing the piston in with mole grips as you'll get more leverage than using your fingers.

Chris

[whisperdancer]

Brakes are almost new, although I have them for about 6 years.

Moments ago I cleaned the outside of the pistons with WD40. Bad idea, as when I assembled them again they were much stickier than before. I then sprayed them with some thin silicone oil and washed them again with detergent, warm water and a toothbrush. They went back like they were before using WD40.
I don't think I can clean them better than they are now... but I wonder if some silicone oil will help the piston travel, as they seem to be somewhat sticky, or the spring (if it exists) isn't helping.

[w2zero]

I have at best recollection, six sets of Maguras.  Mostly from 1995/6 in red, neon yellow and dark gray HS-22.

I just unwrapped my instruction manual (still bagged from purchase 18 yrs ago) for the HS-22's and one of the first directions is to retract the wheel cylinders completely with the micro adjuster under the lever next to the handlebar.   I know that might not fit your present situation.

Have you considered flushing and replacing the hydraulic fluid or bleeding possible air out of the brakes? 

Internal wear on the pistons equates to crud collecting where they move.

several possibilities present themselves. 

Vessel is too small...  or conversely, too much stuff in the sealed system.  That would suggest letting stuff (air or excess fluid) out.   Or make system   bigger by adjusting screw to allow more retraction of master cylinder at lever.   Spongy lever feel at full braking would suggest air in system.  Anything but smooth movement at any cylinder would suggest contaminants in system.

as was suggested by another poster;  Very worn pads run for  a long period of time would allow the piston to mis-align slightly at maximum extension and cause a wear problem of the cylinder and piston that could make the retraction of the pad less than smooth and equal side to side.

My first step is to go with the least invasive and cheapest procedure and turn the micro adjuster anti-clockwise and see if the offending pad will retract.  Count the turns so you can go back to zero should that be proven inconclusive.

[whisperdancer]

Thank you for the answer.
Pads are new (although they are the original ones). These brakes must have around 500Km on them (mostly on road), since I don't ride much.
The setup of the brakes was made with a gap of 1.5mm to the rim with the adjuster in the minimum position.
Believe me the brakes are like new.

What seems to me is there is some air in the system (but they work well with no sponginess) or there's some fluid missing in the inside (the pistons weren't fully retracted when they were bled in the factory)... or it's the age...

[w2zero]

Not sure if it applies but here is a quote from the Magura manual:

"Under normal conditions it must be noted that brake pads may not act in complet unison, although they will always apply the same pressure to the rim.  This may occur because the connection between the two slave cylinders means that one brake pad is closer to any force applied by the brake lever than the other." 


That second sentence is a little sketchy, one of my bikes has Y connections at the ends so there is equal length tubing to both slaves and the pads still don't move at the same time.  Checked both bikes that are on the road and only one set has pads that move in unison..... three sets don't.