Hydraulic rim brake cilinders don't extend enough

[silva]

Brand Magura model HS33 .
I recently placed new brake pads and I had to turn the small regulator wheel at the brake lever to its max out position in order to have some braking force. So when brake pads now wear, I have no range left to compensate.
What can explain this?

 

[fossyant]

Try a bleed, but have the adjuster wheel turned back

 

[silva]

In the past the rear brake line broke at a most front mount under the handlebars, due to a short turn.
The line went along the upper tube, causing the need for the short turn.
To solve it, and to mechanically protect the line, I mounted a flexible tube with trajectory along the down tube then back up to. The dealer put a new hydraulic line (pvc), new oil in it, and replaced the pad.
Since, and maybe from bike purchase time, the rear brake never worked well and now that I think about it, also quite short, likely for the same reason as I now noticed since I replaced the pad myself.
A possible reason thus is a hydraulic line too long, pressure loss or so.
On the other hand, I saw new bikes in the shop, same frame as me, with the hydraulic line running along the lower tube per default, indicating it shouldn't be a problem.
I'm gonna try to measure the distance that the cilinder head moves and compare it with the front.

In the manual of the Magura brakes "rim width min-max 18-28 mm. Mine is 22 and maybe now 23.
The min max difference is 10 mm so 5 mm for 1 cilinder. I don't know how to interprete this, what hydraulic system parameters bring that min max?

 

[tiredtyre]

Brand Magura model HS33 .
I recently placed new brake pads and I had to turn the small regulator wheel at the brake lever to its max out position in order to have some braking force. So when brake pads now wear, I have no range left to compensate.
What can explain this?

The brake cylinder is held in place by a clamp fixed by allen bolts, loosen this clamp and the cylinder can be moved inwards to adjust for rim width. Back off the regulator wheel first. The brake cylinder has adjustment rings to help with this. It can be a bit fiddly to get right so take your time. Google the HS33 manual page 17. Magura have instruction videos online in German Language which may help . The manual in English can be hard to follow.

 

[silva]

I tried in the past, and past half hour I tried again.
I can't find how to move the cilinder perpendicular (closer to/farther from) to the rim.
All I can do is rotate it from a center, as to aim the brake pad parallel to the rim wall.
If I losen the clamp I can move it somewhat, but when tightening it moves back to that center.
Between the clamp's hole and the cilinder there is some plastic formed abit like the rubber one of a light mounted on a tube, probably to prevent the mating surfaces to slip. The cilinder surface has some ridges alike those stamped in the plastic.
The videos I found also don't show it precisely.
Ex.
View: https://www.youtube.com/watch?v=lrKoflwpAxw

At 01:46 you see the guy pushes the cilinder towards the rim, it's like it just shifts.
I can't do that on mine. The innard of the clamp on my bike isn't cilindric, it's like a toroidal, which pushes the cilinder to its middle when tightening the bolt of the clamp.
As it looks like, the back of the cilinder with it's 90° corner shape towards the hydraulic line connectors, already sits as close as possible to the corner, seen from the back of the cilinder, there is nothing left visible of the ridges to give grip, also indicating it's already as close as possible to the rim. For what it matters, since it doesn't look like adjustable anyway due to its toroidal shape.

Addition: if you think about it, there has to be something that serves as support for the force that the cilinder puts on the rim. If it was a cilindrical inside, even with some antislip provisions alike those ridges, it could be not enough since the mating surfaces of the small reeds/ridges are quite small in the force direction. A toroidal shape gives a much bigger surface to support. But with the latter, how could the cilinders be adjustable in distance to the rim? A requirement to be adjustable conflicts with a strong support. Normally, screwthread is used in such cases (alike a chain breaker tool), but the inside of the clamp / the outside of the cilinder, doesn't have any but those grip alike reeds.

 

[silva]

According to the dealer (that apparently is open again) the likely reason is given as dirt / dust inside de brake lever, that causes the cilinder to not return completely. Until some past they cleaned the cilinder in such case, but that caused leakages afterwards so that they now inject oil to increase the pressure.