oldbobcat

Right.

Bicycle hydraulic brakes are self-adjusting. That's why when you squeeze the lever without a rotor between the pads you have to pry the caliper open to get the wheel back on. If you doubt this, take a look at your caliper with worn pads and tell me if the gap between the pads and the rotor has increased.

A soft brake lever means there's air in the brake line. By all means, check your pads for wear, but when your lever bottoms out it's telling you it's time for a bleed.

Mtracer

You're confusing self adjust piston position with compensating for lever throw. No one is saying the pistons don't compensate for wear. Also, an increasing lever throw doesn't mean the braking is soft. Just that there is effectively more free stroke before the brakes engage. I'm only familiar with Shimano hydraulic brakes. With these there is a small "reservoir" that has a diaphragm that more or less allows the system to be at ambient air pressure when not engaged. As the pistons move out due to pad and rotor wear, the extra fluid needed comes from the reservoir. This, I believe (but do not know) is to help compensate for the gradual movement of the pistons due to wear. But, it's a sealed system. So, the system must gradually develop a slightly negative pressure relative to ambient, as the diaphragm expands into the reservoir. I believe it's this reason that the compensation is not perfect.

I believe that without the reservoir and diaphragm system, the change in throw would be extreme, but again the system is not prefect. So, there is an effect on lever throw as the pads wear.

Redbullet

I am sure the pads are not worn. Their thickness is 3.7 mm and a change is recommended below 3 mm. I don't think they are designed to be replaced after 2200 km on flat roads with sporadic mild braking. If so, then pro cyclists would need 2-3 pairs of pads for a long course in the mountains.
I have just investigated how disk brakes work and, indeed, the pistons compensate for pads wear. My brakes levers had a long course before they "bite" since they were new, but after that point the brake was strong. Maybe this is by design. I'm not happy with that, because when the "bite" started 5mm further away (for no apparent reason), the lever started to touch the handlebar.

I applied a workaround which made the brake fully functional as it was at the beginning: I forced the pistons to extend more by squeezing the lever after putting between the pads a spacer which is thinner than the rotor (1.5 mm versus 1.85mm). But I'm not comfortable with the solution, thus, I'll try a "bleeding". I'm curious to see the results, given the fact that the brake levers had a long course before the bite, even when the bike was new.

rosefarts

At 11 months with light use, I would suspect that the brakes were done incorrectly when new.

Not totally wrong or you’d have found out right away but wrong enough that the problem didn’t present itself immediately.

I’m thinking incomplete bleeding, shortening the hoses without a bleed, installing olives that weren’t totally clean, or using brake fluid that had been open for a while. Or you sprung a leak.

I might try to diagnose the problem myself but from my experience with SRAM brakes, I’d take it to the shop to fix.

grumpus

Sounds like the seals have always been sticking in their bores, by extending them with a narrow spacer you've managed to force them to reposition as intended, so it's a legitimate fix, as long as they're still sealing adequately. They may even self-adjust now, or you may need to encourage them again as the pads wear.

Redbullet

Finally, dirty bleeding did the job.
I had endless failed attempts to push the pistons back into the caliper. Finally, I had to remove and disassemble the caliper, I lubricated the pistons with DOT 5.1 (although forbidden by SRAM). Then I managed to push back the pistons by strongly squeezing the “half” parts of the caliper using pliers with long arms, then re-assembled the caliper. At the end of the bleeding procedure, I lost 5-10 drops of fluid while removing the syringe and screwing caliper cap - there is no way to avoid that (or... should I rotate the bike upside-down before removing the syringe, to avoid leaking? It looks hilarious to me).
Wow! After 11 months and 2200 km with a new system: 60 EUR spent for the kit and fluid, plus 2.5 hours of uncomfortable and undesired work, only for one brake (front). I just entered in the new world of disk brakes... missing my old rim brakes .

smd4

You must have done it wrong, based on the number of posts I see here claiming that hydraulic disc brake maintenance is as easy as, if not easier, than working on rim brakes.

Bob Ross

Thread Drift: is it possible to convert SRAM hydraulic brakes to use mineral oil?

soyabean

The only issue I can think of is that the oil might swell up any rubber seals.

Anything soft and supple will get even more soft and supple.

Brake fluid doesn't do this.

Bill Kapaun

New to disc brakes myself, but one video I watched, they simply unbolted the caliper and rotated it as necessary to let the air bubble(s) rise.
If you had a friend, they could help you "manipulate" the bike. Even a piece of rope slung over a rafter for an impromptu, bicycle lynching party.

Bill Kapaun

I'll join your drift.
Having absolutely no previous experience with disc brakes, can you-
Rest the bicycle upside down to remove a wheel etc. for whatever reason?

Reason I ask is I made a cassette change. With the rack & folding baskets installed, it was a real pain to R & R the wheel, keeping the disc from getting mangled upon reinstall while trying to hold a VERY HEAVY Ebike. With the baskets installed, it reduces visibility need to line up the brake disc properly.
I'm getting old, weak & feeble which doesn't help matters.

BTinNYC 

Bleeding or fluid replacement can be a messy PITA. Now I've done it a few times it's just messy. I remove the rear brake caliper from the stay so it can dangle at a low point.

13ollocks

When I crack a bottle of glycol-based brake fluid (DOT 3, 4, 5.1) I use what I need and dispose of the remainder - it will inevitably absorb atmospheric moisture, so there’s no point in trying to store it

Polaris OBark

I've read that you cannot. Various piston seals, etc, are incompatible. (Off the top of my head, I would think it would be easier to do that then to go in the other direction of conversion.)

In the overall scheme of things, it might be simplest to replace the brakes. Some new version of SRAM brakes are now mineral oil-based.

Weogo

Gosh I like my cable-actuated discs!