erhan

Weird things happen to me. I just got back from a ride with almost no brakes.

Everything was fine in the beginning. The front brake was just a little spongy but I've had it like that for about a month. I was just too lazy to bleed it. Anyway, about 45 minutes into the ride the rear brake started to feel spongy, and in about 2 minutes it was completely gone. I stopped and checked for leaks, but none.

I had no idea what to do so I decided to turn around in case I lose the front as well, which almost did happen. When I got back home the front lever was touching the handlebar and it was barely holding.

So the weather was not too cold at all, it was probably around -4/-5 degrees Celsius (low 20's F?). I had used regular Magura Martas in colder conditions with no problems. I replaced them with marta sls in August, and this was the first time I used them in sub freezing temperatures.

Anyway, tomorrow i will bleed them and check everything if there is anything out of the ordinary.

Anyone ever had a similar experience?

erhan

the title sucks.. hydos?

rankin116

I'm not familiar with your brakes, but what fluid is in them? Do you store the bike indoors, and if so, are they functioning now?

erhan

Fluid is mineral oil, just like shimanos, and I keep the bike indoors. I just checked it and I think the front feels a little better. However the rear is the same. There is a tiny bit of movement in the pads but not even enough to touch the rotor. It's all warmed up to room temp now, may be not related with the cold?

rankin116

Checkthis out and see if that helps. I would look for a leak in the lines or in the calipers. The temperature you were riding in should not have that effect.

never

I've used the Marta SL brakes in really cold conditions and haven't had any problems. The worst issue I had was snow packing into the caliper on this ride which affected braking a bit (mainly on the rear).

erhan

So I bled the brakes. Apparently cold had nothing to do with it.

There was almost no fluid left in the rear brake reservoir, and too much air in the hose. What I still don't understand is where all that fluid has gone without any sign of leaking, and how come it felt perfectly fine for almost and hour and suddenly decided to give up.

The problem with the front was even more interesting. The lever adjustment screw got loose

rear


front

erhan

Similarly I had packing issues in snow.. no big deal though, makes it more fun This year I haven't seen a single snow flake yet

apclassic9

it sounds like your rear brake lost it's fluid all at once... were the connections secure? Once you have bled the lines & refilled it, check to make sure it doen't happen again... I recall a friend who had this problem a few years ago (he was eventually stopped by a tree) and it was caused by a loose connection of the line to the caliper. It LOOKED ok, but all the fluid just shot out after the brake was used a few times.

Bike Lover

Exactly. Once you get the fluid back in there and are able to get the pressure up, you will be able to check your connections for the leak. Although you can't find it right now, the fluid had to go somewhere. Just check the hose and your connections with pressure on the brakes. You may be able to put white paper towels or something like that under to try and help with finding where it's comming from. Just make sure you are able to find it's actual leak point as fluid is funny and isn't always obvious.

erhan

Thanks for the suggestions. I checked for leaks twice and nothing. Though I think I have an idea now... Last summer was very hot, and after long descents when the brakes got very hot, some fluid was coming from the breathing hole on the top cap. I didn't care at the time but if that happened after every long downhill, then it must be normal to run low on fluid.

pdq 5oh

It's not really normal to run low on fluid, generally speaking. As the pads wear, the piston moves out and fluid has to fill the void in the caliper.