Front brake failing mid-ride

Rockbottom

Member
I was riding Trumbull this past weekend when my front brake failed mid ride. During one of the steeper descents my front brake went from tight and responsive to spongy with almost no power. I was squeezing the brake lever down to the grip and getting only about 20% braking power. Took the pads out, pushed the pistons in to re-set, replaced everything, and after 2 lever squeezes, the brake was back to 100%. 2nd steep descent and the issue repeated itself yet again.

Back home I decided to get the brake checked out at my LBS. Squeezing the brake while walking it to my car and the brake went from spongy back to fully responsive just by me pumping the lever a few times (no piston re-set this time) I'm happy that the issue seemed to have resolved itself, but wondering what may have caused this? Took the bike for a quick ride in my neighborhood and all seems good.

Brake setup: Magura MT7
 

JDurk

Well-Known Member
Had a similar issue with Magura MT Race, 2 different times and was the front as well. Pumping helped during the ride, but had them bled at the LBS. Eventually replaced with Hopes.
 

Rockbottom

Member
When was the last time you bled your brakes?
I bled them a few days prior to the ride seeing the front brake was a bit less responsive than the rear. Seemed that I had a successful bleed, but I'm an amateur with most bike maintenance so I can't be certain.

Seeing the brake is okay now, I'm reluctant to send it to my LBS. Perhaps I'll try a local ride this week and see how the brake fares. Would hate for this to happen again on more tech trails like Sourlands.

I'm loosing faith in Magura recently, but you know, the caliper color kinda matches my bike, soo.... :)
 

BPaze

Well-Known Member
I have a set of Magura MT7 sitting in my spares pile. They are awesome brakes with a ton of power, but they are a pain to get bled properly, which is why they are in my spares pile. I moved to Shimano BR M8020's which are super simple to bleed. I really want to get the Magura's working because they really are great when they work, but I have been told this is a pretty normal issue with the Magura's.
 

Rockbottom

Member
I have a set of Magura MT7 sitting in my spares pile. They are awesome brakes with a ton of power, but they are a pain to get bled properly, which is why they are in my spares pile. I moved to Shimano BR M8020's which are super simple to bleed. I really want to get the Magura's working because they really are great when they work, but I have been told this is a pretty normal issue with the Magura's.
I truly hate the bleeding process for Magura brakes. It never seems to go smoothly. Agreed that Shimano brakes are much easier to bleed. I have a pair of M447 on my other bike. Makes it so easy to bleed given there is a shut off valve for the oil reservoir when taking out the syringe.

I reached out to Magura for assistance but they're quite delayed in their response time.
 

BPaze

Well-Known Member
I truly hate the bleeding process for Magura brakes. It never seems to go smoothly. Agreed that Shimano brakes are much easier to bleed. I have a pair of M447 on my other bike. Makes it so easy to bleed given there is a shut off valve for the oil reservoir when taking out the syringe.

I reached out to Magura for assistance but they're quite delayed in their response time.
There are a bunch of videos and it makes it seem so smooth and easy, but anytime I would bleed them they would be good for 1-2 rides then go to shit again and the process was so convoluted that it would take forever and make a mess. I even had shops try to bleed them with the same results, the best part is that when I brought them in they basically said we never have decent success with these things are you sure you want us to give it a go and pretty much warned me about the headaches. That being said they are phenomenal when I got them working so I want to try again.
 

Rockbottom

Member
There are a bunch of videos and it makes it seem so smooth and easy, but anytime I would bleed them they would be good for 1-2 rides then go to shit again and the process was so convoluted that it would take forever and make a mess. I even had shops try to bleed them with the same results, the best part is that when I brought them in they basically said we never have decent success with these things are you sure you want us to give it a go and pretty much warned me about the headaches. That being said they are phenomenal when I got them working so I want to try again.
I’ve wondered why this was myself. It’s a closed system so if there is no leak, how does air continue to get into the brake system?

But yes I agree, when they work right, man are these brakes responsive.
 

Karate Monkey

Well-Known Member
I’ve wondered why this was myself. It’s a closed system so if there is no leak, how does air continue to get into the brake system?

But yes I agree, when they work right, man are these brakes responsive.
2 ways: Atmospheric moisture (brought in past the caliper seals, in particular, when actuating the brake; a leak in the system (check hose joints where they enter the caliper/lever). Bicycle brakes are actually widely classified as 'open' hydraulic systems, since they have a reservoir with a membrane in it that allows expansion. Hope/others made a closed system, which lacks temperature compensation--you would have to physically dial the reservoir cap back to open/close the resting position of the brake pads. Except in a very few choice circumstances (trials riding, for instance), it is an inferior design for 99% of riders out there.

*edit* There is a big #1 third possibility, and that is that the air is self inflicted. If you are not careful to make sure any connected hoses are purged of air trapped in the bleed nipple/orifice, you will introduce the air. Gravity bleeds largely avoid the problem, though only Shimano makes a bleeding system that is built around it.
 

Rockbottom

Member
2 ways: Atmospheric moisture (brought in past the caliper seals, in particular, when actuating the brake; a leak in the system (check hose joints where they enter the caliper/lever). Bicycle brakes are actually widely classified as 'open' hydraulic systems, since they have a reservoir with a membrane in it that allows expansion. Hope/others made a closed system, which lacks temperature compensation--you would have to physically dial the reservoir cap back to open/close the resting position of the brake pads. Except in a very few choice circumstances (trials riding, for instance), it is an inferior design for 99% of riders out there.

*edit* There is a big #1 third possibility, and that is that the air is self inflicted. If you are not careful to make sure any connected hoses are purged of air trapped in the bleed nipple/orifice, you will introduce the air. Gravity bleeds largely avoid the problem, though only Shimano makes a bleeding system that is built around it.
Really interesting info, I never knew this. Thank you. Given that this past Saturday was a very humid day, perhaps some moisture seeped through the caliper seals then causing the issue. Prior to the ride, I did tighten the bolt that connects the line to the brake caliper about a quarter turn thinking there was possibly a leak there. Not sure if this may have compromised anything.

On my last bleed, I removed the syringe from the bleed port while holding the caliper horizontally, rather than vertical to prevent spillage. Perhaps this introduced air into the system?
 

ebarker9

Active Member
Great, I'm just transitioning from Shimano brakes to MT5's because I was tired of the variable bite point issues. Guess I'll be extra thorough with the bleed.
 

Karate Monkey

Well-Known Member
Really interesting info, I never knew this. Thank you. Given that this past Saturday was a very humid day, perhaps some moisture seeped through the caliper seals then causing the issue. Prior to the ride, I did tighten the bolt that connects the line to the brake caliper about a quarter turn thinking there was possibly a leak there. Not sure if this may have compromised anything.

On my last bleed, I removed the syringe from the bleed port while holding the caliper horizontally, rather than vertical to prevent spillage. Perhaps this introduced air into the system?
The moisture thing is largely a long-term problem. I could only see it happening shortly if you were using the brake underwater.
 
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