Bloody disk brakes

I love disk brakes, I really do. I couldn’t go back to rim brakes on my MTB. But if there’s one thing I hate about servicing a modern mountain bike it would be bleeding disk brakes.

About DOT and oil in disk brakes

Last year I switched from a hydraulic disk brake 1 with DOT to one with mineral oil. DOT sucks water and with water comes air. Air is highly compressible under pressure. So if there’s air in you brake hose the brake has no bite point anymore and will stop working at all eventually. Mineral oil doesn’t suck water. And it’s less poisonous as DOT. So I personally prefer oil in my brakes. But that limits the number of brake manufacturers I can chose from. For example there are Shimano, Magura and Trickstuff which use oil. But SRAM (formerly known as Avid), Hope and Formula use DOT.

Shimano XTR

The disk brake I bought last year was the Shimano XTR Race BR-M9000. It is Shimanos top of the line Cross Country brake. The XTR is well known and has a hight reputation in the scene. When it arrived I was very impressed by the brake. It has a well defined bite point and the braking power is immense! After I shortened the hoses the necessary bleeding went well.

I already wrote about he pressure point problems with the Shimano XTR brake. Back in January I thought about buying a Magura MT8 and I did.

Magura MT8

The moving pressure point of the XTR was the main reason I bought a Magura MT8 early this year. This is again the top of the line Cross Country brake from Magura. I always liked the idea to own a Magura brake because Magura build’s and develop’s its brakes in Bad Urach. That’s very near the town I grew up. I read before that the bite point of Magura brakes is not as defined as Shimanos. In the bike boards they always said that Magura brake are “better controllable”. When the MT8 arrived I was a bit disappointed because I could pull the lever to the bar very easily. The braking power was ok but I was not able to move my back wheel up when I used the front brake.

Bleeding the MT8

So I bought the “professional bleeding kit” from Magura. The bleeding was a bloody disaster. In my first try I sucked additional air into the system because the “professional bleeding kit” is so bad manufactured that there gets air inside if you push the syringe too strong. In my second try I was a bit gentler and it looked very well. No bubbles at all. Perfect I thought. So I closed the system again. But when I pulled the lever it felt even worse. The level was next to the bar immediately. I was furious.

Bleeding it again

After that I used a little trick. I removed the wheel and pulled the lever so the brake pistons came out a bit. The I opened the bleeding screw on the brake lever and filled in more oil. After that I pushed the pistons back in and reassembled the wheel. After that the disk dragged a bit so I opened the bleeding screw a little bit to let one or two drops of oil out. Now the disk didn’t drag and the bite point was where I would expect it.

Feels like rubber

But it still feels like rubber when I pull the lever. There is now power but I still can pull the lever until the bar. I’m still not able to lift the back wheel when using the front brake. There just isn’t enough braking power. I wonder how I can make the Magura MT8 more powerful. At the moment I’m almost missing my XTR. With this one I could at least do everything I wanted when I kept its flaws in mind.

What now?

I have two top of the line disk brakes which both don’t fulfil my needs. I could try the Trickstuff Piccola but that brake is rather expensive. A set of it costs 750€. For that money I can almost get a complete SRAM Eagle group set. Because it it so expensive there are not many reports by real users. So I’m not guaranteed to get a working brake either.

Another option is the Brakeforce One H2O. This brake is especially nice because it does neither work with DOT nor with mineral oil. It works with water. That means you don’t have such an ugly mess bleeding your brake like I had today with oil. It’s just water. You can bleed your brakes in your living room. But that is not the whole truth. I’m living in Germany and in one half of the year it may get really cold. Because of that it is required to put 20% glycol into the brake system – at least in winter. And with a price point 594€ it’s not really cheap either.

For now I’m back on the Shimano XTR. I was almost relieved when I pulled the brake lever of the XTR the first time again. The pressure point felt SO good compared to the MT8. Even the pressure point seemed to move less.

The MT8 is at Magura at the moment. I sent it to them unannounced. I wrote a description of the problem.

But maybe DOT?

There’s another option I don’t like. There seem to be several DOT disk brakes on the market which work rather well. The SRAM Level Ultimate is very popular. With around 450€ for the set it is not exorbitant expensive. And I think I could use my old Avid disks. With this brake I will be able to use only one clamp for the brake and the trigger for my (future) Eagle rear derailleur.

Also I always hear that Hope is one of the best bike accessories manufacturer on the market. It seems that Hope provides great quality and an awesome customer service. They make the Race Evo X2. It is specifically designed for Cross Country racing. A set is just under 400€. That is almost cheap.

I’m not ready yet to get into the DOT mess again. In the meantime I will use either the XTR or the MT8 until Eurobike when new brakes will be announced. Maybe the next version of the XTR doesn’t have those bite point problems.

  1. Of course I’m only talking about hydraulic disk brakes here. I don’t know why mechanical disk brakes exist.

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