Soooooo…. I’m getting back into this after a long time out. Can anyone explain how a disc is better than the Maguras I was using in 2007. Those were so powerful as they were and lighter. The disc seems vulnerable compared to Maguras being up and out of the way. Is there some advantage to a disc beyond what the market wants us to buy?
Are you talking about the Magura HS33 ?
The two most important advantages of disc brakes compared to rim brakes are:
- Disc brakes don’t lose much power when wet. Rim brakes, on the other hand, quickly become weak under the rain. So, if you want to keep a consistent braking power, disc brakes are better there.
- If your rim isn’t perfectly true, then rim brakes feel strange. That isn’t an issue on disc brakes.
However, discs make wheels asymmetric, so they are harder to true and a bit less sturdy.
- You can use wheels of different diameter in the same frame (as long as the disc diameters are identical). And you can use wheels of the same diameter with (very) different rim widths.
- Some say that discs are less prone to touching the brake pads due to the frame being distorted when riding hard. Though I would argue that discs can be difficult to run straight in the first place.
- (Better availability of parts and greater selection of manufacturers, if that is important to you. )
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I love my Rim Brake. For me, rim brake significantly better. Dics brakes aren’t for me on Munis. They’re very difficulty to control, or the brakes aren’t at all and that’s with the Magura MT7 Pro with a 293mm Rotor. You have to decide for Yourself what is the best.
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A well setup set of Maguras would probably outperform any disc in the right conditions. On the other hand discs, especially mechanical ones, are very easy to setup and maintain.
Business wise, Maguras need extra mounts on the frame and a machined rim surface so there’s probably some costs saved from new unicycles only supporting disc rather than both.
Also, first post since 2017. Anyone know why external disc seems to have stopped being a thing?
Hope brakes are very progressive and powerful. I’m pretty sure top quality disc brakes are more powerful than rim brakes
Not necessarily true with KH Spirit cranks and symmetric hubs. I absolutely love this setup. It also allows for use of different diameter wheels in the same frame.
- You can remove the wheel without having to deflate the tire
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I agree and to clarify, this (disc setup) includes a wide selection of carbon rims if that’s important to you.
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Well, that’s right. But as noted before by @davejh:
Spirit cranks aren’t produced anymore, so I don’t count your point as valid 
In reply to @davejh, I guess there are 2 factors:
- KH was the only manufacturer to offer this standard, so quite hard to maintain and keep alive. The fact that he wanted to use the Qaxle interface to make his unis even lighter has probably been a decisive factor.
- Schlumpf hubs now provide support for inboard disc, so they don’t need such external disc brake standard anymore.
What is a good brake for you? The Shimano Brakes I had never worked because there quite to cheap, Shimano SLX. That’s why I switched completly to Magura Brakes. For me the Magura HS33 and the Magura MT7 Pro are good but the MT7 Pro is for me to bad for ride Muni with it. The best brake for Muni is the rim brake HS33.
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I ride a SLX 7120 on my G36. With a 220 mm rotor, it works perfectly fine. Did you have a large rotor? Small rotor are shitty for muni.
Indeed – I don’t think you’ll see anyone on the World Cup Downhill Mountain Bike circuit running with a set of V-brakes or a U-brake or roller-cams….
- A disc doesn’t suffer from frame-flex as some rim brakes create (ie not an issue with callipers), so you don’t need things like brake-boosters for high brake loads to add stiffness – this is probably less of an issue for unicycles given the frame construction and brake force though.
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180 mm Rotor.
In my understanding, the outboard disc and Sprit cranks were developed as a solution to support a disc brake solution for the Schlumpf hub, but I may be wrong.
Having an inboard disc gives it (and your leg) a bit more protection from damage. Also I guess from a manufacturing perspective with an inboard disc you only need to have one crank blank as you don’t need to have one with lugs which you can machine to attach a disc. (or maybe you just have one with lugs and machine them off)
Also the braking torque does not need to be transmitted through the crank/axle interface – this is probably not a major issue for ‘standard’ hubs but it is an issue for the Schlumpf as that torque needs to go through the gearbox and is not applied directly to the wheel/hub as with an in-board disc.
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- Brake heat. Hot rims are a threat for the tube. Hot discs not.
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It’s valid now, two years from now, or a hundred years from now. Spirit cranks allow for a symmetric wheel build period.
By the way, Spirit cranks are still in stock at UDC US (limited options) and better options are available at UDC UK.
That sounds about right but older Schlumps really aren’t great for discs. They have enough force being held back by friction between the hub and frame without adding a disc to the picture. If they slip, you will get hurt. Coupled with more of a movement to 125mm frame spacing, it makes sense to move to an inboard disc.
Fortunately UDC UK still has Spirits in stock so i’ve snapped up a spare pair so I don’t need to completely redesign the 32 if i damage my current ones. Personally, I don’t get on with 125mm frames (leg strikes) with straight cranks and dished 100mm big wheels are a nightmare to build.
Maguras as jagur is describing them are hydraulic rim brakes. Regardless of how much less performance the calliper might offer than a top of the line disc calliper, they effectively have a 500mm+ rotor.
I don’t think heat would be a factor given the size and the much lighter use we put on brakes than a road or downhill mountain biker freewheeling down a mountain.
None of my KH unis is light. I doubt weight being the (only) decisive factor here; I do not have any inside though.