Hydraulic brakes and having uni up side down

Some months ago I went to the LBS because the disc brake on the Nimbus 29" didn’t have any pressure. Whenever it lies down (like in the car) or occasionally stands upside down, so it is easier to place it in the house, the brake fluid leaks out. The LBS fixed it last time, but now it is the same problem again. I can see that the actual brake fluid comes out, because when I grab the uni I always end up having some on my hands. Aren’t those systems supposed to be air tight, or well leak proof, however I hold the unicycle?

Brake system : Tektro Auriga Sub A6061

Also I read about the bubble in the cable going to the opposite side of gravity, which could give more play in the brake handle, but in my mind I don’t see why the fluid would leak out over time. Then it is not a sealed system.

I have owned several hydraulic brakes on my regular bikes from various vendors Avid, Shimano, Tektro and Magura. I have changed pads, shortened hoses and bleed a lot of brakes. They are not supposed to leak no matter how you treat them as far as I know. I would expect it be a defect. Figure out exactly where it is leaking. Is it the connection between the hose and the lever (there is usually a rubber cap you can move down the hose to expose the actual connection) or is it the lever itself? If it’s the connection - maybe it can just be tightened slightly or you can likely cut 2 cm of the hose and fit a new olive+pin and remount + bleed the brake. If it’s the lever it likely needs to be replaced. Sometimes it’s cheaper to get a complete new brake set than only the lever itself.

I have read/heard a few times that hydraulic brakes should not be stored up-side down otherwise they could leak. I don’t know whether that’s a defect as @Hammer said but that’s something common - I have the same issue with at least one of my brakes.

Interesting … that seems strange to me. Could be that some brakes have this behavior.
I would switch it to another one then. Would hate to have oil leaking out. Because “oil out = air in” and then the power of the brake would weaken and you would have to bleed the brake frequently.

It is not that I use the brake regularly, but at some downhills it is nice to have it, so I don’t have to fight back with my knees. Also given what Duff has been trying to brake stop the uni for gliding/coasting, I’d like to give that a try. The 29er is the smallest uni I have that has a brake… oh no the Hatchet also has a brake and it is a 26, but that isn’t as comfy to ride as a narrow wheel.
I think it is strange that ur not supposed to keep a bike with a hydraulic brake upside down when it is supposed to be a closed system.
Instead of ordering a new brake system from unicycle.com, I reckon the LBS would sell similar brakes. Or are they especially adapted to unicycles?

Unicycle brakes and bike brakes are exactly the same. However, you can have a few issues:

  • the brake caliper can be too large for the unicycle so it’ll rub the spokes ;
  • the brake caliper is too powerful and your frame will break => that’s really uncommon but it can be an issue on some setup - like a 203mm disc, a 4-piston brake and a RGB frame while doing a big drop :upside_down_face:
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I used a TRP Spyre mechanical disc brake on my 36er. It is highly rated, low cost, reliable and will never leak or need bleeding.

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Two things to your issue:

  • the leak is not normal. bikes are meant to be carried, laid on the side, suspended, etc, the brake fluid is meant to stay inside.
  • the presence of a bubble can indeed lead to problems as storing the uni upside down will allow it to travel “up” to the caliper or the hose, resulting in a “spongey” feeling when you brake. With a bit of experience, you can bleed the brakes with no air inside.

I store my two KH unis upside down and have never had a problem. (knock on wood)

Storing unicycles upside down is bad because you put over 1 meter of liquid column pressure on the piston and the liquid reservoir. The way pressure works the width of the hose doesn’t matter, only the height. The seals on the liquid reservoirs of some brakes, especially inexpensive ones, aren’t built to sustain this pressure (as opposed to the caliper assembly on the other end). That’s why you shouldn’t hang bicycles on their rear wheel.

Should not be much of a problem at all, especially not if you go to a decent shop were they sell high end mountainbikes (mantel for example).
If you register on mountainbike.nl you can surely find someone in the neighbourhood selling a 2nd handed set. Last set I bought 2nd handed was 60 euros for 2 (front and rear) Shimano XT brakes, which are already a lot better than the standard unicycle brakes you’ll find at unicycle.com :wink:

And yes, storing upsidedown should never be an issue. If it is, then you might not have a closed system (could be on purpose, but I wouldn’t recommend keeping it). If your pads / disc get contaminated with the oil you can pretty much throw them away immediately :wink:

I can’t tell if you’re being serious or just deadpan silly, but the pressure from the column of liquid is only a couple of psi. Pressure from a strong pull on the lever, times the lever’s mechanical advantage, divided by the small area of the cylinders, must be in the hundreds or thousands of psi.

Storing a bike or uni upside down should be 100% fine unless you’ve got air in your system, or something else wrong.

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I’m 100% serious but you missed that I was talking about the seals of the liquid reservoir. When you pull the lever, the pressure is built up between the caliper unit and the piston, not in the reservoir.

However, maybe this was only a problem with pre 2010 brakes. I haven’t experienced such leakage since then.

True enough. Still a tiny amount of pressure, that shouldn’t bother a brake in good repair. But if your seals were basically broken you could have a functioning brake that leaked.

I’ve never had a problem, with any brand, going back to the 90s with my trials bike.

I hang my unicycles upside down from hooks and I do the same with bikes. So far no issues with the brakes.

What is low cost in ur mind. On the Dutch mountainbike site they sell them for 74 euro. Are brakes generally much more expensive. I do like that they are mechanical.

I also hang my muni upside down for storage and never had any oil leakage. I got a used Shimano XT 785 on which I did a good job bleeding, so I never had any issues with oil bubbles as well. With my bikes I have bubbles inside and need to pull my lever several times to restore the breaking point if it was stored goofily. If your seals are damaged (don’t know how that would happen) maybe you will find spare parts at your lbs. At least for Shimano reservoir seals that would be true.

I paid about $65 USD (54 euro) for my trp spyre caliper and see the same on ebay (USA) now. My installation is a little different because I made a custom lever but the total cost was less then half of the hydraulic brake that UDC was selling at the time.

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Damn, that is expensive… The Shimano MT200 hydraulic brakes that come as standard on most unicycles nowadays are 30€ or so, and that does include the brake lever.

UDC doesn’t seem to get good deals from Shimano, so the kits they sell seem quite expensive to me (although they often include every single part you would need to bolt it on to your unicycle, disk, post mount adapter etc.)