Disk Brake Troubles

So i bought a Nimbus 24" Oracle about a month ago, basically because i wanted to build a 24" freewheel and needed a Uni to put it on as well as a disc brake, and it therefore seemed like a good excuse to get a new unicycle :wink:

Just got my freewheel delivered 5 days ago, transferred the disk brake over to it, and have been happily enjoying the thrill and extreme frustration of effectively learning to ride a unicycle all over again.

Until today that is, when i discovered the brake had failed, which as it happens is quite a vital piece of equipment on a freewheel unicycle. I discovered some drops of fluid on the caliper which led me to believe there was some sort of leak. So i tightened everything i could find, and may have fixed the leak but am not too sure. This is my first experience with hydraulic brakes, so i was hoping someone with a bit of knowledge could give me some insight.

If i pump the brake lever a few times, it seems to come back up to almost full power, but then shortly after it seems to lose pressure again. Is this a sign that there is air in the lines and it needs bleeding? If so, where can i get a bleeding kit to suit the Bengal Disk Brake? I’ve been riding on concrete with my freewheel and was falling over a lot to begin with, so i’m worried i may have done some damage to the caliper (cracked it or something), is this likely? Do all disc brakes have the same mounting holes? If i were to go buy a new brake from my LBS would it fit? I am tempted to get a mechanical disc brake as i’m a bit more comfortable fiddling with them.

I just want to get back to training on my freewheel ASAP, so i just want to figure out the quickest solution.

That sounds like you have a leak, indeed, and some air (it doesn’t need much) got inside the brake line. When you pump several times, it compresses the bubble(s) so you regain almost all power. After a short time, bubble(s) expand again and you’re back to sloppy brakes.
I think most bike shops sell universal bleeding kits, with all the adaptors required.

I don’t know much about bike brakes, but I would assume that they’re all the same since mounting points on the bikes are always at the same place. Then the little metal “bridge” places the caliper further or closer to the wheel centre, depending on the size of the disc.

Mechanic brakes were a bit of a joke when they first appeared. I might be wrong nowadays. But a good set of hydraulic brakes will be more precise and self-adjusting as the pads wear out.

And good luck on the freewheel, that seems just impossible to ride…

Agree with pierrox. Mine has a slow leak that needs bleeding every few months. One thing I’ve found is that storing the uni upright keeps the air in the brake fluid reservoir and so the brake works well until fluid at critically low level. I figured this out from having the same issue you describe after hanging my uni by the wheel upside down.

There are good brake air bleeding videos on you tube- you can have your LBS do it but it is easy and satisfying to do yourself. If you have a major leak though might need to get it repaired by a pro.

You know the best solution would be a mechanical brake :p.

I agree with Killian that a mechanical brake will fix the troubles. On a uni the The brake line is so short that there is no real gain in going hydraulic. Even with average cables, and housing you would be hard pressed to feel much resistance from the line.

On to your problem. If you see/saw fluid you have a leak. The fix would involve a bleed, but also a little trouble shooting to find the leak and get that taken care of. IF the leak isn’t fixed the bleed will be a very temporary fix. Teflon thread sealing tape like plumbers use is a very handy thing to have on hand when you are fixing problems like this. On a new brake I think it is more likely that something was not tight enough rather than a seal being blown, or jeopardized. So, you may have gotten it by tightening everything down.

It can be a little risky to tighten things on brakes without knowing a bit about what’s going on inside so be careful. For example, on shimano brakes the bleed nipple fits against a pin inside the caliper that will brake if the nipple is over tightened. A new caliper later, and it’s not likely that you’ll make that mistake again.

On that thought has anyone tried the spyke or found another replacement for the pre-recall spyre that is narrow enough to fit on a uni.

I run the Spyke on the 24" freewheel I’m bringing to Unicon17 and I like it a lot. I measured it at 43mm wide vs. 40mm for the pre-recall Spyre. I have a 180mm rotor and a custom disc tab welded on a 24" Nimbus frame. It may be too tight a fit for a 160mm rotor and a 24" wheel.

Post-recall spyre fits just fine. If you run a 180mm rotor, you won’t have to shim. If you run the stock 160mm rotor, you will need to add a few rotor shims, but after that they fit just fine. I use these. They come in a pack of 8, and I use 4 per rotor. Clearance is no tighter than it was with the pre-recall spyre, and I haven’t run into any issues yet (knock wood).

I’m slowly moving all of my uni’s over to Spyres. I love 'em.

To the OP, my reply was tongue-in-cheek. I’d try and fix what ya got first, but it continues leaking as Pstrick’s does, I’d seriously consider a Spyre. You shouldn’t have to hang your uni upright even with hydraulic brakes.

Thanks guys, that’s what I love about living on the otherside of the world to most other people, I can post a question just before bed and then have all the answers waiting for me when I wake up :wink:

I’ll try and get a bleed kit from my LBS, pretty small bike shops where I am though so I don’t know they’ll have what I need. Otherwise I’ll grab a mechanical brake if they’re not too pricey, I’d rather have some thing on my uni that I’m comfortable working with anyway.

How long have you been riding your freewheel for waalrus? I’m quite surprised by the lack of people riding them. Are you at a stage where you can ride it as comfortably as a fixed wheel? I have big plans for my freewheel, but it seems like largely uncharted territory at the moment and I have no idea if what I envision is even possible. Exciting times though, it’s really frustrating not being able to ride…

I’ve been riding freewheel unicycles just over a year. I created this thread and this video playlist. I would say that I can ride comfortably although I have more UPDs than I would on fixed wheel unicycles. Hardest for me is riding fast over rough terrain and I’m hoping the fat freewheel I’m building will be better at this. I’m not sure why the trend hasn’t caught on yet but I’m positive it will eventually.

Oh right, I didn’t realise you were "THE " freewheel guy.

Haha I’ve already stalked you on all your threads. While I’ve got you here, have you got a good freemount for freewheels? The only thing I’ve thought of so far is a jump mount with a bit of a rolling start. I’ve still got a bit of work to do before I get started on that though.

Have you seen this video tutorial I put together? I shot that before I started using a brake and although I can now do a rolling mount I still use basically the same technique except that I usually hold the wheel steady with the brake in the middle of the process.

Do you have a coasting background? I think that being able to coast may make the initial learning curve less steep but I don’t know how much it helps in the long run. In my opinion the ultimate goal, which I didn’t realize until relatively recently, is to be able to have a steady base with the pedals level and pushing the wheel forward and backward for balance whereas in fixed wheel coasting you use the upper body more for balance (at least I do). However, that style of riding is more advanced and your goal should be to get down the road or trail any way you can!

I thought of locking the cranks with a second brake operated with a shifter. Mentioned the idea to Nurse Ben when he was experimenting with freewheeling and it seemed to him it wouldn’t work.

haha nope i haven’t actually seen that, i guess i need to work on my stalking skills. And no i’ve never done any coasting, only been unicycling for just under a year!

But i’ve had 7 days practice now, and it feels like my body is slowly getting the hang of it. I can now ride it relatively normally by applying some slight pressure to the brake and can do the odd little bit of coasting here and there for a metre or 2. I’ve forced myself not to ride a normal unicycle while i learn this, so my body can get properly used to it.

Actually thats a question i wanted to ask. Do you find it easy switching between a fixed wheel and a freewheel? Or do you pretty much exclusively ride the freewheel?

Oh and just to finish off the reason i created this thread, i’m currently waiting on a Bengal bleed kit which i had to order from Taiwan. I did however find a temporary solution that seems to work. It’s a technique called burping. Rather than try to explain it here’s a video

It worked pretty well, i can now use my brake again. Although it’s not quite back to full strength, so i’m still going to do the proper bleed when the kit arrives.