They’re not pretty, but they make a Shimano 1 finger brake lever much more functional.
The handle extension is just a piece of delrin rod that I heated with a torch and bent into an s shape. Delrin is cheap and any plastics shop should have it. I’m sure it could be heated on a stove top too. It’s held on with four zip ties and wrapped with electrical tape.
The cord eliminates pre-travel. I found that even with the pre-travel adjustment all the way in there was still way too much pre-travel for a unicycle and that the brake handle was way too far from the handlebar. It’s just a simple loop of cord.
If using this method, make sure to put the plastic in some water so it is evenly heated, otherwise the bottom will probably burn.
Looks like a very functional brake setup, and I like the look of something that is definitely home made but also extremely solid and ready for the abuse it needs to withstand. If the zip ties ever give way you could also use hose clamps, but unless it’s cold out the zip ties are probably fine.
I get the zip ties from my work and they’re a good bit tougher than the typical ones you’d find in a hardware store. I suspect the delrin or the brake handle itself might break before them, but the brake would lock up long before that. I went with total overkill on my brakes. Really only a hard impact from a crash would cause a problem.
One other thing, I don’t think you could heat delrin hot enough in water to significantly soften it. When I bent it I actually had it on fire and then doused it in water. I handled it with two pairs of pliers. It sounds way more difficult and dangerous than it actually was. I just used a propane blowtorch and heated it until it was soft. Yes, it caught on fire, but the flames are about as large and aggressive as you would see on a cigarette lighter and you can blow them out with your breath. Have a bucket of water nearby that you can dunk it in. It will both put out the flames and harden it up in the correct shape.
Yes, unfortunately the “bite point adjust” on Shimano brakes is pretty much useless (for bikes too). No one wants any more dead travel than they already have in the minimum position. The only time adjusting that screw has any use is when you bleed the brakes (because it doesn’t like to be fully in).
Yeah, I considered replacing the screw with a longer one as that would be a far cleaner modification, but I wasn’t sure if it could potentially cause any damage and a loop of cord seems to be equally effective.
That doesn’t work unfortunately, you would have to modify the cam that the screw pushes on to actually push the piston in deeper.
One thing to be aware of with your mod, is that you are potentially always keeping the piston in so deep that it blocks off the reservoir. Which could become an issue on long downhills, when the brake fluid heats up.
That’s interesting. So there actually is significant piston travel long before brake engagement? I assumed it was just pre-travel on the lever that occurred before piston engagement. I doubt the fluid heating up will be an issue however as there aren’t any descents of more than 100m in elevation on the trails that I ride. Also, wouldn’t that be a problem without the cord too, assuming you used the brake for the entire descent?
Exactly, that’s why I mentioned it.
I don’t know exactly how far into the piston travel the reservoir vent port is, so I don’t know if it is likely that there could be an issue. I only know that on very long descents with a lot of braking, I had the bite point noticeably move out until I let of the brake - probably not something you can achieve with only 100m of elevation.
Hydraulic leverage is typically between 6:1 and 8:1. I’ll guess somewhere around 0.5 mm piston retraction at the caliper (total guess, I couldn’t find any figures, but with the piston seals pulling back the pistons and maybe some knockback from the disk it seems in the range to me), which would mean 3-4mm of master cylinder piston travel from the vent port being shut to the pads hitting the disk. So not a ton, but somewhat significant. At your braking finger, that would be somewhere around 15-20mm of movement, which seems about right. (servowave etc obviously makes that a bit different)
I’ll have to measure the travel when I get home and see what I can do to better understand the working of the brake. There’s far more than 15-20mm of travel including the extension, but I’m not so sure about just the handle. I set it up so that I could both easily reach the handle with my fingertips and still lock the brake up hard if necessary. The lever adjustment knob makes it very easy to dial in. I just loosen it until the brake starts to drag and then tighten it back up a little.