80 MPH mobility scooter: Hydraulic brakes, speedo - 8/6/15
Posted: Thu Aug 06, 2015 10:43 pm
Well, I finally gave up on the cable disc brakes. with different length cables the stretch was unequal from one side to the other and they were impossible to balance, which meant that every time I grabbed them I would swerve to the right. Not super confidence inspiring...
As an added bonus, when I took it out on Halloween one of the calipers froze up and locked the front left wheel while I was evading some.. uh..concerned parents, leading to an eventual blowout.
I finally concluded that hydraulic was the only real way to get balanced braking. Conveniently the pressure ratio between the MC and calipers actually work out in my favor with hydraulic unlike the motion ratio with the cable brakes which does the opposite. As a bonus, they have also now been around for long enough now that you can get old used ones on eBay for cheap. The bad news is that bike brakes have only one caliper per brake lever.
A "T" in the line is an obvious solution, but proved hard to find and more expensive than I wanted to spend on this. Instead, I found a rather elegant idea on a Trike forum (because of course there is a forum for that..): Remove the bleed screw from one caliper and connect the hose for the second caliper to it, placing both in series on the same circuit and effectively using one of the caliper as your "T". Brilliant.
I picked up a set of used Hayes HFX9 brake calipers + levers for $35 shipped on eBay. Of course the fitting that connect to brake lever is completely different from the one that connect to the caliper, so that needed some adaptation. Knowing pretty much nothing about bike brakes, I took them down to the local bike shop (Gregg's Bellevue Cycle) to see what kind of fittings they had. After I explained what I was trying to do and after they stopped laughing at me, a guy named Don took me back to see what kind of fittings they had that we could make work.
Here is what I ended up with.. for Free!
Cut the old lever connection off of one caliper, attached the new fitting, and screwed it into the bleed port on the other caliper:
Ran the lines, installed the lever, and tied everything up so it won't chafe while in use:
Bleeding bike brakes requires a very large syringe full of brake fluid on the caliper side, and a tube going to a catch can on the lever (master cylinder) side. They sell kits for like $25-$30 online. I'm too cheap for that so I went to my cat's Veterinarian instead and they hooked me up.. for free! Add $0.10 cents of vinyl tubing, an empty beer can, and you're in business. Behold my classy brake bleeding setup:
I used the large syringe to bleed the system, then used the small one to pre-load they circuit and take the excess lash out from between the pads and the rotors. This is important with this setup because my master cylinder is still the same size but I now have two calipers worth of lash to take up before the pads contact. Without doing pre-load on the system the pads barely make contact before the master runs out of travel.
I downloaded a speedometer app for my phone, taped it to the dash of the scooter, and took it for a spin around my neighborhood tonight. The new brakes are FUCKING AWESOME!! Perfectly balance, powerful, and immediate. Exactly what this thing needed to make it less sketchy. Cruising the neighborhood I got it up to 31 MPH. Need to take it to a back road and see how fast I can comfortably go now.
Oh, and get some more videos!!!
As an added bonus, when I took it out on Halloween one of the calipers froze up and locked the front left wheel while I was evading some.. uh..concerned parents, leading to an eventual blowout.
I finally concluded that hydraulic was the only real way to get balanced braking. Conveniently the pressure ratio between the MC and calipers actually work out in my favor with hydraulic unlike the motion ratio with the cable brakes which does the opposite. As a bonus, they have also now been around for long enough now that you can get old used ones on eBay for cheap. The bad news is that bike brakes have only one caliper per brake lever.
A "T" in the line is an obvious solution, but proved hard to find and more expensive than I wanted to spend on this. Instead, I found a rather elegant idea on a Trike forum (because of course there is a forum for that..): Remove the bleed screw from one caliper and connect the hose for the second caliper to it, placing both in series on the same circuit and effectively using one of the caliper as your "T". Brilliant.
I picked up a set of used Hayes HFX9 brake calipers + levers for $35 shipped on eBay. Of course the fitting that connect to brake lever is completely different from the one that connect to the caliper, so that needed some adaptation. Knowing pretty much nothing about bike brakes, I took them down to the local bike shop (Gregg's Bellevue Cycle) to see what kind of fittings they had. After I explained what I was trying to do and after they stopped laughing at me, a guy named Don took me back to see what kind of fittings they had that we could make work.
Here is what I ended up with.. for Free!
Cut the old lever connection off of one caliper, attached the new fitting, and screwed it into the bleed port on the other caliper:
Ran the lines, installed the lever, and tied everything up so it won't chafe while in use:
Bleeding bike brakes requires a very large syringe full of brake fluid on the caliper side, and a tube going to a catch can on the lever (master cylinder) side. They sell kits for like $25-$30 online. I'm too cheap for that so I went to my cat's Veterinarian instead and they hooked me up.. for free! Add $0.10 cents of vinyl tubing, an empty beer can, and you're in business. Behold my classy brake bleeding setup:
I used the large syringe to bleed the system, then used the small one to pre-load they circuit and take the excess lash out from between the pads and the rotors. This is important with this setup because my master cylinder is still the same size but I now have two calipers worth of lash to take up before the pads contact. Without doing pre-load on the system the pads barely make contact before the master runs out of travel.
I downloaded a speedometer app for my phone, taped it to the dash of the scooter, and took it for a spin around my neighborhood tonight. The new brakes are FUCKING AWESOME!! Perfectly balance, powerful, and immediate. Exactly what this thing needed to make it less sketchy. Cruising the neighborhood I got it up to 31 MPH. Need to take it to a back road and see how fast I can comfortably go now.
Oh, and get some more videos!!!
