Apartunis
Regular
Hydraulic brakes only get one chance to show me how they fail. When they inevitably fail then I replace them with advanced versions using stainless steel wires instead of baby oil or paint remover.
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Full Suspension Leaf Bike 1500W Build
- Thread starter GoFastGus
- Start date
DanGT86
Power poster
I agree about the hydraulic brakes. I want to like them. They feel amazing. But my first hydro brakes were Sram. They would lock up when the sun heated up the lever. I bled them a couple of times and they ruined several planned rides. I have 2 friends who have had similar problems with their SRAM brakes. Apparently they have released entire generations of garbage hydraulic brakes that require constant bleeding yet they will still ruin your day.
My whole fleet runs BB7 cable brakes with odyssey linear cable. They are the best cable brakes I know of.
Looks like the bike is coming together nicely.
My whole fleet runs BB7 cable brakes with odyssey linear cable. They are the best cable brakes I know of.
Looks like the bike is coming together nicely.
GoFastGus
Established
How do they do for heat management and brake fade on e-bikes? My understanding was that hydraulic brakes did better with heat management. Plus the higher-end hydraulic calipers (ex. Sram code) have larger pads than BB7 calipers. What have been your use cases for BB7 calipers?
Thanks! Over time, over budget, and overstressed, but it’s been quite the learning experience.
GoFastGus
Established
Can you give me a little more insight into your chassis/powertrain/brake setup? I’d love to learn more about what’s worked well for you and what hasn’t.
Apartunis
Regular
Life is hard for my ebikes. I replace them more often than I would prefer due to cars hitting them, booby traps in the bike lane or frame breakage from heavy batteries and luggage on bad roads. When I build one I use whatever parts are available to me and cheap. There is not a repeated formula. I have gotten away from mid drives and controllers that use displays. I use steel frames for repairability and more reasonable tubing shapes, but when I break one I usually replace it rather than repair.
I use e-car or server rack battery modules that are always rectangular so they go on the rear rack.
I use no nonsense V brakes or long reach caliper brakes when the bike supports them. I use cable discs when that is the only simple way. My "newest" e-bike is a Surly Preamble with electric parts transferred from two earlier broken frames. Because the bike does not support rim brakes I have Avid BBDB brakes on it. Those were the predecessor of BB7. They are about 25 years old but work great.
I would not recommend the Surly Preamble for e-bike conversion because it not only does not support rim brakes, it does not support any kind of kickstand. It disappoints me that way every time I use it.
One of my other operational bikes started out as a cruiser so I adapted it with a rear BB7 disc because that was easiest. V brake on the front of that bike.
The only other two wheel e-bike I have running uses a V brake in front and a U brake in rear. I have two e-trikes with coaster brakes in the back. One has a Tektro Aries front cable disc and the other has a big caliper brake in front. Both use front hub motors.
What made that understanding? The heat is generated and concentrated at the point where the rotor and pads abrade against each other. Called friction brakes. The friction generates the heat. All other things being equal (pad material and size, rotor size, etc.), hydraulic vs. cable operated shouldn't have any difference in heat management.
Can you make that hole smaller? So the bolt just barely fits thru the hole? That would make it even better, if you can achieve the precision.I also redesigned my right torque arm so it attaches to the frame via a bolt hole instead of snugly fitting into the corner. I still need to cut it out of metal.
DanGT86
Power poster
I run a DH bike with a heavy MXUS hub and 72v 10ah battery. Its probably 80lbs and I'm 185lbs. Ive done some paved track racing with hard braking from 50mph to 10mph. Basically as hard as I could brake without going over the bars. I have not noticed any issues with excessive fade.
The DH non Ebike is 203mm rotors and BB7s. Never had any instance where the power was inadequate.
I think heat management has more to do with the rotor size and design as well as the pads. I actually take a bit of comfort knowing I cant boil my cables the way one could boil fluid.
Im my opinion any disk brake I have ever ridden can lock up the wheel. The improvements in brakes are for modulation and lever feel. Cable brakes are old tech and do require more pull force. There are reasons the industry has gone all hydraulic. The majority of riders do fine with them.
I just couldn't stand the idea that I could pack up the bikes for a dream mtb trip and have a bleed I did perfectly still fail for no reason. I'm willing to sacrifice the fancy tech for reliability and easy quick repair.
GoFastGus
Established
There are significant differences in the mechanical and hydraulic disc brakes on the market that impact heat management. 4 piston hydraulic brake pads are generally larger than 1 piston mechanical brake pads (source: having replaced pads on my Tektro Orion, Sram Code, and Avid BB5 brakes). To be fair, 2 piston hydraulic and 1 piston mechanical brakes probably have similar pad sizes. Theoretically, the fluid behind the pistons helps conduct heat away from the brake pads, but I don't have any data as to heat shed through fluid. Caliper design also plays a role shedding heat to the air, but again, I have no data on differences. I found this paper on thermal models of bike hydraulic disc brakes, but I don't know enough about the subject to fully interpret the paper. Here's a thread on specific heat absorption capacity which touches on some of the differences between brake systems.
To be clear, I concede that 1 piston mechanical and 2 piston hydraulic systems with similar pad material, pad size, rotor size, etc. probably have negligible differences in heat management. The market offers 4 piston hydraulic calipers, but not 2 piston mechanical calipers, so if I want better heat management than either the 1 piston mechanical or the 2 piston hydraulic, the 4 piston hydraulic caliper with ≥8" rotors seems like the way to go.
GoFastGus
Established
What are you envisioning as a fastener for the top derailleur hole? I don't have a good idea of what kind of fastener to use. It's not threaded on the inside, it just has a hex key hole. The bottom derailleur hole isn't bolted to the frame, but it notches in and will be pressed against the frame by the axle nut. Unless/until I figure something out with the top derailleur hole, using the axle nut, the TA fitting snugly into the frame, and the bottom derailleur hole will (hopefully) hold me for the freewheel side.
GoFastGus
Established
That's good to hear!
I agree. OEMs and successful race teams study brake thermal load and carefully match rotor size and pad material among other factors to their constraints.
If this hydraulic system shits the bed I'll cobble together a cable system. If that's anywhere near as good as a hydraulic system at its best I'll probably be a mechanical brake convert.
The only thing that puts a bigger frown on my face than re-bleeding my brakes is rebuilding my shock. The worst part about mechanical brakes is running cables through a frame, but that can be mitigated with a length of string.
Okay, I had to really zoom in to see that it was not a threaded hole there in the dropout like I thought at first. So can you drill and tap a hole in the flat part of the dropout where I marked in red, with a hole in the same location on your TA, just large enough so the bolt can barely pass thru with no slop?
