Long descents where there is significant energy to recover are not that common for most riders.
The most unusual thing I ever saw in my EV days... We had a full Ford Focus Electric on a chassis dyno to debug some problems. After several hours of tuning and data collection we realized the car needed to be charged to get it back to our own facility. The dyno place had no high power chargers. So we set the dyno somewhere around 40mph, put the car in drive and left it. With no foot on the gas it would do a light regeneration at that speed. The strange part is that we sat around a table to analyze the days data about 5 feet from the car. We're at a table next to a car tied down and going 40mph and its almost dead silent charging via regen. Analysis done, car charged, untie it and off we went ;-)
A bike has very little rolling resistance, nearly all of the energy used to propel the bike on level ground is going toward fighting air resistance. Even on rolling hills, I rarely use my brakes on the downhill, any regen braking used on the downhill is just going to increase the energy needed to go up the next hill. (and due to less than perfect efficiency, you lose energy on both the regen capture and powering the motor again, so it's a big loss).
So yes, you might recover some small amount of energy used to decelerate the bike at a stop sign, it's not going to be significant percentage of the total power requirements, and you're going to be paying a price in dollars, complexity and weight for this feature.
It's a different story with a 50 ton train where a 20 KW resistor bank is not a significant amount of weight, but adding a 500W resistor bank to a bike (since you need somewhere for energy to go when the battery is fully charged) is probably not going to be worth the weight and expense.
Plus you need some sort of blending between regenerative and friction braking, so it's yet another thing that needs adjusted and maintained.
It's firmware limited to 20 mph which _feels_ slow but is probably a sane compromise. We only hit that going down hill, and are far from the fastest cycle; but we average 12-15 mph on mild uphills and flats when conventional cycles usually average a few mph slower.
I love my ebike, it makes a daily commute taking two kids to school then getting on to work feasible, regardless of weather or relative personal energy level.
Yes, V-brakes.
> I wouldn't run anything less than hydrolic disks on something that fast. Preferably dual piston like the ones Sram are making now.
I actually didn't specify anything about the speed of my bike in the post, but mostly I ride below 25km/h. The 35-40km/h quoted was coasting down a steep hill, and I would have gone the same speed without the motor. It's just that the added load caused the V-brake stirrup to bend open over time, and then it finally popped out in that situation.
I think idea that disc brakes, mechanical or hydraulic, are "more powerful" than V-brakes or canti's is a misunderstanding. If you think about it, the absolute limit to a bicycle's braking power is as much force as possible without locking the front wheel and sending the rider over the handlebars. Any bicycle brake can do that, and if it can't it should be returned to the store as defective. The reason I switched to discs was that the whole assembly seemed more solid than V-brakes (no loose coupling like in the harness). The other big reason to switch is the feel of the lever (better control over braking modulation), and needing to put less force on the lever for more braking power, so your hands get tired less.
The main reason I went for mechanical disc brakes vs hydraulics is the ability to service them on long trips. I'm not going to bring tools to bleed the hydraulic system on touring trips.
EDIT: Another reason I picked mechanical is that it's simpler to wire a motor safety shut-off switch to mechanical brakes. For hydraulics you need to do the reed-switch mod I mentioned which is a bit more finicky, or install a hydraulic sensor which requires bleeding the system.
As an aside, it's weird that in the bicycle world we talk about disc brakes vs rim brakes since they are all disc brake systems (in a rim brake, the rim itself takes the place of the rotor). I don't think I've ever seen a bicycle with a drum brake :)
Hope makes some nice DH brakes: http://www.hopetech.com/product/tech-3-v4/
Avid has the Code: https://dirtmountainbike.com/bike-reviews/brakes-gears/avid-...
And other manufacturers also make calipers with >=4-piston calipers.
Again for rotor size, 160mm is typically standard for XC, road bikes run 140mm usually, some "all mountain" bikes have 180mm fronts, and 200mm is typically seen only on DH/4x/trials/dirt jump bikes but likely what you want for a fast ebike.
All that said, competition-level road bikes generally hold up fine at speeds up to 60mph (and the riders hit those speeds going down hills) and their brakes work fine. You obviously don't just mash them, and the rim surface they're clenching matters a lot, as do the pads, but the tech works well and has worked for the past 100 years. Weight distribution and even application of both brakes help a lot.
For >750W e-bikes that go over 28 mph you'd normally need DH brake tech, 180 rotors at least. Shimano Saint Ice tech is good, Magura brakes are also top notch, even the lower end models. Avid Code looks rather flimsy and advertises low weight. I would avoid any calipers w/o metal bodies as it does not dissipate heat well. The Hope caliper looks especially good - lots if surface, lots of metal. The brakes and the steering are the last things to save weight on.
I think the failure mode of cable-operated disk brakes might be better (though I've since ditched the bike, so that's speculation).
This cannot be stressed enough. The amount of new builds on ebike forums where people are building essentially electric motorcycles on bicycle frames with no upgrades to non-drivetrain components is scary.
Even with my 500W motor (illegal here, but would be legal in the states, and puny compared to the stuff the article's author is talking about), I found myself wishing the brakes were more responsive. I upgraded the brake pads which made the ratio of stopping power to acceleration acceptable.
Then after a year of using that, the aluminum stirrup that the brake noodle slides into bent enough for the noodle to pop out, putting my front brake out of service. This happened while I was applying braking power during a steep downhill descent going 35-40km/h, I lost control and fell off the bike. The stirrup wasn't designed to handle the braking forces I was applying to it with the new brake pads, so over time it bent outwards and eventually gave way.
Don't neglect your brakes! After this I upgraded to mechanical disc brakes.
EDIT: Regarding "if the throttle gets stuck wide open" - if you don't have motor safety cutoffs installed on your brakes, you should do so now. I've had my PAS controller get into a state where it decided to just apply power even with no movement on the pedals. Always have a cutoff switch! If you dislike the chinese ebrakes (and they do suck), there are inline wire sensors you can install to keep your existing brake handles, and it's also fairly simple to modify your existing handles with a reed switch.