> Oh, and make sure that your brakes are able to stop your 1000W+ motor if the throttle gets stuck wide open.

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.

Don't you guys have regenerative braking via the electric motor? From the sound of it, the motor controllers out there are rather primitive in this market. Thoughts?

There's not a whole lot of energy to recover -- most of the eBike's energy is spent fighting wind resistance, so there's not much left to recover when you're slowing to a stop at a stop sign.

Long descents where there is significant energy to recover are not that common for most riders.

A stop should provide almost as much energy as starting back up again. How about an e-bike with a fixed gear? You get assist when starting, but pedal yourself at speed, regen to stop, and perhaps some option to charge the battery via the pedals that's up to the rider.

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 ;-)

Define "almost as much energy". Bike motors aren't super efficient, especially at low RPM's (like when you're coasting to a stop).

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.

Well you could just use the drive as an electromagnetic brake w/o necessarily recovering all power by diverting all or just a part of it to a load. Train engines do this.

Well you could, but it comes at a cost (in dollars, complexity and weight), and is likely not worth it since the bike still needs friction brakes.

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.

Even a DC motor driven with an H-bridge can dump mechanical energy back into the battery. It's trivial.

My Bionx Xtracycle has regenerative breaking and it is as implied super-useful as a speed moderator here in SF when going downhill with a load (my two kids) would build up speed.

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.

Towards the bicycle end of the spectrum you probably want it to be able to freewheel.

I expect it is a cost/benefit thing, where an ebike is already quite pricey, and equipped with a very reliable fallback.

You upgraded to mechanical disk brakes? What were you running before? 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.

> You upgraded to mechanical disk brakes? What were you running before? V brakes?

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.

Disc brakes use different materials than the rubber blocks on cantilever or v brakes. I would exect that more friction can be applied. It will also handle heat differently.

Yes, I know, I'm just saying that the extra braking power isn't useful because you can already apply the maximum safe braking power with any bicycle brake. Anything more will just send you flying over the handlebars. There are other reasons to prefer discs though, as I mentioned.

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 :)

People go over the handlebars on braking because they use the rear brake, or are not properly braced on the handlebars. If you use the front brake (and brace properly) there is little practical limit to braking force. You are more likely to skid the wheels than go over the handlebars.

It's physically impossible to go over the handlebars using only the back brakes.

I've destroyed two sets of Avid Juicy 7 hydraulic disc brakes with upgraded pads just by mountain biking, and these are almost top tier of bicycle brakes. Can't imagine people are running electric bikes with a lot of power without matching it with appropriate braking system.

I'd only use original pads and discs from the brake manufacturer. If you upgrade your brakes it's best to upgrade the whole system, not just the pads. Overbuilt components with more metal and more surface would normally dissipate heat better, reducing the prospect of brake failure. Also, mechanical brakes are easier to inspect, maintain and fix. You won't see if your DOT fluid absorbed humidity or you won't notice a leak until the brake fails, but you will certainly see a broken cable.

If you're running a >30mph ebike, you probably want something larger than 160mm rotors and something heavier duty than XC disc brakes. I'd suggest some downhill gear, including DH forks, headset, bars, cranks, etc. Shimano has the Saint line: http://bike.shimano.com/content/sac-bike/en/home/components1...

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.

Competition level road bikes are new and get used for max one Tour de France season, so chances of wearing the rim, or the calioer material are minimal. I doubt they even wear the pads too much.

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 had some heavy-duty hydraulic brakes fade on me on my 2kW electric mountain bike. Scary times.

I think the failure mode of cable-operated disk brakes might be better (though I've since ditched the bike, so that's speculation).

Hydraulic disc brakes on mountainbikes are ridiculously effective.

Spot on.

If you want moped speed, get a moped. You can't safely upgrade one component; you need to upgrade them all. And it's not just your safety, it's the safety of the public, and they have a right to legislate that you don't drive a dangerous vehicle on the public highway.

I agree. I personally don't care if this guy cracks his own head open but I believe "my freedom ends where yours begins" and if he's going fast enough to seriously injure or kill someone on the sidewalk he needs to carry some form of insurance to cover the liability. "Here take my iPhone brah” isn't enough for someone who will never walk again.

Also if he wants to play around and weave in and out of cars at 30 mph+ and he ends up as a road waffle too bad, so sad.

What makes you think he's riding on the sidewalk? Riding on the sidewalk is a rookie move and anyone that rides more than once a year knows it. Author has been riding seriously for 40 years. I've been riding nearly daily for 15 years and not once have I ever come in physical contact with a pedestrian. I've been hit by 2 cars though, both times by drivers not paying attention.

>Riding on the sidewalk is a rookie move and anyone that rides more than once a year knows it.

Eh, depends on the location. My sister rode a bike every day for about 4 years (she didn't have a car). She always rode on the sidewalk because she rode at a slower pace, the sidewalks generally didn't have any people on them, and in her neighborhood if you tried to ride in the road you'd get mowed down by vehicles. There's really some places where it makes most sense to ride on the sidewalk even if you aren't supposed to.

Yes, cyclists take the sidewalk, but not cyclists who go fast.

It should be illegal to ride any vehicle w/ engine >250W capable of >12 mph speeds on the sidewalk.

Or bike lane, or cross walk. It doesn't matter where he hits the person. He is describing a literal motor vehicle it should be treated as such.

I'd say Californian law is spot on.

My understanding is that he rides the powerful ebikes in the forest when snow is on the ground. When there is no snow he rides a regular bike.

Regarding the general question of danger to pedestrians: good urban planning works wonders.

Right. If you want an electric motorcycle, get an electric motorcycle. There are some very nice ones.[1] Now that's not underpowered. 90MPH top speed, 200 mile range. That's their entry level model; they have electric superbikes, too. If you're going to be riding in traffic at speed, bigger tires and brakes can get you out of trouble. You can turn harder and stop faster.

The next step down is electric scooters, which are around $1000-$2000. They aren't pretend bicycles, but are more street-suitable.

[1] http://www.zeromotorcycles.com/zero-s/

This doesn't look like something that can be stored in an apartment, unlike a bike (and presumably an electric bike, which are about the same size). Having to park it outside is a huge hassle and theft risk, I'd never leave my bike outside.

A motorcycle/scooter isn't a major theft risk, because its big/heavy enough to resist theft on its own (and has front and back wheel locks and motion-activated siren alarm)

Speed is one factor, difference in speed is a more useful measure of the risk of harm. If you're going 15mph on a road marked 35, you are in danger BECAUSE you are slower than the rest of the traffic on that road. Other vehicles expect traffic to go at or near the posted limit, if conditions allow it. Hitting a wall at 15mph is one hazard; getting hit by a car going 20mph faster than you is a bigger hazard.

In Hawaii, because some people tend to drive too slowly and doing so causes crashes, they post the minimum speed below the limit on a lot of roads. Across the US, it is illegal to go more than 15 below the limit in clear conditions.

Once a cyclist has a motor, it seems they are more likely to 'claim' a lane and then they need to keep up or risk being a roadblock. It's less safe either way, and I'm not sure there is a viable solution. Part of the thrill of cycling in traffic, I guess.

Momentum matters as much as speed. Suppose you are doing 35mph on a bike the road and you get sideswiped by a car doing 35mph. The direct impact is negligible, but now you've got angular momentum that is going to send you into another car or the ground at high speed.

And even if you are doing 35mph, and claiming a lane, you'll still be passed (often unsafely) by cars doing 40, 50mph. (Source: motorcyclist who can't go fast up hills)

> In a 50kph collision, that jumps up to a 50% chance of death and 95% chance of non-minor injury.

Oh come on. Exactly how was that statistic collected? When people have non-fatal accidents they usually don't report it.

In fact, the link you posted above is to a guy complaining that the stats you quoted don't stand up to reason.

http://www.safespeed.org.uk/killspeed.html

Admittedly I just picked the first speed versus fatality chart I could find with references (and they do link to the government site where the data came from).

Here's another study: https://www.aaafoundation.org/sites/default/files/2011Pedest...

This one shows a fatality rate of 2.3% for speeds from 10.0 – 19.9 mph, and 35% for speeds from 30.0 – 39.9mph. Even though the rate is different, it's still showing over a 10X difference in fatality rates at the higher speeds.

Consider this, at 30mph a cyclists body has to dissipate 4 times more energy than a 15mph cyclist. There's not much in a bike to absorb energy like in a car.

> Oh, and make sure that your brakes are able to stop your 1000W+ motor if the throttle gets stuck wide open.

Fortunately, a lot of custom sinusoidal controllers have a voltage gap between 0-1V and 4-5V (or whatever full throttle is for a build) to prevent full throttle or full braking with any electrical component in the case of wiring failure.