CharlieFree

I'm looking into an ebike for commuting and grocery-getting. What are the pros and cons of the 20mph and 28mph versions? (pedelec vs speed pedelec/ class 1 vs class 3). If you have one or the other, what are your experiences? I believe only Class 1 is allowed on bike paths here but on the other hand, more speed on the roads would be nice! Other considerations?

linberl

My motor will go 28 mph but I have not found any need to go more than about 18mph, period. If you ride in a city with stops and lights and traffic or on regulated pathways, that 28mph is pretty pointless. What matters to me more is how quickly in the stroke from take-off the assist engages and how well it
climbs.

2old

Worth it to me to have 28 mph even though I don't use it all the time. When I have the opportunity it gets "opened up". Wouldn't argue with anyone who felt differently; different strokes ....

Nightdiver

Many 20mph bikes will start to taper off 1-2mph before the limit, so you're generally maxing out around 18-19 which on some roads can feel a bit slow. Having the 28mph option can be nice in those situations even if you only ever go 23-25mph. One consideration is battery range, especially if you're buying a bike with more upright posture as the wind resistance at the top speeds will really start eating into your range.

However, as you noted, many areas are adopting the model ebike legislation of class 1-3. Now, would anyone actually know what type your bike is and is there any enforcement? Probably not. But personally as someone who wants to promote/support responsible bicycling, I would feel a total hypocrite using a Class 3 on a bike path even if keeping at lower speeds.

fly135

I have a class 3 street bike and a class 1 MTB. I bought the street bike w/ 500watt hub drive initially because it felt so powerful. The 250watt mid drive on the class 1 MTB felt anemic. Bottom line is you will get more speed for your money with a hub drive. Although unlocked to 28mph, the street bike (DAS-Kit hub drive) basically accelerates to 24mph without much effort. It's great if you don't want to work hard to go fast. You can adjust power level and PAS (2 different settings) to make it work however you want. And you can get exercise when you desire. I live in Florida and so far I've seen no evidence of needing to worry about legality riding a class 3. It's a simple matter of reprogramming to class 1 anyway.

OTOH, I ride my class 1 MTB almost exclusively. It has a Bosch mid drive with torque sensing. It feels more like pedaling a regular bike. The motor starts to cut out at 19mph and you have to pedal your a$$ off to keep it at 20mph. The motor overcomes the inherent limitations of riding a heavy plus size tire bike. And the thing is like a tank. The other riders in the group are always pointing out stuff on the path to avoid, and I joke they are pointing it out for me to run over. One of our runs has MTB trails at the turnaround. So I go run the trails while everyone else is taking the half point rest. I also take short off road jaunts whenever some nice terrain shows up along the MUP paths we ride.

Bottom line is that you need to define your needs. For me I realized that I like the adventurous nature of going off road more than the raw speed of the street bike. In hindsight I would have bought the eMTB and not the street bike. But like most people when I first got on the street bike I was smitten by the power and acceleration.

woodybr

I have a very naive question about PAS. What does it mean to have a max speed for PAS? What happens if I just keep pedaling past that speed? Does the motor shut off completely?

fly135

The PAS on my DAS-Kit rear hub drive does fade the motor out at different speeds based on PAS setting. So if you want to go 14mph you might set it to 3 (of 1-6 on mine). I can't remember the exact speeds, so I'm just giving the idea. It appears the motor does fade out completely at 14, but starts giving less power at 13. This is with light pedaling.

If you pedal harder the speed you achieve at a PAS setting will be about 1-2mph higher than if you just lightly spin the pedals. In most cases you won't get too much higher speed after the motor cuts out because most ebikes are heavy with hybrid tires. But there is nothing other than drag that prevents higher speeds. I've been over 32mph on a 20mph eMTB going downhill.

woodybr

Got it. So it's probably to comply with regulations that it simply doesn't output its max power and let you supplement with your legs

allan6344

The factory PAS ebikes will cut off the power the speed limit. I have a Class III 28 mph Specialized Turbo S that I used for a long commute. If I am pedaling on the flats and reach the control 28 mph limit there will be a sudden step in the effort required as the motor power stops contributing so the real max PAS speed is about 25-26 MPH. It depends your local riding conditions as to whether the Class I or Class III is better. The so called 28 mph PAS bike allowed me to get through some road section that were nominally 25 mph with a little less exposure.

woodybr

This is all very helpful. As a follow up - if I have an ebike (pre-built) and let's say I have it in PAS 1. My understanding is that it would be effortless to reach some lower speed (say, 10mph). However, at this low level of pedal assist, is it easier to get to, say 20mph with some extra leg effort, or does the motor also stop helping after a lower cutoff speed?

I want an ebike so I that I still get some exercise if I want, without turning it off completely, since they're very heavy. With JUMP bikes, I feel that the pedals are essentially a throttle, since I don't need any effort at all to get to a reasonable speed. That's not the experience I'm looking for.

2old

FME, you can set the level of assist and still get exercise. You just need to coordinate effort and assist. it's also possible with a throttle using the same rationale.

fly135

Using my DAS-Kit as an example, if you set the PAS to 1 (which say gets you to 10mph), you won't be able to get the bike to 20mph with extra leg effort unless you have gorilla legs. You can always get exercise by setting the PAS to about 1 or 2mph below how fast you want to go. That extra 1-2mph will create a lot of resistance at the pedals.

As you might have noticed I'm not claiming all brands of motor act the same. I only know specifically my DAS-Kit hub drive and Bosch Performance CX mid drive.

woodybr

Thank you for the clarification. This description makes things more clear, but also makes me confused about what pedal assist actually mean. This system doesn't sound like something that amplifies your efforts. Rather, it sounds like a throttle that is activated by foot and gets you to the set speed with virtually no effort, and beyond that you're basically on your own.

My naive understanding of ebikes was wrong and I appreciate the help. I thought the PAS system would amplify your regular efforts to different degrees (from a little help to a lot of help), but it seems more like a pedal activated scooter than anything.

fly135

Amplifying your effort requires a torque sensing motor. Hub drives like my DAS-Kit only sense the pedals turning (cadence sensor). The Bosch mid drive in my mountain bike has a torque sensor and does amplify your effort. The Bosch mid drive doesn't even use PAS terminology. Instead it has different modes that change how much boost is applied and the motor always cuts out at 20mph, which is unlike the multiple cutout speeds with PAS on the DAS-Kit.

Torque sensing also has the advantage of being immediate. So when you stop pedaling it immediately cuts the motor. Cadence sensing is usually slower to cut out and needs brake sensors to make sure you cut power immediately when brakes are applied. A torque sensing motor will likely feel more like pedaling an unplugged bike than a cadence sensing motor.

https://www.bosch-ebike.com/us/produ...mance-line-cx/

Here's a link to the Bosch web site. The term PAS doesn't even appear on the product information. Instead you will see in the tech specs that each mode produces a percent boost (up to the motor limits). So if you put it in the lowest boost mode (ECO = 60%), you can get to 20mph maybe if you have strong legs. The motor will produce that 60% boost up to the fade out range (19-20mph).

woodybr

Thanks, this helps a lot. I understand it now. Since I can't shell out the cash for a mid drive ebike with torque sensor, I'll just have to get used to this style.

bhtooefr

Note that there are lower-cost torque-sensing mid-drive systems.

The Tongsheng TSDZ2 is fairly popular because it can be retrofitted to a frame that has a standard 68/73 mm ISO threaded bottom bracket shell, instead of requiring a frame with motor mounts instead of a BB shell like this:



Additionally, it being fairly readily hackable (with third-party firmware available) has helped with the popularity. I do know it has some weak points (overheating causing a nylon gear to be softened - there's metal retrofit gears, as well as the third-party firmware adding support for temperature monitoring), though. I haven't ridden one to say how well they ride.

There's also torque sensing bottom brackets available for use with hub motor systems, although the controller needs to be aware of torque sensors to use one. This doesn't get you the broader useful speed range of a mid-drive (existing hub motors are a compromise between low and high speed performance, whereas mid-drives get to take advantage of multi-speed gearing), but it can get you the much more natural feeling of one.

Also, some of the cadence-sensing systems can have their parameters adjusted such that the selected PAS level only controls power, not top speed. (This does mean that if you want to hold a speed lower than the top speed, though, you'd have to stop and start pedaling frequently, or select a mode with low enough power as to not help too much.)

browngw 

I recently purchased two 2019 Giant Lafree city bikes for my wife and myself. After trying many over the last few months, these seemed the most natural pedalling. The 250W Giant/Yamaha mid drive coupled with Shimano hydraulic brakes and 8 speed Shimano Altus is a good setup for town/rail trail/ multiuse. They have geared it so that at 32km (20mph) where the power runs out that you are spinning out anyways. I have been riding it and checking battery use in real world conditions. With 80km (50miles), there is 30% battery left and I have not been trying to conserve in any way. There are five tunable levels of assist (between 50% and 300%) of your effort. There is also an "auto" setting that claims to use 6 sensor inputs to introduce assist as you need it. It works much better than I expected and is reasonably quiet. The bikes were listed at $2499ea. CDN. Acceleration is instant and smooth. In Ontario, Canada, this is bike meets the regulations.