hub drive vs mid drive

I installed a 350W hub drive with 36V, 11.6 Ah (+/- 280 Wh) battery from Clean Republic on the front wheel of our tandem. The hub is rated at 45 N.m. and 260 RPM. It seems to hit it's maximum capacity on any grade over 5%. I'm considering the purchase of a Gepida Thoris tandem with Bosch Performance drive and 500Wh battery, which is rated at 63 N.m. I assume we'll see better performance and battery life from the Bosch system. Any input? Thanks!

As far as mid-drive vs hub motor torque just go drive a 5-speed manual transmission car in 3rd gear all of the time. A bigger engine will help but it’s always going to be a compromise.

Now drive that same manual transmission with all 5 gears available. Much easier, eh? In fact, a very small engine can move things around pretty easily with the right gearing.

Front hub motors aren’t usually too bad for maintenance/installation but any hub motor requires tools/wrenches in order to R&R wheel.

And weight distribution is another “thing” which hub motors come up short, IMO.

I'm guessing that you have a Q100H, which is a tiny motor, hardly suitable for hauling two people and a heavy bike up a hill, even though it packs a fair punch for its size.

A 48v system would give you 30% more torque, but if you go up to 20 amps as well with a middle sized motor, like a Q128H or Bafang SWX02, you'd get more torque at a fraction of the price of the Bosch one.

There's also the 25 amp BBS01 kit from Em3ev, which is relatively cheap, European legal and gives more torque than the Bosch stystem.

How much battery you use depends on how much power you want. The more assistance you get, the more battery you use. I doubt that you'd notice any difference in any system if you do the same rides in the same time.

Couldn't a tandem owner install a Bafang BBSHD kit and a 48V battery, print a little sticker that reads "250 Watt" and apply it to the motor? Do cops in Europe actually inspect closely enough to discern the output?

Raisedeyebrows said:

Couldn't a tandem owner install a Bafang BBSHD kit and a 48V battery, print a little sticker that reads "250 Watt" and apply it to the motor? Do cops in Europe actually inspect closely enough to discern the output?

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That's fraud. You can be locked in jail for that and then you have a serious criminal record that will affect the rest of your life. If you get caught on an illegal bike, you'll probably get told not to use it again.

It's not fraud to remove any markings, but it is fraud if you add a false one.

Because you can gear down for the hills, any kind of mid drive is going to outperform the tiny hub motor when its loaded down with two people. The front motor you chose is not really designed for that much weight, unless the grades are very mild.

A more powerful hub motor could climb steeper hills, faster than a mid drive in the lowest gear you have, but only by using a lot more power.

Most likely, you will get up the hills on the least battery power, using a mid drive like the one you are considering. The bosch system is a very good one.

Just curious. I always thought that the rear crank (stoker?) on a tandem does not have a free wheel so rear pedal speed is locked to that of the front crank. Seems like that could make a BBS02/BBSHD implementation on a tandem unwieldy for the rear rider at speed. But then again, it's not always about speed and I suspect it takes enough skill to ride a tandem that my wife and I would crash a regular unpowered one.

Does that Gepida Thoris have a free wheel?

There is no freewheel in the stoker position. The stoker's chainring, as well as the "timing" ring, are larger than the motor's chainring, which slows the cadence for the stoker (think single bike with small inside chainring on triple crank and large cog). I appreciate all of the "kit" recommendations, but I'm reluctant to get into that much DIY, which is why I went with the product from Clean Republic. I've also heard that when installing a mid-drive conversion on a tandem there is the risk that the eccentric bottom bracket will not resist the torque of the motor. I think dogman dan is correct - because changing gears is connected to the drive mechanism (pedal assist), it's a better setup.

Thanks to everyone for the input.

Ykick said:

As far as mid-drive vs hub motor torque just go drive a 5-speed manual transmission car in 3rd gear all of the time.

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A better example would be to drive a Tesla. Gas motors have very limited torque bands; electric motors do not. (And Teslas are always in the same gear.)

billvon said:

Ykick said:

As far as mid-drive vs hub motor torque just go drive a 5-speed manual transmission car in 3rd gear all of the time.

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A better example would be to drive a Tesla. Gas motors have very limited torque bands; electric motors do not. (And Teslas are always in the same gear.)

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That is a good point however I'm not talking about something rivaling Tesla motor selection and V/RPM but instead the limited choices of most available bicycle hub motors and controller systems.

d8veh said:

That's fraud. You can be locked in jail for that and then you have a serious criminal record that will affect the rest of your life. If you get caught on an illegal bike, you'll probably get told not to use it again.

It's not fraud to remove any markings, but it is fraud if you add a false one.

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Last sentence - You've got to be joking right, and I mean that in all seriousness.
The first bit is a joke, locked in jail. Caught and not to use it again, yeah ok. But fraud, come on.
The street cop has no clue, he is too busy with speeders, crack heads, drunks, accidents, and thieves.
I am still trying to understand this fascination with obeying silly laws.
Obeying ebike laws is like obeying speed limit signs.

Innocent people die because jackasses ignore speed limit signs.

Chalo said:

Innocent people die because jackasses ignore speed limit signs.

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I would venture to say, that more people die in auto accidents, not because of excessive speeding, but because of texting/cell phones/ drunk driving ,etc. Id rather encounter a sober driver doing 8 mph over the speed limit, then a drunk driver doing the speed limit.

slacker said:

do not waste time arguing with chalo, he is the poster boy for abortion. His parents must be proud.

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\

Well, I think he sometimes just likes to jerk peoples chains a bit. I don't mind it, cause any strong debate with logic, can counter weaker points of view.

markz said:

d8veh said:

That's fraud. You can be locked in jail for that and then you have a serious criminal record that will affect the rest of your life. If you get caught on an illegal bike, you'll probably get told not to use it again.

It's not fraud to remove any markings, but it is fraud if you add a false one.

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Last sentence - You've got to be joking right, and I mean that in all seriousness.
The first bit is a joke, locked in jail. Caught and not to use it again, yeah ok. But fraud, come on.
The street cop has no clue, he is too busy with speeders, crack heads, drunks, accidents, and thieves.
I am still trying to understand this fascination with obeying silly laws.
Obeying ebike laws is like obeying speed limit signs.

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Don't worry too much about the police but do consider the situation where there is an accident and someone is injured. The lawyers will be looking for anyway to settle the blame on you (regardless of the country).

slacker said:

do not waste time arguing with chalo, he is the poster boy for abortion. His parents must be proud.

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A shame you can't accept facts.

"Past NSC research has indicated that alcohol, speed and distracted driving are the three major causes of fatalities on the road, contributing to 30.8, 30 and 26 percent of motor-vehicle deaths respectively."

So booze only leads speed by 0.8 percentage points. Fact before attacks, please.

tomjasz said:

slacker said:

do not waste time arguing with chalo, he is the poster boy for abortion. His parents must be proud.

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A shame you can't accept facts.

"Past NSC research has indicated that alcohol, speed and distracted driving are the three major causes of fatalities on the road, contributing to 30.8, 30 and 26 percent of motor-vehicle deaths respectively."

So booze only leads speed by 0.8 percentage points. Fact before attacks, please.

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Oh come now, Our friend Chalo is the king of " attacks" on this forum. Also, I was correct in guessing that drunk driving leads to more accidents then speeding and I still
stand by my position that Id rather encounter a sober driver doing 8 mph over the speed limit then a drunk driver doing the speed limit. I know you werent responding to me with your above reply, but I'm sure Chalo can take some verbal attacks, since he hands it out so often. Also, as more and more people become TEXTING machines while driving, I would venture to say that the distraction issue causing accidents, will only increase. In fact, it may become a primary reason for accidents involving teenagers who have become social media narcissists/zombies.

I have much more disdain for drunk drivers, because it is something that cannot happen accidently , doing over the speed limit can happen accidently and most of us have done it in our lifetimes.

Hmmm, the tandem poses a problem for both mid drives and hub motors.

The tandem I have ridden had both cranks turning together at the same cadence. Because a tandem carries the weight of two riders and a heavy frame, I'd be inclined to try the mid drive for climbing. For climbing, select a big cog in the rear and let the electric motor spin easy while reducing the power contribution of the riders. A mid drive should require far less motor torque, but higher motor rpm than a hub motor, assuming both are providing the same power at the tire.

When one tandem rider is pedaling, both cranks revolve, a mid drive would not change that, it just would add some power to that of the riders.

Keep us posted on what you try and the results.

The concept of a police officer looking at an ebike for legal power limit, seems silly to us here in Texas. It would be very embarrassing to the cop to do that trivial kind of thing. Besides that, just imagine the taunting from fellow officers and from his watch commander. More than taunting, the watch commander would probably be unhappy with the officers poor choice of priorities. When I ride my ebike I'm sort of invisible to police, (and especially invisible to go-faster roadies). I do make it a habit to pedal with some effort and to look like other riders. It is unlikely that a police officer will notice that a bike has electric assist and since that assist is legal, the LEO will not care. Any way, that's how it here in San Antonio, TX.

I get no static from the cops so far, it's the Lycra crowd throwing the dirty looks towards the Ebikers, the purists who think if you don't struggle up hills you're dog sh&t on their shoes. Well I've been riding steep hills on standard bikes all my life so I just ignore them.

I also know the main reason a lot of motorists hate cyclists and feel it's their duty to run them over is the way the Lycras oftentimes ride side by side on two lane roads in arrogant fashion. The result is the guys in the monster trucks play their little games of "chicken" with all bicyclists.

Raisedeyebrows said:

I also know the main reason a lot of motorists hate cyclists and feel it's their duty to run them over is the way the Lycras oftentimes ride side by side on two lane roads in arrogant fashion. The result is the guys in the monster trucks play their little games of "chicken" with all bicyclists.

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So who's being arrogant in this scenario? (Hint: while they're also threatening the lives of others. And claiming for themselves far more space on the road than any small group of cyclists could.)

I hate when there is plenty of room for drivers to pass a bicyclist, yet they give them little space when passing.
That is precisely why I take the full lane.

markz said:

I hate when there is plenty of room for drivers to pass a bicyclist, yet they give them little space when passing.
That is precisely why I take the full lane.

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I hate that too,... especially when there's no opposing traffic or otherwise plenty of room.

As a motorist,... EVERYTHING on the road is a hazard, pedestrians, bikes, trucks, pets, wildlife, even other motorists.
As a HAZARD,.... I do all I can to NOT make myself a "target"!!

Given the same power input,...
DD hubs, while super simplistic and dependable, will have a rather limited range of application.
Geared hub,... a little less simplistic, durable, with a broader range of use.
Mid-drives,... a wonder of engineering design! Tough,... depending on drive train, and far more versatile.

huffinandpuffin said:

I assume we'll see better performance and battery life from the Bosch system. Any input? Thanks!

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"We build bikes for "PERFORMANCE",... with speed,... with power,... with long battery life! You may have your choice of any two! (note: extra range will cost extra)" :lol:

Chalo said:

Raisedeyebrows said:

I also know the main reason a lot of motorists hate cyclists and feel it's their duty to run them over is the way the Lycras oftentimes ride side by side on two lane roads in arrogant fashion. The result is the guys in the monster trucks play their little games of "chicken" with all bicyclists.

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So who's being arrogant in this scenario? (Hint: while they're also threatening the lives of others. And claiming for themselves far more space on the road than any small group of cyclists could.)

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I notice anytime there's an article locally concerning bicycle issues the auto drivers are very very vocal trying to villanize cyclists as being law breaking outlaws who run every stop sign and traffic light. They view cyclists as a direct threat to their existence or something, never could figure that out.

Raisedeyebrows said:

I notice anytime there's an article locally concerning bicycle issues the auto drivers are very very vocal trying to villanize cyclists as being law breaking outlaws who run every stop sign and traffic light. They view cyclists as a direct threat to their existence or something, never could figure that out.

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People get very defensive when they know they are in the wrong, but they don't want to change.

Raisedeyebrows said:

... if you don't struggle up hills ....

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What is a "hill" ? ? ?

Raisedeyebrows said:

I also know the main reason a lot of motorists hate cyclists and feel it's their duty to run them over is the way the Lycras oftentimes ride side by side on two lane roads in arrogant fashion. The result is the guys in the monster trucks play their little games of "chicken" with all bicyclists.

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Texas has a "vulnerable road user law" and several cities have enacted their own ordinances for same. Some of those monster truck drivers could face fines of up to $500 for their actions.