Question about mid drive vs hub drive pedaling efficiency

[uhmwpolyethylene]

I've test ridden a bbshd bike and a 20" fatbike with standard 1000w rear hub, the latter was rather heavy so it was hard to tell how much difference pedaling made.

But wondering, if I want full power output from my legs, are mid drives like HD very efficient in using your leg power? Is the mid drive eating your watts?

Is the rotational weight of the rear hub a major detriment?

Does a rear hub interfere with a bikes tuned groupset if you have a nice bike?

Geared vs direct + statorade? For weight savings.

I could get away with low power on flats but I do want enough power to tackle hills like 1000-1200w

i did like with the hub motor it felt like you could feel your pedaling more.

(Do kits include torque sensors, I assume it might ruin a nice bottom bracket you already have?) (If I score a nice bike with a good groupset all around, do I want a front hub motor?)

I didn't mind the turbo boost feeling of the hub motor, and couldn't tell if my pedaling was really doing much or not on the HD

 

[neptronix]

I don't know a lot about mid drives, most of my experience is with a bbs02 and lightest.bike mid drive.
bbs02 i remember reducing 1-0.5mph when the power was off.
lightest.bike mid drive with the dual chainring reduction will shave off a mph, not sure about single chainring.

Even the best small DD you can buy ( Grin all axle ) can cut 1-3 mph off your pedaling speed in a large wheel ( this is pretty good by DD standards, the bigger, the more drag )

Geared motors are where it's at, the MAC motor is the best freewheeling one i've ridden, an average geared hub will at worst cut off a MPH.. these also tend to have low rotating mass versus a DD, so when you have a MAC or smaller, this ~1lb of aluminum that spins is no big deal.

Dual reduction geared motors tend to either be as draggy as the best DD at their worst.. at their best, they can be just like single reduction gear drives. If the application is mostly occasional blasts up a hill, with lots of cool off periods, their high power to weight ratio might be the ticket, but i don't know of one that's confirmed to be not draggy.

What kind of grades do you need to climb?

 

[99t4]

I've test ridden a bbshd bike and a 20" fatbike with standard 1000w rear hub, the latter was rather heavy so it was hard to tell how much difference pedaling made.

20" fat tire bike is near the worst pedaling efficiency model you could have chosen Absolute slug. To make an accurate comparison you would have to compare similar chassis bikes, one with mid drive, one with hub drive.

There is a MULTIpage thread here somewhere endlessly debating the benefits and drawbacks of each system.

Is the rotational weight of the rear hub a major detriment?

Higher rotational weight can affect instantaneous acceleration and deceleration effects. Higher unsprung weight impacts handling.

Does a rear hub interfere with a bikes tuned groupset if you have a nice bike?

Can be harder to fit more cogs. A mid drive can quickly destroy a tuned groupset.

Geared vs direct + statorade? For weight savings.

Geared can be lighter. DD+statorade can shed heat much better.

 

[uhmwpolyethylene]

Occasionally I'll need to climb some very steep urban grades. On the flats I'm sure I could get away with low power usage, but how much pedaling power does a mid drive steal, if any, if I just want to add 150-500w on flats? Acceleration/deceleration issues on a hub probably wouldn't be a big deal, but I dunno if the rotational weight added would slow me down a lot. The tongsheng and toseven models I've seen recommended as well with torque sensing, but idk if they're really as reliable as good ol bbshd. And yeah it was the only one I could test, actually I rode a VanMoof with like, 500w rear hub or something long time ago but can't remember the feel much.

 

[gromike]

I put together a bbs02 mid-drive bike and it works great. I was going next to do a bbshd install, but with my experience with the bbs02 I dropped that plan. The bbs02 provided all the power I needed. So the next bike I put together had a 500w (labeled) rear direct drive Grin hub motor, it's fed up to 1200w and is also super great. It's as about as powerful as the bbs02 but has torque sensing PAS and regen. Another win. Then I put a 36v tszd2b in a bike and hated it, though maybe if I went to 48v and through the OSF rigmarole I might like it.
The cadence PAS bike is a work horse, the torque sensing bike is a pleasure ride.

 

[A-DamW]

But wondering, if I want full power output from my legs, are mid drives like HD very efficient in using your leg power? Is the mid drive eating your watts?

Talking specifically about the BBSHD, at 48V, it wants to spin around 200rpm cadence.
So even if you like spinning at 100 rpm, you are lugging the motor.