Is there a gearing comparison table for hub Vs mid-drive?

[Manc44]

After biking up Winnats Pass the other day on my hub motor with a lowest gear of 24x32, it got me thinking again about swapping to a mid-drive setup, so it can utilize my gears. I was doing about 4 MPH up that hill for most of it and I actually started to feel sorry for my hub motor at one point!

The drawback to a mid-drive for me, was always that I'd have to ditch my triple chainrings and run a single chainring - now that just scares me but at the same time, a mid-drive utilizes the gearing - but does that effectively give you lower gearing, or about the same? I have no idea because I've never tried a mid-drive eBike!

I mean lets say I have a hub motor on and use a 24t inner chainring with a 32t low sprocket on my cassette - that's 19.22 gear inches.
With a 42t chainring and 46t low sprocket on a mid-drive setup, that increases the lowest gear to 23.40 gear inches. A gear increase of 21.75%.

In other words I guess it's like losing about 1.5 gears on the cassette. It's turning a 24x32t (hub) into a 24x26t (mid-drive).

What I am getting at then is, would 24x26t, or rather 42x46t... be considered a low gear on amid-drive setup? Can that get you up a hill with less effort required than if you had 24x32t on a 500W hub motor?

I'm just worried about having to ride the bike if there's no power, for whatever reason that might be. On a hub it's not even anything I think or worry about. On a mid-drive, the gears simply have to be higher due to the need for a single chainring, it's a bit of a deal breaker for me, but at the same time I don't like stressing my hub motor on these 20% gradients I want to climb!

I wish there was some sort of calculator to tell me, I mean where you'd just put in a bunch of gears on a single chainring for hub and mid-drive, put the Watts in for each motor, then it could tell you the Watts required to go at X speed up X gradient, or just show you that one needs whatever percentage more effort compared to the other.

I can't even fit a mid-drive because of my press-fit bottom bracket shell... and I'd have to buy all the 11-speed stuff again to end up with that 46t huge low sprocket, but if it's so much better for hills than my hub, it's worth doing it.

 

[Ocsid]

I'm just worried about having to ride the bike if there's no power, for whatever reason that might be.

That clause alone, if indeed a deal killer nails things for you; a mid drive with a single crank wheel that is practical for use with assisted drive, will be harder work climbing, compared to your three ring set up, once there is no assisted drive. You can't odds that with an otherwise general use ebike.

However, assisted where the mid drive electric motor can run at a better optimised rotational speed, will be very much more able to climb, on like for like comparisons. The rear gears allowing the motor speed relative to the road speeds, be more optimised.

 

[Nealh]

Both the BBS and Tsdz can accomodate 2x front rings, 34t being the lowest one can go.
Some derailleurs don't reach over far enough, I use a an older negave (shimano) front mech to get the throw when I had BBS01 with 2x set up. One may suffer some cross chaining so not all gears may be accessible due to chain line.

BBS needs an adapter the Tsdz already has the adapter for 2x rings.

 

[Nealh]

What current is the controlelr rating ?
One assumes the climbing is done in top assist level ?

 

[Manc44]

Cheers Nealh. If it's possible to have 2 chainrings, then that changes things!

My hub motor controller is rated at 18A.

The way my hub motor works on a steep hill (15%+) it doesn't matter if it's on PAS 1 or PAS 5 (the max). It doesn't go any faster or supply any more power in that situation. This is why having a mid-drive sounds better. I just don't know what sort of a difference it makes, using the drivetrain to it's advantage unlike a hub.

 

[Nealh]

Certainly more wear/tear and a shorter maintenance schedule then the hub bike drive chain. I think it depends on ones power and strength, I found for me the BBS01 wasn't much better then a hub for when things got tough.
I would still be struggling along at 5mph on inclines, once my energy levels were gone a hub I found was easier going with more gear options esp with a triple.

I'm still waiting for some bits to come for my Tsdz for the cargo bike but am wondering now if I should have gone with another small front hub as I remember my BBS01 riding experience wasn't that fantastic as I would try and eke out the range for long rides so the power was no different on inclines then a hub.
It all depends on the use and how one is using the bike, If it is short rides then one can use the max power more on inclines but if you are out for long rides you are going to need a lot ore capacity or use low pas more.

Like cars, if one want's range one has to adapt the ride power for range or simply carry more battery and a heavier bike, for me if going on a 100k plus ride it means being frugal with battery use.

 

[Ocsid]

just don't know what sort of a difference it makes, using the drivetrain to it's advantage unlike a hub.

The hub just offers one peak torque to the road wheel, anything you need more there comes from you.
The mid drive itself has a unique peak torque, but talking where it matters, at the road wheel, the chain set gear enables this to be multiplied by any of the gear ratios then in use; that simple.

 

[Bonzo Banana]

No question mid-drive is the hill climbing king for legal 250W ebikes although it has motors that pushes the legality of such bikes i.e. Bosch using close to 800W at its peak torque output.

Some low power mid-drives 40-60Nm aren't that great though, there are power losses through the chain and if you put on gearing that isn't particularly low it can easily be worse than a good geared hub motor.

Mid-drives have the advantage that they not only scale the power of the rider through the gears but the power output of the motor itself plus because the controller PCB and motor are together in the same housing means the controller can have a far higher transfer of current compared to a hub motor with a separate controller connected by a cable.

No question though if you have a geared hub motor with something like 60Nm and you have a 3x gearing setup you'll have great hill climbing ability no question but it won't quite match the best hill climbing ability of e-mountain bikes fitted with high torque mid-drive motors. However on the plus side it should be more reliable, no chain snaps, massively reduced drivetrain wear etc.

I personally don't want amazing hill climbing ability, I just want easier hill climbing but I still want exercise just not the suffering of very steep hills with a conventional bicycle where I'm all over the road climbing and doing only 3mph.

 

[Nealh]

One can't compare a hub offering 450/500w up against a midrive putting out 800/850w of power. It needs to be like for like.
In the early days of mid drive when they were equal nm to hubs, the hubs used to trounce the mid drive on hill climbs at the Bristol hill climb races.

 

[Nealh]

A BBS01 250w is comparable to most good hubs in torque and amps so the best match for testing, one will find little difference between the two. One has to test like for like and not pick a superior wattage or current rated motor.
A lot of the branded mid drives and kits will out perform hubs which is obviouse because they are tweaked power wise and have an advantage.
The bosh and yamaha etc , output a claimed 800/850w this can only mean the controller rating for a supposedly 250w 36v motor is in the region of 22 - 24a max current.
Most hub bikes will be running 17 or 18a if that.

It's like racing a motorbike with a moped and saying which is faster.

 

[Bonzo Banana]

A BBS01 250w is comparable to most good hubs in torque and amps so the best match for testing, one will find little difference between the two. One has to test like for like and not pick a superior wattage or current rated motor.
A lot of the branded mid drives and kits will out perform hubs which is obviouse because they are tweaked power wise and have an advantage.
The bosh and yamaha etc , output a claimed 800/850w this can only mean the controller rating for a supposedly 250w 36v motor is in the region of 22 - 24a max current.
Most hub bikes will be running 17 or 18a if that.

It's like racing a motorbike with a moped and saying which is faster.

If the controller is inside the housing with the motor in a Yamaha/Brose/Shimano/Bosch etc then it can drop voltage to give huge current, so I personally don't see why a battery delivering 36V at 22A can't be delivering close to 12V at 70A inside the motor housing from the controller because they are together they could have a connection capable of handling 80A internally between controller and motor. I've read of close to 800W from Bosch so about 22A from the battery and then converted down to a lower voltage inside with high current to give that 85-95Nm torque output. Not something a hub motor could do easily without higher current connections. I think a bafang 9pin connector is capable of about 40A peak maybe 30A sustained. It's a world apart in delivering current to the motor.

 

[flecc]

After biking up Winnats Pass the other day on my hub motor with a lowest gear of 24x32, it got me thinking again about swapping to a mid-drive setup, so it can utilize my gears. I was doing about 4 MPH up that hill for most of it and I actually started to feel sorry for my hub motor at one point!

The drawback to a mid-drive for me, was always that I'd have to ditch my triple chainrings and run a single chainring - now that just scares me but at the same time, a mid-drive utilizes the gearing - but does that effectively give you lower gearing, or about the same? I have no idea because I've never tried a mid-drive eBike!

I mean lets say I have a hub motor on and use a 24t inner chainring with a 32t low sprocket on my cassette - that's 19.22 gear inches.
With a 42t chainring and 46t low sprocket on a mid-drive setup, that increases the lowest gear to 23.40 gear inches. A gear increase of 21.75%.

In other words I guess it's like losing about 1.5 gears on the cassette. It's turning a 24x32t (hub) into a 24x26t (mid-drive).

What I am getting at then is, would 24x26t, or rather 42x46t... be considered a low gear on amid-drive setup? Can that get you up a hill with less effort required than if you had 24x32t on a 500W hub motor?

I'm just worried about having to ride the bike if there's no power, for whatever reason that might be. On a hub it's not even anything I think or worry about. On a mid-drive, the gears simply have to be higher due to the need for a single chainring, it's a bit of a deal breaker for me, but at the same time I don't like stressing my hub motor on these 20% gradients I want to climb!

I wish there was some sort of calculator to tell me, I mean where you'd just put in a bunch of gears on a single chainring for hub and mid-drive, put the Watts in for each motor, then it could tell you the Watts required to go at X speed up X gradient, or just show you that one needs whatever percentage more effort compared to the other.

I can't even fit a mid-drive because of my press-fit bottom bracket shell... and I'd have to buy all the 11-speed stuff again to end up with that 46t huge low sprocket, but if it's so much better for hills than my hub, it's worth doing it.

SRAM used to make the solution for your problem, their DualDrive. It was a cassette with 8,9 or 10 sprockets, coupled with a three speed gear hub, the latter replacing the triple chainrings up front. Sadly they discontinued them several years ago:

 

[Nealh]

The dual drive was far form maintenance free and at times rather troublesome it also was the achilles heel for the Swizzbee that also used the dual drive.

 

[AndyBike]

The drawback to a mid-drive for me, was always that I'd have to ditch my triple chainrings and run a single chainring - now that just scares me

The vast majority of non E MTB's only use a single ring.

We have triple ring cranksets and multiple cogs to make it easier to turn the pedals on hills etc. But with a powered motor doing the most of the work, you dont need so many gears.

 

[flecc]

The dual drive was far form maintenance free and at times rather troublesome it also was the achilles heel for the Swizzbee that also used the dual drive.

They still have their fans and that 3 speed hub was the most efficient of all the three speed hubs. The concept is ok and there is a demand, it just needs someone to design a cassette hub gear that is both tough and slick changing. It shouldn't be that difficult, it is only two gears after all, the middle gear being just direct drive.
.

 

[Manc44]

The vast majority of non E MTB's only use a single ring.

We have triple ring cranksets and multiple cogs to make it easier to turn the pedals on hills etc. But with a powered motor doing the most of the work, you dont need so many gears.

I agree with that but I have gone up 20% inclines with my hub motor, using a 24t chainring and 32t low sprocket and although it was manageable, I was only just managing, it was hard to balance because it was hard to pedal fast on that sort of gradient even in that gear. It's 19.22 gear inches on my setup.

I guess hills like that are so rare (on the road) and so short when they do pop up, it is probably pointless swapping to a mid-drive. For me anyway, because I'd need a different bike frame and an 11-speed setup that would cost too much to justify doing it.

The gear range can be made acceptable though, with a single chainring - something like a 40t chainring with a 46t low sprocket would give me 22.29 gear inches. Still not the 19.22" I have now (even a 36t chainring won't get it that low) but probably close enough to it. That 3" difference with a 42t chainring is like one gear on a MTB cassette so it would be like having a 28t low sprocket instead of 32t. Factoring in that the mid-drive is pushing in that gear, I just thought maybe it would be a lot easier to pedal on a mid-drive, up a 20% gradient. If it's not "a lot easier" then it's a bit pointless swapping to one.

Certain things always end up putting me off a mid-drive (apart from the cost), it's the need for a gear shift sensor as well. I'm probably just going to stick with my hub after all this!

 

[sjpt]

I agree with that but I have gone up 20% inclines with my hub motor, using a 24t chainring and 32t low sprocket and although it was manageable, I was only just managing, it was hard to balance because it was hard to pedal fast on that sort of gradient even in that gear. It's 19.22 gear inches on my setup.

By the time you are going that slowly a hub motor will be at very low efficiency, much of the effort will be yours. The more effort you put in the faster you will go, which will also bring the motor efficiency and power up.

 

[AndyBike]

I agree with that but I have gone up 20% inclines with my hub motor, using a 24t chainring and 32t low sprocket and although it was manageable, I was only just managing, it was hard to balance because it was hard to pedal fast on that sort of gradient even in that gear. It's 19.22 gear inches on my setup.

Thats with a motor. Sorry but maybe a bit more effort on your part is needed in a higher gear. I've often been up Gardner st in Glasgow on the bike and thats the non Ebike.

One of the main probs ive also found is when you are using the lowest of the low is speed affecting your balance, and its sometimes better to go higher ,which does mean more effort, but you move a bit faster and can retain your balance easier.

I've often fantasized what it would be like if we removed all the cars, and blocked the side roads to Gardner st so i could bomb down it.

Of course, you would need more than mechanical disc brakes at the bottom of that run

Gardner St. It's a belter. Legs like jelly at the top lol.

 

[Manc44]

I worked out the above street is 14.56%

The toughest one near me is "Apple Street" on Werneth Low, although it's very short, it's just ridiculous.

The toughest one was Winnats Pass...

All stills from my videos

 

[flecc]

Try these, 20% and 25% in parts: