Geared hub kit drag

Fordulike · Jun 8, 2017

Nothing2SeeHere said:
I commute with my bike and currently, the BBS mid drive kit I have seems to be well suited for that.

However, its a pretty draggy solution when riding without any assistance. This means I always end up riding with at least some assistance.

Is the same true of hub drive motors. i.e. with the battery removed and on flat ground, would it feel somewhat like a slightly heavier bike or more like a bike with the brakes partially rubbing all the time?

The way I see it, is that whilst, yes, hub motors and mid drives do have some extra resistance pedalling unpowered. If you are always riding a bike with assistance, then unpowered feels horribly treacle like. This is probably due to the fact, that the muscles that are normally used in the pedalling motion, just don't get built up enough.

brightonebikes · Jun 8, 2017

Resistance from the bbs motor at the cranks should be really quite minimal, zero at the wheel hubs obviously.
Try taking the chain off the chain ring and rotating the cranks alone. Only a marginal increase compared to an average standard bottom bracket, nothing to write home about.
If there is considerable resistance then it could be faulty or need lubricating?

Sent from my E5823 using Tapatalk

Fordulike · Jun 8, 2017

Nothing2SeeHere said:
The drag on the BBS is enough to be noticeable. Enough to decide to take another bike if I'm just nipping to the shops. Its most noticeable when you hit the limiter on the flat and that extra mph from 16 - 17mph requires a noticeable amount more effort.

Sounds like a geared hub is similar so I won't look to change. Mid drive is well suited to commuting for what I do at least. If only it was less wet here then friction drive might offer a better option for me. I had this idea of being able to use a lighter battery with less motor use but I admit I haven't thought out the peak power usage as I'd be using assistance mainly on the hills.

Thanks for the information.

You might be able to offset the peceived drag, by reprogramming the 'Keep Current' in the controller settings. You will need a programming cable, software and laptop/pc. This shouldn't technically change the legality of your bike, but will help with assistance at the 15.5mph cut-off level.

brightonebikes · Jun 8, 2017

Fordulike said:
You might be able to offset the peceived drag, by reprogramming the 'Keep Current' in the controller settings. You will need a programming cable, software and laptop/pc. This shouldn't technically change the legality of your bike, but will help with assistance at the 15.5mph cut-off level.

Also, you could try increasing the speed percentage in the lower assist (or for all assist) levels so that the selected Amp percentage of assistance will continue up to the 15.6mph mark?

Sent from my E5823 using Tapatalk

Deleted member 4366 · Jun 9, 2017

It's not drag. It's an illusion. You just lost 500w of help, so it's like you chucked out an anchor.

Contrary to popular belief, there is some drag from the BBSxx motors. You can feel it when you turn the motor without a chain on; however, it's not significant compared with the loss of power when you exceed the assistance limit.

harrys · Jun 9, 2017

I've got a BBS02 and when I pulled the chain off the gears, sure didn't feel like there was any more resistances from the pedals than any other bike. Maybe if we put a meter on it, it would measure higher.

It's probably like my geared hub motors. I know there's real drag because a regular hub will spin for a minute or more while geared hubs will go 10 seconds. But on the road, I can't feel any drag if I run PAS 0, which I often do to get exercise.

Deleted member 4366 · Jun 9, 2017

Hmm! Every one I tried turning the crank by hand with no chain on had quite a lot of resistance. You don't feel it when you're pedalling because it gets hidden in with the normal pedal effort to make the bike go. Did you actually test with the chain off?

harrys · Jun 10, 2017

No drag on my unit.

Deleted member 4366 · Jun 10, 2017

That's quite a lot of drag. Try spinning one on a bike without a motor to see the difference.

harrys · Jun 10, 2017

This is a tough audience, but I learned something, I tried it on my best (and only) non electric bike.

You were right. A normal bottom bracket does spin much better, but if I set the pedals even and place a coin on one of them, should the heavier side go down. Mine don't. Needs something heavier like a 18 mm socket. Bummer.

Well, it's still like geared hub motor drag. It's there, but comparatively small given the other power robbing factors like heavy tires or an old chain?

Fordulike · Jun 10, 2017

harrys said:
This is a tough audience, but I learned something, I tried it on my best (and only) non electric bike.

You were right. A normal bottom bracket does spin much better, but if I set the pedals even and place a coin on one of them, should the heavier side go down. Mine don't. Needs something heavier like a 18 mm socket. Bummer.

Well, it's still like geared hub motor drag. It's there, but comparatively small given the other power robbing factors like heavy tires or an old chain?

If you ever open up the final drive cover of a BBSxx, then you will see why this unit has some drag. When the pedals are rotating forwards, the large cog is still turning the smaller cog. Even though there is a one way bearing, which prevents the motor from turning also, grease and cog friction, inevitably take their toll on drag.

Deleted member 4366 · Jun 10, 2017

harrys said:
This is a tough audience, but I learned something, I tried it on my best (and only) non electric bike.

You were right. A normal bottom bracket does spin much better, but if I set the pedals even and place a coin on one of them, should the heavier side go down. Mine don't. Needs something heavier like a 18 mm socket. Bummer.

Well, it's still like geared hub motor drag. It's there, but comparatively small given the other power robbing factors like heavy tires or an old chain?

What do you mean by geared hub-motor drag? Here's Kirstin's motor. Where's the drag?

Motors like the Xiongda and Q-series have the clutch between the motor and hub, so that the motor is completely separated from the hub when free-wheeling and the only parts turning are the bearings, just like any bike wheel. Their drag is even less than that shown in the video. Hub-motor drag is just an illusion.

Benjahmin · Jun 10, 2017

Did the same test on my Ezee (now about 4000 miles old) same result. I must admit that, when the motor was new, it wasn't quite the same but it soon loosened up. That treacle feel is just because you've got used to having 20 year old legs again - then the power goes off

harrys · Jun 11, 2017

Go spin a regular wheel up to 25 mph and see how long it spins. And the end with the air valve will wind up on the bottom, if allowed to spin free.

To be serious, I laced up two new Q100H motors this Spring and there's a little drag there. Shove the wheel and it spins only 5-10 seconds. I doubt anyone but a roadie in lycra can feel that. The Q100H's were new though. I got a 500W geared motor that spins about 20 seconds with a shove.

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Geared hub kit drag

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