Hubs...current "State of Art" and Hill Climbing....

[NoDTMF]

I'm curious now with the "state of art" of hubs. I have a Bosch Active line mid drive. It is geared with 11-40 rear cog. I can not make it up some very steep slippery gravel hill climbs. Two reasons: I get tired, or it is so steep that I hit a rock bounce the front wheel sideways and then basically lose balance (not enough forward momentum)

I imported one of my rides into Strava which calculates grades and it claims a portion of the climb at 25%! I definitely was pushing up that! I would say the grade exceeds 20% for very short periods of time and can be 15-18% for a ways. Really the only way to make those is with speed to carry you through it.

Here is the Strava page:
https://www.strava.com/activities/596271115
Click on the graph and move the mouse around, and it display Stats at any given point.


So, my question: Would a throttled plus peddle assist hub make it? Basically can one keep the speed up?
I would like to try a higher power mid drive as well. BTW, I also worry about range...that ride above uses up most of the battery on the Active motor. Be nice if there was a switch to engage regenerative braking...I tend to go way too fast down hill, just to make sure the brakes survive.

BTW I have yet to see any other bike on the trail trying to go up. Occasionally, I see some guys coming down. I think I will go to the bottom one day and just watch to see how others get up.

 

[flymeaway]

"state of art" of hubs

I think you risk overheating the controller and/or motor. I'm assuming when you are riding up that steep grade the rear wheel is turning very slowly? If that's the case you will be placing maximum energy into a very slow turning geared hub, not really the best situation.

Court J.

 

[Nirmala]

I wonder if one of the "all wheel drive" models with two hub motors would work. It would give you more traction. Or you could add a front hub motor to your mid drive bike.

 

[Cameron Newland]

I'm curious now with the "state of art" of hubs. I have a Bosch Active line mid drive. It is geared with 11-40 rear cog. I can not make it up some very steep slippery gravel hill climbs. Two reasons: I get tired, or it is so steep that I hit a rock bounce the front wheel sideways and then basically lose balance (not enough forward momentum)

I imported one of my rides into Strava which calculates grades and it claims a portion of the climb at 25%! I definitely was pushing up that! I would say the grade exceeds 20% for very short periods of time and can be 15-18% for a ways. Really the only way to make those is with speed to carry you through it.

Here is the Strava page:
https://www.strava.com/activities/596271115
Click on the graph and move the mouse around, and it display Stats at any given point.


So, my question: Would a throttled plus peddle assist hub make it? Basically can one keep the speed up?
I would like to try a higher power mid drive as well. BTW, I also worry about range...that ride above uses up most of the battery on the Active motor. Be nice if there was a switch to engage regenerative braking...I tend to go way too fast down hill, just to make sure the brakes survive.

BTW I have yet to see any other bike on the trail trying to go up. Occasionally, I see some guys coming down. I think I will go to the bottom one day and just watch to see how others get up.

A geared rear hub motor might make it up the hill, but the ideal solution is to use a mid-drive with >70nm of torque. The Bosch CX/Performance line, the Bafang Max/BBS02/BBSHD or the Yamaha mid-drive would be your best bets.

I've ridden a 500W direct drive hub motor for a year and a half and it's good on slight to moderate hills, but it has a lot of trouble climbing steep hills (>15% grades) and often gets bogged down due to a lack of torque and because it's far from its optimum RPM range when traveling at low speeds. Now I've got a full suspension mountain bike with a mid-drive (Bafang BBSHD with 200nm of torque) and it's a much better climber.

The only advantages that hub motors have over mid-drives when climbing hills is that hub motors don't cut motor power when shifting. Here's a video that shows a Stromer ST2 with a hub motor beating a mid-drive Kalkhoff on a hill:

The Stromer's motor power peaks around 1200W, whereas the Kalkhoff would be lucky to hit 550W at peak, so this isn't exactly a fair comparison, but it does illustrate the benefit of having uninterrupted power under shifting.

 

[NoDTMF]

@Cameron Newland Way cool video.

I really like my bike, be cool if I could just upgrade the motor, but Bosch won't let me.

@Nirmala I think the front hub is interesting, but the front tire gets very light, but maybe with good balance one could get some traction. But where to put the hub battery?

 

[MLB]

My dual hubbed Big Bud climbed a very steep hill that my Haibike couldn't, but just barely, not a huge difference. That's a 350w hub motor in back and a 250w motor in front, both geared hubs. The hill was steep enough that the front wheel was coming up on each pedal stroke even with the weight of the motor in the front.
Mid drives use the gearing which lets them multiply with gearing, but they are usually the smallest and weakest motors compared to hubs.

 

[Hugh Jardon]

Not all hub-motors are born equal. The average 250w hub-motored ebikes sold in Europe would struggle to climb as well as a Bosch, but there's plenty of others that would blitz it. The 500w geared ones like the Bafang BPM and CST or the 500w MAC can run at 48v and 25A or more, which is double the power of the Bosch and I would say close to double the torque, depending on the Bosch gearing.

If the question is more about traction than brute climbing power, then for off-road slippery surfaces, 2WD works very well., especially on difficult surfaces like snow and wet grass. Two small 250w motors can get you up 30% hills with a bit of pedalling.

The important thing with hub-motors is the KV (maximum RPM). If you choose one that's too fast, it's efficiency will suffer at low speed, which will make it heat up. For 25% climbs, you need one with a maximum RPM around 200 to 230. On the flat, it'll max out at about 20 mph. You can use a faster motor, say 260 rpm as long as the hills aren't too long.

There's also the Xiongda 2-speed hub-motor that can change down into a lower gear for climbing using a double clutch and reversing its internal direction. The 36v version has similar power and torque to a Bosch, but the 48v one has more climbing power. It can manage 30% climbs with steady pedalling.

These are still generalisations.

Here's my off-road 2WD bike:

 

[NoDTMF]

Thanks for the info. I take it there is one battery for both motors?
How do you control the front hub? Is it independent from the rear hub? Perhaps I should read more about 2wd ... Any links?

 

[MLB]

Yes one battery. You can run front only, rear only, Both all the time or Eco (my choice) which starts out with the larger 350w rear motor and then as speed rises it switches to the smaller and faster spinning front hub motor that is more efficient at higher speeds. It's pretty neat and the full time 2wd (with limited slip!) is nigh on amazing for offroad.

 

[EddieJ]

Perhaps I should read more about 2wd ... Any links?

If you are going to be riding off road, then I would suggest sticking to crank drive.

• Work on physical fitness. (with no disrespect intended )
• Work on riding skills, and in the case of rocky climbs such as below, use the light front end to your advantage. A light front end makes even manualling up the steepest rocky climb less of an effort, and you soon learn to use balance to steer the bike in the right direction, along with using the rear end to guide the bike. (once again no disrespect is intended with the skills comment. )
• Another very important factor is bike geometry and set up. I all to often see people shortening stems, raising bars, saddles too low etc, in fact everything opposite to what they should be doing to make climbing easier. Gearing and tyre choice is also very important.

It's good to see that you have stats to back up your rides, as just saying that something was hard or steep is just pointless. Admittedly it is a shame that you don't have the extra toque of either a Performance line or CX motor, but I wouldn't get hung up over it, as I was frequently cursing the torque level on some of the recent rides, as it was working against me.

To put hill climbing claims into perspective, here are some of the continuous climb length and elevation gain over the last two weeks of riding. Note that I have said continuous climb length, and not ride length.

• 6.3 miles of climbing with 4,214ft of elevation gain.
• 10.5 miles of climbing with 3,712ft of elevation gain.
• 10.4 miles of climbing with 6,428ft of elevation gain.
• 6.3 miles of climbing with 3,136ft of elevation gain.
• 6.3 miles of climbing with 4,295ft of elevation gain.
• 9 miles of climbing with 5,349ft of elevation gain.
• 9.6 miles of climbing with 4,975ft of elevation gain.
• 13 miles of climbing with 6,430ft of elevation gain.

Two examples. Steepest percentage grade detailed




Ride conditions, which as you can see, are pretty technical and difficult.

 

[MLB]

Wow, wow WOW. Too cool. You're a lucky guy.
Flat as a pancake where I live.

 

[NoDTMF]

Thanks for the input. Cool trip. Btw, I'm afraid you'll need to ride back to the top and retake the picture of the sign post, can't read it

 

[EddieJ]

Thanks.

I booked next trip before heading off home again, so I'll be sure to get another photo upon my return.

I will need to buy a new camera though before the trip, as it went missing yesterday on the way back through France.

 

[ATXBill]

A geared rear hub motor might make it up the hill, but the ideal solution is to use a mid-drive with >70nm of torque. The Bosch CX/Performance line, the Bafang Max/BBS02/BBSHD or the Yamaha mid-drive would be your best bets.

I've ridden a 500W direct drive hub motor for a year and a half and it's good on slight to moderate hills, but it has a lot of trouble climbing steep hills (>15% grades) and often gets bogged down due to a lack of torque and because it's far from its optimum RPM range when traveling at low speeds. Now I've got a full suspension mountain bike with a mid-drive (Bafang BBSHD with 200nm of torque) and it's a much better climber.

The only advantages that hub motors have over mid-drives when climbing hills is that hub motors don't cut motor power when shifting. Here's a video that shows a Stromer ST2 with a hub motor beating a mid-drive Kalkhoff on a hill:

The Stromer's motor power peaks around 1200W, whereas the Kalkhoff would be lucky to hit 550W at peak, so this isn't exactly a fair comparison, but it does illustrate the benefit of having uninterrupted power under shifting.

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Nice video. I also live in Austin and have abiding respect for Jester (the Molester) Hill. I noticed your Heart Rate got up there quite a bit (180)...how much assist were you getting from the motor in terms of percentage? With over 400w rider output and your HR that high, I'd suspect you were getting nominal assist. I ask b/c I'm torn between a mid-drive (BBSHD or BBS02) vs. a hub drive. I have a couple of blown vertebral discs, so climbing is excruciatingly painful now...thus I need some help from Mr. Tesla. Any thoughts here?