Geared rear hub build questions (EBIKELING VS GRIN)

[Benoksanen]

Sorry for the long question. I've read a ton here and really appreciate it.

About me. I recently bought a used Ride1up Roadster, and really like it for a lot of reasons. Quiet, light, smooth, simple, and no noticeable resistance when not e-powered. I bike a ton and love pedaling hard, and this sure lets you do that. I weigh about 185 and love to team up with the electric assist to go fast. I am really looking for a workout, but would like a fair amount of help on standby if needed of my off/long days. I intend to use it as a commuter 15 miles each way with about 1100 feet of elevation, and think it (or I) might not be up to the task for a few reasons.
- 36V by 7Ahr battery is a bit too small. Big long climbs really drain the battery. It would have NO chance making it home if I forgot to charge it at work.
- single speed belt drive limits my speed (at times I want a heavier gear to go over 25 mph that I get when pedaling really fast) and climbing ability (hard to make it up STEEP hills even with full assist - and I am standing and jamming).
- though the Shengyi motor is very quiet and smooth ... it may be a tad underpowered up steep hills, especially when I'm actively conserving battery power while riding. It states 350W 40nM.
- the aluminum frame has almost no compliance, man is it a rigid ride. Here in the Northeast bumps and holes really translate through to my back, especially if hit by surprise. The bike is very twitchy and steep.

So I'm planning on building an ebike using a conversion kit to address these issues. I will be using a 1987 Specialized Rockhopper frame that I put flared drop handllebars on ... chromoly frame and fork. This bike is built up nicely for $250 all in, so trying to keep costs down. With wider tires and steel frame, it feels a lot more comfy to me.

I'm considering three options. Will bold my questions below.

1. Get a range extender battery for the existing Ride1up bike. It would be $375 for an additional 36Vx7 Ahr water bottle type battery. This leaves me with a rough ride and no spare ebike for tooling around on.
2. Add a rear hub conversion kit to the 87 Rockhopper. Two I am considering that are ready to ride (includes built up rear wheel and hub):
- Grin Technologies Shengyi SX2 geared rear hub with a 36V14.5 Ahr battery. I believe this is about the same motor that the Ride1up has, just a battery that is twice as big. All was looking good until I added up all of the parts including shipping ... $1431. I read a lot of good stuff about them, but I don't understand the technology and value.
- Ebikeling 36V 500W geared rear hub conversion kit with a 36V 20Ahr battery for mid $800s shipped. THIS IS THE CURRENT PLAN.

My questions:

1. DOES THE EBIKELING REAR GEARED HUB PEDAL SMOOTHLY, QUIETLY, AND WITHOUT RESISTANCE? This is very important to me, as that is a major part of the fun for me, and the Ride1up Roadster/Shengyi motor does a great job of this.

2. WILL THE EBIKELING MOTOR BE MORE POWERFUL/AS POWERFUL AS THE SHENGYI THAT I'M USING NOW? SHENGYI SAYS 350W & 40NM, EBIKELING SAYS 500W AND 40NM.

3. IS THE EBIKELING OPTION LIKELY TO BE AS RELIABLE AS THE GRIN TECHNOLOGIES/SHENGYI OPTION? I'M CONCERNED ABOUT MOTOR, BATTERY, AND WHATEVER THE HECK ELSE CONTROLS THEM.

4. IS THERE SOME OTHER OPTION THAT I SHOULD CONSIDER?

If it matters, I've ridden both mid drive (Bosch on a Niner eGravel bike and Specialized Vado) and rear hub (Ride1up uses a Shengyi motor). Though the mid drives were awesome, I found the rear hub to be a bit quieter and lighter, and I suspect easier to maintain for me. I like the idea of the motor not putting force through my drivetrain.

Thanks for feedback.

Ben

 

[2Dicebikes]

I can only respond to #3 based on experience. Grin is the best I've come across, custom build most of their products in N America, have excellent customer service, intelligent with electrical engineers on staff. They know their s**t. They are more expensive but worth it.

 

["A"]

If you're spending $1400 to convert a Rockhopper.. you might as well spend a few hundred more and get a complete ebike.
750 W rear geared hub motor with 95Nm of torque

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electrek.co

 

[m@Robertson]

Since the original question was posted last August, I am guessing he already went ahead and tried to solve his problem on his own.

For whoever comes around next, there is a root issue that has been missed: @Benoksanen has noted he has little power on the Ride1Up and has a major issue getting up one of the grades he has to climb regularly. This is a common issue with hub drives. Geared hubs are better than direct drive hub motors, but he is good enough to tell us the 40Nm torque output of the motors in current use and under consideration. And... 40Nm is a pretty low number. And it doesn't get any better with the Grin so he would gain nothing over his current ride in terms of added assist. If you want better hill climbing ability you need a motor with better torque output.

Unfortunately even the baddest of the bad geared hubs (fat motors giving up to 85 Nm) have this issue. You can't make it go away as a hub motor is single-speed. It powers thru the hub and ignores the gears. The hub motor hates life going up a hill just like you would if you try riding up a hill with a single-speed bike.

The solution is a mid drive. Mid drives have higher torque output, and they can magnify the usability of that output because they can use the gears just like the rider can. If you build it smart - which many do not do - you will not have additional wear and tear issues.

For a basic bike with no frills, a low-cost BBS02 is going to provide 120 Nm of torque. Go a little avante garde and an even less expensive Tongsheng TSDZ2 is going to give you 80 Nm, and that 80 Nm can be run thru the gears.

If you skip the hills, or keep them low and rolling, hub motors are in their element. Throw in hills and - especially if you already know hub motors struggle in hills from personal experience - its time to use the right tool for the job, and thats a mid drive motor.