What is the best gearing set up for an E-bike?

[Cybersnow]

I am planning on building my wife an E-Bike this Spring. It will be powered by a BBSHD motor and now I am trying to decide on the crank and rear gear set. Riding will be primarily roads in a rural and very hilly area. There are a couple of very steep hills that are about 300 yards long so she will need a good low end and she loves to ride about 18 mph so a good high end is needed. Her typical cadence is around 70ish. Any idea in the optimum set up?

 

[indianajo]

You should measure "very steep". 7/8" rise on a 6" spirit level is 14.6%.
I traverse a very hilly area and I have available 24:32 to 52:11 . I never use the top end as I do not like to go over 28 mph, but sometimes, especially when the throttle is dead due to rain and I am carrying 60 lb groceries, I use the 24:32 up 14.6%. I have a hub drive, on front to maintain the triple front sprocket and 8 speed rear. My rear derailleur has gotten to where it only upshifts 500 yards after I push the trigger, so I leave the rear on speed 4 and shift the front down to 24 when I am climbing. Up to 42 on the flat. I have replaced everything but the sprockets, including slick stainless cable and lubricated jaguar housing, and it does not help. I notice a trek 7100 MTB has the housing interrupted in the middle to cut the friction. I do not have a battery in the winter, when it goes below freezing here.
Standard mid-drive sprocket is 46, with some internal down gearing. Unless your wife is very light and never carries cargo, I would suggest buying the 42 option. On road you probably will not need a rear sprocket bigger than 32. 11 is not strictly necessary, and may skip.

 

[Jeremy McCreary]

I am planning on building my wife an E-Bike this Spring. It will be powered by a BBSHD motor and now I am trying to decide on the crank and rear gear set. Riding will be primarily roads in a rural and very hilly area. There are a couple of very steep hills that are about 300 yards long so she will need a good low end and she loves to ride about 18 mph so a good high end is needed. Her typical cadence is around 70ish. Any idea in the optimum set up?

Have some tools that might help with this, but need more data.

Q1. Max gradient she'll need to climb?

Q2. Gross weight (bike + rider + cargo)?

Q3. Wheel diameter?

Q4. Her minimum comfortable balancing speed? (Mine's ~3.5 mph.)

Q5. Minimum cadence on hills and maximum cadence on flats or pedaled descents?

Q6. Strong or average pedaler?

Q7. Motor peak torque and mechanical power?

Q8. Will she have a throttle, and would she be willing to add some throttle to her uphill pedaling?

 

[SpinningGears]

Depends on budget really but.....sram xd hub, get the gx 10 52 cassette (shifters and deraileur will depend on budget). BBSHD chainring may be limited by chainstay clearance so check that. Also chainline may be an issue depending on bottom bracket size and OLD (rear hub spacing)

Really you need to start at the beginning - whats the donor bike? Budget?

 

[m@Robertson]

I am planning on building my wife an E-Bike this Spring. It will be powered by a BBSHD motor and now I am trying to decide on the crank and rear gear set. Riding will be primarily roads in a rural and very hilly area. There are a couple of very steep hills that are about 300 yards long so she will need a good low end and she loves to ride about 18 mph so a good high end is needed. Her typical cadence is around 70ish. Any idea in the optimum set up?

I build for that sort of thing all the time. Same cadence range too. That BBSHD pulling hard up hills is going to cause some specific stresses that you want to build for and deal with. I am going to do a Cliffs Notes version here and skip a lot of detail for the sake of covering everything in less than novella length.

The TL;DR is at the bottom with pretty pictures. I have the day off and am stuck in the house while it rains so you have to suffer thru me using this post to fill my time.

1. Don't try and gear your bike like you would an analog bike without a motor. Different rules apply. The trick is to build with those rules in mind, and bias the build and the motor settings to give someone who wants to pedal the ability to do so without the motor running away from them.
2. The standard-issue DIY front chainring recommendation is for a 42T ring. The very last thing you want to do is go with a big front chainring. All kinds of bad things happen when you try and do that on a bike that has to negotiate hills. With that said, the ring you choose is going to depend somewhat on chain alignment. I personally would recommend a Luna Eclipse chainring as it offers the maximum inboard offset (22.2mm) versus all alternatives, except the Lekkie Pro which I think by now is completely out of stock anyway. The Luna's deep offset is going to give you just enough extra offset to get to one more cog inboard than you would be able to reach otherwise, or it will give you the same cog with slightly less skew, which is crucial to avoid drivetrain wear.
3. Chain alignment and gear usability together make up an inexact science that varies by bike and by components chosen. NOBODY is going to be able to give you a correct answer for your bike out of the gate unless they hit it by luck. So... lower the cost of your learning experience so it is palatable. Use a cheap but quality chainring out of the gate to give yourself a real-world ballpark as to reality on your bike. A Gustavo 42T ring available on AliExpress is a $30 clone of the $150 Lekkie 42T ring, and provides an 18.8mm offset (ignore the advertised offset... its for-reals 18.8mm). This will give you a $30 test rather than a $150 test, and if it works, the Gustavo is actually a pretty good ring and you can leave it until it wears out.
4. Crankarms: I despise the cheap Bafang cast crankarms. But here again, you are experimenting. Just use the ones you get in the kit. They will have an offset of 18mm on the non drive side which is almost always needed to center the pedals under the rider. This centering-up will be a part of your build process for a rider who pedals. There are tricks to dialing this in including using two pedal washers on one side and none on the other to move the pedals 3mm to one side or the other, or go extreme with uneven pedal spacers. Here again once you actually build the thing you will know versus guessing. If you want to upgrade crankarms then Shimano sells the right square-taper config for reasonable pricing, Minerva sells some nice ones as well (neither have a non drive side offset and you will have to see if your bike can handle that). Lekkie sells the best ones with that offset to one side but they are priced high.
5. Derailleur and shifter: Most DIY builders will tell you that the motor reduces the need for having many gears, and if you throttle the bike this is true. If you pedal, then the need to dice up your cadence options is still there just like an analog bike. 9s-to-11s drivetrains can be perfectly robust if chosen for the job at hand vs. an analog bike's needs. Myself I most prefer 11s and my 11s bikes handle super heavy cargo loads (450 lbs total system weight) and I pedal up 16% grades without issue. If however you go 12s, thats where you start seeing people reporting snapped chains and taco'd chainrings (on singletrack, usually). I have used SRAM, Shimano, Box Components and more recently Microshift. If you had asked me 5 years ago if I would recommend Microshift I would have said Hell No. But for an ebike... even for 11s, they are splendid, surprisingly high quality and inexpensive. Probably the best clutches I have ever used, too.
6. Speaking of tacos and such, never, EVER use your smallest 11T cog if your rear cluster has one. Max chain skew coupled to minimal tooth engagement matched up to BBSHD power makes bad things happen. 11T cogs wear out real fast too. It is in fact a decent rule of thumb to figure the smallest cog isn't there and the biggest one is a glorified dork disc, also never to be used. This makes 11s even more attractive. You will see whether this is smart or not after you build the bike and get a good look at the hard chain skew at either end, which is an additional problem over and above what I already mentioned.
7. Rear cluster: Steel is real. Regardless of what speeds you choose, you want a monolithic cluster (the cogs are pinned together) so that force is distributed across your cassette body, which is going to be punished. You also want steel cogs for strength and durability. You can find strong steel clusters in sizes ranging from 8s to 11s although I recommend you stay away from 8s as its not a pedalers' choice. This link covers mid-drive-strong drivetrain parts across all gear choices (8s up to 11s). The Shimano Linkglide system is not one I recommend in that article and their rear cluster is probably the best 11s, and is the widest ranging, but its also double the cost of the almost-as-good alternative. Linkglide 11s chain works great for both 10s and 11s. Microshift hardened steel clusters range in price from $40 to $65 so that again benefits you when it comes to your first build and the guesswork that comes with that.
8. Rear hub: Not something you mentioned but its the next failure point. A steel cassette body is paramount or it gets dug into. Less so if the cluster is monolithic. If cassette body is steel, the next failure point are the pawls and the hub itself and there's no repairing a hub with that kind of failure. Just be aware of it for now and don't panic. If you have a problem, ratchet engagement hubs are the answer. The pinned-together cluster may make the difference between replacement and survivability if the hub itself holds up (and many do).

The Short Version: For the use you describe, three drivetrain versions on the same bike. For your first try I would do #1 below (buy the matching $35 Microshift shifter) and sub in a Gustavo ring and save a hundred bucks or so while you assess viability:

1. Most recent: 11s, Microshift 11s derailleur with clutch, SRAM GX shifter (re-used without issue from #2 below), Microshift H113 hardened steel 11-46T cluster, Shimano Linkglide 11s chain, Luna Eclipse chainring. The Eclipse biases the chain better to the big cogs for less skew. Big cog can be reached but on this short-stay bike, skew is too much to expect things to not break (you'll know it when you see it on yours). Chain is same as when I used the GX so its 2 links shorter than it could be.
   
   
2. Previous setup: All the same except SRAM GX derailleur and a Wolftooth Roadlink that, despite what the manual says, works great to get the 42T-max GX to function on a 46T cassette.
   
   
3. Original, ran for years: SRAM GX still, 52T Lekkie up front, Sunrace CSMS7 11-42T all-steel cluster. Flat land only with hardly any shifting and straight chainline was dead center in the cluster for a cadence of around 70 and top speed around 31-32. This is an example of what not to do if you have hills.
   
   
4. 9 speed, more money but has the hill climber 40T chainring up front. Box 2 XW derailleur, Box 1 shifter, Lekkie 40T front kit including a new motor cover to fit the small ring but keep the offset. Microshift Advent 11-48T steel cluster. I originally had a Box 2 12-51T cluster and replaced it as the Box clusters at that time were rebadged Sunrace and came in I think 4 parts. Not as strong. The new ones are stronger but pricey. This bike will pedal up pretty fast on the second-from-the-bottom cog despite the 40T ring.
   
   
5. Just in case you are thinking about smaller chainrings than 40T. Smaller rings lose the offset because they can't fit over the motor casing. The smaller rings are great but only for specific circumstances, partly because of that loss of chainline correction.
   
   
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[Gionnirocket]

Q4. Her minimum comfortable balancing speed? (Mine's ~3.5 mph.)

I'm sorry... But that's hysterical

 

[SpinningGears]

I'm sorry... But that's hysterical

Every specialized owner knows this data, it is absolutely vital to correctly guide DIY BBSHD builds.

Me personally, i trackstand; MTB101.

 

[Gionnirocket]

Every specialized owner knows this data, it is absolutely vital to correctly guide DIY BBSHD builds.

Me personally, i trackstand; MTB101.

Ohhh Specialized... Now that explains it.
As for vital.. my BBS* build came out just fine without that data point.
And it's still hysterical

 

[Cybersnow]

Thanks for all the great info. It is almost time to fire up the wood stove in the barn and start pulling the 7 year old BBS02 off the hardtail and start getting the bike ready for the new set up in March…If Luna’s shipment arrives on time.

 

[Gionnirocket]

Thanks for all the great info. It is almost time to fire up the wood stove in the barn and start pulling the 7 year old BBS02 off the hardtail and start getting the bike ready for the new set up in March…If Luna’s shipment arrives on time.

You may have more hills than me but I found the BBS02B very capable. From what I understand you can get the BBS02B a bit more refined than the HD due to the different firmware.
More important... make sure you're getting a UART motor or there won't be much end user programming.

 

[Cybersnow]

You may have more hills than me but I found the BBS02B very capable. From what I understand you can get the BBS02B a bit more refined than the HD due to the different firmware.
More important... make sure you're getting a UART motor or there won't be much end user programming.

I have the BBS02 on two other lighter bikes that we rode for about 4 years. I was tired of transporting bikes between houses so bought my wife a bike in Souther CA and she loved it so much that she bought a second one. The two BBS02 bikes are now bikes used by guests when they want to take a bike ride in the country or around one of the lakes in Idaho. We like to ride a lot on dirt/gravel roads that connect a number of villages (towns?) and the tires on the two road oriented bikes are too thin for the glacial sand in our area. Consequently I am planning on taking my hardtail MTB and powering it for her use.

 

[JoeDirt]

I am planning on building my wife an E-Bike this Spring. It will be powered by a BBSHD motor and now I am trying to decide on the crank and rear gear set. Riding will be primarily roads in a rural and very hilly area. There are a couple of very steep hills that are about 300 yards long so she will need a good low end and she loves to ride about 18 mph so a good high end is needed. Her typical cadence is around 70ish. Any idea in the optimum set up?

Spinning gears post, that says it all I would not burn your brain cells trying to figure out ratios everything is very variable. But a 10:52 covers everything from top to low.

Also you don't want to go anything deeper than a 10-speed. And of course your bottom bracket and your large ring in the front measured width.
Meaning you don't want a lot of chain Swing or in layman terms angle to your lowest gear. And of course your rear derailleur needs to be compatible with a 52. Just my two cents..