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How do I size the proper mid-drive for off road use?

Posted: Oct 15 2020 10:56am
by geosped
So I'm not new to e-bikes. I built a really cool off road mountain bike that I used for years. BMC Rear hub on 50v made well over 1000w and had plenty of power. Actually with all the weight including the battery on the rear tire it was very sketchy at times. All I do is just ride for fun and exercise off road on mountain bike trails. So I want a new mid-drive but how do I size the right one?

1) Strictly off road mountain biking trails.
2) 250lbs
3) Trails are I ride have some really steep sections with lots of big thick roots. Not uncommon where I have to get off and walk around it.
4) lots of tight single track with lots of switch backs. Very slow and challenging especially when going up hill.

I'm using a 26" full suspension bike. Now the big question is how much power do I need? There are several great mid drives out there. All of the commercial hard core mountain bikes ($3500) and up seem to use a much lower power system and much smaller batteries that what I'm seeing. Tenshong and Bfang offer 500w 750w 1000w on 48v and 750w 1200w 1500w on 52v batteries respectively. Assuming the controller is setup to take the higher voltage batteries. So how do I make sure I get a system strong enough to carry me up the hill with out burning anything out and at the same time not too powerful where it's dangerous? Do I really need 1500w to get me up a steep hill?

Thoughts and suggestions.

Green bike is what I used to ride. This hub motor easily made 1200w but like I said it was very sketchy the way I had the battery pack mounted. Not ideal at all. In the end I burned out the halls sensors and decided to go in another direction.

Blue bike is the new donor bike. Just need help in deciding to go to the 750w 48v - 1200w 52v BBS02 option OR should I go with the BBSHD 1000w 48v - 1500w 52v option?

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 15 2020 11:31am
by Wolfeman
geosped wrote:
Oct 15 2020 10:56am

Blue bike is the new donor bike. Just need help in deciding to go to the 750w 48v - 1200w 52v BBSH02 option OR should I go with the BBSHD 1000w 48v - 1500w 52v option?
Good morning. I have 2 bikes with BBS02 drives from Luna Cycle that max out at 1.3kW and I love them both. That being said, my next MTB build will be a BBSHD just for extra durability. I think the HD gives you more room to grow/hotrod later on. Put on a 36T Lekkie chainring with a good battery and you will not be disappointed. Mid-drives are really fun.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 15 2020 1:07pm
by markz
BBSHD is the better choice. How many gears are on the rear (8,9,10,11,12 speed?) of those two bicycles?

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 15 2020 1:20pm
by MikeSSS
Battery location: My FS bike is much like the green bike, uses a rear MAC motor with 52v, 20ah, 14s, 8p battery.

Battery in the bag made it hard to handle when stopped or riding uphill, especially in tricky conditions.

I moved the battery to the left side of the mid frame tubes, adjacent to where the battery would be if there was a center triangle to mount it in. Now the bike is much easier to handle when stopped or in slow climbing or tight stuff. I don't notice any problems from the weight offset to one side. I did use a pedal extension on the battery side.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 15 2020 1:45pm
by geosped
markz wrote:
Oct 15 2020 1:07pm
BBSHD is the better choice. How many gears are on the rear (8,9,10,11,12 speed?) of those two bicycles?
Both bikes have a 9sp cassette in the rear.

From what I've read the BBSHD is better than the BBS02 in several ways someone correct me here. 1) steel housing is bigger heavier better cooling 2) internals are beefier 3) motor handles a lot more power. 4) larger controller. 30a vs 25a

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 15 2020 7:09pm
by kcuf
bbshd = bbs03

somewhat more rugged

hd about 3lbs heavier than 02

hd motor seemingly less efficient windings


hd likely hold up better off roading


can be found in wider BB spacing too

fat tire bikes hmm

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 1:03am
by Balmorhea
The less power you have in a mid drive, the lower the gear ratios you'll need to deal with any given situation.

Conversely, the more power you have, the faster you can ride uphill or on difficult surfaces.

So it becomes less a question of how much power you need, and more about how fast do you want to go? (And how often do you want to break your toys?)

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 2:00am
by markz
Carry a spare chain or 2 just in case, the long walk home is a good time for pondering the ebike life.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 9:49am
by geosped
markz wrote:
Oct 16 2020 2:00am
Carry a spare chain or 2 just in case, the long walk home is a good time for pondering the ebike life.
I have a couple of chain links I carry in my back pack but wow your saying carry a whole chain? Has anyone waxed there chain? A couple of youtube video's on doing a DIY chain wax increases the durability and reduces a lot of the friction blah blah blah.... Just curious if this is a "thing" in the e-bike community seeing how much more stress we put on the bikes. The guy seemed very convincing. His video series was pretty cool. And was thinking about going through the trouble but I dont have an extra crock pot to spare lol.

Let me know if this is worth doing.

https://www.youtube.com/watch?v=HHr9znwpwmQ

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 9:55am
by geosped
I just noticed I created two identical topics. Man getting old sucks. lol sorry about the two threads which cover the same topic. If I could merge the two I would.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 10:24am
by kcuf
carry chain breaker and spare links + master

if when derailleur craps

or chain breaks

can usually rework chain

for limp mode


chain lube over rated

measure chain wear

replace $10-$15 chain showing minor wear

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 10:51am
by 2old
My BBS02 has survived five years of socal fairly hilly off road travel without a whimper, but I like to pedal and the BBSHD probably would be overkill. One thing you'll learn if riding tight switchbacks is how to pedal smoothly since you can't stop pedaling "going round the bend" or the power shuts off. Also, I carry a chainbreaker and extra link, but have never broken a chain in probably 500 outings. An eight-speed drivetrain is inexpensive and wears well. AFAIK, chains from eight-speed to at least eleven speed have the same inner width, and only the outer changes. Seems to me the thicker chain would wear less.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 12:34pm
by HrKlev
If you're building a bike for exercising and like pedaling, why not build something lightweight with proper torque sensing assistance to keep the bike feel?

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 16 2020 1:19pm
by markz
Because you all know a bicycles drive train, crank, chain, front der, rear der is designed and engineered for 10+ times human power
:oops:

Sarcasm

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 17 2020 12:37am
by Balmorhea
HrKlev wrote:
Oct 16 2020 12:34pm
If you're building a bike for exercising and like pedaling, why not build something lightweight with proper torque sensing assistance to keep the bike feel?
Until there's a reliable system for DIY torque sensing power assist, I'm going to recommend against that. It would be nice. What we actually have is either fussy, fragile, expensive, complicated to install torque sensing enhancements for the Cycle Analyst, or TSDZ2 which is a flaming bag of turds.

If you know of something better that's DIY friendly, please let us know.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 17 2020 2:15am
by HrKlev
Balmorhea wrote:
Oct 17 2020 12:37am

Until there's a reliable system for DIY torque sensing power assist, I'm going to recommend against that. It would be nice. What we actually have is either fussy, fragile, expensive, complicated to install torque sensing enhancements for the Cycle Analyst, or TSDZ2 which is a flaming bag of turds.

If you know of something better that's DIY friendly, please let us know.
I will have to agree for the most. There are solutions out there, but they are not in the bolt-on category. So it depends on how much fab work OP would be willing to do. For bolt-on, If I had the patience for it, I would wait and see how the first lightest.bike kits will perform. Having owned a couple tsdz2's myself, they are awesome when they work, but I would not recommend it because of all the flaws.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 17 2020 11:29am
by Balmorhea
I had not heard of lightest.bike systems. I hope they work out.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 17 2020 3:16pm
by markz
Balmorhea wrote:
Oct 17 2020 11:29am
I had not heard of lightest.bike systems. I hope they work out.
Can only hope they are truthful about their advertisement.

Re: How do I size the proper mid-drive for off road use?

Posted: Oct 17 2020 6:29pm
by geosped
I assume there is no way to add a torque sensor to the existing BBSHD and hooked up with some custom firmware or cycle analysis or someone would have mentioned it. Also I was strongly considering the tsdz2 at 52v but ultimately I decided against it as I didn't think it would be all that durable hauling my 250lbs up and down the hill. Curious what's wrong with it?

I put in my order last night for the BBSHD with a 52v 17.5ah thanks for all those peeps that contributed. :)

Re: How do I size the proper mid-drive for off road use?

Posted: Nov 08 2020 9:53am
by geosped
I got most everything setup. For off-road this is awesome. I can not advocate strong enough how well the gear sensor is working out. The small delay in the motor cutoff in switching gears is well worth it. I wasn't used to having to stop pedaling before switching gears. Now I don't have to worry about.

Also using the eggbeater display is great. The pedal assist and the way it's set up is more than adequate in helping to get up steep trails. I keep it around 4 and swap up or down. It really helps to know the trail so your more efficient but it works great.

My minor gripes about the BFANG BBSHD kit from EM3EV.
1) Triangle battery fits per template great but the battery pack they use SUCKS. It's also really big. It's like a totally generic bag. It would have been awesome if they put a small access port or zipper so you can QUICKLY access the charging port and or power button.
1a) There is no access port for the battery lead wires through the battery bag. You got to create a small hole in the bag to draw the wires out of. Not a big deal but still.
2) if your using the eggrider app you can't use the battery app at the same time. one of them crashes. The battery app on the EM3ev triangle pack via BT is very cool.
3) a better chainring and or options should be part of any kit BBSHD. I could not have used the stock chainring without using spacers and really messing with my chainline.
4) for off-road use the gear sensor should be included. Can't see using this kit off-road with out it your gonna brake shit or just really compromise how you ride.
5) the position of the charging port on the battery is in an awkward position and not easy to get too. Would be much better if it was easliy accessible when unzipping the bag.

Re: How do I size the proper mid-drive for off road use?

Posted: Nov 08 2020 2:30pm
by markz
How exactly does the EM3EV battery "pack they use SUCK" ?
Everyone seems to love their battery packs.

geosped wrote:
Nov 08 2020 9:53am
My minor gripes about the BFANG BBSHD kit from EM3EV.
1) Triangle battery fits per template great but the battery pack they use SUCKS. It's also really big. It's like a totally generic bag. It would have been awesome if they put a small access port or zipper so you can QUICKLY access the charging port and or power button.

Re: How do I size the proper mid-drive for off road use?

Posted: Nov 10 2020 3:14am
by rocwandrer
Something I didn't see mentioned anywhere, at least with the 860C, holding the minus button is context dependent. When not moving, it activates walking mode, but when moving it activates pause mode, which allows you to shift without power, and then regain power after releasing the button and pausing pedaling for a fraction of a second. Manual shift pausing for free.

Does the shift sensor require you to stop pedaling for a moment before it will restart after pausing? Is there a setting to adjust this behavior?