bbs02 - what size chainring for my commuter?

[Ariane]

Hi Kim,

If you have pull the trigger 42 T is really a great choice this way you get more torque, less heat issues (like me) and may be a little loss in top speed overall I think is the better choice for a BBS02.

Ariane

 

[kim319]

Hi Kim,

If you have pull the trigger 42 T is great choice this way you get more torque, less heat issues (like me) and may be a little loss in top speed overall I think is the better choice for a BBS02.

Ariane

ok thanks you!

I'm not exactly sure how fast I ride currently because I never got a bike computer but I'm pretty sure I chug along somewhere between 10-12mph on avg. Prob 15-18mph max speed when i am peddling hard.
(estimates based on what i remember when i had a road bike + computer like 10 years ago)

I think I will be more than happy being able to comfortably ride at 15-20mph.
I guess I have the BBSHD+new bike to look forward to in the next 2-3 years

 

[Balmorhea]

would these "cotterless cranks" be compatible with the bbs02?
and would i just buy 2 of either? (there is no left or right specific crank?)
https://www.unicycle.com/united-black-cotterless-cranks-140mm/
https://www.unicycle.com/united-cotterless-cranks-150mm/

Those are the kind of cranks I’m talking about. They come in pairs, and they are right and left specific because right and left pedals have different mounting threads.

 

[2old]

IMO, you made a good choice with the cranks since they resolve the 10-15mm offset difference between the right and left crank arms and their respective chainstays. Also, the throttle was useful to me when road riding to "make a light" or when I needed to respond quickly to a situation. Initially I used the 46 tooth Bafang with an 11-34 cassette and didn't have any problem on hills. Also, would check the motor and it never got hot even when the outside temperature was 90-95 degrees. Be careful of the bottom bracket (BB) downtube interface since some newer systems make the motor hang down like a cow's udder. Also, you need to be careful if the BB is 73mm, since you wont be able to use the "jam" nut to secure the motor to the frame, but some have had success with Locktite; I changed frames.

 

[Balmorhea]

IMO, you made a good choice with the cranks since they resolve the 10-15mm offset difference between the right and left crank arms and their respective chainstays.

Your feet will do that by themselves if you have adequately large pedals.

 

[kim319]

would these "cotterless cranks" be compatible with the bbs02?
and would i just buy 2 of either? (there is no left or right specific crank?)
https://www.unicycle.com/united-black-cotterless-cranks-140mm/
https://www.unicycle.com/united-cotterless-cranks-150mm/

Those are the kind of cranks I’m talking about. They come in pairs, and they are right and left specific because right and left pedals have different mounting threads.

lol im so glad i asked and you answered. i totally thought they were for just 1 crank and i would have bought 2 sets.

 

[2old]

IMO, you made a good choice with the cranks since they resolve the 10-15mm offset difference between the right and left crank arms and their respective chainstays.

Your feet will do that by themselves if you have adequately large pedals.

There are individuals who have stated that their biomechanics couldn't adjust to the offset. I didn't seem to have a problem, but for me, it was a no-brainer.

 

[kim319]

IMO, you made a good choice with the cranks since they resolve the 10-15mm offset difference between the right and left crank arms and their respective chainstays. Also, the throttle was useful to me when road riding to "make a light" or when I needed to respond quickly to a situation. Initially I used the 46 tooth Bafang with an 11-34 cassette and didn't have any problem on hills. Also, would check the motor and it never got hot even when the outside temperature was 90-95 degrees. Be careful of the bottom bracket (BB) downtube interface since some newer systems make the motor hang down like a cow's udder. Also, you need to be careful if the BB is 73mm, since you wont be able to use the "jam" nut to secure the motor to the frame, but some have had success with Locktite; I changed frames.

I measured my BB and it is 68mm and the raleigh website lists the spec for the redux 1 to be 68mm.

You said "initially i used the 46 tooth bafang..."
are you saying sometime later down the line you made a change to your chainring selection?

 

[2old]

IMO, you made a good choice with the cranks since they resolve the 10-15mm offset difference between the right and left crank arms and their respective chainstays. Also, the throttle was useful to me when road riding to "make a light" or when I needed to respond quickly to a situation. Initially I used the 46 tooth Bafang with an 11-34 cassette and didn't have any problem on hills. Also, would check the motor and it never got hot even when the outside temperature was 90-95 degrees. Be careful of the bottom bracket (BB) downtube interface since some newer systems make the motor hang down like a cow's udder. Also, you need to be careful if the BB is 73mm, since you wont be able to use the "jam" nut to secure the motor to the frame, but some have had success with Locktite; I changed frames.

I measured my BB and it is 68mm and the raleigh website lists the spec for the redux 1 to be 68mm.

You said "initially i used the 46 tooth bafang..."
are you saying sometime later down the line you made a change to your chainring selection?

Yes, but only because I started using the bike off road only, and didn't care about top speed.
Great IMO that your bike has a 68mm BB. Use a good tool to cinch the retainer nut and lock ring and get them as tight as possible (I found that a Hozan Lockring "wrench" worked great to secure the nut and a Shimano BB tool for the "jam" nut). Be aware that you may need to space out the plate that helps position the motor in the frame and make sure you install it with the "proper side in". Also, cinch the nuts on the crank arms well and maybe check them after a couple of rides. PITA (and maybe permanent damage) if they become loose. I always put a little (very thin film) of grease where there is metal to metal contact (including screws before tightening), but others may disagree.

 

[1boris]

46t on 29" works fine for me in hilly Norway.11-34 casette and 107 kg rider.42t would be to high cadence for me

 

[tln]

I'd choose the BBSHD if I were planning another bike, for the torque. That helps you get off the line at traffic lights and for a modest 2lbs is more future proof. The BBSHD bikes I've borrowed have been more fun.

It would help get a higher speed too. Tbh that raleigh doesn't look like a bike I'd want to go 30mph on, especially on Chicago streets.

You can game the max pas speed on the display by using a smaller wheel size. If you choose one that is 1.6 times smaller (about 18" for a 27.5" tire) then switch to km/h the number will show your mom.

https://electricbike.com/forum/forum/knowledge-base/motors-and-kits/bbshd/8464-bafang-display-programming-instructions-and-manuals

 

[tln]

Lol, I meant "show your mph", not "show your mom".

Everyone has already seen your mom.

(Couldn't resist, sorry)

 

[kim319]

It would help get a higher speed too. Tbh that raleigh doesn't look like a bike I'd want to go 30mph on, especially on Chicago streets.

Ya this was one of the main reasons why I decided to go with the BBS02 over the BBSHD for my first foray into ebikes.

Figured I could get the BBSHD+new bike in the future if I liked my experience with the BBS02.

 

[tln]

It would help get a higher speed too. Tbh that raleigh doesn't look like a bike I'd want to go 30mph on, especially on Chicago streets.

Ya this was one of the main reasons why I decided to go with the BBS02 over the BBSHD for my first foray into ebikes.

Figured I could get the BBSHD+new bike in the future if I liked my experience with the BBS02.

I'm sure you will I think the choice of 46 vs 42 will be more about

a) whether it fits (chainstays flare out and larger front cogs will foul)
b) whether your chain stays on

rather than top speed

 

[kcuf]

smaller chainring always better bbsxx

until chain line becomes too severe

42t and up chainrings usually clear housing

moves chain more inward

and helps reach bigger rear cogs

20-25mph is comfy zone for bbsxx

my front 42t rear 36t bbshd

climbs until loses traction

also use short crank arms

nice when cornering

helps contribute to relatively fast moving chainring

 

[karlInSanDiego]

Hi Kim, what did you decide on? My full suspension BBS02 750W ebike with 46T stock and 11T in the rear was great for commuting and my standard pedaling mildly hard speed was 30mph. I did burn a couple of controllers when I went too high with Amp settings, but the problem isn't having too high of gearing, but as you pointed out, starting out in middle gears to help allow legs/motor to get going without lugging motor. Just like a car/motorcycle, you must force yourself to downshift (but before stopping). I would have used 52T if it'd fit my bike. Then I would have been able to use my whole rear cog. I almost never use my lowest gears (24T & 28T). Now I'm going to try the BBS-02 750W with 52T on a Greenspeed GLR trike.

 

[kim319]

Hi Kim, what did you decide on? My full suspension BBS02 750W ebike with 46T stock and 11T in the rear was great for commuting and my standard pedaling mildly hard speed was 30mph. I did burn a couple of controllers when I went too high with Amp settings, but the problem isn't having too high of gearing, but as you pointed out, starting out in middle gears to help allow legs/motor to get going without lugging motor. Just like a car/motorcycle, you must force yourself to downshift (but before stopping). I would have used 52T if it'd fit my bike. Then I would have been able to use my whole rear cog. I almost never use my lowest gears (24T & 28T). Now I'm going to try the BBS-02 750W with 52T on a Greenspeed GLR trike.

I ended up returning the lekkie bling ring 42t (+$100) and the lekkie buzz bars (+$100)
and bought the 44t, 48t, 52t chainrings from bafangusadirect.com (-$73 shipped for all 3)
and bought the 114mm and 140mm cranks from unicycle.com (-$48.40 shipped for both pairs)

After doing a quick test of the 44t, 46t, 48t, 52t stock bafang chainrings, I've settled on the 44t chainring for now.
May go back up to the 46t in the future because I did notice a dip in top speed, but I did also notice the corresponding increase in torque which is why I settled for now on the 44t.

average extended cruising speeds while jamming throttle and medium pedaling in 11t gear on:
44t ~30mph
46t ~35mph
48t/52t ~37mph

average burst top speeds while jamming throttle and hard pedaling in 11t gear on:
44t ~ 35mph
46t ~ 40mph
48t/52t ~ 42mph

I would definitely rule out the 52t on my bike setup. Did not notice any benefit over the 48t. Only thing it seemed to do was increase power draw, lower torque, motor ran much hotter, with no increase in speed over the 48t. The only reason I can think of to ever try out the 52t again would be if I switched the bbs02 over to a much lighter and nimble road bike.

I do not regret purchasing all 3 extra chainrings, thought it was a steal at $73 just for the fun I had experimenting.
Even the 52t I can imagine using in the future with a lighter bike so no regrets even with that one.
Also shipping for bafangusadirect is a flat $25 no matter if you buy 1 chainring or 3. the chainrings themselves are just $16 each.

The 114mm cranks were a joke lol. Completely unusable on my bike. But I love the 140mm cranks, felt very weird for the first 10 minutes, but I adjusted very quickly and noticed many benefits over the stock 170mm cranks. The main benefit I noticed was a smoother pedaling experience with less variance in the side to side rocking motion of my hips. Especially when pedaling hard out of the saddle. Also I liked the additional ground clearance and the fact that I could raise my seatpost a bit higher. I'm pretty sure these benefits I noticed disappear for anyone much taller than I am (5' 5" with shoes). I wish I had purchased 140mm and 150mm instead of the useless 114mm cranks lol.

 

[tomjasz]

We've seen a number of fried BBS02 motors with 52T rings. It's very easy to overheat a BBS02 if not actively shifting.

 

[Balmorhea]

I think using the 11t sprocket with a mid drive is a mistake. It's too destructive to the chain (which then transfers its wear to the other sprockets).

I consider 13t to be a practical minimum size sprocket for a mid drive system. It's gonna tear your stuff up eventually anyway, but you don't have to help it do that.

 

[kim319]

I think using the 11t sprocket with a mid drive is a mistake. It's too destructive to the chain (which then transfers its wear to the other sprockets).

I consider 13t to be a practical minimum size sprocket for a mid drive system. It's gonna tear your stuff up eventually anyway, but you don't have to help it do that.

I rarely ride in the 11t gear. dont know what the next gears down are but I ride in the 6/8 and 7/8 gears 90% of the time. I ride with the 11t gear only when I am already going 30+mph on big streets and want to go faster to keep up with traffic.

I always shift back down to the 6/8 gearwhen coming to a stop at red lights.

 

[Balmorhea]

I think using the 11t sprocket with a mid drive is a mistake. It's too destructive to the chain (which then transfers its wear to the other sprockets).

I rarely ride in the 11t gear. dont know what the next gears down are but I ride in the 6/8 and 7/8 gears 90% of the time. I ride with the 11t gear only when I am already going 30+mph on big streets and want to go faster to keep up with traffic.

That makes more sense. Because you only specified the 11t in your test results, that's what I thought you were using generally.

You'd be surprised how many folks with MTBs and hybrids ride around in the 24/11 gear at all times. It makes me want to slap their mothers.

 

[kim319]

That makes more sense. Because you only specified the 11t in your test results, that's what I thought you were using generally.

You'd be surprised how many folks with MTBs and hybrids ride around in the 24/11 gear at all times. It makes me want to slap their mothers.

lol, I can feel and hear the difference in the motor speed when it is straining vs not. I find it actively unpleasant to ride in the highest gear when going under 30mph. it just feels so inefficiant and sluggish.

 

[karlInSanDiego]

Thanks for the extensive report back, Kim. Most people aren't interested in the high speed travel unless they are using the bike for utility on long open road travel. Then it becomes a big advantage. With most bikes you start hitting that aero wall, which is why I think many people say there is no reckoning with the 52T. Their argument is, that the motor will do better at higher RPM if you just let it do that, but there is a physical limitation to human cadence, so gearing at high speeds must still be conducive to pedal input. I commuted with my ebike 38 miles a day a few years ago, and giving up more than 2 hours a day to the commute was asking a lot, so every bit of speed when possible was welcomed. As bikes become less hobby/rec and more for utility for many, we'll want good solutions that aren't just flyweight e-motorcycles, but where we can contribute to the transport (al biet a smaller percentage) while we travel at greater rates of speed on appropriate roadsides.

In my case I'll be using 52T x 11T + 36% internal hub ratio gain, but driving a 20" tire. I think the best gearing probably barely makes use of your most extreme ends of your gearing. On my ebike, I was undergeared using 5-9 sprockets always, sprocket 4 for on-hill starts, and almost never gears 1-3, except ironically enough on the massive grade coming back the last two hundred yards into my neighborhood.

In fact, I once had a crappy accident starting at a light making a right hand turn after climbing a steep hill. I hadn't shifted to 4th gear (still in 2nd maybe), clipped in as I started, and the excessive torque of the 750W combined with extremely low gear and starting to lean the bike into a turn ended up in a clipped-in wheelie and subsequently eating shit while cars drove around my still clipped in hot mess. I cracked a rib.

 

[Michael B]

I'm using a 54T chain ring on my mid drive kit ebike. While I initially looked at the BBS02 in the end I discovered the TSDZ2 and went with that because of the BB torque sensing feature. I haven't fitted the throttle and just set the desired assist level when turning on and then let gear selection, pedal pressure and cadence do the rest. The doner bike is a Cannondale caadx cyclocross 46/36 at the front and 11-34 11 speed cassette. 175mm cranks I think.

I started by just fitting the 48V 500W kit as it came. Single 42T dished chain wheel. 170mm cranks. I'm 185cm tall, 84kg, 60 yo male and ride a cadence around 80rpm. Much faster is just too fast for me and the TSDZ2 assist drops away somewhere just higher than that. Anyway perfect chain alignment turned out to be 19/42 combo which is too slow for me on an ebike (23kph).

So needing to change some things I did the maths and settled on a cheap new flat aluminium 54T narrow wide chainring and swapped the cassette to an 11-40. New chain too. Right side 170mm Bafang crank to help with q factor. Now perfect chain line is 17-54 (33kph) right where I want to be. I make extensive use of the gears 31 to 13. Hardly use the 11 (down hill only at a lower cadence short duration). 35 and 40 are badly out of line and adjusted so I can't select them. My rear derailleur won't work with the 40 anyway. Spend a large percentage of time in 15/54 or 17/54.

I monitor the current via a bt bms and phone app on the home assembled 48V battery. Usually between 5 and 9 amps so very loosely somewhere between 220 and 450 watts depending on battery voltage at the time.

 

[spinningmagnets]

Since Chicago is pretty flat everywhere, you might consider the option of an Internally Geared Hub / IGH. I suspect you dont use many gears, so an affordable Nexus or Sturmey 3-speed might work well for this application.

I rarely ride in the winter snow, but if you occasionally do, an IGH has been reported to be less fussy, compared to a derailleur.

Many years ago, I spent an entire winter in the Chicago area...only once.