bbs02 - what size chainring for my commuter?

[kim319]

hi I am thinking of purchasing a bbs02 mid drive kit with a 52v battery for my bike and was wondering if anyone could give me some guidance on the chain ring selection.

my bike is an urban commuter bike (Raleigh redux 1) with
27.5" wheels
2 inch tires
1x8 drivetrain (front 40t, rear 11t-34t)
no suspension

I live in Chicago il which is pretty much completely flat.
I plan to ride exclusively in the street with traffic.
no plans to take it off road ever.
plan to use only in PAS mode and pretty much never touch the throttle.

I am leaning toward going with the 52t default bafang chainring for higher top speed.

but I've read some troubling posts about how going from a 46t to a 52t can lead to drastically increased power draw when paired with the bbs02 and also about how u can prematurely wear out the nylon gear.

for riding in the streets with zero hills which would u guys advise between 42t, 46t, 52t?. either lekkie bling ring or stock bafang?

also any rough guesses on the top speeds I could get in PAS only with 46t vs 52t?

thank you!

 

[Tommm]

Bafangs are irrelevant. Good as a frisbee. Not narrow wide, will drop your chain constantly. Lekkie 42t. I have it and the last 2-3 cogs have the same top speed (26" wheel and 31mph/50kph top speed hard pedalling+max assist, and 38mph/60kph sprinting+throttle). Going higher size will make even more of your cassette useless and hill climbing more difficult.
Not to mention the plastic gear will melt under high torque + heat. And big chainring = less rpm for same speed = higher torque required.


Also check if your bike will even fit a useless ring as huge. The chainstays will usually interfere.

 

[tomjasz]

52T is a controller burner if not a avid user of the appropriate gears.

 

[kim319]

hmmm I am trying to decided between a lekkie 42t vs a 46t

 

[MikeSSS]

Rpm based pas is just wrong. Torque pas is better but a BBSxx doesn't have it. Throttle is best, you add the assist that feels right. BBSxx controllers are now programmed incorrectly. Therefore, BBSxx is not a good choice.

 

[kim319]

Bafangs are irrelevant. Good as a frisbee. Not narrow wide, will drop your chain constantly. Lekkie 42t. I have it and the last 2-3 cogs have the same top speed (26" wheel and 31mph/50kph top speed hard pedalling+max assist, and 38mph/60kph sprinting+throttle). Going higher size will make even more of your cassette useless and hill climbing more difficult.
Not to mention the plastic gear will melt under high torque + heat. And big chainring = less rpm for same speed = higher torque required.

Hi Tommm thanks for the reply, but I have a couple of questions.

I am assuming when you say "... and the last 2-3 cogs have the same top speed..." that you mean you spin out while pedaling on all of your last 2-3 smallest cogs.

Correct me if I'm wrong but doesn't that mean going with a bigger chainring like a 46t or 52t would accentuate the differences between the 2-3 smallest cogs? and actually make more of them useful?
Everything I've read upto now has said that one of the reasons people go for the bigger chainring is that you can keep pedaling for longer before spinning out.

 

[kim319]

52T is a controller burner if not a avid user of the appropriate gears.

Hi tomjasz thanks for the reply.

If I was planning to diligently drop down to my lowest gear when coming to a stop and shifting through the correct gears at all times to try to maintain a high motor speed, could I go with the 52t and not worry about burning out the nylon gear? (also keep in mind there are zero hills in my area)

Or do you think even in that scenario a 52t would still be more likely to result in the nylon gear needing to be replaced vs a smaller 46t or 42t chainring?

 

[tomjasz]

52T is a controller burner if not a avid user of the appropriate gears.

Hi tomjasz thanks for the reply.

If I was planning to diligently drop down to my lowest gear when coming to a stop and shifting through the correct gears at all times to try to maintain a high motor speed, could I go with the 52t and not worry about burning out the nylon gear? (also keep in mind there are zero hills in my area)

Or do you think even in that scenario a 52t would still be more likely to result in the nylon gear needing to be replaced vs a smaller 46t or 42t chainring?

It has nothing to do with the nylon gear. A long overthought and non existent problem. Replacement gears are the worst selling aftermarket part. It’s mostly blather.

IMNSHO Fried and overheated controllers are more likely. Latest B versions are an improvement with better FETs.

 

[kim319]

It has nothing to do with the nylon gear. A long overthought and non existent problem. Replacement gears are the worst selling aftermarket part. It’s mostly blather.

IMNSHO Fried and overheated controllers are more likely. Latest B versions are an improvement with better FETs.

I see, so is it your opinion that a no matter how careful I was with shifting, I would be at risk of frying my controller if I went with the 52t vs a 42/46t ?

 

[Tommm]

What I mean since you are already power limited at 42t front 14t rear while doing 25-28mph, while still having 13 12 11t cogs unused, it doesn't make sense to have a 52t which would result in you having 16 14 13 12 11 cogs unused for the same reason. You won't go further or faster. You could have a 100t at front, the motor will not have more power or heat dissipation ability to change your top/cruising speed.

Hi Tommm thanks for the reply, but I have a couple of questions.

I am assuming when you say "... and the last 2-3 cogs have the same top speed..." that you mean you spin out while pedaling on all of your last 2-3 smallest cogs.

Correct me if I'm wrong but doesn't that mean going with a bigger chainring like a 46t or 52t would accentuate the differences between the 2-3 smallest cogs? and actually make more of them useful?
Everything I've read upto now has said that one of the reasons people go for the bigger chainring is that you can keep pedaling for longer before spinning out.

I suggest you check out bikecalc.
http://bikecalc-staging.herokuapp.com/speed_at_cadence
90 rpm cadence is the norm now and for top speed runs you can do 110.

Oh, and forget using the bafang as a motorbike. It will cook above 700w continuous (22mph), if you want to go faster you will be pedalling, moderately hard. In general if you are hoping to go at speeds which would spin out a 42t the motor simply isn't up for it. This is the reason luna sell their x1 with a 34t front.

I have already met steep grass hill sides with a 42t front 34t rear that the motor couldn't climb, and I am a light guy. With 52t front you will have a hot running motor with a bunch of useless tiny rear cogs and big rear cogs that aren't big enough to climb off road.

 

[kim319]

I suggest you check out bikecalc.
http://bikecalc-staging.herokuapp.com/speed_at_cadence
90 rpm cadence is the norm now and for top speed runs you can do 110.

Oh, and forget using the bafang as a motorbike. It will cook above 700w continuous (22mph), if you want to go faster you will be pedalling, moderately hard. In general if you are hoping to go at speeds which would spin out a 42t the motor simply isn't up for it. This is the reason luna sell their x1 with a 34t front.

I have already met steep grass hill sides with a 42t front 34t rear that the motor couldn't climb, and I am a light guy. With 52t front you will have a hot running motor with a bunch of useless tiny rear cogs and big rear cogs that aren't big enough to climb off road.

oh wow thanks again for the detailed reply, i really appreciate the numbers you provided and the bikecalc website.

i had been under the impression that a 42t front + 34t rear was small enough to handle any hills.
(i am also relatively light, 5'4" 150lbs)

i have been waffling back and forth on whether to go with the 42t or 46t lekkie, and honestly been leaning toward the 46t.
you have convinced me i should def go with the 42t.

Thank you!

ps
do you have any experience with the BBSHD?
now i am wondering if it might be worth it to spend another $200 and go up to the BBSHD.
oh and i have zero experience with ebikes so far. never even test rode one.
would you suggest just going with the bbs02 for my first conversion and upgrade to the bbshd later down the line?
would your recommendation on the chainring change if i was using a BBSHD?

 

[Tommm]

I suggest you check out bikecalc.
http://bikecalc-staging.herokuapp.com/speed_at_cadence
90 rpm cadence is the norm now and for top speed runs you can do 110.

Oh, and forget using the bafang as a motorbike. It will cook above 700w continuous (22mph), if you want to go faster you will be pedalling, moderately hard. In general if you are hoping to go at speeds which would spin out a 42t the motor simply isn't up for it. This is the reason luna sell their x1 with a 34t front.

I have already met steep grass hill sides with a 42t front 34t rear that the motor couldn't climb, and I am a light guy. With 52t front you will have a hot running motor with a bunch of useless tiny rear cogs and big rear cogs that aren't big enough to climb off road.

oh wow thanks again for the detailed reply, i really appreciate the numbers you provided and the bikecalc website.

i had been under the impression that a 42t front + 34t rear was small enough to handle any hills.
(i am also relatively light, 5'4" 150lbs)

i have been waffling back and forth on whether to go with the 42t or 46t lekkie, and honestly been leaning toward the 46t.
you have convinced me i should def go with the 42t.

Thank you!

ps
do you have any experience with the BBSHD?
now i am wondering if it might be worth it to spend another $200 and go up to the BBSHD.
oh and i have zero experience with ebikes so far. never even test rode one.
would you suggest just going with the bbs02 for my first conversion and upgrade to the bbshd later down the line?
would your recommendation on the chainring change if i was using a BBSHD?

If you mean hills on roads, it does them easily. I meant hills in forests, that are difficult to walk up.

Bbs02 is 25a, bbshd is 30a, some reports of newest ones being 28a. Pointless. It is just bigger and heavier. Better to go 52v instead of 48v and having cells that don't sag (get battery made with cells that handle 8a+ discharge).

If you want a step up in power get a 72v battery and get the gng upgraded cyclone
https://www.gngebike.com/gng-2019-3000w

 

[Balmorhea]

Bafangs are irrelevant. Good as a frisbee.

Bafang rings are made of steel, so they wear longer than aluminum rings in most environments. They have correct offset for non-Boost MTBs and most utility bikes. And they are very cost effective.

Narrow-wide tooth geometry is fashionable at the moment, but it’s a pretty janky and expensive way to do chain retention. Without a clutched derailleur to go with it, it doesn’t even help that much. DH type chain retention guides, cut-down front derailleurs, or even “jump stop” inside guides in combination with the stock Bafang outside guard, are all more positive ways of keeping the chain in place, and much less expensive than relying on CNC machined narrow-wide rings.

If you seek function and not vanity, there isn’t a good argument to be made for aftermarket rings on Bafang BBSxx systems.

 

[Tommm]

Yea you will need some chain guide, modern bikes don't always have a mount for it, but they do have clutched derailleurs.
Without a chain guide, one pothole throws your chain while on throttle, your carbon bike will have a deep gash in the chainstay.

 

[Balmorhea]

Yea you will need some chain guide, modern bikes don't always have a mount for it, but they do have clutched derailleurs.
Without a chain guide, one pothole throws your chain while on throttle, your carbon bike will have a deep gash in the chainstay.

“Function without vanity” doesn’t really leave room for carbon e-bikes. But yes, some kind of chain retention is key for single-ring bikes, regardless of frame material.

I’ve been doing single ring bikes for almost 30 years now, when “one-by” meant a 12-38 Suntour Winner Pro 7-speed freewheel and a Suntour V-GT derailleur that would’t crash into the big sprocket.

 

[kim319]

thanks everyone for your help.

the only options for the stock bafang chainring from lunacycle was the 46t and 52t.

so i ended up ordering the
-BBS02 kit with stock 46t
-52v Luna Wolf V2 Samsung 30q 12ah
-Lekkie Bling Ring 42t black
-Lekkie Buzz Bars (Offset Type) 160mm cranks

I am 5'4" tall and had always wondered if shorter cranks would feel more comfortable.
My current raleigh redux 1 has 170mm cranks.

 

[Tommm]

thanks everyone for your help.

the only options for the stock bafang chainring from lunacycle was the 46t and 52t.

so i ended up ordering the
-BBS02 kit with stock 46t
-52v Luna Wolf V2 Samsung 30q 12ah
-Lekkie Bling Ring 42t black
-Lekkie Buzz Bars (Offset Type) 160mm cranks

I am 5'4" tall and had always wondered if shorter cranks would feel more comfortable.
My current raleigh redux 1 has 170mm cranks.

I have 140mm cranks on my ebike, I can just about notice the difference compared to 170mm... you probably won't notice 160mm being different. Why offset type? Generally if you can go without offset it is preferable. Less change of smashing your leg/pedal into something.

 

[kim319]

I have 140mm cranks on my ebike, I can just about notice the difference compared to 170mm... you probably won't notice 160mm being different. Why offset type? Generally if you can go without offset it is preferable. Less change of smashing your leg/pedal into something.

oh wow you had to go from 170 to 140 to notice a significant difference? may i ask how tall you are?

is there a place i can get 140mm or 150mm cranks for under $100?

i dont really know much about ebikes or bikes in general.
from the marketing i had read i was lead to believe that the offset version fixed some q factor issue with the bss02 motors not being centered.

most of it kind of went over my head
and the lekkie cranks looked pretty.

 

[Tommm]

I have 140mm cranks on my ebike, I can just about notice the difference compared to 170mm... you probably won't notice 160mm being different. Why offset type? Generally if you can go without offset it is preferable. Less change of smashing your leg/pedal into something.

oh wow you had to go from 170 to 140 to notice a significant difference? may i ask how tall you are?

is there a place i can get 140mm or 150mm cranks for under $100?

i dont really know much about ebikes or bikes in general.
from the marketing i had read i was lead to believe that the offset version fixed some q factor issue with the bss02 motors not being centered.

most of it kind of went over my head
and the lekkie cranks looked pretty.

If both are offset cranks, they still won't be centered. I wouldn't bother myself.

Trials cranks. Most of them have a standard freewheel interface. Available in isis or square taper.

https://www.trial-bikes.com/en/bike-trials-cranks/

 

[Balmorhea]

I have 140mm cranks on my ebike, I can just about notice the difference compared to 170mm... you probably won't notice 160mm being different.

oh wow you had to go from 170 to 140 to notice a significant difference? may i ask how tall you are?

is there a place i can get 140mm or 150mm cranks for under $100?

I used 152mm unicycle cranks on my BBS02. I found I could maintain a higher pedal speed more easily, to keep pace with the motor an an efficient range. The cranks were steel (so less likely to work loose) and retailed for about $16/pair at that time. The unicycle cranks had negligible flare to them, which narrowed the distance between pedals.

It’s easy to get them in 140mm or 127mm as well.

 

[Ariane]

Hi Kim,

I own a BBS02 at 52 Volt with a 52 T Chainring, if you plan to use it with traffic a BBSHD is better in every way, in term of torque and power and probably speed too. Any hard tail bike without suspension at 30 Mph is not cool and not fun to use it just my opinion. I just bought a dual suspension frame to fit my BBS02 on this bike to get more comfort at high speed. I plan to buy a BBHD with a Grin Phaserunner in the future to run this bike at 72 Volt or so.

As for the chainring a 52 T is too much for this motor 46 T is better like many have said, good day!

Ariane

 

[kim319]

Hi Kim,

I own a BBS02 at 52 Volt with a 52 Chainring, if you plan to use it with traffic a BBSHD is better in every way, in term of torque and power and probably speed too. Any an hard tail bike without suspension at 30 Mph is not cool and not fun to use it just my opinion. I just bought a dual suspension frame to fit my BBS02 on this bike to get more comfort at high speed. I plan to buy a BBHD with a Grin Phasrunner in ther future to run this bike at 72 Volt or so.

Good day!
Ariane

Ariane thanks for the reply, I have definitely been wondering what the limits of comfortable riding speed on a bike with no suspension are.

-When riding on paved streets how fast can you go before thing get uncomfortable? 20mph? 25mph?
-Did you have any issues running a 52t chain ring on your bike with the bbs02?
-Were u using a road bike or an urban commuter bike like mine?

 

[kim319]

I used 152mm unicycle cranks on my BBS02. I found I could maintain a higher pedal speed more easily, to keep pace with the motor an an efficient range. The cranks were steel (so less likely to work loose) and retailed for about $16/pair at that time. The unicycle cranks had negligible flare to them, which narrowed the distance between pedals.

It’s easy to get them in 140mm or 127mm as well.

oh nice thanks for the lead.

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/

 

[Ariane]

Hi,

-When riding on paved streets how fast can you go before thing get uncomfortable? 20mph? 25mph?
20 Mph and over

-Did you have any issues running a 52t chainring on your bike with the bbs02?
No but i use an Shimano HD chain and many gear on this cassette are used even if i didn't ride allot with my bike and the motor is very hot and the controller too after any ride. A 46 T chainring gives you more torque and if have to do it again i will choose this setup.

-Were u using a road bike or an urban commuter bike like mine?
Its a cheap cross trail bike (CCM Krossport) with a cheap fork, I have change wheelset, cassette
with 700C x 38 tires I have changed the cassette for specific Shimano HG and now I used a DNM USD6 Fork.

Ariane

 

[kim319]

-Did you have any issues running a 52t chainring on your bike with the bbs02?
No but i use an Shimano HD chain and many gear on this cassette are used even if i didn't ride allot with my bike and the motor is very hot and the controller too after any ride. A 46 T chainring gives you more torque and if have to do it again i will choose this setup.

Ariane

if given the choice between 42t vs 46t, you would opt for the 46t? or would you be fine with either option?
(just asking cuz i already pulled the trigger and bought the 42t)