Bafang crank arms are crap

JRA

Well-Known Member
It is not just the initial tightening down of the bolts (both sides) to spec that is the problem. It is riding the bike for a bit and the not re-tightening down the bolts as the aluminum crank arms need to seat themselves on the steel bb spindle taper. They will loosen enough to take more tightening with just a test ride around the block. I even recommend a third effort after a few good rides as you will get even more. Once the crank is seated it will stay there but still a good idea to check it once in awhile. Because once they come loose the taper interface is basically ruined and the crank will need to be replaced.

This isn't just a Bafang problem but ALL square taper systems require this treatment. Also I would suggest that you keep an eye on the actual motor mount nut, for lack of a better term, that secures the system to the bb. It will also come loose and as it isn't on a taper will continue to do so over time and keeping an eye on it is a good thing to put in your normal maintenance program.
 

rich c

Well-Known Member
A little grease on the taper, and on the pedals when you thread them in helps. But the cheap alloys are soft enough that as JRA says, you have to constantly check the bolt and pedals to make sure they are tight. An eBike is heavier than a standard bike, and that also adds to the load on the crank arms.
 

Dewey

Well-Known Member
Nursing the bike home tonight was an education, the retaining screw kept coming undone every 100 yards so I had to ride pushing only the right pedal. I stopped into a Trek shop to be told they had a square taper left crank arm but incredibly the Bafang crank arm has the hole at a 45 degree angle in a diamond shape rather than square on, why the change? Thankfully I got home by stopping and tightening the screw every now and then, ordered two crank arms and new retaining screws from California ebike.
 

Sage Oz

New Member
I'm having a difficult time sourcing some higher end ISIS crank arms to fit my Ultra unit, especially as I'm trying to find 160mm or at most 165mm arms. Best I've found online are the RaceFace aeffect arms which should fit but everywhere is out of stock. Miranda is another possibility but hard to source here in the USA. Seems like there is a small need for bafang upgrades, especially in the Americas as the European market is a couple years ahead in the ebike popularity and sales availability. Strange why Bafang would choose to make the main drive and display so nice but yet crank arms are an obvious cheap quality cast and other parts like the thumb throttle are such chintzy plastic. Anyone have a source for such crank arms or nice thumb throttles?
 

Pegasus

Active Member
A friend I cycle with has a Bafang system and has had a crank arm come loose on two occasions. I think the answer is to tighten them on a regular basis as it does seem the aluminum arm allows for expansion on the square taper - hence looseness. I now check mine weekly.
 

Thomas Jaszewski

Well-Known Member
7 BBSxx bikes, and 14 crank arms. Never a problem. Thaks just my personal bikes. I've sold scores of kits and typically it's user failure. This is an issue with kits. N00bs to building make simple mistakes and the manufacturer gets the blame.
Use a bit of Loctite blue and recheck the torque. This is what a professional LBS would do, or should. Admittedly they are soft aluminum, but proper torque will avoid any failure.
 

Sage Oz

New Member
I'm just surprised that in the world of something as mass produced as bicycles are, that completely obsolete tech standards are still being used. I get that square arms are cheaper to manufacture than the much better and yet still outdated ISIS standard(so unluckily named now) or any other newer spec, but both customer and manufacturers have to start striving for higher quality and longer lasting products even at base levels. Square taper should have been phased out completely for all new bikes way back in Y2K. Cheap things including bikes that prematurely end in landfills and cost twice that environmental impact just in the process of manufacturing are saccharine sweet.
 

Thomas Jaszewski

Well-Known Member
I put 9000 miles on my BaFang cranks and never had an issue. I just upgraded to a set of Lekkie off-set cranks... mostly for the looks and for the off-set.

https://imgur.com/a/3w6izz7 - Bike and Trailer
https://imgur.com/a/DKpcF0a
https://imgur.com/a/zXXlyuv
Check out 70 miles w/front panniers & trailer on Relive! https://www.relive.cc/view/g37290970278
they’re the typical $500-$700 dollar bike quality. Most problems come as a result of inexperience installing bike parts. Not torqued down correctly they loosen and the hardened steel crank eats the aluminum up. I have two 5 year old builds with original cranks. I support Lekkie products but am to cheap the fix what I’ve never broken
 

BBassett

Active Member
they’re the typical $500-$700 dollar bike quality. Most problems come as a result of inexperience installing bike parts. Not torqued down correctly they loosen and the hardened steel crank eats the aluminum up. I have two 5 year old builds with original cranks. I support Lekkie products but am to cheap the fix what I’ve never broken
Sometimes I want more than just the minimum.