Bafang bbs02 does not work with 73mm bb

lukesjr

1 mW
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Sep 25, 2020
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I install the bbs02, and while it technically fits it doesn't not really fit. The crank arms are way offset. I even put on a 18 mm offset left arm crank and the left is still 15mm closer to the chain stay then the right side.

15mm is quite a bit offset when you arre clipped in and riding. I searched the internet and don't really see much discussion about this. People talk about lekkie bars but that is only 18mm offset and would still leave an imbalance of 15mm. I really think its not even great for the 68mm. Even with an offset bar on a 68mm bb you still would be left with around 6mm difference left to right.

Any thoughts on this?
 
That's how it is. BBSHD is even worse, if that helps.

If you use regular flat pedals instead of clipless or toe clips, your feet will work out the difference as much as they need to.

Lekkie Buzz Bars cranks are asymmetrical to compensate for the offset at the bottom bracket. But that means your feet will be even wider apart than necessary.
 
Why doesn't someone make a 30 mm offset left crank arm? Seems like that would fix the situation pretty easily.
 
lukesjr said:
Why doesn't someone make a 30 mm offset left crank arm? Seems like that would fix the situation pretty easily.

Putting your feet wider apart isn't fixing the situation. It may appeal to your desire for symmetry, but for most people narrower is better.

You can use a very "square" low-offset unicycle crank arm on the right, and that would help reduce the asymmetry and the excessive tread width at the same time. Or you can use them on both sides, keeping the asymmetry but narrowing tread significantly.
 
Balmorhea said:
lukesjr said:
Why doesn't someone make a 30 mm offset left crank arm? Seems like that would fix the situation pretty easily.

Putting your feet wider apart isn't fixing the situation. It may appeal to your desire for symmetry, but for most people narrower is better.

You can use a very "square" low-offset unicycle crank arm on the right, and that would help reduce the asymmetry and the excessive tread width at the same time. Or you can use them on both sides, keeping the asymmetry but narrowing tread significantly.

Wider apart is better than poor symmetry. Fatbikes generally run wider q factor which you can deal with, but unequal symmetry can really mess with your riding, seat pain, knee, and most importantly hip pain.
 
lukesjr said:
Balmorhea said:
Putting your feet wider apart isn't fixing the situation. It may appeal to your desire for symmetry, but for most people narrower is better.

You can use a very "square" low-offset unicycle crank arm on the right, and that would help reduce the asymmetry and the excessive tread width at the same time. Or you can use them on both sides, keeping the asymmetry but narrowing tread significantly.

Wider apart is better than poor symmetry. Fatbikes generally run wider q factor which you can deal with, but unequal symmetry can really mess with your riding, seat pain, knee, and most importantly hip pain.

That's the opposite of what cyclists have determined over generations. Your feet don't know where the frame center is; they refer only to the seat and pedals. If that implies a centerline that isn't quite plumb to the bike, big deal-- the bike probably isn't plumb to anything else at any given time. But if your pedals are father apart than your feet want to be, then potentially you can get problems. Some folks are more sensitive to this than others.

https://en.m.wikipedia.org/wiki/Q_factor_(bicycles)

And like I said earlier, if you use flat pedals without clips, your feet will work out the difference if they need to. Most people's bodies aren't as symmetrical as you'd think, anyway.
 
I don't disagree that flat pedals can fix it, but if you want to clip in I disagree. I can definitely feel the offset when I pedal with clips. It feels almost like pedaling with my body rotated.

In thinking about it, it really is mind boggling that they didn't just set this up properly at the factory. They could have just added 30mm more axle length (plus housing) to the left side. Quite frankly I am shocked more people aren't bothered.

Maybe the type of riders that would be bothered by it buy already built bikes from trek or such with it properly centered and spaced.

Seriously though, a 30 mm offset crank would fix this simply.
 
Are you sure you haven't got a 100mm model? In my observation, these things run offset to the right, not the left.
 
no mine was the 68/73mm model.

the crank is way closer on the left chain stay then on the right. It is about 30mm closer to the left chainstay then the right.
 
lukesjr said:
no mine was the 68/73mm model.

the crank is way closer on the left chain stay then on the right. It is about 30mm closer to the left chainstay then the right.

Gotcha. When you wrote this, it implied the opposite:

They could have just added 30mm more axle length (plus housing) to the right side.

I am a bit perplexed why they furnish arms with a lot of offset, rather than low offset arms, or one of each.
 
lukesjr said:
I don't disagree that flat pedals can fix it, but if you want to clip in I disagree. I can definitely feel the offset when I pedal with clips. It feels almost like pedaling with my body rotated.

In thinking about it, it really is mind boggling that they didn't just set this up properly at the factory. They could have just added 30mm more axle length (plus housing) to the left side. Quite frankly I am shocked more people aren't bothered.

Maybe the type of riders that would be bothered by it buy already built bikes from trek or such with it properly centered and spaced.

Seriously though, a 30 mm offset crank would fix this simply.

How does Bafang anticipate the wide variety of frame geometries? Some frames are just not easy to kit. In 4 years of BBSxx suport I've had a handful of bikes that were just not good candidates for a BBSxx series motor. I have 3 BBSxx kits with 73MM BB. No problem. Well except that ther's insufficient space for both lockrings.
 
tomjasz said:
lukesjr said:
I don't disagree that flat pedals can fix it, but if you want to clip in I disagree. I can definitely feel the offset when I pedal with clips. It feels almost like pedaling with my body rotated.

In thinking about it, it really is mind boggling that they didn't just set this up properly at the factory. They could have just added 30mm more axle length (plus housing) to the left side. Quite frankly I am shocked more people aren't bothered.

Maybe the type of riders that would be bothered by it buy already built bikes from trek or such with it properly centered and spaced.

Seriously though, a 30 mm offset crank would fix this simply.

How does Bafang anticipate the wide variety of frame geometries? Some frames are just not easy to kit. In 4 years of BBSxx suport I've had a handful of bikes that were just not good candidates for a BBSxx series motor. I have 3 BBSxx kits with 73MM BB. No problem. Well except that ther's insufficient space for both lockrings.

This doesn't make sense. The frame has nothing to do with the crank offset. The bbs02 is manufactured such that it is shifted to the right by 30mm.
 
FME with two different MTB's, a 2000 GT Zaskar and an inexpensive steel frame (Nashbar) with 68 mm BB, Lekkie cranks resolved the difference between the crank arms and chainstay (which was about 15 mm before the Lekkie cranks were installed). I tried an aluminum frame with 73 mm BB, but didn't use the system since there wasn't enough room for the jam nut.
 
Sure of course you're right. It has nothing to do with frame geometry. ARGH!
 
tomjasz said:
Sure of course you're right. It has nothing to do with frame geometry. ARGH!

I wasn't trying to be rude. But you could just measure from the center of the motor out and see that motor is shifted to the right about 30 mm on a 73mm BB. On a 68 mm BB it is shifted 25 mm to the right. That is what I meant by it has nothing to do with frame geometry. No matter what the frame is, it has either a 68 or 73 mm. Now, unless the BB on the frame is not centered, which is not the normal frame, it wouldn't matter about the geometry.
 
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