February 29, 2024

For years I’ve been anxiously waiting for someone to pull together and mass-produce steel gears to replace crappy nylon gears in the BBSHD. Mad scientists at Lunacycle designed and machined a replacement steel gear for $42 here. The gear is slightly smaller than the nylon gear it replaces and was pre-lubricated with the quietest lube they could find. This post explains all the reasons I hate nylon gears (they fail), and why this steel gear is a must-have option for anyone running a BBSHD at the limit of its capabilities. If you’re rocking a Ludicrous 60 amp controller or plowing through deep snow every time you spread peanut butter on your nylon gear, do yourself a favor and buy this replacement gear instead of the nylon gear.

You can see that the steel gears are slightly shorter, which greatly reduces weight and noise

The original nylon gears were the weak point of the BBS02 and BBSHD drive units. I understand why Bafang chose to use nylon gears, as it is the point of failure on the drive unit, and if there are serious heat or stress issues, the nylon gears are more likely to fail than the motor to be damaged. Best of all, nylon gears are also much quieter than steel gears.

The original nylon gear weighed 98 grams, so adding a steel gear would add about 70 grams

Lunacycle sent me an early steel cog to test, it was much heavier at 340 grams and it worked great. They decided that the gears were too big, and not only reduced the size, but also reduced the large amount of steel inside the gears, which was unnecessary. This extra effort shaves 175 grams off the gear, effectively halving the weight. The gears are also much quieter since there is less metal in contact with the motor. These steel gears can be noisy when you first put them in, but they quickly become quiet as the gears “break in”. The steel gear also comes in a plastic bag filled with grease (be careful not to get the grease inside the gear where the bearing clutch is).

This shows the weight of the gear with grease and a foam plug protecting the bearing clutch (the claimed weight of the gear alone is 165 grams)

The installation of the nylon gear is relatively simple, and the controller and motor need to be removed. While you can do this with the BBSHD on the bike, I find it much more difficult to do so, and I recommend pulling the motor off the bike to replace that gear. For complete instructions on replacing the nylon gears on the BBSHD, you can refer to this old article. I’ve replaced about 5 nylon gears on the BBSHD over the past 4 years, and 3 nylon gears on the BBS02, but I’ve also beaten my drive in deep snow. Even with all this experience, it still takes me about 40 minutes to change a gear, and I often strip the insulation off the motor wires when pulling the motor out. I’ve found that simply putting heat shrink tubing over the phase wire where the insulation is torn is the easiest way to fix the torn insulation.

I’m currently testing the rig and will post any updates to this article if I run into issues. It’s slightly louder than the nylon gears, but I expect, like my M600 with the steel gears, to quieten down after the first 100 miles or so.

Here you can see the original prototype of the steel gear, it’s full size, the one you get will be much smaller

This steel gear has been in use for years and I can’t wait to try it out. I find it crazy that it took this long to bring this product to market because there seems to be a huge demand for them. I bet a BBSHD with steel gears could easily make 100 amps peak without self-destructing, it’s about time someone devised a more Ludicrous controller that would put the 60 A Ludicrous controller to shame.

Maybe we can play grid.


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