For years I’ve been anxiously awaiting someone getting their act together and mass-produce a steel gear to replace the crappy nylon gear in the BBSHD. The mad scientists at Lunacycle have designed and machined a replacement steel gear and are selling it for $42 here. This gear is slightly smaller than the nylon gear it replaces and comes pre-lubed with the quietest lube they could find. This article is about all the reasons I hate nylon gears (they fail) and why this steel gear is a must-have option for anyone who is running their BBSHD at the limits of its ability. If you are rocking a Ludicrous 60 amp controller or plowing through deep snow, whenever you get around to peanut buttering your nylon gear do yourself a favor and buy this replacement gear and not the nylon one.
The original nylon gear is a weak point in both the BBS02 and the BBSHD drive units. I understand why Bafang chose to use the nylon gear, since it is a failure point on the drive unit, if there is a serious issue with heat or stress it is much more likely that the nylon gear will fail rather than the motor getting destroyed. On top of that, the nylon gear is also much quieter than a steel gear would be.
Lunacycle sent me an earlier steel gear to test that was much heavier at 340g which worked well. They decided that the gear was just too big and machined down not only the size but also a good deal of the steel inside the gear which was unnecessary. This extra effort shaves a 175g of weight off the gear effectively cutting the weight in half. Since there is less metal in contact with the motor the gear is also quite a bit quieter. These steel gears can be noisy when you first put them in, but they get quieter quickly as the gears ‘break-in’. The steel gear also ships in a plastic bag full of grease (be careful not to get the grease inside the gear where the bearing clutch is).
The nylon gear installation is relatively straightforward and involves pulling off the controller and the motor. Although you can do this with the BBSHD on the bike, I feel that it is much tougher to do it that way and I recommend pulling the motor off the bike to replace this gear. For full instructions on replacing the nylon gear on the BBSHD you can reference this old article. I’ve replaced about 5 nylon gears on BBSHDs and 3 of them on BBS02’s in the last 4 years but I also beat the hell out of my drive units in deep snow. Even with all that experience it still takes me about 40 minutes to replace the gears and often I end up stripping the insulation off the motor wires when pulling the motor out. I find that just putting heat shrink tubing over the phase wires where the insulation rips is the easiest fix for torn insulation.
I am currently testing this gear and will post any updates to this article if I have issues. It is slightly louder than the nylon gear, but I expect that like my M600 with steel gears, it will quiet down quite a bit after the first 100 miles or so.
This steel gear has been in the works for years now, and I’ve been chomping at the bit to try them. I find it crazy that it has taken this long to get this product to market, as it seems like there would be a huge demand for them. I bet that the BBSHD with a steel gear can easily produce 100 Amps peak without self-destructing, now it’s time for someone to design an even more Ludicrous controller which puts the 60 amp Ludicrous controller to shame.
Maybe we can hit plaid.