Mobilgrease 28 & BBSHD/BBS02 : Because A Good Mid-drive Is Better Seen - E Smart Way

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Mobilgrease 28 & BBSHD/BBS02 : Because A Good Mid-drive Is Better Seen And Not Heard

Posted by Tom Lee on

There has been a near-mutiny of BBS02 owners (rioting in the streets) who have been disgruntled that their BBS02 units have shipped either without any grease in the secondary reduction gears or with the ill-suited white lithium grease in the secondary reduction gears. Both setups are not appropriate and will cause premature secondary pinion destruction and wear as well as making your drive unit much louder than it should be. A properly greased BBS02 running at full tilt should sound as loud as a large handheld drill and no louder.

“What did you say?”




Strawberry, Vanilla or Chocolate. The white lithium grease is not viscous enough and the black moly grease degrades the nylon gear. The Goldilocks Mobilgrease 28 is just right. Yes, I actually eat off that table. Gross.

For reference:


  • The secondary gear reduction is located under the plastic cover on the BBS02 and is very easy to get to. Most BBS02 units have a thick black axle grease on these gears except for a few hundred units in mid-2015 that have shipped with no grease or with white lithium grease. Bafang has started using black axle grease on this reduction stage from here on out. The BBSHD has always had black grease on the secondary reduction gear as far as I know.
  • The primary gear reduction you have to remove the motor to get at and uses a large white nylon gear. Bafang has always used white lithium grease on this gear and has never shipped drive units without grease here. There is problems with the lighter lithium grease spinning off the gears or hardening up when it gets several years old.

A few weeks ago I concluded that my nylon gear failure was probably caused by the black axle grease leaking through the bearing from the secondary reduction into the primary reduction. Because I felt that this was unacceptable I started shopping for other grease options that I could use to replace the black axle grease that Bafang was using and install it in both reduction areas. The Mobilgrease 28 I settled on is specifically designed for aircraft parts and is nylon gear safe and sells for about a buck an oz (available here) and is cherry flavored to boot (yum).


I recommend using heavy-duty black Nitrile gloves when working with grease of any kind, you can buy a box of 100 gloves from Walmart or Lowes for about $10. Get the extra thick black ones and not the crappy thin blue ones which are better suited for prostate exams. These greases are toxic and many kinds of solvents can absorb into your blood stream directly through your skin. Wanna know how I got so stupid? Washing my hands with Tetraethyllead to keep my 1961 Dodge Phoenix on the road for 8 years as a daily driver. Dumbest thing I ever did, except that one time I ran away from home to join the circus. They said I wasn’t tall enough to be The Giant and so I ended up working as the world’s most pathetic clown riding around on a children’s tricycle and setting people’s pants on fire. Living the dream baby. (not a true story)



This is what your secondary reduction gears should look like, packed with grease from the factory. If it doesn’t then you need to take action. The pinion gear is the small gear in the top left.

Putting Mobilgrease 28 into the secondary gear is literally a 5-minute job. Unscrew the 5 or 7 screws on the plastic cover of your BBS02 and pull it off. If there is black grease then wipe as much of it off as you can with your finger or use your wife’s toothbrush. Then take a fingerful of Mobilegrease 28 and mush it into the teeth all the way around the big ring and the little ring. Screw the cover back on and you’re done. See, all that complaining and rioting in the streets was for nothing.


The motor removed, I can't believe they are using toothpaste in there. Yuk.

The motor removed, I can’t believe they are using toothpaste in there. Yuk.

If you’re hardcore like I am and want to replace ALL the grease in your BBS02 with Mobilgrease 28 then you will need to follow the steps below. The entire process takes about 30 minutes.

  1. Remove plastic cover as above and wipe off the black grease so it doesn’t get everywhere
  2. Pull the controller off with 2 hex screws. Make sure you use the right wrench and it’s fully engaged. Bafang puts these screws in WAY TOO TIGHT and you can strip them, I have.
  3. Remove the silicone around the 3 large phase wires where it goes into the case, remove the large white plug that also goes into the case and is encased in silicone.
  4. Unscrew the motor opposite the controller with 4 hex screws. As above these are put in way too damn tight.
  5. Carefully wiggle the motor back and the 3 phase wires on the controller side will slowly pull through.
  6. Remove the rubber triangle plug-in the top corner and then remove the triangle cover for the nylon gear.
  7. These 3 Philips screws are a bitch to get out. You need to brace the case hard and then use the right sized Philips screwdriver pushing down with all your might and then turning the screwdriver with a pair of vise grips. It’s insane to tighten Philips screws this tight, they are extremely hard to remove. Don’t give up.
  8. Remove the cover plate and then use lockring pliers to remove the lockring on the nylon gear. You might have to clean the white lithium grease off the top of the nylon gear.
  9. Clean the entire compartment of any white grease. It may start to be greyish from the black grease leaking through the bearing, it is on most drive units I have disassembled.
  10. Put Moblegrease 28 in the teeth of the nylon gear and the motor teeth. This is the best place for this grease to be.
  11. Remount the cover plate, motor and the controller. Do not over-tighten any of the screws, just make them sorta tight not Chinese prison laborer tight. When putting the motor back together carefully pull the phase wires in as the motor closes back together. You might want to re-silicone the controller connectors to make them watertight again.
  12. Use the Bafang axle removal tool to remove the 2 locking nuts on the opposite side of the axle as the secondary reduction gear.
  13. Pull the axle out about an inch. Do not remove the axle grease from the axle, there is no way for it to migrate into the primary reduction gear. Clean the grease off both sides of the large reduction wheel with a rag and you’re son’s toothbrush. Don’t tell him what you’re doing, just put his toothbrush back in the holder when you’re done and see if he notices. (That joke never gets old)
  14. Replace Mobilgrease 28 in the teeth of the large secondary reduction gear and push it in around the pinion gear.
  15. Push the axle back in, put the first locknut on so it is a little tight then put on the rubber washer then put on the 2nd locknut and tighten that down really tight. Test the friction of the bearings by turning the axle when you are done. The axle should not be loose (wiggle back and forth) and should not be so tight that you can’t turn it with your fingers both ways.
  16. Put the plastic cover back on. Don’t screw it back on with anything other than a handheld screwdriver. If you use a cordless drill you will probably crack the cover.
  17. That’s it, you’re done.
Clean this area out as well as you can.

Clean this area out as well as you can. Lick that motor clean boy.

There is another article I did about replacing the nylon primary reduction gear on the BBS02 located here which also might be worth a look before you undertake this task. It has more descriptions that above and a lot more pictures as well.

Best way to coat the nylon gear with grease. Never use black grease on this part.

Best way to coat the nylon gear with grease is to squeeze it into the teeth. Never use any black grease on this part. It breaks down the plastic and makes it soft, like the Stay Puft Marshmellow Man.

I used to use black moly automotive axle grease on the secondary reduction gear of my 8 BBS02’s and honestly it works great, but it can seriously deteriorate plastic parts over time. All my tubes of grease are designed to be fitted into a gun and shot out into grease fittings, but you can also just stick your finger into the end of the tube and scoop some out. Try to resist the urge to taste it. When your finger no longer reaches just use a mat knife to cut the whole cardboard tube down a little shorter so your finger will reach.

My feeling is that the white lithium grease that Bafang uses on the primary reduction gear is not viscous enough and tends to easily get flung off the nylon gear at the thousands of RPMs that the primary reduction gear runs at. The Mobilgrease 28 is a far more elegant solution as it has some clay mixed in to thicken the grease and to keep it sticking to the gears even when they are spinning around very fast. The white lithium grease that Bafang used to use on the older drive units seems to dry up and stop being gooey after a few years. My spellchecker doesn’t like the word gooey, but I do.

Cover plate replaced and motor about to be reinstalled.

Cover plate replaced and motor about to be reinstalled. Don’t forget that rubber plug-in the top right-hand corner like I always do.

For some great videos from our favorite Aussie Speed-freak Bruno has done this video on the white lithium grease problems. Bruno used the black moly grease which I don’t recommend because it can leak through to the primary reduction gear. Volume control warning: You might want to check your computer speaker volume before you click on Bruno’s videos. You would be insane NOT to subscribe to his youtube channel as there are TONS of great videos on fixing the BBS02 and BBSHD and dude is funny. Not like Karl Gesslein of electric-fatbike funny, but actually funny, as in actually make you laugh funny.

This is the best way to grease the secondary gear in my opinion.

This is the best way to grease the secondary gear in my opinion. Don’t clean the main axle. Nothing is going to work as well for the needle & thrust bearings than black moly grease.

30 minutes of proper maintenance on your BBS02 might be worth thousands of miles of uninterrupted service. Considering how much maintenance most people do on their cars, it is a small price to pay. If you find yourself in a place of shaming or blaming your BBS02 vendor, remember that they are not responsible for Bafang’s mistakes and shipping out hundreds of BBS02 drive units without grease on the secondary reduction gear is a serious blunder. If you must have the exact black moly grease that Bafang provides on the BBS02 then contact Eric at Lunacycle who has a tub of this very expensive stuff I’m sure he’d be happy to send you some if you bought your drive unit from him. Even if you didn’t buy your drive unit from him, Eric is a very nice guy and if you promise to give him all your ebike business till you die and sound really pathetic then he’ll probably just send you some. Bafang throws in a free Kentucky Fried Chicken bucket of black Moly grease with every $250,000 order.

If you have a BBSHD I do not recommend that you do this procedure at this time. If I find the black Moly grease seeping through to the Nylon reduction gear I will do a separate article for the BBSHD which is put together quite a bit differently. You should subscribe to this blog if you have a BBSHD and don’t want to miss the article.

Ride on.


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