Bafang BBSHD Madmods Conversion
I did it! With just a few hiccups along the way, I have successfully mounted a Bafang BBSHD 1000 watt mid drive motor to my Sondors Madmods. I ordered the kit from a seller on AliExpress for $530 which is an excellent price. The kits now come with a crank arm puller, the lock nut tool, a lock ring tool, a headlight, and even a pair of white gloves. My first BBSHD had none of these with the kit and I had to buy the necessary tools for the installation.
The first problem was a big one and was due to the frame having a flat bottom below the bottom bracket. Traditional bike frames are rounded below the bottom bracket but the Madmods frame is flat. When trying to insert the BBSHD one of the threaded nubs hit the frame and the motor would only insert about halfway. The nubs are used for this fixing plate to help keep the motor from loosening and pivoting forward. Having already mounted Bafang mid drives on 2 other bikes, I know that it doesn’t matter how tight you get it, the motor will still work its way forward. I have a stabilizer brace attached on my Giant MTB and on my wife’s bike, I simply rotated the motor up against the down tube with a piece of protective rubber between the tube & motor so it can’t rotate.
I solved the problem by grinding off the nub that was hitting & the motor just barely (and with a lot of wiggling & sweat) fit nice and tight against the flat bottom of the frame so there is no way for it to rotate either forward or backward. I used 6mm of spacers on either side of the 120mm threaded shaft casing and the round gear case on the drive side just barely cleared the frame & I then tightened it up with the nut and lock ring.
The decision to grind the nub off was not taken lightly and I halted the project for an hour while I thought about whether to do it or forget the whole mid drive idea. If I ground off the nub and the motor still would not fit I would be stuck with a mid drive for a fat bike but no fat bike to put it on. I do have another ancient aluminum Merlin Newsboy copy bike I could put it on but it would need about 25mm of spacers on each side so the pedals would be pushed pretty far outboard. Plus I imagine trying to resell the kit with the missing added tightening procedure would be tough and I would have to price the kit pretty cheap but so far, so good.
I then mounted a 44t aftermarket chainring with a 20mm offset. The chainring is pretty darn close to being straight but I have a 42T chainring on order from Luna Cycles & it has a 24.8mm offset so it should be perfect. Even if the offset is too much I can always add some spacers to get the chain line absolutely straight. I had to move the original PAS magnet disk & sensor for the hub drive to the left side due to spacing issues on the drive side and it works fine in its new location.
For the time being I have an extra generic 48v battery that I strapped to the top tubes. After I get everything tweaked and providing the motor does what I want it to and gets me up hills without exhausting myself pedaling as hard as I can in the lowest gear. I will be 70 years old in 4 months and I am not as strong as I was in the 1990’s when I mountain biked everywhere from the Pocono Mountains in PA, the White Mountain area in NH, and Pocahontas County/Monongahela National Forest in WV. There is plenty of room in the storage box to mount a battery and I will also explore where I could connect the factory frame mounted battery to the mid drive but I am getting ahead of myself as I still have a couple of problems to work out.
I am unable to get the rear derailleur to shift to the smallest cog on the 7 speed cassette. I have loosened the cable, adjusted the limit screws but it just will not move far enough outboard. The cable is definitely not too tight as I can apply just the slightest pressure on the derailleur with my finger and it moves easily & shifts as it should. I’m not sure what model derailleur it is because it just says Shimano with no other markings. I know people have had similar problems with twist shifters but the Shimano RevoShift 7 speed shifter always worked before.
I have a Deore XT 11 speed shifter on order & because it should
theoretically have a wider range of motion, it should do the job. I am also replacing the stock chain with a KMC E8 chain which KMC states has more strength than their other chains and is made for the strain of mid drive motors. I will also need to add the Bafang shift sensor which I have found is a must-have for these powerful motors. The project took me about 5 hours from disassembling the original BB, cranks & chainring to my first test ride.
So that’s it for now. I will update this thread after I get all these last little kinks (hopefully) ironed out. All in all, the project is progressing nicely and on my initial rides, the conversion has worked well with no dropped chain or chain suck. I get a top speed of 25mph with the throttle only but it is the added torque on the hills that I am after. I don’t want to work it too hard at the moment until I get the new parts and the chain line nice and straight. On my much lighter Giant MTB with a 48T chainring I can get up to 35 mph with PAS but this Madmods weighs 135 pounds and it is a heavy beast. Check out the photos and check back later for the final results.
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