Last month the Bionx back wheel of my Dahon Mu SL fell out of the drop out when I hit a rut on the bicycle path. The wheel locked up and the bicycle skidded to a stop. Luckily I was on the flats so no injuries. The consol turned off and battery stopped working. I remounted the wheel and installed a spare battery that I usually carry in a backpack on longer trips. I rode the bike at assist level 4 for a mile and then the motor started making a harsh grinding sound and would not spin freely under power. It still freewheeled and pedaled fine with the power switched off, so I just pedaled to my intended destination without the Bionx motor assist.
I started this topic to warn all Bionx owners that reads this forum to make sure the Bionx wheel motor nuts on their bicycle are tight before each ride to avoid this fate.
On the positive side, when I was shopping to replace the broken motor, I found the new high speed Bionx 500W system. Bionx does not make a 20" rim high speed 500W wheel, so I purchased the 26" kit and respoked it with the rim and spokes from the broken Bionx 350W wheel. So far so good with the new system.
Did this happen to anyone else?
Hasn't happened to me, but it would be a lot more disastrous if it did. Front failures are usually much more injurious O_o.
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I was going only about 17 to 18 mph when the wheel fell out of the drop out and locked up. With the 350W Bionx kit, I was able to attain speeds of 25 mph or more on steep down hill runs. Failure at that point would have been disastrous as well. With the 500W high speed Bionx kit, I am now able to attain down hill speeds of 33 mph or more coasting down the same hills due to less resistance from the higher speed, lower torque 500W motor. Needless to say, I check the drop out nut before each ride now.
This almost happened to me on my first ride. I checked the lug and noticed it was halfway out of the dropout. I immediately tightened the axle nut MUCH tighter. I have subsequently noted that on p.18 of the Bionx "User Guide" they recommend tightening the nuts to "38 to 40 N.M."
I havn't had the wheel drop out but on my S&B Tadpole trike the dropout is not as long on the back side as the front and when I use the regenerative braking the axle rotates backword out of the dropout. I have had to disable the regeneration to avoid this. I don't think there is a solution for this it is a design flaw of the trike.
It may be wise to come up with a torque arm set up like the more powerful hub motors use. This reduces the possibility of the wheel working its way loose considerably.
Before the multi-speed bikes, derailleurs, etc. became the norm, single-speed bikes had a coaster brake. To apply the brake you back pedalled to locked up the rear wheel. These systems had just such a torque arm. If the arm became unfastened the arm would spin around the first time you hit the brakes.
Might be a good concept for the Bionx but it would complicate the installation a bit ..