Bafang mid drive. Clunky gear change only when power on.

[Encantador]

I have become aware over the last few rides that my gear change is a bit clunky when changing under power. When power is turned off, the gear change feels normal.

I fitted the gear sensor to cut off the motor when it senses the cable moving, having messed the gears up when doing this I took it to a cycle shop and they put on a new cable and set up the gears, I did not leave the battery so they would have only been able to test it without power.

As the pedal assist kicks in after about half a revolution of the pedals, I am guessing it is this together with the gear change that is causing the problem. it is hard to tell whether the clunkiness is at the front or rear of the drivechain.

Any help, ideas, suggestions as to what might be causing this welcome.

Thanks

Steve

 

[jimriley]

There are some good YouTube videos about setting up your derailleur, worth a look, clarified a few things for me. Park Tools was the one I followed. Is the gear change sensor cutting the power?

 

[Encantador]

Thanks for the reply. Yes I followed those, including the Park Tools one, failed miserably, hence the shop visit. Cant fault the gears as they seem fine when power turned off.

 

[cyclebuddy]

On my torque sensor Bafang mid-drive with gear-sensor, I don't find the gear sensor too helpful: The gear-sensor works fine on the flat, but on even a slight incline where you have gravity working against you and you're losing momentum more quickly, I find it reacts too slowly and cuts the power for too long.

All the gear-sensor is doing is cutting the power to the motor for a small pre-set period of time... but even as soon as the power is cut, the motor still has some momentum as it continues to over-run for a short fraction of a second, by which time your chain is already midway between gears and crunching.

I find a better technique is simply to stop pedalling a fraction of a second before changing gears, so power is cut to the motor earlier. An even better method I find is to peddle backwards a 1/4 turn, which disengages the motor completely from the drive. It sounds a little odd, but it enables a faster gear-change without crunching. It's just adapting riding style which you soon get used to, and after a while it soon becomes second nature.

It works on my second mid-drive too, which is a different crank motor system more akin to a cadence-sensor BBS, and without a gear-sensor. Slick, quick gear-change without any crunching. Your gears and chain should last longer, and saves you £50.

 

[Terry777]

If your bike has brake lever cut offs you can use that too to cut the power for longer to suit your gear change needs too. Just touch the lever a tiny bit to cut the power but not enough to actually brake. Just do a couple practice shifts and you can get it pretty honed. I have the Sram derailleur which doesn’t perform the mechanical gear change until you release the trigger shifter, this gives you the extra second to cut the power so you get a smooth change. Most derailleurs do the change as you press the shifter which is not the best for ebikes. Hope this helps….

 

[Encantador]

Thanks for the replies.

I think I will disconnect the gear sensor and change normally, if the problem still exists I will try the two options suggested. If neither makes a difference, that would rule out the gear sensor being the problem at least.

My gut feeling is that the problem is because the gear shift does not complete without pedalling and just at the wrong time as the gear is changing the power is kicking in, but I may be wrong.

Thanks again.

 

[Terry777]

Thanks for the replies.

I think I will disconnect the gear sensor and change normally, if the problem still exists I will try the two options suggested. If neither makes a difference, that would rule out the gear sensor being the problem at least.

My gut feeling is that the problem is because the gear shift does not complete without pedalling and just at the wrong time as the gear is changing the power is kicking in, but I may be wrong.

Thanks again.

That’s why I suggested the brake lever trick. I had a internally geared hub before which did the same as yours by the sound of things. By touching the lever you can keep the power off till you completed the change.

 

[Encantador]

Sorry, I missed the words "for longer" in your reply. So hold the brake lever in slightly until after the gear has changed, not just a flick to turn the power off.

Will give it a try, thanks.

 

[Deus]

Are you sure the gear sensor is actually working ? does it cut the power at all? sometimes the wire gets some lube on where it touches the small wheel inside the sensor and the wire slips instead of rotating the wheel

 

[vfr400]

Are you sure the gear sensor is actually working ? does it cut the power at all? sometimes the wire gets some lube on where it touches the small wheel inside the sensor and the wire slips instead of rotating the wheel

As soon as I red the title, I was asking the same question.

 

[Encantador]

The light was flashing on, not looked for a while will try it. Thanks