Shifting under load and the art of precision shifting.

[Trail Cruiser]

Warning: This may not apply to late model mid drives unless it has cable actuated inline shift sensor or it has a manual power cutoff to execute the shift (such as brake cut-off switch).

This idea originated from a standard (non motorized) bicycle application. I always make sure that there is minimal load while transitioning from one gear to the next. This is done by reducing the pedal effort (ghost pedaling) while executing the shift and then resume the normal pedaling effort once the shift is completed.

That is fine and dandy but what about if you are going up an incline and interrupting your pedaling effort means losing momentum and dropping your speed dramatically? It can still be done, you can continue your high pedaling effort and then time your shifting at exactly the lowest torque point of your pedal rotation. If you look at the illustration below, the lowest torque is when your pedal cranks are at the vertical position

wattmatters.blog/home/2015/01/the-sin-of-crank-velocity.html

As also mentioned on this archived blog:
"Shift when one foot is down and you're at the "floating stage", as I like to call it, when the flex of the bike helps lift that 6:00 foot up. Right when you start to press down with the opposite foot. Just go practice it a couple of times; once you find out how to do it, it's easy. Note: I always do it with the same foot. It wasn't conscious, but it just happened to work out that way."

reddit.com/r/bicycling/comments/1g6ay8/questions_about_shifting_under_load_while/?ref=share&ref_source=embed&utm_content=body&utm_medium=post_embed&utm_name=66e8d427797d434192aa28d6e2d1a3ec&utm_source=embedly&utm_term=1g6ay8

The mid drives that I happened to ride can be configured to have a brake cut-off switch which I use as a manual power cut off when shifting. I like it better than the inline cable shift sensor.

In my particular instance, there are 3 things that I have to execute simultaneously when performing the shift. The timing has be right while the crank is in vertical position, left brake is partially tapped, and right hand pushing the shift lever, all of them at the same time. I performed this over and over until I mastered it and became second nature. If you ride a dirt bike, you will understand the fun part of it.

On hub drives, it's the same (minus the brake cut off).

 

[AlanDB]

Would this same technique work for an internally geared hub like my Shimano Nexus 8?

I notice on the write up about the Nexus 8 on Shimano's web site they say you can shift while pedaling. But the tech at my LBS told me to get in the habit of briefly pausing pedaling while shifting and the Shimano transmission would last a lot longer. This is of course the opposite of how I learned to shift the derailleur, but I have been practicing doing it that way. On an uphill climb under load, it is awkward to stop pedaling to complete a shift..

 

[JRA]

I messed around with the brake cutoff as a clutch for awhile but it didn't work out for me and I cut the wires off. Although I have had many moto's It was just too foreign a move over what I normally do to shift my pedal bikes which I have done for a long time under load. What I find works best is to anticipate the trail/road and shift down before you get to an uphill but I can even shift down in the middle under load, as long as you are making good forward progress and don't wait until you are almost stopped, while keeping the assist active by slightly/barely backing off and making a quick and positive shift of my well tuned drivetrain. I have over 800 miles on a chain with no stretch issues. Sorry I don't have any graph's to support this but to me it is no different than riding my regular bikes now that I am not trying to make it something it isn't.

It is very important while underway to keep the assist active which keeps momentum fluid. The major reason why eMtb riders are seeking shorter and shorter cranks is because they are experiencing lots of pedal strikes due to the fact that it is harder for them to time their cranks because if they stop pedaling to make adjustments the motor shuts down
taking a 1/4 to 1/2 turn to activate and won't reactivate the PAS . This phenomenon has been going on for years with mtb's in general and timing or ratcheting your cranks is one of the skills you learn riding technical trails.

What works for me is what always has. I grab enough rear brake to keep tension on the pedals, and slightly slowing forward movement, get the pedals where I want them and release the brake and get ready to do it again. Doing the same procedure on an e bike with the constant pressure on the pedals keeps the PAS active, this is of course assuming you have a torque assist PAS, so that when you release the brake the motor response is instantaneous. I know there aren't many eMtb peeps on here but it still applies in any situation where you just want to adjust your cranks and not have the PAS shut down.

 

[Trail Cruiser]

Would this same technique work for an internally geared hub like my Shimano Nexus 8?

I notice on the write up about the Nexus 8 on Shimano's web site they say you can shift while pedaling. But the tech at my LBS told me to get in the habit of briefly pausing pedaling while shifting and the Shimano transmission would last a lot longer. This is of course the opposite of how I learned to shift the derailleur, but I have been practicing doing it that way. On an uphill climb under load, it is awkward to stop pedaling to complete a shift..

It depends on what motor you have and if it has a cable mounted shift sensor or a brake cut off switch. Otherwise, the general principle behind is the same.