Does the motor software need changing when....

I met a guy on Pivot FS eBike today, with the Shimano Steps e8000 motor. He told me that he changed his front ring from the standard 34 to a 36 to make better use of his cassette. The bike started behaving oddly when on swooping terrain, as though the motor was lagging behind and then catching up. He mentioned to his bike shop and they contacted Pivot. Pivot said that the software needs changing to deal with the larger front ring. They sorted it out at Pivot and sent the patch to the bike shop, who then loaded it into the guy's bike. Apparently, his phone app could not do the job. And the bike shop guy was surprised too, he'd never heard of it! The patch fixed the problem.

I didn't get chance to ask him these questions, so I'm hoping you guys can answer them , or ask and answer better questions!

Is this really a Pivot thing, as I would have thought it was a Shimano thing?
Maybe Pivot answered the question by going to Shimano?
What other simple things can you do that will affect the way the motor delivers its power? For example, the ring change altered the gearing by 36/34 ie 5.9%. A change of crank length from 175 to 165 is 5.7%. Does that also need a software change? Tyre changes would also affect the overall gear ratio, although by a smaller amount unless you do something truly unusual, does that need a software change? What about a tyre change and a crank length change by 5mm instead of 10mm. That may add up to something heading towards 5%, maybe. Would that require a software change?
Is this a Shimano thing or does this affect all eBike motors?

I'm so new to eBikes that I don't even have one yet (on order), so I have no real understanding of what sensors there are that would require such a software change. I am aware of a rev counter on the rear wheel, a torque sensor in the motor area, maybe a few temperature sensors. I believe that the location of the torque sensor would be very important, so where is it? Is it inside the motor (where I'd put it), which should make crank length and ring size unimportant. Or is it somewhere else?

There are two ways of altering the shimano system, by the phone app which is very simple, and basically allows you to adjust the assistance levels in the individual modes, and also update the firmware. This connects via bluetooth to the bike.

There is also a more advanced piece of software, laptop/pc based which allows you to change far more, however it requires a special cable and costs a fair bit. This is called the SM-PCE1, and is essentially a diagnostic tool allowing you to update firmware and settings.

What i suspect is that it was the later software that was required to make the alterations, which the bike shop had.

More info on Shimano system here:

Service & Support - Shimano Steps E6000

I personally have changed tyres between different sizes, and run 160mm cranks, and haven't altered anything, nor felt the need to.

Pretty sure others have changed chainrings and cassettes without issue too.

I'd be keen to know the answer too. I was planning to swap to 36t NW ring today.
I remember reading a post not long ago from Gary that he swapped ring to 36t Aluminium bit he got for cheap, but not sure whether it was for his Shimano bike.

I already swapped shorter cranks, no problems whatsoever in 300km's I did on them.

May just swap the ring and try it out, fairly simple job.

@Gary - you had any issues when you did your chainring?

Gee Rob, you must must be a night-owl... Close to midnight according to my watch (have some relatives in Europe, better keep an eye on the time before calling them at 2 am to say hello)

Saturday morning here, changing ring right now and when the annoying drizzle stops I'll take it for spin.

Using the SM-PCE1 connector and the default e-tube app on PC doesn't allow you to change any sizes for the chainring. Shimano (& dealers?) might have access to another version which allows for more customisation.

I remember running the diagnostic output on mine and it said 34T - so it seems there is some setting stored in the bike (which may or may not get used for something).

Shimano reps themselves have a different login to us dealers, we have to get the shimano tech in store once a month to change the speed limit from 25kph to 32kph (New Zealand) to our new bikes. But we can do all the firmware updates and also change the parameters although I have never looked into doing a chainring swap.

I know that you can program your ebike to think you have 20" tyres even though you run 27 to make your top speed faster although not sure how that would sway if you had a warranty claim haha

From the replies so far, it looks like chain ring size is of some importance, otherwise why would it even appear as a value on the diagnosis ouput? If that has some importance what else is there? That appears to be unknown. Also whether this is just a Shimano thing or is common to all motors is also not known (by those on this thread at least).

I am not complaining about anything, just wanting to understand what things I can change before I have to go back the shop.

R120 said:

@Gary - you had any issues when you did your chainring?

Click to expand...

None at all

Gary said:

None at all

Click to expand...

What motor was that?

Shimano e8000 -Gary has a Vitus E-Sommett

Yeah. E8000 as R120 says.

After two trail rides, around 80km total in all modes, I found no difference in motor behaviour.
I haven't tried the gear combination which I have no use for i.e. 11-13-15t in boost.