More torque sensor issues ... suggestions?

T

tbar23

Member
I posted about a torque sensor issue I had back in early March here: https://electricbikereview.com/forums/threads/torque-sensor-question.41234/
Yesterday, I encountered a similar, but different, issue. After the March issue, I have made a practice of calibrating the torque sensor before almost every ride. Here is what I saw when I did that before riding home from work last night:
E8FCBFEE-397E-43A2-90F7-E8A893CB111C.jpeg

I power cycled the Omni computer - no luck. I also found that I had no assist. I quickly pulled up EBR and found out how to get into the service menu and found this:
C7037B61-C116-41BB-822B-208DD6582CB9.jpeg
30AF3993-33C9-4ED4-93E8-A6D8064F70C3.jpeg

The first photo is with no load on the pedals while the second is with some weight. Clearly the sensor was changing based on torque, but the offset looked way off to me. And oddly enough, the “RESET OFFSET” menu item that you see wasn’t doing anything.
@Ravi Kempaiah suggested that I remove the rear axle and re-torque, but that didn’t solve the problem, either.
Out of options, I started to ride home. What a reminder not to gain 50 lbs!!
Before heading home, I emailed Stromer USA with the photos above (my bike shop mechanic had already left for the day).
About 13 miles later, the bike suddenly came alive - in other words, it “fixed itself”. The remaining 8 miles of ride were just like usual with full assist.
When I got home, I went into the service menu again and found this:
E152E6FD-B667-4BAC-A6EC-C40DF7403616.jpeg

(Unloaded) Not only had the sensor output voltage increased by ~900mV, but now the RESET OFFSET button would clearly do something. I could tell that the offset would change to precisely match the sensor voltage when pressed - at least for a few hundreds of milliseconds before the voltage drifted 10 or 20 mV away (as can be seen in the photo).

Needless to say, I am not super excited to ride 2/3 of my commute without assist again - it takes too darn long. But I have no idea why the sensor acted up in the first place and/or why it “fixed itself”.
Stromer USA got back to me and said that the recent firmware update could be reasonable. They sent the last revision of firmware to my bike, and I installed that last night. I’m not convinced that this was the problem since the sensor output voltage, itself, seemed whacky.
Any thoughts?

Thanks!
 
Thanks @Ravi Kempaiah - I pulled the rear wheel and cleaned up the sensor a bit. The sticker is starting to peel off (ordered another one from Stromer USA). It is handy to know the service menu secret handshake as now I can at least check on it if things are acting up.
 
tbar23 said:
About 13 miles later, the bike suddenly came alive - in other words, it “fixed itself”. The remaining 8 miles of ride were just like usual with full assist.
Click to expand...

In almost all cases, the sensor crisis came from manipulations in area of the rear axle. An invisible torsion is sufficient. The "self repair" tells me, the sensor plate is not in perfect position - and then vibrations during a ride have effects.
 
tbar23 said:
Thanks @Ravi Kempaiah - I pulled the rear wheel and cleaned up the sensor a bit. The sticker is starting to peel off (ordered another one from Stromer USA). It is handy to know the service menu secret handshake as now I can at least check on it if things are acting up.
Click to expand...
I have the same issue, after you cleaned it did it work?
 
@ryeo I’ve had intermittent issues with the torque sensor. I un-installed, cleaned and re-installed the torque sensor. I did receive a replacement sticker but when I uninstalled, that didn’t appear to be a significant issue. There is a Stromer TSB (that I’d have to dig up) on lubricating the head mating surface of certain sensor mount bolts. I’ve done it all, and I still get occasional torque sensor issues. None nearly as bad as the day that prompted this thread, but I regularly go into service mode to look at the sensor voltage output, and I regularly zero-out the offset.
I can’t believe that the sensor can’t be unplugged back at the rear drop-out (it has to be fished through the frame up to the control module) or else I would just have a backup handy.
All of this said, I’ve put less than 100 miles on the bike since May (was doing about 100-200 miles per month prior to that).
I’ve had a few minor hiccups here and there, but nothing major since the April 21 post.
 
Hi Andy , how are the bikes ?

Do you think this would be a good procedure for all TMM4 sensors? I believe I have the same one on a BH ..
 
opimax said:
Hi Andy , how are the bikes ?

Do you think this would be a good procedure for all TMM4 sensors? I believe I have the same one on a BH ..
Click to expand...
I'd imagine that the specific torque settings that Stromer has recommended have to do with the design of the plates that their TMM's are mounted in. I don't know if would translate to other company's designs.

As for the bikes, I'm still in the thick of it. I've disassembled the ST2s down to its bones, checked and cleaned every electrical connection, and am now slowly building it back up. I'm pretty confident about that one.

The ST1 has a bad motor. Something is shorted inside the motor and it's actually frying any display that is connected to it. That's the reason you were seeing the NO_BATT message. I've been able to use other parts from it though, so I'm happy.
 
I really wished I had a better Stromer experience , love that bike when working well. I guess the st1 is done glad I gave up on it .wishing you the best with them , don’t forget pictures some day :)
 
tbar23 said:
I posted about a torque sensor issue I had back in early March here: https://electricbikereview.com/forums/threads/torque-sensor-question.41234/
Yesterday, I encountered a similar, but different, issue. After the March issue, I have made a practice of calibrating the torque sensor before almost every ride. Here is what I saw when I did that before riding home from work last night:
View attachment 85401
I power cycled the Omni computer - no luck. I also found that I had no assist. I quickly pulled up EBR and found out how to get into the service menu and found this:
View attachment 85402View attachment 85403
The first photo is with no load on the pedals while the second is with some weight. Clearly the sensor was changing based on torque, but the offset looked way off to me. And oddly enough, the “RESET OFFSET” menu item that you see wasn’t doing anything.
@Ravi Kempaiah suggested that I remove the rear axle and re-torque, but that didn’t solve the problem, either.
Out of options, I started to ride home. What a reminder not to gain 50 lbs!!
Before heading home, I emailed Stromer USA with the photos above (my bike shop mechanic had already left for the day).
About 13 miles later, the bike suddenly came alive - in other words, it “fixed itself”. The remaining 8 miles of ride were just like usual with full assist.
When I got home, I went into the service menu again and found this:
View attachment 85404
(Unloaded) Not only had the sensor output voltage increased by ~900mV, but now the RESET OFFSET button would clearly do something. I could tell that the offset would change to precisely match the sensor voltage when pressed - at least for a few hundreds of milliseconds before the voltage drifted 10 or 20 mV away (as can be seen in the photo).

Needless to say, I am not super excited to ride 2/3 of my commute without assist again - it takes too darn long. But I have no idea why the sensor acted up in the first place and/or why it “fixed itself”.
Stromer USA got back to me and said that the recent firmware update could be reasonable. They sent the last revision of firmware to my bike, and I installed that last night. I’m not convinced that this was the problem since the sensor output voltage, itself, seemed whacky.
Any thoughts?

Thanks!
Click to expand...
So as of today March 26, 2022 my TMM sensor suddenly works, I was trying to troubleshoot for the past couple of months! I did not tinker with my rear axle wheel. What is your firmware version?

Thanks!
Rob
 
ryeo said:
So as of today March 26, 2022 my TMM sensor suddenly works, I was trying to troubleshoot for the past couple of months! I did not tinker with my rear axle wheel. What is your firmware version?

Thanks!
Rob
Click to expand...
Hi ryeo - interesting. I rode my Stromer a few weeks ago and had issues with the torque sensor. These days, I know enough to go into the right secret menu to reset its zero voltage, but this is more than just a shifting output from a sensor. When working, the sensor output is around 1V unloaded. When not working, it drops to around 0.2V (with several tens of millivolts of variability) - as you can see in my early photos of this thread.
I’m out of town now, but when I return, I’ll check my firmware version and see how things are working.
Did you notice a firmware up-rev?
 
When reinstalling the wheel greasing the threads and the top of the head is recommended for accurately retorqueing the wheel. Maybe you guys can try that.
 
-your V is way too low(maybe too low NM on the Thru axle ? ) ; it should be 0.5 Min. when no load on the pedals. Pref. 0.8V , anything lower then that, the Stromer or any other ebike with TMM sensors(BH) will be to slugish. Try also too unscrew/retighten the screws holding the TQ sensor in place, air duster on it also.

This thing it's just very sensitive esp. for Stromer ebikes ! I've had zero issues on my BH Nitro and all tbe above steps always would fix any TQ sensor issue in my case. A cable re seat would be helpfull also(it's a few inches long that hoes inside the frame , that can be carefully pulled out and re seated).


They call me THE ebike/escooter guru around the big city😁⚡️

Ps.- After finishing the thread , i c that you got it to work. Hope that it stays that way. Winter or cold weather( snow/salt def. can impact it's performance also).
 
Last edited:
What's the difference between a strong but limp and a strong and agile e-bike?

It's the torque sensor and how the controller deals with its values. For sure, there is no free lunch; a sensitive sensor goes along with a difficult handling of the sensor. If you have the mechanical skills, the company provides a bunch of tools to support your work. If not, like I do, your official Stromer bike mechanic is in charge.
 

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bluecat said:
What's the difference between a strong but limp and a strong and agile e-bike?

It's the torque sensor and how the controller deals with its values. For sure, there is no free lunch; a sensitive sensor goes along with a difficult handling of the sensor. If you have the mechanical skills, the company provides a bunch of tools to support your work. If not, like I do, your official Stromer bike mechanic is in charge.
Click to expand...
While this may be true - when the sensor output randomly jumps from around 1V no load to around 0.2V no load, that’s not sensitivity. That’s an issue.
One that neither I nor the Stromer tech support folks have been able to resolve.
My suspicion is bad sensor but given the way they are wired it isn’t (yet) worth the effort to swap it out.
I wish they had put the connector at the dropout rather than the controller.
 
tbar23 said:
I wish they had put the connector at the dropout rather than the controller.
Click to expand...
should be exactly like in the pic, and the end part( prob. inside the right chain stay like on my Bh, i'm not very familiar with the insides of Stromer ebikes) you could swap it from a new one ! I Did just that a few years back and issues was solved.

Could also change the whole TMM sensor plate and the end cable.
 

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