Stromer ST2 Pulsing (Please vote)

[Mitchell Waite]

PLEASE VOTE IN THE POLL.

When riding the ST2 in the highest gear and assist mode #3, the peddling was almost effortless. But every 2 to 4 seconds the peddling became resistant. It was as if the engine was slipping into the mid-setting #2 or turning on the regen mode. If I kept peddling it would go back to the no resistance mode in a few seconds. I all it a kind of pulsing. This was a disconcerting experience and I thought maybe something was wrong with this particular ebike. But my sales person was not sure what was going on; he thought it might be the “clogging” whatever that is. The Specialized I tested had no such pulsing effect but its not as great a bike IMO as the Stromer ST2.

Do you think this is a problem with this particular ebike I tried, or a characteristic of the Stromer ST2 or just normal behavior and I’m being a woose?

 

[Ravi Kempaiah]

I experienced this several times during the first ~400 miles on my bike.
I believe I learned how the Torque sensor works and haven't had such pulsing for the next 1.5K miles or so..

The sensor has to experience enough strain to maintain certain assistance level. If your cadence wasn't enough or you were pedaling in assist 3 on a flat road, then it would be difficult to maintain steady strain on the sensor and it cuts off/on and hence the pulsing feeling. Also, few times, both my panniers were loaded to the full capcacity and the pannier which was directly above the TMM4 caused such pulsing. Thereafter I started loading the pannier on the other side and problem solved.

So in conclusion, this is one of those nuances that comes with TMM4 sensor on Stromer St2 ( BH bikes experience so substantial difference in Sport & Bosst mode for similar reasons). Once you become accustomed to how the bike works, it shouldn't be an issue.

 

[Rick Huizinga]

I have experienced the same power pulsing/stuttering after a long ride, or after going up a long steep hill. Until now, I had assumed it was a thermal cut-off meant to prevent excessive heat build-up in the motor.

In my case, I had noticed the power cut-off while applying torque via the pedals. It wasn't a case where the torque sensor was unloaded.

I would like to conclusively understand what is going on. When it happens, you get the sensation that something is not right.

@Mitchell Waite It is normal to feel this sensation when the max-speed cutoff is reached or when the torque sensor becomes momentarily unloaded (i.e. when changing gears).

 

[Mitchell Waite]

I have experienced the same power pulsing/stuttering after a long ride, or after going up a long steep hill. Until now, I had assumed it was a thermal cut-off meant to prevent excessive heat build-up in the motor.

In my case, I had noticed the power cut-off while applying torque via the pedals. It wasn't a case where the torque sensor was unloaded.

I would like to conclusively understand what is going on. When it happens, you get the sensation that something is not right.

@Mitchell Waite It is normal to feel this sensation when the max-speed cutoff is reached or when the torque sensor becomes momentarily unloaded (i.e. when changing gears).

If this pulsing is normal then I would say this is not a well designed ebike. I had no such experience on the Specialized Turbo S. And even though I like the ST2 better this pushing is a significant enough distraction that I would not buy the ST2. The only thing that might move me back is the comment by Ravi: " I believe I learned how the Torque sensor works and haven't had such pulsing for the next 1.5K miles or so.." however he really doesn't say how he managed to eliminate the pulsing.

 

[Ravi Kempaiah]

If this pulsing is normal then I would say this is not a well designed ebike. I had no such experience on the Specialized Turbo S. And even though I like the ST2 better this pushing is a significant enough distraction that I would not buy the ST2. The only thing that might move me back is the comment by Ravi: " I believe I learned how the Torque sensor works and haven't had such pulsing for the next 1.5K miles or so.." however he really doesn't say how he managed to eliminate the pulsing.

Mitch,
I think you experienced this in assist 3. Am I right?
This happens mostly when you're on higher assist levels and your cadence is not high enough to maintain steady strain. Now, once you understand this nuance, you can easily maintain 27mph for long stretches without experiencing this pulsing.
If you can wait for few days, I'll upload some nice videos.

 

[Steve Plattner]

I have experienced what I think you're describing on my last three rides (each between 15 and 20 miles) will cruising along between 12 and 15 mph in Eco, City, and Tour modes on flat land on my ST1, with 2 different batteries. Everything is going fine but it begins to feel like you're suddenly pulling a fairly heavy trailer--almost but not quite the same feeling as turning the power of entirely. For a second or so you begin to get back to normal but then the same sensation comes back and it stays that way for several minutes before gradually getting back to normal. I've tried: shutting down and restarting, removing and reinserting the battery, stopping for 10-15 minutes, and even unplugged the control unit and both brakes for a few seconds and then reconnecting. I am going to take it to the dealer new weekend for a look, but I've only ridden 390 miles and I just hope it isn't one of those weird things that no one can figure out. Any thoughts on this would be greatly appreciated!

 

[ProfSharona]

I don't mean to mock your experience, so please take with the good will in which it was intended. Is it possible your legs were overtired? I've had the experience that when I bike more than usual or I've been doing other strenuous activity it seems so much harder to get the bike to move. It feels like the bike is the problem, but I'm pretty sure it's me.

 

[Deleted member 803]

This sounds pretty normal to me. I've ridden just a few ebikes, may 30 or 40 and at certain power levels torque sensors behave erratically for exactly the reason that Ravi articulated. What i suggest is that you find a steep hill and see if the problem continues to exist. Once you are at the minimum threshold for the sensor the motor will burp on/off. I have a Neo Carbon, which, while I love, cannot use anything more than eco mode unless I have a very steep climb. There is always a tradeoff between torque and speed. The key is to always match your cadence to the appropriate power level. And, this is an individual thing. I prefer a slower harder cadence that gives me strong acceleration. I sometimes ride with others who prefer to have a faster cadence in a lower gear. No right or wrong here.

 

[Steve Plattner]

I don't mean to mock your experience, so please take with the good will in which it was intended. Is it possible your legs were overtired? I've had the experience that when I bike more than usual or I've been doing other strenuous activity it seems so much harder to get the bike to move. It feels like the bike is the problem, but I'm pretty sure it's me.

Hi Professor, Thanks for responding, and I take your posting in the spirit in which it was intended. But I am sure the problem I am encountering isn't my leg strength or being overtired. The first time it occurred was on my longest ever ride--61 miles mostly level on the Little Miami Trail near Cincinnati (highly, highly recommended)--and the problem happened about 5 miles into the ride and continued until mile 11 or 12. I stopped for water, got back on the bike, put the setting on City, and wound up riding 20 miles non-stop averaging over 20 mph with some triathletes. I don't really understand the whole torque issue so need to brush up on that and take it in and have the dealer take a look. But when it happens, it feels like someone attached a trailer with two 50 lb. kids all of a sudden. I don't recall it ever happening on a steep hill--just level ground.

 

[Mark_0]

Yes I get the pulsing too. Always in setting 3 assist. And usually after a steep hill. And I agree with Ravi it is due to the torque settings and the bike trying to adjust to your riding. In fact if you watch your bike display you can see the little power bar go up and then disappear. That is the pulse you feel as all the assist goes away. You can "clear" it by changing gear or cycling "harder" for a short while until the bike seems to get used to your new cadence.

I think Steve is referring to a different issue. Which seems to me to be a problem. Sometimes after I stop at lights and set off again it feels like I suddenly got stuck in mud. Embarrassing when you are trying to quickly move through a busy junction as I almost stop. The first time this happened I stopped and reset the bike. But I since found that if you quickly change gear to the next easiest setting it clears immediately.

 

[Rick Huizinga]

Has anyone tried changing the torque sensor sensitivity in the main menu? It sounds like increasing the sensitivity could alleviate the power stuttering, but it's not entirely clear what this feature does. It almost sounds like it does the same thing as adjusting the torque in the tuning feature.

 

[BTB]

When I had the problem after taking delivery of my ST2, I increased the torque sensor to 75%, which took care of the problem in power mode 3 for my style of riding, which is pedaling in consistent circles. If that doesn't work, move it up to 80 or 85% and see if that works better for your style. Keep in mind that the "Tuning" settings on the Stromer app are for power mode 2, so you have to change the basic torque sensor on the bike in order to change the sensitivity in power mode 3. I also have speed, torque, and agility set at 75% in power mode 2 to give me a different experience than power mode 3, plus it extends the battery range over 3. I would be surprised if anyone has power stuttering going up an incline, since the bike adjusts itself to hills, but I agree power stuttering on the flats would be annoying if the bike was unadjustable.

 

[Berlin]

If this pulsing is normal then I would say this is not a well designed ebike. I had no such experience on the Specialized Turbo S. And even though I like the ST2 better this pushing is a significant enough distraction that I would not buy the ST2. The only thing that might move me back is the comment by Ravi: " I believe I learned how the Torque sensor works and haven't had such pulsing for the next 1.5K miles or so.." however he really doesn't say how he managed to eliminate the pulsing.

Hoi Mitchell W.
this is not just something , it's a pretty problem

With my ST2, i encountered the same annoying problem

This problem occurred after I had pressed my two brakes.
So, i aksed this problem on a local thread, and i came to know more about this issue

I think the problem is in the brake sensor.
You can even test out - when you push the left / right brake, their appears a arrow on the display for braking/recup. Normaly the left and right must have the same sensitivity.
1)In the beginnen, i braked with the front and rear brake at the same time.
2)now i brake only with the rear brake, and I have a lot fewer problems - very occasionally

After a while a went to my bike dealer to solve this. He found out that it is the rear brake sensor, currently my ST 2 is in for repairs. ( and replaycing the sensor)
I hope this problem will be solved - i also hope stromer is up to date with this phenomenon.....
I hope so

 

[Mitchell Waite]

Hey Berlin:

Thank you for all the information, it is very helpful. I certainly appreciate all the other responses, but of all the responses your's seems to hit the nail on the head. I still have some doubts about whether this pulsing issue is endemic to the design of the Stromer or just an issue with some of them. I am going to try out some of the ideas you describe like braking with just the rear brake and see if the problem goes away. I will also ask my dealer to look into the rear brake sensor and see if that has a problem.

I hope you let us know if the dealer solves the issue for you.

Steve Plattner - Your description is very articulate and very similar to my experience:

• "I have experienced what I think you're describing on my last three rides (each between 15 and 20 miles) will cruising along between 12 and 15 mph in Eco, City, and Tour modes on flat land."

I do not however have as an acute experience as you describe here:

• "Everything is going fine but it begins to feel like you're suddenly pulling a fairly heavy trailer--almost but not quite the same feeling as turning the power of entirely."

DEFINITION OF MY PROBLEM: What happens to me is I am peddling at a steady rate, on a flat surface, moving between 15 and 20 mph and applying a constant pressure to the pedals. It feels like the assist mode is cutting in and out. For example I will feel the assist for about 4 seconds, then its like assist has been turned down (not completely off) and the peddles have resistance. The peddles require more pressure. After applying that pressure for about 2 to 3 seconds the assist comes back on and there is no longer resistance.

I don't experience anything as bad as pulling a fairly heavy trailer. That would be very alarming and if that is what is happening to you I would submit its something else.

Bottom line is I find this cutting in and out of power to be annoying and I would not spend $7,000 if this is "the way it works".

Note I do not experience anything like this with the Specialized Turbo which further convinces me this is not "normal" behavior as some people are indicating. I like the Stromer much more than the Turbo, it has a much more state of the art design and more advanced features. Could it be that this advanced tech is the issue?

But I defer to those with more experience and I am open to hearing that this is the way Stromer designed the ebike and 90% of the riders don't mind this pulsing. However I would prefer to find out something is wrong with a sensor as Berlin indicates or maybe the batch of bikes at my dealer have this problem.

Ravi - Its not just in Assist mode 3, its in Mode 2 as well. I'd like to see those videos you mention.

Anyway sorry for rambling on here.

Thanks

Mitch
PS Maybe I should start a poll and have people vote on whether they experience this cogging, or pulsing or whatever it is so we have a larger data set?

 

[fxr3]

That sounds VERY annoying- to say the least. My st1 or st2 have never done anything like that. I complained that when I stopped pedaling to coast, a noticeable "drag" occurs after a split second of coasting. Stromer said that is the "assist" deactivating- and I agree. I don't think cogging is that exagereted(although, idk. My st1 does not do it at all). But if that was happening off and on as I was pedaling along, I'd call dealer and mfg. asap, for answer. And, if I was mfg.(or, North American master distributor-stromerUSA), I would have already posted and contacted you directly.
I could not make my bike "pulse" yesterday, regardless of pedal effort, mode or gear it was in, etc......
Rest assured, it is not the design, yours has a serious defect, that likely is easily fixed. By someone who knows what they are doing. For the record- this is the most popular US forum for stromer, right?

 

[Mitchell Waite]

fxr - you ARE a fixer, with a very concise response about your experience on both models of Stromer and good advice that the dealer call Stromer and describe the situation. I have passed on your suggestion and will let everyone know what they hear.

Mitch

 

[Mitchell Waite]

Has anyone tried changing the torque sensor sensitivity in the main menu? It sounds like increasing the sensitivity could alleviate the power stuttering, but it's not entirely clear what this feature does. It almost sounds like it does the same thing as adjusting the torque in the tuning feature.

Yes we tried adjusting the Torque sensor. Raising it to 100% "seemed" to decrease the pulsing but not eliminate it to my satisfaction.

 

[Mitchell Waite]

So far here are the responses to this pulsing issue:

1. Pulsing is normal for a DC motor. (86 and still kicking)
2. It is caused by the TMM4 Torque sensor and your cadence (1).
3. There is always a tradeoff between torque and speed.
4. The pulse you feel is all of the assist going away or coming back on.
5. When you exceed the max speed of 20 mph you will feel the bike slow down. This is the normal speed limiter.
6. Going up a hill, once you are at the minimum threshold for the [torque] sensor, the motor will burp on/off.
7. You won't feel the "stuttering" going up a hill.
8. Adjusting the Torque sensor will help lower it. Start with the Torque sensor at 75% then raise it to 85%.
9. You can "clear" [the pulsing] by changing gear or cycling "harder" for a short while until the bike gets used to your new cadence.
10. It might be caused by braking; only brake with the rear brake to minimize pulsing.
11. It may be caused by a bad rear brake sensor.
12. It may be caused by thermal cut off. (Rick H)
13. There is a serious defect". (fxr3)
14. Besides "pulsing" this has been referred to as cogging, burping and stuttering.

Some articles about torque sensing​

e-bike an exercise in torque technology
Now, it's not a perfect system. I found that the torque sensor on the Gazelle eased the motor off a little too quickly when my own pushing decreased when going up a hill, creating an undesirable pulsing sensation at the top of every turn of the crank.
http://www.afr.com/lifestyle/ebike-an-exercise-in-torque-technology-20150226-13fyq0

ebike pedalling sensors
The second kind of ebike sensor, called torque sensor, is more advanced, because it can pick up the effort that you put into your pedalling. Basically, it can tell how much intensely you are pedalling, whether you are just strolling along or really pushing. It can do so by picking up the mechanical torsions which are generated when you pedal.
http://www.ebikeportal.com/general-info/ebike-pedalling-sensors

 

[fxr3]

You forgot mine " your bike has a serious defect".
Although this forum has a great amount of useful info, the list of excuses above only lead you and others to the conclusion that bike is an inferior design. Although #11 could be that serious defect that could easily be fixed.
#7 gets my vote for worst excuse. Even a ebiker doesn't want to ride uphill all the time.
#5 ain't much help either, as st2 shuts off at 28, not 20
#4. The pulse you feel is assist coming back on, not going away(although I'm sure that's what they meant).

 

[fxr3]

Article on torque sensors is pretty interesting. But Stromer in picture is 2 generations old( at least 3 years, I'm guessing). If you ever get to Ventura, you can ride both of mine. I am truly altruistic when it comes to stromer bikes and their customers! Barry 8056250223