ST2 power cutouts


Hey all,

Clocked about 3k miles on my ST2. Started out great. Increasingly, now up to about half the time I ride, I experience power dropping out completely every other second or so when riding at a good steady pace. On the screen, I see the power meter going to zero and then coming back up a second or two later. A few more seconds of power, and then it cuts out again.

Every other ride or so, the bike performs normally.

My theory is that it has something to with the brake sensor on my right (rear) brake. Tonight I discovered through experimentation that my right brake handle doesn't trigger any regen when it's lightly pulled, when the bike is in this annoying "mode". In comparison, if I even slightly pull on the left brake, all power is cut for as long as I'm on it, like usual.

My bike shop doesn't seem to know about this problem, and I'm far away from them on a trip. Does anyone know if there's a way to reach Stromer USA and get a part or help for this? Has anyone else seen this same problem and fixed it?

I read the long thread about pulsing, which is not what I have (well, I had pulsing on day one, until I adjusted power level 2 and made it go away), but I think mixed in there there might be at least one person who has this issue. I started this separate thread to try to get clarity on it and so as not to confuse the torque sensor pulsing problem with [whatever this thing I'm experiencing is].

Thanks everyone.


Active Member
Yes I believe I am having the same riding effects. Not sure what causes it yet. Doesn't occur everytime I ride, so right now I attribute it to my riding skills. Sometimes when I ride away from a stop it feels like my brakes are on momentarily.Yesterday I noticed St2 is sensitive to touching brake lever, causing this drag on motor, which I think is what you are desribing. I just attribute it to the St2 requiring smooth operation of riding skills to perform at a level optimum of performance.


In normal operation, any movement of either brake lever I believe cuts the motor entirely. It's possible that it also triggers regen, but I don't know for sure (and don't care too much).

It's definitely not "smooth riding skills" causing my problem. I ride a ton, and the same flat road can be fine or a crappy experience from one hour to the next. And it's getting worse.

I wish there was a way to put the computer in debug mode so it would show the state of the sensors. That would make it easier to narrow it down. But I suspect it is the brake detection hardware that is flaking out.


Well-Known Member
You can disconnect the electronic s of the the brake levers by pulling the the connectors apart and going for a test ride. Also verify your rear wheel is tight. On my older Stromers sounds similar to the batteries at the end of their life, any way to swap batteries to verify?

I am not suggesting any of the above is definitely your issue but these steps are not too hard to verify technically that they aren't


Thanks for the tips, opimax. The next time I'm on a ride when it's wigging out, I'll pull the brake cable and see if things improve.

I'm pretty sure the battery's okay... it's about a year old, I baby it, and every other ride I do just fine for many miles. My range is generally about 50 or 60m, or less when I'm towing the trailer.

I have a torque wrench and have removed my rear wheel a few times to swap axles, but I'll recheck this as well if the brake cable doesn't yield any insight.