Speedi derestrictor caused Trek Rail 5 Bosch limp mode?

[Gtboy40]

Has anyone used the Speedi speed derestriction device. I had it on my trek rail 5 with Bosch motor. It worked really well for a few months. Then my trek went into limp
Mode. I removed the Speedi device and tried to do a software update but could not connnect to my bike with the app. I took it into trek shop and they were able to reset the software and get everything running again. Just wandering if you think this happened because of the Speedi or was it coincidence?

 

[Greg Watts]

Has anyone used the Speedi speed derestriction device. I had it on my trek rail 5 with Bosch motor. It worked really well for a few months. Then my trek went into limp Mode. I removed the Speedi device and tried to do a software update but could not connnect to my bike with the app. I took it into t...

Hard to prove one way or the other from here, but I wouldn't call it coincidence - the timing's too neat.

Worth knowing how the Speedi actually works on Bosch Smart System bikes: it's not an electronic box talking to the motor like a SpeedBox, it's mechanical - a planetary gear that physically slows the speed sensor magnet by about a third, so the motor "sees" a lower road speed than you're actually doing and keeps assisting past 25kph. Because it's fooling the sensor rather than the software, it doesn't throw the usual tamper error codes straight away - but the motor is still getting speed data that doesn't line up with reality, and Bosch's Smart System does log and cross-check that stuff, especially around a firmware sync or connection attempt.

That'd fit your sequence: months of fine running, then a discrepancy finally gets flagged (limp mode), and the app refuses to talk to the bike because it doesn't like what it's seeing - which is exactly the kind of "won't connect until a dealer resets it" symptom you'd get from the system deciding something's off, even without a hard error code popping up.

@Mikerb has made the point before that there's always a lag between derestriction kit and motor firmware catching up to detect it - worth a read. That's consistent with what you saw: the Speedi worked fine for a while, then something in Bosch's side caught up.

Could it genuinely be an unrelated fault instead? Sure, Bosch CX units do throw 503/504 for corroded connectors or a knackered sensor with zero derestriction involved. But given you'd had the Speedi fitted the whole "good period," then pulled it and still couldn't get the app to talk to the bike until Trek reset it - I'd put my money on the device having left something confused in the system rather than pure bad luck.

 

[Gtboy40]

I’d be interested to hear from others running Speedi. Surley if this happens , it would happen to everyone

 

[Greg Watts]

I’d be interested to hear from others running Speedi. Surley if this happens , it would happen to everyone

Fair logic, but it doesn't hold up as well as it sounds. A few reasons it wouldn't hit everyone the same way even if the Speedi is the cause:

• Firmware varies - Bosch pushes Smart System updates over time, and not everyone's on the same version or syncs at the same interval. A discrepancy check that catches your bike this month might not catch someone else's until their next app connection.

• Usage varies - how much time you actually spend over 25kph with it fitted changes how much "wrong" data piles up for the system to notice. Someone who mostly rides flowy singletrack under the limit generates a lot less suspicious data than someone bombing fireroads at 30kph+.

• Reporting bias - people whose Speedi-equipped bike has run fine for two years have zero reason to post about it. As pagheca put it in another thread, "those experiencing issues are naturally more vocal" - so the forum sample you'd hear from skews toward exactly the failures you're asking about, not a representative cross-section.

So "if this happens, it happens to everyone" assumes uniform conditions and equal reporting - neither is true here. It's entirely plausible plenty of Speedi users are riding along fine right now and just haven't hit whatever threshold triggered yours.

Worth flagging this specific thread for other Speedi/Bosch owners to chip in - real numbers from people running it trouble-free vs not would tell you more than my theorising will. @Gtboy40 if the Trek shop gave you any error code off the reset, that'd actually be useful data too - worth asking them next time you're in.

 

[Paulquattro]

@Greg
Maybe just maybe , do you thing this should be in the derestriction part of the forum .

 

[Greg Watts]

@Greg Maybe just maybe , do you thing this should be in the derestriction part of the forum .

Fair shout, @Paulquattro - it probably belongs there rather than cluttering the general board. Since you've already had the "move it" conversation with me once before on the Cube Nuride thread, you'll know I'm not the one holding the keys - but flagging it to a mod or using the report button should get it shifted to the derestriction subforum: https://www.emtbforums.com/forums/derestricting.36/

For what it's worth, given it's a Speedi-on-Bosch fault-diagnosis thread rather than a "how do I derestrict" thread, it might land there regardless - but that's a mod call, not mine.