• Warning!!

    Riding a tuned or deristricted EMTB is not a trivial offence and can have serious legal consequences. Also, many manufacturers can detect the use of a tuning device or deristricting method and may decline a repair under warranty if it was modified from the intended original specification. Deristricting EMTB's can also add increased loads for motors and batteries. Riding above the local law limit may reclassify the bike as a low-powered bike, requiring insurance, registration and a number plate.

    Be aware of your local country laws. Many laws prohibit use of modified EMTB's. It is your responsibility to check local laws. Ignoring it, has potential implications to trail access, and risk of prosecution in the event of an accident.

    UK Pedelec Law

    Worldwide Laws

    We advise members great caution. EMTB Forums accepts no liability for any content or advice given here. 


MEGABOBRA: Bosch Smart System Derestriction for Rim Magnet - DIY Project with Support

megabobra

Active member
Jul 24, 2022
189
200
Australia
For those who have been following the existing Derestricting bosch smart system thread, this will be old news, but I figured it be a good idea to branch the build of the Megabobra device into its own thread to manage questions without cluttering the existing topic.


Quick Refresher:

The Megabobra device is an arduino-based open source derestricter for the bosch smart system with rim magnet . It's tested and working with the Performance Line CX range of motors only - please note it is not working with the standard Performance Line range (non-CX). It uses a small electromagnet to replace the rim magnet, allowing the existing speed limit to be lifted to a value of your choice. The build needs some soldering experience but nothing too complicated once your source the components.

I've put together a detailed build guide here.

Some FAQ:
  • YES it will disrupt your total trip distance and odometer, but it's a simple multiplication to get the true figures. ie reported trip distance * chosen multiplier = true trip distance.
  • YES it should work on setups without the rim sensor. Instead of positioning the elctromagnet against the motor case, position it against the speed sensor.
  • Total power usage when the magnet is firing is ~2.4watts, and negligible when it's not firing (ie when the bike is stationary). Magnet is firing only around 8% of the time.

Assembled Option:

For those who would prefer to purchase a pre-assembled Megabobra device, I'll be offering a small batch of ready to install systems as outlined int the post below.
 
Last edited:

megabobra

Active member
Jul 24, 2022
189
200
Australia
I've spent some time sourcing components that would be needed for this project and worked out some costing.

This would comprise all necessary components to install the Megabobra to replace the rim magnet, including the genuine Bosch LPP cable to plug into the motor:

  • Arduino loaded with Megabobra code and additional electronic components soldered in place
    • Covered with double-wall heat shrink for protection
  • Waterproof reed switch
  • Hand wound electromagnet coil
  • All wiring in place and secured
  • Light weight plugs between components to assist with install
  • Bosch LPP cable
  • Magnet for disc rotor
  • Some strips of double-sided tape for reed switch and coil
  • Short install guide to assist with connection/placement/troubleshooting
Total cost per device would be 99USD/80GBP/90EUR or equivalent in your favourite currency. This include shipping worldwide. Payment by Paypal.

Now to manage expectations, this isn't a commercial product. The finish isn't going to be as nice as you might get in a product off the shelf simply because I don't have access to the customisation that large scale affords. For example, where the big companies might have a reed switch with custom-length cable for the perfect fit, I'll instead need to extend that cable myself to make it work. However, all builds would be carefully assembled and tested prior to going out, and I'd be happy to replace any that are not working.

The idea with this is that you unpack the device, feed the reed switch through the frame, position the coil, plug in the LPP and get going ASAP - probably an hour's install on the first run giving it's pretty tight around the motor on some frames?

IMPORTANT
Running from the LPP on the motor requires that port to be activated. If it's not already activated, you'll need to have your local dealer enable it. That's done through the USBC connection on the smart controller on your bars.

There's no integration with the Kiox display, so the display will work as before though all metrics will be offset by the multiplier value you choose. I've been running my device on Bosch's latest firmware version, but critically, ensure you're not using GPS when running the device - I've got no confirmation on this, but I would expect detection if GPS speed doesn't agree with sensor reported speed.

Assuming there's still interest now that you know the pricing, please like/reply to this if you're happy to go ahead so I can understand numbers for the components I'll need to bring in. Time frame wise, it would probably be 4-6 weeks before I can get any devices out due to the lead time with these required components. Ordering just be through Private Message where you can specify the required multiplier and wheel circumference for your setup.

Tagging a few who had expressed interest already: @littleleye @Lavouch @dlatch @timothe @Zave @przemass
 

megabobra

Active member
Jul 24, 2022
189
200
Australia
Hi all,
Interesting development with the Flow app here.

While I've always suggested disabling GPS/location when using the megabobra, this update from Bosch means you can't access the Ride screen without location being enabled. Not an issue once you're up and running (as long as you don't intend on using the app as your display), however it does make the setup mode a bit tricky.

Where setup mode will pulse an ongoing fake speed to the motor to assist with coil placement while stationary, you'll only be able to view the speed in the Ride screen, with location enabled. I suspect it wouldn't take much for the app to see that the wheels are turning (by the setup mode) but GPS is stationary...

I don't have a Kiox display, but I THINK it would be unaffected by this? Is anyone able to confirm?

Thoughts on this?
 

tatane

New Member
Jun 25, 2023
59
40
Southern France
Guess we'll just have to enable GPS for setup mode then, and ensure we disable it afterwards.
I can't see any valid legal ground for them to flag the bike as tampered with just because wheels are turning while GPS is stationary; this ought to happen when working on a bike stand and forgetting to turn off the motor befor turning the pedals (happenned to me more then once)

Edit : it also wouldn't register any motor assistance at that time since we don't push hard on the pedals and assistance may be disabled for the duration of the test too, making it very akin to what happens regularly on my bike stand when working on the shifter for example ... )
 
Last edited:

megabobra

Active member
Jul 24, 2022
189
200
Australia
Guess we'll just have to enable GPS for setup mode then, and ensure we disable it afterwards.
I can't see any valid legal ground for them to flag the bike as tampered with just because wheels are turning while GPS is stationary; this ought to happen when working on a bike stand and forgetting to turn off the motor befor turning the pedals (happenned to me more then once)

Edit : it also wouldn't register any motor assistance at that time since we don't push hard on the pedals and assistance may be disabled for the duration of the test too, making it very akin to what happens regularly on my bike stand when working on the shifter for example ... )
Excellent points here, thanks tatane.
 

mav75

New Member
Jul 9, 2023
4
1
Wales
Hey all
After a lot of digging around on what to do to my Smart CX with rim magnet I've discovered this . Thanks @megabobra ! I'm glad I didn't buy the 1st chip I saw after all of the conflicting posts I've seen around this thread . I'm interested in buying the ready made kit,,, just out of curiosity, how do you turn off the GPS ?
 

megabobra

Active member
Jul 24, 2022
189
200
Australia
Hey all
After a lot of digging around on what to do to my Smart CX with rim magnet I've discovered this . Thanks @megabobra ! I'm glad I didn't buy the 1st chip I saw after all of the conflicting posts I've seen around this thread . I'm interested in buying the ready made kit,,, just out of curiosity, how do you turn off the GPS ?
Hi Mav, no worries I'll add you to the list.
For GPS, simplest is just to turn off location services in your phone. If you do want to use GPS for another purpose while riding, for Strava or something, just ensure you don't grant Flow access to it. Does this help?
 

Spagnol

Member
May 2, 2019
93
49
Italy
Hi Mav, no worries I'll add you to the list.
For GPS, simplest is just to turn off location services in your phone. If you do want to use GPS for another purpose while riding, for Strava or something, just ensure you don't grant Flow access to it. Does this help?
Count me as well 😊
 

Okelo

New Member
Jul 12, 2023
4
5
Bulgaria
Hello @megabobra
Please please please,... if the is the remotest chance that I could be included as well, please drop me a line.
I have spent the best part of a year going from one place to another here in Bulgaria, trying to get this issue resolved.
 

megabobra

Active member
Jul 24, 2022
189
200
Australia
Hello @megabobra
Please please please,... if the is the remotest chance that I could be included as well, please drop me a line.
I have spent the best part of a year going from one place to another here in Bulgaria, trying to get this issue resolved.
No worries Okelo, happy to add you on 😎

Still a few weeks away though!
 

megabobra

Active member
Jul 24, 2022
189
200
Australia
Sign me up please!

The first batch of ten Megabobra's is spoken for. Assuming they're positively received, I'm happy to build some more if there's further need. I suspect their might be given Ashley's success with the standard speed sensor (ie non rim magnet) here ;) ;)

For those of you who already making up that first group, I'll reach out directly by private message. Sadly I'm still waiting on the Bosch cables - hopefully in the next week or so.
 

mo02ny

New Member
Jul 17, 2023
2
1
Sydney, Australia
Hey @megabobra good to see a fellow Aussie on here
Please count me in for one from the next batch. If you have capacity to allocate one from the first batch, that would be awesome, as I'm ready to go. I can't DM as I've just signed up, but I'll lookout for a message from you. Thanks!
 

megabobra

Active member
Jul 24, 2022
189
200
Australia
Hey @megabobra good to see a fellow Aussie on here
Please count me in for one from the next batch. If you have capacity to allocate one from the first batch, that would be awesome, as I'm ready to go. I can't DM as I've just signed up, but I'll lookout for a message from you. Thanks!

Gday mo02ny,
No dramas. Are you running the rim magnet? Let me drop you a message.
 

megabobra

Active member
Jul 24, 2022
189
200
Australia
Finally, most of the components turned up for the first batch of Megabobras. Still waiting on the Bosch LPP cables, but the remaining parts are assembled and are waiting to drop the cables in.

There have been a few upgrades since the original tutorial. These models all now run on the RP2040 boards; more than 10x faster clock speed and less than half the size than the original Arduino Nanos. These devices now also feature the Setup mode jumper cable to assist with electromagnet placement.

Once the Bosch LPP cables are installed, these will be sealed up in heatshrink end caps. I'm finalising a manual to assist with setup and operation - this will be ready by the time the cables arrive.

Now is a good time to remind everyone that these devices, as with any which lift the assistance speed, are only for use on private property, may increase wear on your drive train and may void the warranty on your motor.

I'll begin reaching out to everyone directly by direct message in the order they expressed interest once the Bosch LPP cables have arrived.

mega1.jpg mega2.jpg mega3.jpg
 

EMTB Forums

Since 2018

The World's largest electric mountain bike community.

499K
Messages
24,250
Members
Join Our Community

Latest articles


Top