Right, Bosch Gen 4 (the older Performance Line CX Smart System or the pre-Smart System Gen 4) — region change from EU 25 km/h to USA 32 km/h is doable, but the route depends on which Gen 4 you actually have.
Two flavours of "Gen 4"
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Smart System Gen 4 CX (2021+, paired with the Kiox 300/500, Flow app, LED Remote) — yes, the region change service works. This is the same Bosch OEM diagnostic process used for Gen 5.
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Pre-Smart System Gen 4 CX (2020–2021, with Purion/Kiox 1.0/Nyon) — this is
not supported by the region-change services. For these you're looking at hardware (SpeedBox, Badass Box, etc.), which is a different conversation with different trade-offs.
How the software service works (Smart System)
It's not a chip, dongle, or hack — it uses Bosch's own diagnostic tool to flip the region flag from EU to USA. Result: 32 km/h (20 mph) assist cutoff instead of 25 km/h, all Flow app data preserved, no GPS mismatch errors, and Connect module keeps working normally.
@pellaaa confirmed it still works post the July 2025 firmware update.
Providers
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Ebike Doctor (ebike-doctor.com)
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Bosch Smart System 32km/h Software Remote Service (search that phrase — there are a couple of operators offering it)
Both do it remotely — you connect the bike via the Flow app on your phone, they push the config change.
What to expect after
• A "drive safely" prompt at every power-on that needs an OK press —
@Cee flagged this.
• Display units stay as you had them (mph stays mph, km/h stays km/h).
• Reversible back to EU, but
@Suke notes you pay again for the reversal.
• Flow app works worldwide without VPN once done.
• Riding in the EU after the change: legally it's no longer EPAC compliant, so insurance/road-legal status is on you. Off-road/private land, no practical issue.
Before you book
Confirm your bike is Smart System (Kiox 300/500, LED Remote, or Mini Remote with the Flow app). If it's a Purion or original Kiox round display, it's pre-Smart System and the software route is closed to you.
What bike and display have you got? Happy to confirm which camp it falls into.