What is a Rim Magnet & How to Check if Your Bike Has One
From 2025, many Bosch-powered eBikes use a rim magnet speed sensor, and knowing whether your bike has one is crucial for choosing the correct tuning kit. Scroll to the bottom for links to our recommended tuning kits.
What is a Rim Magnet?
A rim magnet sensor looks like this. It's a small magnetic sensor attached to the rear wheel's valve stem. It works with a sensor in the motor to measure your wheel's rotation and calculate your speed.
Why does this matter? A lot of eBikes from 2024 onwards are fitted with these sensors. They require a specific type of tuning kit. Our plug & ride kits will not work with this sensor.
Why This Matters for Tuning Kits
Using the wrong kit type will not work - the kit is designed to interact with a specific type of speed sensor
How to Check if Your Bike Has a Rim Magnet
Step 1: Look at Your Rear Wheel Valve
Check the area around your rear wheel's valve stem (where you pump air into the tyre). If you see a small black module attached to the rear valve, you have a rim magnet.
If you don't see a small black module on the valve, you may have an internal sensor as shown in the example on the right above. Rather than be visible on the valve stem, it's hidden within the wheel rim.
Visual Guide
Rim Magnet System (see images above)
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Small module attached to the valve on the rear wheel (either outside or inside the rim)
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Common on newer Bosch Powered bikes from 2025 onwards
No Rim Magnet (see images below)
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A physical magnet will be on the rear wheel spokes
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Or, a rotor magnet will be found near the rear cassette
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Common on older Bosch systems and Smart System bikes pre 2025
They look like this;
Or:
My bike has a Rim Magnet, what kit do I buy?
Currently we only supply tuning kits for eBikes with either a Gen5 CX (BDU code 38) or Gen4 CX (BDU code 37). We do not have kits for Performance Line Gen3 or SX motors. If you're unsure what motor your bike has, you can contact us here
Our Recommended Kit
For Bosch Performance Line CX Gen5 + Gen4 with Rim Magnet:
→ VOLspeed for Bosch CX + Rim Magnet (PN 1405)
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For Bosch Smart System without Rim Magnet:
→ VOLspeed for Bosch Smart System (PN 1358)
For older Bosch powered bikes (up to model year 2022)
→ VOLspeed V4 for Bosch Powered Bikes (PN 1233)
Not Sure? Here's What to Do
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Take a photo of your rear wheel (near the valve) and your chainstay
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Send it to us - we'll confirm whether you have a rim magnet
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Or share your bike make, model, and year and we'll look it up for you
Need help? Contact us with photos of your rear wheel area and we'll identify the right kit for you.