Brose motor: belt snapped or slipping? Symptoms, the right belt kit and costs

October 1, 2026

In short: In the Brose motors Drive C, S, T and TF, a toothed belt transmits the power from the electric motor to the drive. If it snaps, the assistance fails, but the bike can still be pedalled without the motor. For replacement, there are belt kits for motors with aluminium and with magnesium housings. They are fitted with the motor opened.

What the belt in the Brose motor is for

In the Brose Drive, the electric motor drives a toothed belt via a gearbox, and the belt transmits the power to the belt pulley. Under the belt pulley sits a freewheel that decouples the motor when you pedal without assistance. The newer Brose Drive³ Peak, by contrast, works without a belt, using helical gears.

How to recognise a defective belt

Assistance suddenly gone: This is the typical sign of a snapped belt. Some workshops also describe a high-pitched whistling.
Unusual noises: A worn or loose belt can make conspicuous running noises.
Assistance fluctuates: Riders report that the power repeatedly surges and fades when the belt tension slackens.

Distinguishing it from the freewheel: If the crank spins without any power getting through, or the pedals turn along when coasting, a freewheel is more likely to be the cause. See our guide Brose freewheel defective

Known cases with the Drive S Mag

In 2020, BIKE-Magazin reported on snapped belts in the Drive S Mag from model year 2019. Brose named isolated torque peaks as the cause and released a software update via certified dealers. According to nimms-rad (2024), a longer-lasting belt followed in 2021. The specialist dealer can read out whether your motor has the update.

Which belt kit fits?

What matters is the housing material of the motor:

Aluminium housing: kit for Drive C, S, T and TF with alu housing. Retailers often call it “Gen. 1”.
Magnesium housing (Mag): separate kit, often called “Gen. 2” in the trade. The Drive S Mag arrived in 2018 as the first Brose motor with a magnesium housing.

“Gen. 1” and “Gen. 2” are retailer designations, not official Brose names. Do not confuse them with the 2nd-generation Specialized Turbo Levo, which uses a Brose motor. According to retailer information, the Brose kits contain the belt, seals, a grub screw and an O-ring; the Mag kit additionally includes housing screws. The belt tensioner pulley is a separate part. Exactly what our kit contains is stated in the respective product description.

How the replacement works

To change the belt, the motor is opened and then closed again with a new housing seal. Retailers recommend installation only by specialist workshops and experienced mechanics with special tools. Brose handles service via registered specialist dealers. As long as the statutory warranty or a guarantee applies, the specialist dealer is the first port of call.

What the belt change costs

Belt kit at bikely: €69.95 for Drive C/S/T/TF Alu, €94.95 for Drive S Mag (as of 1 October 2026).
Workshop: A specialised Brose repair service quotes €199 for replacing the belt and seals, plus €149 for removing and refitting the motor and €49 for the diagnosis (price list brose-reparatur.de, retrieved 1 October 2026).
Replacement motor: The same provider quotes €799 to €999 depending on the model.

You can find a comparison for all brands in our guide How much does an e-bike motor repair cost?

Matching parts: Belt kits for Brose · Freewheels for Brose · All Brose spare parts

Sources: emtb-news: Brose motor taken apart (2017) · BIKE on the Drive³ Peak (2023) · BIKE: update for the Drive S Mag (2020) · nimms-rad on the development of the S Mag (2024) · Workshop information on belt replacement · Retailer information Mag kit · Retailer information Alu kit · Brose service procedure · Price list brose-reparatur.de. As of: October 2026.