Aventon e-bikes offer an important safety feature, motor-interrupt brake levers. These special brake levers turn off the motor of your e-bike when you squeeze the brakes. If you make an abrupt stop, the motor will stop running, even if you forget to stop pedaling or release the throttle.
The sensitivity of the brake levers is adjustable. When correctly adjusted, the bike operates normally and the levers turn off the motor when squeezed. When incorrectly adjusted, the brake levers might turn off the motor without being squeezed (too sensitive) or not turn off the motor at all when squeezed (not sensitive enough). The adjustment process is the same for Tektro hydraulic and mechanical brake levers. Error 25 might appear on the display of your bike if the lever sensitivity is too high. This will prevent the motor from turning on because the system thinks you are pulling the brake lever. If the lever has the sensor adjustment (all Tektro) the sensor should be adjusted first and if this does not resolve the issue, the sensor may be faulty and the brake should be
replaced.
Diagnostics
1. Ensure both brake levers are connected to the e-bike electrical system. Follow the cables from the brake levers to the first plug where it connects to the bike. Ensure each is firmly connected and free of grit or contamination.
2. Depress both brake levers and release them several times. Restart the bike without touching either brake lever. If the error does not clear move to step 3.
3. Disconnect both the left and right brake sensors to see if Error 25 clears from the display. If the error does not clear, replace the wire harness and the controller. If the error clears, plug back in the right sensor plug only. If the error remains present, adjust (or replace) the right lever. Now unplug the right side and plug in the left side lever sensor only. If the error returns, adjust (or replace) the left lever.
How to adjust the lever sensitivity
Most Aventon e-bike brakes have adjustable lever sensitivity (Tektro). Notably, Bengal, Zoom, and Magura brakes do not, in which case Error 25 means immediate brake lever replacement or the error is not applicable.
1. Begin by loosening the lower lever clamp bolt to allow the lever to be rotated up. This will make the set screw more accessible. (Figure 1)
Figure 1
2. Each brake lever has an adjustment bolt and a set screw that holds that adjustment. The adjustment bolt is located where the electrical cable exits the brake lever (red), not to be confused with the brake hose compression bolt (blue). (Figure 2) The sensor adjustment bolt can be turned using a 7mm open-end wrench.
Figure 2
3. The older style of Tektro lever will have a sensor connection with a cable to the harness connection (Figure 3). The newer style will have the harness plug directly into the lever sensor (Figure 4).
Figure 3 / Figure 4
4. The set screw is located on the underside (Tektro) or on top of the brake lever. The Old Tektro uses a 2mm hex(Figure 5), New Tektro uses a philips head screw(Figure 6)
Figure 5 / Figure 6
5. Loosen (but do not completely remove) the set screw to allow the adjustment screw to move. 2mm hex (Figure 7), Philips (Figure 8)
Figure 7 / Figure 8
6. Turn the bike on and monitor the display.
7. Use your 7mm open-end wrench to turn the adjustment bolt out (counter-clockwise) in order to turn the sensitivity down. Old/ New styles are shown in (Figures 9 & 10). Sensitivity can be increased by turning the adjustment bolt in (clockwise).
Figure 9 / Figure 10
8. Turn down the sensitivity until Error 25 clears from the display.
9. Turn up the sensitivity if the motor is running, but does not stop running when you pull the brake lever.
10. Adjustment is complete when there is no Error 25 on the display, and pulling the lever turns off the motor.
11. Tighten the set screw back down until snug (do not over-tighten) and plug all electrical connections back in. Test for safe and correct operation on the road. If you can’t fix Error 25 via sensitivity adjustment In some circumstances (for example, following a crash), the brake lever might be damaged and the sensitivity adjustment may not be able to be brought into the desired range. If this occurs, replace the brake lever.
Notes
Aventon e-bikes will run without the brake levers plugged into the electrical system in an emergency. This can be used to clear Error 25 if diagnosis and repair aren’t possible (for example, a roadside repair). This could be unsafe and should be avoided if possible.