Cruising at speeds above 28 mph on straightaways, or tearing up hills at only moderately diminished rates, is unquestionably a thrill on an e-bike. Still, the motor on the ST 1 or 2 bikes has a thermal limit (i.e. temperature ceiling), which kicks in when the motor overheats. The motor doesn’t shut down, only reducing pedal assist to prevent damage.
My experience is that overheating occurs mostly when climbing hills, not on flat straight-aways or even gentle climbs. Very steep inclines are entirely another story.
Stromer describes temperature management here, and I offer the following observations below:
- Maintain a Fast and Easy Cadence: According to Stromer, pedal assist works proportionally to the rider’s effort: “Motor output is… primarily dependent on individual pedaling output and not on the temperature of the motor” (see link above). Keeping a steady pace helps the motor maintain optimum efficiency and reduces overheating. If find that even if I can maintain my effort in a more difficult gear, easing up and pedaling fast helps. The easier it is on your legs, the easier it is on the motor.
- Pedal in a Lower Assist Modes: On very steep ascents or even long gradual ascents, it is actually possible to step down to a lower assist mode, from 3 to 2 (except if you have personalized the middle setting), and still maintain a higher-than-average speed. A rather fit individual can easily conquer even very steep, very long ascents in the middle setting. Pedal assist is diminished, but still apt.
- Reduce Weight: File this recommendation under: if possible, unburden your ride. This is not always possible, especially if you are commuting and carrying necessary gear. Though whenever possible, I opt for lighter weight gear. It helps.
- Rest: This only offers minimal relief, for as one returns to the ride, overheating can occur very quickly. Still, resting does give the motor a chance to cool down.
- Keep an Eye on the Power Output: The top-tube display includes a bar, detailing power input. Doing what it takes to avoid the max output (see suggestions above) helps. However, as Stromer states, “Motor output is nevertheless primarily dependent on individual pedaling output and not on the temperature of the motor. A short bar does not therefore automatically mean that the system is running at its thermal limit.”
Awareness of these factors helps considerably.
© 2017, Mark R. Adams. All rights reserved.