Yesterday, Bosch announced a new drive system and expansion to their Smart System for 2024. This included the Performance Line SX motor, a lightweight addition to their range of mid-drive motors, aimed at lightweight e-bikes across urban, gravel and mountain bike categories. We were invited to test them for ourselves just outside of Frankfurt, with e-gravel and e-urban rides on the agenda.
Less weight is inevitably good on an e-bike. Some are so bulky and heavy they border on impractical, particularly if something goes wrong and you need to get it home without pedalling (don’t ask me how I know).
So weighing in at about 4kg for the battery and motor, this new drive system from Bosch is an exciting offering – even in the urban space. We’ve seen plenty of hybrid and urban e-bikes looking less like bulky e-bikes and instead becoming more aesthetically pleasing, sleek propositions. The SX means that you no longer need to compromise on power or torque to get something that’s nice to look at and practical.
Although we didn’t have an urban environment to test the bikes in, I took it for a quick spin up and down the top of the hill we were situated on for the event. Unlike the off-road bikes, the urban options don’t use SPRNT mode, so I stuck it in Auto for most of the ride as it’s dynamic and really helped me to understand how the motor reacts in certain situations.
From a standing start, it’s responsive and I didn’t feel like I was going to struggle to get it going. Point it up the side of a small mountain like I did, and you’ve got watts aplenty to get you up there as fast or as slow and effortlessly as you want.
The test bike also came equipped with the new Kiox 500 display and the Purion 200 on the bars for good measure. If you want to follow navigation on the Kiox (which is very bright and a great size for my bad eyesight), then I completely understand why you would use the Purion as an additional screen. It helps you to keep an eye on battery range and what assist mode you’re in, which are important metrics for many e-bike riders.
You’re right, we need to remove the vowels to talk like we actually know how to ride GRVL bikes. But in all seriousness, having been lucky enough to ride a few lightweight mid-drives best suited to things like gravel riding, the SX is a serious contender for the best yet. It packs a punch into its tiny package, and is 20% smaller than the Performance Line CX option.
Even with a maximum of only 55Nm, the power is impressive – but perhaps most interesting is the way it’s designed to be used. New for off-road bikes is SPRNT mode, (see, fewer vowels = off-road), and this mode is designed to encourage a higher cadence. Ride to a higher cadence, get more power. Simple.
I found that the assistance was seriously quick, which is to say it’s responsive and you barely have to turn the pedals to get it going. SPRNT mode was quickly my favourite for the gravel route we took. Again it’s dynamic and so reacts to how much power you put through the pedals. It’s also not jumpy and doesn't noticeably top out when you reach the assistance speed limiter. Also, while I’m not saying I’d ride miles and miles without it even turned on, there is noticeably less drag than other mid-drive motors when riding above 15.5mph.
It’s seriously quiet too. Obviously you can hear it whirring away when it’s under significant load, but for the most part it won’t detract from your surroundings, so you can still hear bear steps behind you before it’s too late. 55Nm doesn’t sound like a lot for off-road bikes, but it tops out at 600W of power so you likely won’t easily reach the potential of this bike – at least for most of a ride.
The test loop we did was roughly 10km in length with 230 metres of climbing. I started the ride with 87% battery and gave it back to Bosch with 71% even after using the SPRNT and Turbo modes the most. The e-gravel bike was paired with the new 400Wh CompactTube 400, just for reference.
Overall, I reckon the Performance Line SX drive system is an exciting entry from Bosch to the lightweight market and I’m interested to see which brands agree – and hopefully we’ll get to see some of them this week at Eurobike.
Here's a bit more background on the Performance Line SX motor and updates to Bosch's Smart System from earlier in the week.