The folks at Bosch eBike Systems have been in touch to let us know about a couple of updates to their Performance Line CX motor system that will be rolling out on 2019 bikes. Performance Line CX is probably the most widely-used mountain bike motor system, and both changes are to make the CX unit more MTB-friendly.

Support for shorter cranks

We've seen a move towards shorter cranks on e-MTBs over the past couple of years. You don't need the same kind of leverage as you do on a standard mountain bike, and shorter cranks mean there's less chance of grounding your pedals on technical terrain. Many bikes use cranks as short as 155mm, giving an extra 20mm of pedal clearance. Shorter cranks mean that the power is applied by the rider in a different way; in the new software update Bosch has adapted the progression curve in eMTB mode and increased support in Tour mode to get the optimal assistance on uphill sections. 

Better walk assist

Walk assist for an e-MTB generally means pushing a heavy bike up a steep or slippery slope, so it's not the same as easing a city bike up a ramp to the shed. The walk assist update on Performance Line CX motors won't make it any quicker, but it will use sensors to detect the gradient and apply more motor power where it's required, so it's easy to get your bike to the top of the bit you couldn't ride.

Both of these updates sound like they'll make what is already an excellent system even better, so we look forward to trying the updated motors when they start appearing on 2019 bikes later in the year.