New SRAM EX1 E-Bike Specific Drivetrain
Fri 20th May, 2016 @ 9:30 pm
SRAM announces new drivetrain that claims to optimise power delivery on e-bikes. Like it or not, the e-MTB seems here to stay. Pure, untainted ‘push’ bikes will never be replaced, of course, but the movement behind e-bikes is gathering pace and support through its inclusive outlook and e-bikes’ ability to take us further faster. Here’s SRAM to explain the new system:
The EX1 chain is more durable than standard chains to cope with the changes in power delivery
In the early days of mountain biking, riders were forced to settle for products that had been designed for use on road bikes. Modifications were made, but the roots of the design were not completely purpose built, not mountain biking specific. Suspension got better and frame design improved. We began to question the conventional wisdom—challenge the old design ideas that limit what can be done to push the sport into the future. SRAM 1x™ technology was an incredible step forward for the mountain bike drivetrain, and has had a profound effect on not only the way bikes are designed but also the way people ride them.
SRAM EX1 is poised to have the same impact on the E-MTB world. EX1 is the first and only drivetrain available today that was designed from the ground up specifically for E-MTBs.
SRAM EX1 E-BLOCK™ cassette
Until the development of EX1, the E-MTB was seen simply as a mountain bike plus electric assistance. Though that definition is not strictly incorrect, the whole, in this case, is significantly greater than the sum of its parts. The experience an E-MTB provides its rider and the demands placed on each element of the entire system are incredibly different than with a traditional, non-electric-assisted mountain bike. Therefore, the thinking simply has to be different.
Building upon information from motor manufacturers, and its own interpretation of problems associated with using a conventional mountain bike drivetrain on an E-MTB, SRAM’s EX1 development team used advanced data acquisition methods for field testing, combined with traditional lab testing, to create a perfect E-MTB drivetrain solution.
The heart and soul of the EX1 system is its E-BLOCK™ cassette, which is designed to provide the optimum E-MTB gear range, as well as increased battery longevity and component wear life. Its 11- to 48-tooth, 8-speed design allows a 436-percent gear range. Based on its testing, SRAM believes this is the ideal E-MTB gear range.
The EX1 crank is compatible with Bosch, Brose and Yamaha bottom bracket interfaces
The 8-speed design incorporates big (30-percent average) steps between gears. The big steps, in combination with the EX1 group’s single-action shift lever, reduces riders’ tendency to double shift. The single-shift design significantly helps chain and cassette wear.
The cassette, machined from case-hardened tool steel, is narrower than a 10- or 11-speed cassette, which helps maintain a straighter chain line throughout the gear range. Engineers were then able to pair the cassette with a slightly wider, tougher chain to increase durability—which is critical in the E-MTB environment, where shifting is typically done at very high torque and low pedaling cadence, versus the low-torque, high-cadence environment of traditional mountain biking.
The EX1 derailleur employs the rugged, X-HORIZON™ design seen in XX1 and X01 derailleurs
The E-BLOCK™ cassette uses a non-XD™ driver body. The larger virtual front sprocket provided by a midship motor all but eliminates the need for a 10-tooth cassette cog, so the E-BLOCK™ design’s focus is the larger, “climbing” cogs. By combining the proper climbing gears with motor output, battery power is optimized, and lasts longer given the same conditions.
Shifting performance and feel is signature SRAM. As stated previously, the trigger shifter has been designed to shift once at a time—not multiples—but the action is positive and exact. The EX1 derailleur employs the rugged, X-HORIZON™ design seen in XX1 and X01 derailleurs, with a redesigned clutch, cage and pulley design specifically for the 48-tooth cog.
Purpose-built solutions mean greater opportunities.
