Ochain S is a 104 BCD spider damper that lets the chainring rotate rearward a few degrees, so pedal kickback and drivetrain noise are taken out before they reach your feet. This version replaces the original direct mount chainring on a Bosch BDU38 motor, bringing the same effect to an eMTB.

Highlights

• Lets the chainring rotate rearward to decouple the drivetrain from the rider and suspension
• External Travel Adjust dial: Lock, 3°, 6°, 9° and 12°
• Fits the Bosch BDU38 (Gen 5) motor only
• 104 BCD, 3 mm offset as standard
• SRAM-listed weight 165 g (spider)

Set it on the trail

Push the crank forward, pull the knob out and turn it to the setting you want. SRAM suggests 3° for smooth XC and trail riding, 6° for rougher trail and enduro, 9° for consistently rough enduro or park and 12° for the roughest DH terrain; Lock is there for back-to-back comparisons.

Service

SRAM sets an elastomer replacement every 100 hours and a full service every 200 hours or once a year. Both kits are available, and Tune Cycles can do the work in the workshop.

Compatibility and fit

Ochain S and E fit only the Bosch BDU38 (Gen 5) motor and replace its original direct mount chainring; any plastic spacer behind the original spider must be removed. Use a 104 BCD chainring with the short chainring bolts and nuts for the standard 3 mm offset, and tighten SRAM chainring bolts to 9 N·m, rechecking after the first ride. Check chainline and frame clearance before riding.