The Rally system uses Shimano SPD compatibility, with aluminum pedal bodies and steel engagement mechanisms built to handle impacts that road platforms would never see. At 222 grams per pedal for a 444-gram pair, they match the weight of the single-sensing XC100 since both use the same body construction and spindle design. The trade against non-powered SPD pedals runs roughly 50 grams per pedal, which Garmin allocated toward durability rather than minimizing weight. The bodies carry a 105-kilogram rider weight limit and IPX7 water resistance rated for one-meter submersion for 30 minutes.

Accuracy hits plus or minus one percent, matching most pedal and crank-based systems and verified through comparison testing against Wahoo Kickr trainers showing variance within the one-percent tolerance across the power curve. Temperature compensation happens inside the spindles to keep readings consistent as conditions change, with field calibration recommended before rides and a 10 to 15-minute acclimation period for the bike to match outdoor temperatures. The system auto-shuts after four minutes without pedal rotation, requiring a backpedal or half-stroke to reactivate on long coasting descents.

The modular spindle design threads into Rally RS and RK road pedal bodies, which means you can swap between SPD mountain platforms and three-bolt road systems using the same power measurement hardware. The body conversion requires removing the battery board secured by small screws, pulling the spindle from the old body, and installing it in the new platform—a process that takes more time than swapping complete pedals but preserves your investment if you're running different cleat types across road and off-road bikes. Most riders leave the spindles installed in one body type and move complete pedals between bikes with matching cleats rather than converting bodies regularly.

Installation follows standard pedal procedures with 34-newton-meter torque spec and reverse threading on the left spindle. Wrench flats accommodate standard pedal wrenches, and included washers adjust Q-factor from 53mm to 55mm if chainring clearance requires spacing the pedals outward from the crank arms. Pairing with Garmin Edge computers uses ANT+ for stable connections, though Bluetooth works with third-party head units and training platforms including Zwift, TrainingPeaks, and TrainerRoad. The Tacx training app connects for indoor sessions, syncing power data across desktop applications.

The pedals ship with Garmin cleats equivalent to Shimano's SH51 multi-release design, compatible with both SH51 and SH55 cleat types if you're already running SPD shoes. Release tension adjusts via screw mechanism, and engagement happens with the positive click characteristic of quality SPD hardware. Stack height measures 13.5mm, and the platform provides stable contact area when unclipped. Battery replacement uses standard LR44 or SR44 cells accessible through the spindle end cap, with battery board indicators flashing red when power drops below operational thresholds.

The Cycling Dynamics metrics provide insight beyond basic power numbers, particularly for riders analyzing pedaling efficiency, tracking recovery from injury, or optimizing position for specific terrain. Seated versus standing watts reveal whether you generate more power in or out of the saddle on climbs, informing pacing strategy for long ascents. Power phase data exposes dead spots in the pedal stroke where you're not applying force, highlighting opportunities to improve circular pedaling patterns. Platform center offset confirms whether cleat position matches your natural biomechanics or if adjustment would reduce knee strain.