A new Shimano Ultegra FC-R8100 left crank arm with a 4iiii Precision 3+ power meter already fitted. Swap it for your current left arm and you have power data for road riding, racing and indoor sessions, plus Apple Find My to help track the bike.

Highlights

  • ±1% accuracy from three strain gauges
  • Ride Ready: pre-installed on a new Shimano FC-R8100 left arm
  • Apple Find My: locate your bike from an iPhone, iPad or Mac
  • ANT+ and Bluetooth for head units, watches and indoor training apps
  • 9 g pod, CR2032 coin cell, up to 800 hours
  • IPX7 water resistance and a 3-year 4iiii warranty

Single-sided power

The Precision 3+ measures from the left arm, using three strain gauges for ±1% accuracy. For left/right balance you need the dual-sided Precision 3+ PRO, and a Precision 3+ left arm is the base for that upgrade: 4iiii can add the drive side later through its Factory Install dual upgrade.

Set-up and calibration

Wake the pod by turning the crank three or four times, pair it with the 4iiii app to update firmware, then add it to your head unit over ANT+ or Bluetooth. Zero offset before you ride: bike upright and still, cranks at 12 and 6 o'clock with the left arm down. Apple Find My is set up from the Find My app on an iPhone, iPad or Mac; the pod starts reporting its location once it has been still for about four minutes.

Fitting at Tune

Fitting, pairing and calibration are separate workshop services and aren't included in the price. The Tune workshop can swap your left crank arm, set the Hollowtech II preload and pinch bolts to Shimano's torque with the right tools, check pod-to-frame clearance, and pair and zero the meter to your head unit.

Options

OptionValuesWhat changes
Crank Length165mm, 170mm, 172.5mm, 175mmArm length; match your drive-side arm

Compatibility & fit

Replaces the left arm of a Shimano Hollowtech II crankset; 4iiii lists this arm for FC-R8100. Choose the same length as your drive-side arm. For a different Shimano crankset, ask us before ordering. Check frame clearance before you order: 4iiii publishes a printable frame clearance guide for the Precision 3+ pod, and after fitting you should spin the crank by hand and not ride if a pod touches the frame.

Warning: This product contains a button/coin battery. Keep new and used batteries out of reach of children. Swallowing can cause serious injury or death within hours. Seek medical attention immediately if a battery may have been swallowed or placed inside any part of the body.

4iiii warrants its power meters against defects in materials and workmanship under normal use for three years from the original purchase date, to the original purchaser. The warranty doesn't cover damage from improper use or maintenance, accidents, or unauthorised tampering or modification, and it's void if the power meter is repaired by anyone other than 4iiii. For warranty support, return the product to Tune Cycles and we'll manage the claim with 4iiii's Australian distributor. This is in addition to your rights under the Australian Consumer Law. Keep your proof of purchase.
  • 4iiii Precision 3+ pod pre-installed on a Shimano Ultegra FC-R8100 left arm
  • ±1% accuracy from three strain gauges
  • Apple Find My, ANT+ and Bluetooth
  • 9 g pod with a 5.5mm profile
  • CR2032 coin cell, up to 800 hours
  • IPX7 water resistance, 3-year 4iiii warranty
Brand4iiii
ModelPrecision 3+ (Apple Find My), Ride Ready
Crank armShimano Ultegra FC-R8100 left arm, Hollowtech II, aluminium
Fits (per 4iiii)FC-R8100
Crank lengths165mm, 170mm, 172.5mm, 175mm
TypeSingle-sided, left (non-drive-side) crank arm
Accuracy±1%
Strain gauges3, measuring all forces in the pedal stroke (4iiii)
BatteryCR2032 coin cell, user-replaceable
Battery lifeUp to 800 hours (varies with Apple Find My use)
ConnectivityANT+ and Bluetooth
Apple Find MyYes (Apple devices only)
Pod weight9 g
Pod profile5.5mm
Power range0–4,000 W
Cadence range30–170 rpm
Water resistanceIPX7
Operating temperature0–50 °C
Warranty3 years (4iiii power meter warranty)
SKU DSG-4iR8100
Brand 4iiii

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