Mugen MRX-5 1st Gear 17T Precision Pinion - MUGEN AM-MRX5-H0758  [AM-MRX5-H0758]

Overview of the first-stage pinion

The Arrowmax AM-MRX5-H0758 is an aftermarket 1st gear pinion made to pair with the Mugen MRX-5 clutch/pinion setup. Cut from 7075-T6 aluminium and treated with a hard surface finish, the pinion is intended to lower inertial mass while resisting wear, keeping the original clutch interface intact. Available tooth counts run from 16T to 21T so you can tune low-speed drive and initial acceleration on the MRX-5.

Installation is straightforward for anyone familiar with MRX-5 gear swaps: remove the stock 1st gear from the clutch bell, fit the Arrowmax pinion onto the clutch hub, and set the correct mesh with the spur. After a short shakedown run, re-check mesh and confirm temperatures are OK before pushing hard.

In practice, stepping down the tooth count sharpens spool-up and gives crisper launches, while higher counts increase first-stage gearing for stronger pull at low revs. Use the offered tooth spread to tune starts and traction to suit your track surface.

Fitment details

• Mugen MRX-5