.325 7-Tooth Rim Sprocket

This .325 rim sprocket has 7 teeth and replaces the floating drive ring on saws that run .325 pitch chain. Rim sprockets are cheap, quick to swap, and the easiest way to keep a fresh chain from wearing out early.

Rim sprockets and chain life

A rim sprocket is a loose ring that slides onto a splined clutch drum. It floats slightly so it lines up with the bar and chain, and when it wears you replace just the ring, not the whole drum. Worn rims show grooves where the drive links ride. Running a new chain on a grooved rim wears the chain fast and can make it jump.

Common practice is to replace the rim every second or third chain. A 7-tooth .325 rim is a standard size on many mid-size saws.

Keep a couple of spare rims in the saw kit. They take little space and cost less than a new chain, so there is no reason to run a worn one. When you fit a new rim, also check the drum's spline for wear and the needle bearing for roughness, since worn parts upstream will shorten the life of the new rim.

Fit and installation

Rim sprockets come with different spline counts, so match the spline pattern on your saw's drum, as well as pitch and tooth count. Remove the bar, chain, and E-clip or washer, slide the old rim off, check the drum for wear, and fit the new rim.

Shut the saw off and let it cool before working on it, and follow the manufacturer's manual. More parts are in chainsaw parts.