Ring Gear

Ring gear sometimes called a starter ring. The ring gear is a medium carbon steel ring with teeth. These are fitted on the flywheel of an internal combustion engine. The hardened teeth of the starter ring are driven by the smaller gear of the starter motor. The function of the starter ring is to transfer torque from the starter motor pinion to the flywheel. As a result of the torque transfer to flywheel, it makes the engine to begin the cycle.

This is most commonly made by forming a length of square or rectangular steel bar into a circle. Welding is done at the ends together. After which various operations happen to complete it. Above all normalising is done to remove stresses and improve the properties in the weld area. Similarly Turning and generating the teeth by gear hobbing is done followed by heat-treatment operations.


Furthermore the teeth of the starter ring are hardened to increase their strength and wear&tear. The normal hardness at the pitch circle diameter is 45-55 HRC (Hardness  Rockwell C). Likewise the higher the number the harder the material.

The body of the ring is untreated to give ductility and this is done because to weld it to the flexplate and also for shrinking onto the flywheel.

There are multiple types of ring gears available based on the application of the vehicle. The gear ratios can be 80 Teeth, 91 Teeth, 101 Teeth etc