Chain Alignment Tools

This month’s ‘Tool of the Month’ will be of interest to all those who do even the simplest maintenance to all save shaf-driven bikes. I am going to look at the thorny issue of final drive chain alignment, a problem that many doing basic home servicing seem to gloss over. It is of paramount importance that the final drive chain and its driving and driven sprockets line up accurately.

Between the inner plates are cylinders of steel joined to them known as bushings. The pins pass through these bushings with a bearing fit. The pins also pass through the outer chain plates and are peined over either side to rivet the parts together. Around the outside of the bushings, again with a bearing fit are the rollers. On good-quality chains there is a rubber O-ring around the pins between the inner and outer plates, which helps keep the bearing lubricant between the pin and bushing from escaping. Once that oil or grease is gone the pin and bush bearing surfaces will wear very rapidly and the chain will need replacing. People talk about chains stretching, but what actually happens is that wear causes the hole in the bushing to become bigger and the pin diameter to become smaller. Once each pin diameter is reduced then each one loses strength, making it more likely that under hard acceleration one will snap, which is guaranteed to ruin the rider’s day and very likely cause damage to the final drive casing around the front sprocket or even wrap around the rear sprocket, locking the rear wheel…