Chain Stretch

We all get chain stretch at some time and Steve Hilliker has asked us a few questions on the subject, so here are our thoughts on this inevitable problem.

Question:
I recently had my bike tuned. The mechanic told me the chain had stretched. The value he mentioned was “0.75″. When I asked if I needed to change the chain now, he said not yet but soon. What is the rule of thumb for when to change your chain?

My bike is a Cannondale Six with about 600 miles on it. I use chain lube now, but missed that maintenance need for the first 200 miles or so.

Thanks.

Hi Steve.

Chain stretch will hit us all eventually and the easy answer as to when to change your chain is to do it before you need to, in other word before it damages the teeth on the cassette. The problem is knowing when that might be.

Chain wear is different for all of us, because we all ride differently. Some of us ride roughly, and change gears continually putting stress and strain on the chain. While others are more gentle when riding, smooth pedalling and sensible gear use. Strength and weight also plays a big part in how long a chain will last.

The weather in your area is also an important factor in how long your chain lasts as rain, snow, grit, sand and road salt will kill your chain quicker than for someone who lives in a dry region.

Usually the first time we realise our chain is worn is when it skips on the cassette and won’t stay in some of the gears. You will find that the chain and cassette wear at the same time, but more so on the sprockets you use most. If you replace your chain regularly than the more expensive cassette will last longer, similar to why you should change the brake pads on your car before they wear out the disks as they are a lot more expensive.

So, how do you know when it’s time to get a new chain?

Without taking the chain off the bike, measure 20 half links or 10 full links, from the centre of the link pins, with a new chain this should measure 254 mm. You will need to change the chain before it gets 2 mm longer over those 20 half links.

There are special chain wear tools, two very good ones are made by Park Tools. Remember to clean your chain regularly and use a good quality lubricant, this will help it last longer and give you better gear changes and run smoothly.