TeamCBC Weekly Cycling Tip – Chainrings and Cassettes, what do those numbers mean?

Have you ever had another rider start asking questions about your chain set using lots of numbers and you answer, “hmmm, I think so.” Well, here are what those numbers mean and what they mean to you.

A “Compact” chainring is 50/34. This means there are 50 teeth on the big ring and 34 teeth on the small ring. Typically it is paired with a 11/25 cassette or as large as a 11/34 cassette. Just like the chainring, this means the smallest gear on the cassette has 11 teeth and the largest gear has 25 or 34 teeth.

A “Standard” chainring is 53/39 and is typically paired with a 11/25. There are other combinations, but this is the most common.

What does that mean? Your top gear in a Standard chain set is 53 teeth turning 11 teeth as opposed to the Compact which is 50 turning 11. Therefore the Standard chain set turns your rear wheel 4.82 rotations with each turn of the large ring and the Compact chain set only turns it 4.55 rotations. This correlates to you moving 7 more inches per rotation, which, if you supply the same amount of power, will make you go further and therefore, faster.

On the other end, the lowest gear in a Compact is 34 teeth turning 34 teeth as opposed to the Standard which is 39 teeth turning 25. Therefore the Compact chain set, with the smaller, small ring, will allow you to spin more at the low end and go slower.

What does this mean to you? If you’re the average recreational rider, the Compact chain set with a 11/25 cassette is probably right for you. If you like to climb hills, you might prefer the 11/34 cassette. If you’re a strong rider and just want to go fast, then the Standard chain set will probably work better for you.

Again, there are other combinations. For example, the Trek Edmoda has a 53/39 chainring with a 11/30 cassette and the Specialized Tarmac has a 52/36 chainring with a 11/30 cassette.

This is all at a very basic level. There are other considerations such as the smoothness of the shifting or going to a smaller chainring with a cassette that has only a 10 tooth sprocket instead of 11.

Quote of the week: “Make friends with pain, and you’ll never be alone.” Ken Chlouber – Leadville 100 founder

Here is a video comparing a Standard chain set versus a Compact chain set by climbing Passo di Mortirolo. Bill Catchings and I rode up this climb last year with a compact chain set (11/34). We could have used something even smaller. The rider in the video did it in a little over an hour. It took Bill and I over 2 hours. Vincenzo Nibali is the KOM in Strava at under 45 minutes.

Stay safe!

Rick Bunnell

President, TeamCBC