Semi-Compact Chainsets

Both Shimano and Campagnolo are launching a semi-compact 52x36T chainset next year. This is an in-between option with a 52 tooth outer ring and a 36 tooth inner ring (as opposed to the 53x39T standard or 50x34T compact). What makes this intriguing is that Shimano are also making changes to their cassettes to run an 11 to 28 tooth range (as opposed to the old 11x27T maximum). 

Now, if you are already struggling on the climbs with your compact set up (34x27T) then this option probably isn’t best suited for you and you’ll enjoy the benefits of the easier 28T sprocket. However, a lot of people riding on compact chainsets don’t have the ability to spin their legs very fast downhill. This means that when the speed gets into the 60+kph range, you already spinning at 110+rpm. Upping the big ring by 2 teeth to a 52T allows you to ride at 60kph at 5-10rpm lower and sustain a higher speed more comfortably.

At the other end of the scale, a semi-compact 36x28T gear ratio is (as close as makes no difference) the same gear ratio as a compact 34x27T. This means that your smallest climbing gear will be roughly the same. Therefore, you don’t lose anything on the up hills but gain on the down hills; which sounds like a win/win in our books.