I now use a 52t/39t/24t chainring combo with a 36/11 cassette. Running this setup on a road crankset requires a little more thought and care then a traditional combination of gears. It's common for trikes to put on a 26t small chainring with a 50t large chaining. This allows the long derailleur cage to maintain good tension on the chain throughout the range of gears. But when you want to get the lowest gear possible from your 36/11 cassette by using a 24t chainring while still using a 52t large chainring for high speeds requires a little more effort. Of course you can use internally geared hubs and cranksets but I prefer the simplicity, weight and ease of maintenance of the traditional derailleur systems.
In regards to chain tension you'll find that going small/small (using the small chainring and small cog on the cassette) leaves you with a sloppy chain. Not recommended. To avoid this problem simply avoid shifting the chain to the last 4 smallest cogs on the cassette when using the 24t chainring. You'll find the gear ratios that you sacrifice (highlighted in yellow) while using the 24t are duplicated when shifting to the 39t chainring. Just a different combination of cassette cogs when using the 39t chainring (see chart).
|Chain on 6th largest cog and the 24t chainring. Chain tension is still good.|