On my 52/42/24 crankset, I use a vintage Suntour that I believe was intended to be used on a double. I am not sure but I am guessing that the derailleur was built in the 1980s. The sides on the cage are flat, no weird bends in the cage to help lift the chain.



The 24t to 42t shift is not very smooth but it almost never takes more than 50 feet of distance to complete that shift and usually only takes half of that distance. The 24t is an aftermarket chainring so it is not matched to the pins and ramps on the 42t chainring which likely does not help shifting performance.