I am with Dazerjay here.... But mind that wide grip chins alone will not give you fully developed lats, alternate them every workout with medium grip chins. also reverse grip bent rows , dumbell rows and one-arm cable rows are excellent lat builders.
Also I noticed that free chinning is far more demanding than pulldowns but it renders better results. If you just start with them or after a short layoff, it's really hard to do a good amount of reps but you should hang in there and after a month you will do fine.
What i really like to do is some triple drop sets on a chinning station. First I lower the platform to the floor (put a plate on it to keep it down), so that i can use my free bodyweight, on failure i use the platform and the weightstack to assist me a little....