As I remember, the difference between the m520 and the m540 is just a cromo spindle. I use m520's on my MTB and steelie. They are definitely my pick out of the three. They can be had for like $35-40 if you look around a bit. They are bombproof. I've used them on both bikes for a whole season with no noise and no retention problems. I haven't pulled out with the stock tension. If they DO crap out, 35 isn't too much...