M520 V. M540 V. Xt
Its time for new pedals and I'm sticking with SPDs for various reasons.
Besides weight, what are the differences between M520, M540 and XTs? To be totally honest, XTs are a stretch as funds are low and there are a few other purchases that need to be made also. If the differences are significant, then I would consider the purchase.
Currently I have M520s and they served me well, but are clicking and driving me nuts.
I have only done preliminary price comparisons (tree fort has the $57) - if anybody knows where to find them for a great price that would help
From maintenance perspective, I'd go for 540 is your wallet allows. Locking bolts on 520 are nylon (red box), and this can get damaged easily and go out of tune easily if you aren't used to servicing them. Basically the bearing hub/race (blue box) latches in on the pedal body, and locking bolt would preload the axle with just right load. 540 and above have aluminum locking bolts that gets you the exact load necessary. Nylon ones on 520 is a bit tricky to tighten with the “right” preload – I basically made a mistake in preloading too much the first time I took it apart, and I learned how it works from that experience.
I’m rocking my 540 for the last 5 years with bi-annual cleaning/repacking. I’m 150lb so not hard on pedals but I ride ss, so pedal mushing is required. Bearings are still smooth and clip in/out is a snap as long as I change cleats every year. Since weight is not an issue for me, 540 is all I need. But if every gram counts for you, then go with higher ones.