Shimano SPD's What's the differance ?

OK.
PD M520,540 and 770

What is the real differance apart from.......... £20,£40 or £50

On the face of it they look the same. My PD-520's have been great so far.Maybe a couple of winters may change that.But would spending the extra on a set of "official" XT 770's really make all the differance

I don't know but would guess similar to other products in the Shimano range. Lower end will on the whole weigh more and last less long and higher end the reverse.

In some of the older SPDs at least you also had the option of multi-release/dual-release and things like that. Don't know about the newer stuff.

Ummmmmmmmmmm.

Looking at the shimano website at the PDF drwaings of each, there's little differance in fact the pdf shows that a number of parts are interchangable.

If not compared them in the flesh, but the pics don't appear to show any real differances either...

540s have a better axle, bearings and seals than the 520. There's also less plastic parts.

The 770 has polished bearing races and stainless steel bearings. This makes the axle run a bit smoother apparently.

The clip in bit works the same on all of them though. You'll probably notice that the 540s and the 770s will probably run smoother for longer. Other than that it's down to looks and price.

As above really. The 540s certainly look nicer than the 520 and is probably the pick of the range in terms of function/value.