I've been digging more into the slightly vexed subject of cleat compatibility. It is easy for all newer 'open binding' pedals (SM-SH51 or SM-SH56 only
) but not so much if you have older cleats and/or older pedals. There is lots of information out there, and it doesn't help that some of it is wrong (either not correct or wrong by omission) for example this link is usefulhttp://stilen.com/bike_stuff/SPD-SPD-R_SPD_SL_cleats.pdf
but has omissions (even allowing for the date of publication) and contains errors such as suggesting that it is OK to use SM-SH55 cleats with PD-A520 pedals; it isn't. In fact it specifically tells you not
to do this in the relevant SI techdoc.
This link is usefulhttp://pardo.net/bike/pic/fail-031/index.html
Single release cleats are black in colour and include SM-SH50, SM-SH51 models.
Multi release cleats are silver (SM-SH55) or silver/gold (SM-SH56)
There are two versions of SM-SH51 which I distinguish with v1 and v2 suffixes; this distinction is not made elsewhere. Some pedals which used SM-SH51v1 cleats originally suffer much reduced float when used with v2 cleats.
Some images of cleats as they appear in the various EV techdocs
Group A. Applies to PD-M323, PD-M737, PD-M525. SM-SH51(v1) may also be used with PD-M323. This is not explicitly indicated in the currently available SI techdocs for the other pedals in this group. [edit: However in a paper EV techdoc for PD-A525, dated 1998, it lists SM-SH51(v1) cleats as being compatible with PD-M737 and PD-M525 models.]
Group B. Applies to PD-A525, PD-M535, PD-M636, PD-M747.
Pedals in groups A and B suffer reduced float (about zero in fact) if SM-SH51(v2) cleats are used
Group C. Applies to PD-M324, PD-M434, PD-M505, PD-A515, PD-M515, PD-M536, PD-M636, PD-M646.
These are 'universal' SPD pedals; they mostly have the final iteration of the 'platform' binding and can be used with any SPD cleat, i.e. SM-SH50, SM-SH51 (both versions) SM-SH52, SM-SH55, SM-SH56, SM-SH70 (*), SM-SH71 (*) are all permissible, (*) without pontoons on most shoes. However float and release action varies with the cleats selected.
Group D. Applies to PD-M858. No other cleats may be used with PD-858. However SM-SH52 cleats will work with Group C pedals and may also work (but imperfectly) with group B and group A pedals.
Group E. Applies to all 'open binding' SPD pedals, i.e. all other SPD pedals not mentioned above, using MTB-style cleats, with the exception of PD-7410 and PD-6500 (which use SM-SH70 and SM-SH71). Group E pedals are prohibited from using SM-SH50, SM-SH-52, SM-SH55 cleats. Models PD-M520, PD-M540 and PD-M959 all predated the sale of SM-SH56 cleats so only SM-SH51(v2) is mentioned in the EV techdocs. However the SI techdocs for these pedals were subsequently revised to permit use of SM-SH56 cleats.
The final group E combination represents the only SPD cleats which are recommended for use with pretty much all 'new model' SPD pedals launched since ~2003, which share a common 'open' binding design with PD-M520. So cleat selection for these pedals is easy. Pretty much the only exception (from this century) is PD-M858.
more to follow