Are these broader pedals better than normal SPDs?

[drossall]

That's an interesting point, but in a touring shoe where the sole may not be that rigid does the broader pedal help?

Yes, of course it can, depending on how rigid the sole might be. However, try for yourself - good touring/MTB shoes are designed to flex upwards a bit (for walking) but not downwards (for pedalling). By contrast, racing shoes just don't flex at all.

Some of the alternative designs, including Speedplays and Eggbeaters, are used for mountain biking and aren't obviously about support at all, but more about limiting the effects of mud on the engaging and releasing processes. By contrast, most race and sporting riders use variants on the Look design (including Shimano and other rough equivalents), which probably provide more support than any other, albeit with cleats sticking out underneath because they aren't intended for walking at all.

[Brucey]

So is it the D and the M that denote the difference in breadth/support or is it more random than that?

The code is

PD- = 'pedal'

M = Mountain type
or
A = Road Type
or
T = Touring/commuting type


Then there is a number. In theory the higher the starting digit the better quality of the pedal. The number has three (or sometimes four) digits. Some examples

5xx = standard models
7xx and 7xxx = XT models
9xx and 9xxx = XTR models

But there are a few anomalies.

There is a list of SPDs with a brief description of the pedals in the first post of this thread

https://forum.cyclinguk.org/viewtopic.php?f=5&t=66078

however I have not updated it for a while so it is possible that is not complete at present. Obviously most of the models listed are no longer current; if you look for SPD pedals on Madison's website, you will see what ought to be available at present.

cheers

[iandriver]

I've got got several sets of these pedals on various bikes, 530s and XT8000s etc. In all cases, when clipped in the sole is at least 5mm proud of the pedal body. I think most of these pedals will provide no additional support at all.

[Airsporter1st]

Yes, it always the same position-ish. Not horizontal but with the cleat facing down.
My foot knows better than I do! You get your toe a little under it and move forward on top of it which turns it over, then down and it engages. All one quick continuous action, after a while.

I have two bikes now, fitted with these pedals. I ride relatively infrequently (fair weather only!) and I got used to the pedals within two or three 10-mile rides. I find that the muscle memory in my feet (usuall left foot actually) works fine as yours does.I really like them. I use relatively cheap Muddy Fox shoes from Sports Direct and don't feel any lack of support.

[Brucey]

I've got got several sets of these pedals on various bikes, 530s and XT8000s etc. In all cases, when clipped in the sole is at least 5mm proud of the pedal body. I think most of these pedals will provide no additional support at all.

shoes vary. The standard for SPD shoes is to have the bottom of the cleat flush with the sole of the shoe. However on some shoes the cleat pokes out and/or the sole is heavily curved front to back, in which case the shoe won't bear against an extended pedal body. However some shoes go the other way and the cleat is entirely recessed; it is difficult to clip into some pedals with shoes like these because there is a bad clash.

cheers