I also use my MTB spds on some M520s on the road bike, and while they work well, I can’t help thinking my commute would be more efficient and more comfortable on an SPD-SL setup, but I have a friend who uses the single sided A520’s (touring pedal) with Carbon Specialized MTB shoes, swears by the setup, and obviously like me can use one shoe for all his on & off road bikes.
I guess it’s just comes down to making the decision to lay out £100+ on new pedals/shoes for my Road bike when it’s not my main bike… some Raod shoes have fitting positions for both SPD and SPD-SL but so far as I can see they are normally the cheaper models, I assume their soles will be as flexible as an equivalent MTB shoe, in which case they have no advantage over my current setup and I should go SPD-SL, or is that simply not the case?
Road pedals + shoes ain’t cheap, unfortunately I am…