I used to use quill pedals for years and years with toeclips, straps and cleats. The vintage shoes eventually ceased to fit well, and I found I was riding an anachronism! So at age 60 on the advice of my sister, I bought SPD pedals (Shimano PD-M530, a double-sided platform) with road looking MTB shoes. WOW! They were walkable! Then came the emergency stop and I could not unclip even on the loosest setting. Teetered over and felt like the largest fool on the road. No damage, except to my pride.

The tension was full loose and I realized that the unclip motion (twist heel out) was not natural for ME. I did some research and I found Shimano SPD cleat # SH-56 - the silver SPD cleats. The normal SPDs most encountered (and which I was originally using) are the black SH-51 cleats that came with the M530 pedals I was using. The difference is the silver SH-56 cleats are able to release with more types of foot movements.

I was told they were popular with tourists and people who had knee issues due to the easier release, but that they did not pull loose. I started with them on the lowest tension, and try as I could, I could not pull out during accelleration or climbing, but they would twist out easily at a stop. I was hooked and they are my standard. I later upgraded to the Shimano PD-9020 XTR pedal, a lighter design with a larger platform, that I got at a great mid-winter sale. They also seem to better guide the clip into the shoe slot..

From the Shimano website: Sh-51 cleat fits all Shimano mountain pedals with 4 degree float except 858; Sh-56 Fits all Shimano mountain pedals with top plates and 0 degree float except 858.