First generation Shimano SPD pedals for road racing bicycles.
Shimano extended their successful SPD offroad system to road bikes and got rid of the fees they had to pay to Look.
The retention system is not so much different from the Look and PD-7401 system, but the whole design is much more compact. A small, steel shoe cleat is held in place by a small, compact pedal. Easy step-in and step-out, lightweight, excellent cornering clearance, 2 cleat designs for fixed (SM-SH70) and float (SM-SH71), good durability: that's basically all you need.
Disadvantages: yes. The LOOK shoe/cleat hole pattern was (and still is) more or less the world wide standard, besides Time/Speedplay. With their road-SPD system, Shimano forced riders to use shoes with the same hole pattern as the mountainbike shoes: 2 slots, as HSB called it, "Lancia-grill". The odd cleat attachment prescribed Shimano shoes or SPD compatoble soles from other shoe manufacturers. Besides that, the compact cleat and pedal design required a very, very stiff shoe sole. Shimano was one of the first to produce shoes with full carbon fibre soles, stiff enough for these compact cleats. Most other types of shoes were too flexible and riders suffered from a too small platform, a too small area to transfer the power.
I was one of the 1st riders to test these pedals, possibly the 1st Europeam rider. During my 1st ride across the hilly "Bergische Land" near Düsseldorf, Solingen and Remscheid, one of the pedal axles snapped off and I had to call a cab to drive me back to the company. Just in time to inform a couple of world class pro teams not to use the pedals we had just dispatched...
The axles were changed to a stronger, more solid design and never caused a problem anymore.
After approximately 2 seasons, Shimano overhauled the hole shoe/cleat/pedal design and that was the end of this generation pedals (Dura Ace PD-7410 and Ultegra PD-6500).
Too bad that its successor PD-7700 (SPD-R) was giving even more trouble...
