What are they?
SPD-SL refers to a type of clip-in pedal system. Clip-in pedals are traditionally known as clipless pedals. Clip-in pedals are used with cycling shoes that have cleats attached to their soles. You clip the cleat into the pedal so that your shoe is connected to the pedal while you’re pedaling. The SPD-SL cleat attaches to your shoe using three bolts. (Another type of pedal system called SPD uses two bolts).
These pedals have to be used with SPD-SL cleat compatible shoes installed with SPD-SL cleats. SPD SL pedals with 3-hole cleats are popular with road cyclists and triathletes, but may also be found in some indoor cycling applications.
What are their benefits?
The SPD-SL cleat used for compatible clip-in pedals is larger than cleats used with SPD clip-in pedals. With a wider pedal platform and more contact area between the pedal and the cleat on your shoe, your pedal stroke will be more stable. You will also notice improved power transfer and increased efficiency - which will really count when you’re pushing hard.
The benefits of clipping into your pedals will quickly become obvious. You’ll likely be able to pedal with a higher cadence, improved power transfer, and better efficiency. By securely locking your foot in the correct position on the pedal, you will be able to pedal harder and faster without fear of your foot slipping off the pedal.
Your pedal stroke will likely also become smoother when you clip in, as the secure connection enables you to push down through the first half of your pedal stroke (using more of your quads) and pull up through the second (using more of your hamstrings).
Off the bike, walking in shoes with SPD-SL cleats is a little trickier as the cleat protrudes from the sole of your shoe.
How do you use them?
If you are new to clipping into your pedals, you may want to practice the motion of clipping in and out of the pedals on a stationary trainer or in an open parking lot to get a hang for the motion before hitting the open road. With practice the action will become easier and easier until it becomes almost second nature.
You can only clip into SPD-SL pedals on one side of the pedal. Rather than needing to flip over the pedal, you can trust your clip-in target to always be in the same position - pointing upwards. Place the front of the cleat into the catch point at the top of the pedal and push down and slightly forward. You will hear a satisfying click as your foot secures into place. To release your foot from the pedal, turn your heel away from your bike to disengage.
Installation:
Finally, a note about cleat installation. You’ll first need to determine what is the best cleat position for you and your pedaling style. Your local bike shop or professional bike fitter are great resources to help sort this out. Once you’ve determined ideal cleat position, place a small dab of grease into each of the captive nuts on the base of your shoe and then use a torque wrench with 4 mm hex bit to tighten the bolts to Shimano’s recommended torque setting of 5-6Nm (43-52 IN LB). The grease helps keep the bolts from seizing in place, while following the recommended torque setting assures the bolts are sufficiently secure but not overtightened, which can damage your shoes or the bolt.