This is the original SPD concept and so much more versatile that I’ll not say anything more about the several incompatibly different road-only designs that Shimano have experimented with, apart from noting that SM-SH71 is one (which can also be used with some early designs of original SPD pedals). To fit the cleats, you’ll need to make sure your cycling shoes are compatible with the two-bolt SPD cleats preferred for mountain bike shoes and urban riding, not the three-bolt cleats used on road cycling shoes. If you love living life on the edge, trying out crazy stunts, and need that added freedom to escape the pedals easily, the SH56 is calling your name. They’re excellent for beginners too, as they provide a little more room for error. It’s like having a safety net while you test your biking limits. SH51 if You’re a Steady Rider The cleats which are/were compatible with each pedal (e.g. at the time of launch) are indicated on the EV techdoc for each pedal. So for PD-M515 for example, both cleats SM-SH51 and SM-SH55 are indicated. However for the 'open' style binding pedals such as PD-M520 and PD-M540 only SM-SH51 is indicated. are all possible. FWIW I have discovered that under certain circumstances SPD release can be inhibited with cleat/pedal combinations that seem to work OK at first. To get a clean release you need a combination of three things

There’s an arrow at the front of each cleat to make sure you attach them to your shoes the right way round. They’re interchangeable between left and right shoes. Both cleats are compatible with all Shimano SPD pedals, ensuring riders can select the cleat that best suits their preferences without concerns about compatibility. Additionally, both cleats are made from durable materials, ensuring longevity even with regular use. Understanding Shimano SPD SH51 Cleats Design and Construction The exception is PD-M858, a race-special MTB pedal introduced in 2000 along with its own special cleat (SH52) that nevertheless also fitted pre-existing pedals. This pedal was quietly dropped in 2002 in favour of a new MTB racing pedal (PD-M959) that works with the usual SH51 cleat but not SH52, which nevertheless remains in Shimano’s catalogue for the benefit of anyone who bought M858. Ultimately, the choice between the two depends on factors such as riding style, terrain, and desired release options. By understanding the differences between Shimano SPD SH51 and SH56 cleats, you can make an informed decision and enhance your overall cycling experience. Feature Table: Shimano SPD SH51 Vs. SH56 Cleats FeatureShimano’s two-bolt SPD cleats are preferred for mountain biking and urban riding. But why are there two types? Lawrence Crossman-Emms

It’s important to note that both cleats are compatible with Shimano SPD pedals and can be used for any type of riding. It’s also important to properly adjust the tension on your pedals to ensure a comfortable and safe ride. On the other hand, the Shimano SH52 is a multi-release cleat that offers an even easier exit from the pedal, which is perfect for more experienced riders or those who value flexibility and control. The price of the Shimano SH51 and SH52 pedal cleats is relatively similar, with the SH52 being slightly more expensive due to its adjustable release tension and more robust construction. Conclusion: Is There a Winner? Shimano SPD SH51 cleats are compatible with all Shimano SPD pedals, as well as many other two-bolt pedal systems. The cleats are easy to install and can be adjusted for optimal positioning. Shimano SPD cleats, a popular choice among mountain bikers and other cyclists seeking a secure shoe-to-pedal connection, are available in SH51 and SH56. Here’s a brief overview of each:In general, SH51 cleats are better suited for aggressive mountain biking, while SH56 cleats are better suited for less aggressive riding styles or for riders who need to frequently disengage from their pedals. However, it is important to note that the choice between the two ultimately depends on the rider’s personal preference and riding style. The usual starting point is to position the cleat under the ball of your foot and in line with your shoe. You may find you naturally ride either toe in or toe out, in which case you can adjust the cleat angle. You may also find you prefer the cleat further forward or aft. Shimano SPD SH51 cleats provide a secure and reliable connection between the rider and the pedal. The two-bolt design allows for easy engagement and disengagement, making them a popular choice for mountain bikers and commuters. Choose the cleats that best suit your riding style. For many riders, that will be the SH51 cleats. Stan Portus / Our Media

The Shimano SPD SH56 cleats are compatible with all SPD-compatible pedals. This means that they can be used with a wide range of Shimano pedals, as well as pedals from other manufacturers. The multi-release functionality of the SH56 cleats makes them a good choice for use with spin bikes or other exercise equipment. Comparing Shimano SPD SH51 and SH56 Cleats If you’re an experienced rider, love the adrenaline of fast-paced trails, and prioritize a secure connection with the pedals, SH51 is your winner. Once you get the hang of unclipping, you’ll feel like a pro. One of the potential downsides of using clipless pedals is that they can make it more challenging to walk around off the bike. SH51 cleats have a single direction of release, meaning that the rider can only disengage from the pedal by pushing their heel out in a flat plane relative to the pedal or by pushing it in. This design provides a secure connection with the pedal, making it a good choice for aggressive riding styles that require a lot of power and control.The Shimano SH51 and SH52 pedal cleats both have a 4-degree float, which provides a good balance of stability and freedom of movement for most riders. Weight After you’ve pedaled with your new cleats, you might find you need to re-adjust them. With a good cleat position, you should feel that your knees are in line with your toes and that there’s no strain on your joints while you’re pedaling.