Technical Aspects of Clipless Pedals

By Rich Gibbs

Riders who are interested in getting clipless pedals, particularly for the first time, are often confused by the apparently wide array of choices that are available. This article is an attempt to clarify what the dimensions of choice actually are, and also to explain the concept of "float".

Perhaps the most important thing to keep in mind is that clipless pedals really can't be discussed in isolation: they are part of a system that comprises not only the pedals, but also shoes and cleats.

Basic Types of Clipless Pedals

Broadly speaking, the two main types of clipless pedals are those made for mountain (ATB) bikes, and those made for road bikes. ATB pedals generally are two-sided (they have a binding on both sides), and have a more or less "open" design to allow clearing mud and other debris. Road pedals are typically one-sided; many also have a larger platform underneath your foot.

There are also both ATB and road shoes. ATB shoes typically have a lugged, stiff sole, with the cleat mounted in some sort of recess, to make walking reasonably easy (although not necessarily comfortable). Road shoes typically have extremely stiff soles, with the cleat projecting from the bottom at the ball of the foot. Walking in them for any distance, or on a slick surface, is difficult.

Although their names suggest otherwise, either kind of system can be used on any kind of bike -- after all, neither the bike nor the pedals knows the difference. Although there would probably not be much point in using road pedals/shoes on a mountain bike, some riders do use ATB pedals and shoes on road bikes, because it makes walking (at pit stops, for example) much easier.

Compatibility

There are three aspects of compatibility to be considered:

Cleats and Pedals
Cleats and Shoes
Shoes and Pedals

The problem of compatibility between cleats and pedals is easy to solve: just use the cleats made by the manufacturer of the pedals for the pedals that you have. Although there are third-party cleats available, they are usually not materially less expensive. Some of them may offer features such as greater durability; if you know enough to know what you are gettting, then you probably don't need to read this article!

Compatibility between cleats and shoes is a bit trickier. The issue comes down to whether the bolt holes in the shoe match the holes that the cleat requires. There are two main bolt patterns in use today: the Shimano SPD pattern (not the same as SPD-R) which uses two bolts, and the Look pattern which uses three bolts. (For example, when you see a shoe described as being SPD-compatible, what it means is that the shoe's sole is drilled with the appropriate [2] bolt holes for SPD cleats.) Virtually all ATB pedals/cleats are SPD-compatible. Most road pedals/cleats are either SPD or Look compatible. (There is also a high-end road system made by Time, and a new high-end Shimano road system called SPD-R.)

Finally, there is compatibility between shoes and pedals. With rare exceptions, this is basically not a problem. Occasionally, the design of a particular (lugged) sole on an ATB shoe may interfere with clipping in or releasing on a given pedal; however, this can almost always be fixed by a little judicious trimming with an Xacto knife, or something similar.

What about Float?

Early models of clipless pedals locked the rider's foot in a fixed position relative to the pedal (as if the foot were bolted directly to the pedal). While this produces maximum efficiency in power transfer, it can be very bad for the knees unless the cleat alignment is perfect (and even then, it may not work well for some riders).

Most current models of clipless pedals allow what is termed "float". Float allows the foot to rotate a few degrees to either side of the center line without causing the binding to release. The exact amount of float depends on the pedal; some systems (notably Look) allow you to choose whether or not you want float, depending on the cleats you choose.

For most riders, pedals with float are an excellent idea, since they help prevent knee injuries. You should note, however, that having pedals with float is not a substitute for having your cleats set up properly.

Maintenance

If you have clipless pedals, there a few things to watch out for (besides practicing clipping in and out):

Make sure that bolts that hold the cleats to your shoes are tight. It is very difficult to get loose cleats to release.
Keep the pedal mechanism CLEAN and lubricated. It will not release properly if it is all gummed up and full of junk.
Check your cleats for wear periodically; this is especially important with systems (such as Look) that use plastic cleats.

Finally, once again, you do not need clipless pedals to do the AIDS Ride. Many of us, professional racers included, used clips and straps for years before usable clipless pedals were developed.