So you want to go SPD but you are confused by all the different types of SPD shoes there are out there, and the huge variations in prices.
I want to try to end the confusion by breaking it down really simply for you.
Firstly, if you are looking for SPD shoes, that presumably means you have decided on this particular clipless system for your riding and you will be buying SPD pedals to match. For a discussion on that, see here.
So the first thing to make sure of is that the shoes you are looking at ARE actually SPD-compatible (or SPD-SL if you are a road biker) shoes, and not made for some other incompatible system. Bear in mind that many general cycling shoes will have holes for both the 2-hole SPD system and the 3-hole SPD-SL system.
Once we have got that clear we can break them down into two basic groups: mountain bike shoes and road bike shoes. Actually, there are more cycling disciplines than that, and SPD shoes to go with them (such as for triathlon, for indoor/spinning etc.), but let’s keep it simple and look at the basic differences between these two:
Mountain-bike SPD shoes
These are designed to take the two-hole type of SPD cleat (ordinary SPD, as opposed to the SPD-SL system – see below), and are not likely to have holes for the SPD-SL system. In addition, they are designed for the specific needs of mountain-bikers. The cleats are usually recessed, with full studs around them, like a soccer boot, or a walking shoe. Indeed, some of them almost resemble hiking boots.
The reason for this, of course, is that mountain-bikers are far more likely to dismount and push, carry, climb, etc. OK, you don’t! But most of us do and we need a proper sole for that, not the completely flat type typical of road shoes. Because the cleats are recessed, the rider can dismount and walk off-road in them, at least for short intervals, and the cleats will not interfere with that. Actually, they DO come into contact with the ground (and more so on paved surfaces) and will get scratched and worn, but far less than they would if they stuck out like road cleats do. I have some cleats that are actually looking like outlasting the shoes, even though they were bought at the same time!
You should be able to see the recessed holes for the cleats in the first picture on the left on these Pearl Izumi MTB shoes. Because SPD pedals are usually quite small they can fit right in between the lugs on the shoe. You can also see (in the second picture, of the same shoe) how much the shoe studs stick out. You can really do some climbing in those!
Also, typically, the sole of a mountain-bike shoe will be more a little more flexible to allow both for walking and for the increased mobility of the foot in mountain-biking. Having said that, there are also carbon-soled (i.e. completely rigid) shoes for mountain-biking, designed for improved performance. However, unlike carbon-soled road shoes these tend to have a little flexibility built into the toes for when climbing on foot.
That’s really the major distinguishing feature of mountain bike SPD shoes – the soles – otherwise they often do resemble road shoes as far as the shoe upper is concerned, although they do tend to be a little more rugged in order to be able to take the punishment that MTB entails.
You can read more about MTB shoes here.
Road cycling SPD shoes
As you have probably figured out by now, road cycling shoes do not need to have a lugged sole for walking on like mountain-bike shoes do. Road cyclists generally do not anticipate having to dismount and walk (except triathletes!), so it does not matter if the sole of the shoe is completely flat, and if the cleat sticks out a mile – which it usually does if they are using the three-hole SPD-SL system with its big cleats. You may have seen road cyclists dismount and walk very gingerly and uncomfortably, whilst making a clacking sound – well, that’s the reason!
Below, on this Shimano WR40 women’s road cycling shoe (again, without the clear installed) you can see this illustrated perfectly. There are two sets of holes, the triangular 3-hole configuration for SPD-SL and the two slots for regular SPD cleats, so you can use both. Also, you can see the totally flat sole on this shoe.
As mentioned earlier, it is more common for road shoes to have a rigid sole, too. This affects the cost quite a bit, especially if they are carbon soles (the example above is hard nylon), but this is preferred for road cycling since they are not going to be walked on anyway (difficult with rigid soles) and the lack of flexing ensures greater power transfer to the pedals, instead of being lost every time the sole bends.
Well, that’s just a very brief overview of some of the basic differences between SPD shoes. I hope to go into much more detail in the near future, but I hope this has helped at least someone clear up the mystery a little. And if you are knowledgeable and have anything to add to this, please leave a comment and let us know!