Is there anything wrong with wearing mountain biking shoes (SPD) with a road bike? I find that it makes sense because you can still walk around with them on but you still have the ability to clip in and pull the pedal up like a normal road bike shoe would allow. Am I missing any aspect of the situation?
A lot of riders appear to prefer SPD's, which is a great, and can work well (as indicated by the answers here). For interest sake here are some arguments for "road pedals" which are typically the three bolt variety.
Pros - Road Pedals (SPD-SL and others)
Road bike specific pedals (e.g., Shimano SPD-SL) are designed for a single purpose, road cycling, and the pedals do this job well. Road cycling has a lot of repetitive motions (you often sit in the same position for a long period of time) so fit can be key to reducing repetitive stress injuries.
If you get into long rides, high mileage or fast and hard rides you will notice the difference over SPD type pedals. Some of these differences include:
- Smoother Pedal Float - Pedal float is the ability to allow the shoe to swivel (and shift laterally in some systems) slightly during the pedal stroke. This can be important to reducing certain types of injury (and optimizing alignment) as your foot can shift slightly in the pedal stroke. Mountain bike pedals use the shoe tread as the contact point, while road pedals use a specialized cleat as the contact point. As such, road specific pedals can choose materials and control the contact patch better allowing a much smoother float (and often more float) than mountain bike systems.
- Note - Some claim that float reduced power, but there is no real evidence for this idea. See the myth section in Phil Burt's Bike Fit.
- Wider Contact Area - Because they do not require the same ability to shed mud and dirt, or have a recessed cleat for walkability, road pedals have a large interface surface with the cleat.
- Reduced Hot spots - The wide contact area distributes pedal force over a larger proportion of the shoe, which in turn better supports the foot. Assuming your shoe fits properly, this will result in reduced likelihood of hot spots. Hot spots can occur over long periods of riding, where a pressure point exists under a small potion of your foot which causes discomfort.
- Better force transfer - The wider contact area allows for a more efficient transfer of force as there will be less flexing.
- Easier Cleat Adjustment - Because of the larger contact surface, there is more friction between the shoe and cleat and the cleat can be held in place via frictional forces only without requiring the cleat to bite into the shoe as with SPDs. The result is that the bottom of the shoe is not damaged by a road cleat, making fine cleat adjustments easier. With SPD the bottom of the shoe often gets "bite marks" from the cleat making small cleat positional changes hard as the cleat has a tendency to migrate back to the original bit position.
- Lower Profile - Because the tread block is not required the road shoes can often be placed closer to the pedal axel. This can allow less rocking (more efficient power transfer) and allow for more clearance (aka harder cornering)
- Lower Weight/Lower Rotating mass If you care about such things (many do) the road pedal/shoe combo is typically lighter. This can provide minor performance gains.
- Lousy to walk in
- This can cause accidents - After using road shoes for nearly 20 years I finally had my first accident, which hand me sliding across the kitchen floor (while avoiding small children) and crashing into the stove, where as luck would have it my hand landed on a red hot stove element! I still went for a ride though...
- No hike a bike - Suppose you use up all your tubes (@CareyGregory), your frame is cracked and can't be welded because you are out riding across some African plain and there are no good TIG welders around, you are running out of water and you still have 10 miles to go. Well now add your shoes to your list of problems because you are not walking in them.
- They sound funny - Depending if you look hot or like a stuffed sausage when you stop in for your pre-ride caffeine binge, the ensuing clickety-clack caused by road shoes may cause you horrendous humiliation!
While many people use MTB cleats for road use, and are quite happy with them, there are down sides to them. Because the cleat is embedded in the shoe, they are easier to walk on. That same thing requires the cleat to be far smaller than a road cleat.
A smaller cleat is less supportive of the foot that a larger road cleat. On long rides, the additional muscle activation (flex in the sole of our foot) causes cramping and hotspots. Better quality MTB shoes with a stiffer, usually carbon fiber, sole will be better than soft rubber.
You will not likely notice the difference on rides of less than 25 miles. You are also unlikely to notice the difference, if say, you've only ever ridden on MTB shoes and cleats. I would recommend road shoes and cleats as ideal for performance, but there are a myriad of reasons why you could consider compromising performance for ease of use or immediate short distance comfort.
They do design the road cleat for a road bike for a reason, however.
One thing people forget to mention is the use of a top of the line mtn shoe on your road bike. The advantages of mtn shoes are many, walking, not having multiple shoes , etc. If you are using say the S Works mtn shoe on your road bike, you would be hard pressed to notice any difference in performance over the road shoe. Most riders are not tour professionals, so you are splitting hairs over specific shoes.
Float, which is the degree to which one can rotate one's feet while clipped in, can sometimes be an issue. In other words, all clipless pedal systems-- so-called because they replace the toe clips with cleats of some kind-- restrict the amount that you can rotate your feet while clipped in (i.e., while the cleat is connected to the pedal).
This was the primary reason I switched from SPDs to Speedplays. Initially I rode using SPDs, but as the other respondents mentioned, I was getting hot foot on longer rides, and eventually some knee pain, which turned out to be caused by an SPD cleat that was slightly mis-aligned. That was the impetus, because with Speedplays it's not an issue at all. It seemed like a win-win to me: more float, and minimal alignment issues (provided the cleat is correctly positioned on one's shoe). But I am not a commuter.
Here is the amount of nominal float one can obtain from various pedal systems, in no particular order:
- Speedplay: up to 15 degrees (scroll down to see an image);
- Shimano SPD, SPD-SL, up to 6 degrees;
- Look Keo, up to 9 degrees;
And so forth. Clearly there are many factors that go into the choice of pedal/shoe connection, and happily there are more than a few systems one can choose from.
I use MTB shoes for road cycling never had any problems, prefer them over dedicated road shoes. Prefer to wear MTB shoes winter road training or on my gravel bike in case you need to get of your bike and walk. Also handy if you are a victim of road rage being fast on your feet in a punch up instead of sliding all over the place in road shoes giving the aggressor the upper hand.