SPD-SL vs SPD: Road or MTB cleats?

I’m going to attempt to answer the age old question of if road (3 bolt) cleats are better than mountain bike (2 bolt) cleats when using them on a road bike being ridden on primarily paved surfaces. We will concede the fact that the standard 2 bolt cleat, most commonly SPDs, are significantly better off road (mountain biking or cyclocross) due to their ability to tolerate dirt, mud and their “walk-ability” factor due to the recessed cleat and lugged sole.

Just for some background, back when I started riding a proper road bike, a “12 speed”, just shy of 30 years ago, it had toe clips and straps. I rode that until I got my first mountain bike in 1999 and moved to SPD pedals and cleats. The pedals were two sided, one side was a bear claw and the other side had the SPD interface. When I purchased my gravel bike in 2013 I stuck with SPD and put Shimano PD-M540 pedals on it. When the majority of my rides became more paved than not I moved to a set of Shimano PD-A600 pedals. These lightweight, single-sided SPD pedals are classified by Shimano as road pedals and promoted as their “lightest ever at Ultegra level”. Over the past year, I’ve used Giro Empire VR90s, swapping A600 and M540 pedals depending on terrain.

Which brings us to the present day. With the recent purchase of a proper road bike, I began contemplating getting a pair of 2 bolt road shoes. I didn’t need them as the A600 pedals and VR90 shoes were fine but I honestly wanted to see what all they hype was about. The stars aligned one day and I was able to purchase a pair of Giro Empire ACC road shoes at a deep discount. I also dropped the hammer on a set of Shimano Ultegra 6800 pedals (also on sale!) and both were here in less than 3 days.

So for this review I’ll be comparing my 3 pedal systems, 2 SPD (M540 & A600) and 1 SPD-SL (Ultegra 6800). Since my shoes for both systems are both Giro Empires which are basically the same shoe with the same carbon sole that takes any type of shoe variability I might feel out of the question. The only real difference between the shoes is the lugged outer sole on the VR90s and some scuff protection on the uppers.

First lets get the M540 and A600 comparison out of the way. While they are both SPD pedals and share the typical dirt/mud tolerance and high degree of float they are really different animals. The M540 excels at ease of use clipping in due to their 2 sided design. This can be beneficial when starting out with clipless pedals. It’s also helpful if you ride ‘cross as it makes mounting that much easier. On the road they work ok, I’ve heard of people complaining about hot spots due to the small surface area of the pedal/cleat interface but that was never an issue with me. I think shoe choice also plays a factor in this as well.  They are also a tall pedal due to the two sided interface so pedal strikes could be an issue if you pedal too early out of a corner.

The main issue I noticed on the road was a subtle “click” from the cleat under heavy power, like big climbs or out-of-saddle efforts. The pedal’s built-in float lets your foot shift slightly, and sometimes that movement triggered the sound. It wasn’t constant, and a quick foot adjustment usually fixed it, so I mostly tuned it out. Occasionally though it would result in me clipping out which was real annoying when it did happen.

The A600s solved both those issues for me. The wider surface area provides a larger platform for the sole lugs to sit on so if you foot does “float” you shoe still sits on a stable platform. Also I have never had an issue of unintentionally clipping out of them even on the lowest setting, they keep your foot secure to the pedal.

The Verdict: While the M540 pedals will work ok they are better suited for the dirt. The A600 pedals win hands down for the road use. Their wider, more secure design and added ground clearance make them especially helpful when accelerating out of tight corners.

Now, onto the real showdown: A600 SPD pedals versus 6800 SPD-SL road pedals. I’ve ridden both setups on a Wahoo KICKR and out on real roads, giving me a solid foundation for comparison.

Lets first talk about power transfer. An common reason I hear a lot to use 3 bolt road cleats over the 2 bolt cleats is due to better power transfer. Personally I think it’s hogwash. You are pushing down on a pedal, small or big platform the power transfer should be the same. When you pull up on the pedal there may be a slight advantage but I’m not sure that is quantifiable as you are more unweighting the pedal than actually pulling up. I have done single leg drills with SPD cleats and never thought I was missing anything. Well except in the few instance where I unintentionally unclipped and that was only with the M540 pedals.

The hot spot issue could be a valid concern for some but I think that has a lot to do with shoe choice and not solely on the pedal. (see what I did there?)

Verdict: No clear winner.

Now lets move on to walk-ability. A common reason to choose 2 bolt cleats over 3 bolt cleats is due to the walk-ability factor. I admit I was in this camp at one time. 2-bolt cleats sit recessed in a lugged sole, giving riders a walkable grip similar to a running shoe. This setup is ideal if you’ll be walking often, especially through dirt or mud. It’s perfect for mountain bikers, cyclo-cross racers, or bikepackers facing unpredictable terrain. But for most road riders you are out there to ride and not walk miles on end.

The first time I walked in a 3 bold cleat (SPD-SL) I was like “what is the big deal”? They are fine to walk in for the coffee shop or around a rest stop on a supported ride. I can see the potential for them to be slippery on a wet floor. Although I haven’t encountered that yet and haven’t seen anyone take a dive either. My hardest challenge is walking on a carpeted floor. It seems much easier to roll the cleat in that situation. Not sure why but that is my impression.

Verdict: 2 bolt for certain situations, 3 bolt for primarily road riding.

Which is easier to use? This become a little tricky. A two sided SPD pedal is extremely easy to click into, heck I don’t even have to look. With single-sided pedals, you might need to glance down occasionally to align them properly before clipping in. This is where I think the SPD-SL pedals win over the A600 pedals. SPD-SL pedals usually tilt nose-up, so sliding your shoe across hooks the cleat, then a quick press clips you in. With the A600s, they also generally fall nose up but need to be more deliberate with moving the pedal into position before pushing the cleat into place.

Verdict: Neither is complicated and I generally get my foot in on the first shot 95% of the time. I just think the SPD-SL has the advantage here.

What is left now? Weight. It’s obvious that the mountain bike (2 bolt) shoes would be heavier with their lugged sole but by how much? Well with cleats installed on each shoe I weighted them and the difference was a little less than 90 grams. The SPD-SL pedals are about 100g lighter overall—just under ¼ pound—with only a ~13g difference between models. Doesn’t sound huge, but my usual cadence bumped up 1–2 RPM on the KICKR with those pedals.

Am I a 3 bolt/SPD-SL convert now? Will I be preaching the virtues of proper road cleats from the mountain tops now? Yes and no. I still stand by my original assessment of the right tool for the job. If you do mixed riding or always off road then a SPD cleat is the best tool for the job. Pair that with a quality stiff carbon soled shoe and a road style pedal and you aren’t losing much, if anything, to your typical 3 bolt road pedal/cleat system. If pavement is your religion and gravel makes you cringe, stick with a 3-bolt system—it’s built for pure roadies.

If you have multiple bikes for different disciplines and can only afford one good pair of shoes or two mediocre ones, choose quality. Go with the single good pair and run a 2-bolt system across all your bikes. You may get sneers from road snobs but just drop them on the next climb to shut them up.