When it comes to clipless pedals, you have the choice between a three-bolt road-style system, like Shimano’s SPD-SL, and a two-bolt mountain bike-style system, such as Shimano’s SPD, and here we’re going to help you decide which is the best option for you.
Now, although I’ve already described a three bolt system as ‘road-style’, not everyone who rides on the road opts for this type of pedal, and SPDs are certainly not confined to trail use.
One other thing to mention up top is that most of the characteristics of Shimano’s SPD-SL system are shared by other three-bolt designs from the likes of Look and Time. Plus, other mountain bike systems are similar in essentials to SPD. We're sticking to Shimano here to keep things simple, but here's a pic of some Look Keo Blade Carbons, just to show we're not biased!
Oh, and then there’s Speedplay, a unique system that has many avid fans, although for clarity we’re not going to cover it here. Sorry. If you want to know more about Speedplay, which is particularly valuable for those who need a lot of float, go to our article on 10 of the best clipless pedals.
Okay, so what are we talking about when we say SPD and SPD-SL?
Shimano first released its SPD (Shimano Pedaling Dynamics) design way back in 1990. A smaller metal cleat is mounted to your shoe with two bolts, fitting in a recess in the sole. The recessed cleat makes it easier to walk in SPD shoes and helps guide the cleat into the mechanism, so it’s easier to clip in. Originally intended for mountain biking, SPD has become popular with commuting and recreational riders too who tend to go for inexpensive workhorses like the Shimano PD-M520, above, £30).
SPD-SL pedals, on the other hand, are quite similar to the original road racing clipless pedals introduced by Look in 1984 and updated many times since. These have a three-bolt cleat that stands proud of the sole, hooks into the front of the pedal and is held in place by a spring-loaded latch at the rear. You can see the mechanism in the carbon-fibre-bodied Shimano 105 R7000 pedals, above which are popular with road riders and will typically set you back about £80. This allows an uncomplicated, rigid sole, but is awkward to walk in; think of a penguin waddling on ice or a sheep on lino and you’re somewhere close.
"Our pedals are always developed with particular shoes in mind (and vice versa), so we can give riders a complete pedalling system," says Shimano's Ben Hillsdon. "When making a decision on which to go for it's important to consider whether the shoe and pedal combination offer you the right level of usability and comfort for the type of riding you're doing. One of the biggest differences between the two pedal systems is how easy it is to walk in the shoes, which can have a big impact on a rider's experience and mid-ride coffee stop!"
When you walk in SPD-SL shoes, the prominent cleat is in contact with the ground. Little tips on the cleat provide some protection against wear but you get relatively little grip. Most manufacturers make three-bolt soles as rigid as possible for cycling performance, and that’s far from ideal when you’re not on the bike. Really, you want to keep walking to a minimum: getting to and from your bike, tapping in and out of the cafe, that kind of thing.
“Although it's not the most rigid sole ever, it's pretty damn stiff and there's no sense that your power is being directed anywhere but straight into your pedals,” we said.
That’s great when you’re in the saddle, but it doesn’t make for ease of walking. You get very little grip on wet surfaces, while mud and SPD-SL systems really don’t get along.
The fact that an SPD cleat sits in a recess means that when you’re off the bike it’s not in contact with the ground nearly as much as an SPD-SL cleat. Manufacturers can give you a treaded sole that’ll grip on various different surfaces.
“The grip on the sole is pretty fat, chunky and made from SlipNot rubber tread,” said Jo Burt in his review of Specialized’s £200 two-bolt Recon Mixed Terrain shoes. “There's even a little bit of waffle grip mid-sole should you fluff a clip-in or be a little nervous and need to ride a section resting on the pedal not clipped in, and there are studs in the toe in case any rides see you scrabbling up muddy banks and suchlike.
“The tread works well in both on and off-road environments, although they're going to flounder in really muddy situations, and for off-bike applications they're confident even in the slipperiest of surfaces – such as the floor of a gent's toilet in a pub.”
Shoes like the two-bolt Giro Civila Women’s road shoes that we recently reviewed are designed for more recreational riding.
“They are easy to walk in, comfortable for the job and the grippy sole sections offer a much better likelihood of staying on your feet on a tiled or laminate floor than many shoes offering equivalent performance,” we said.
Also, although mountain bike race shoes, like road race shoes, have rigid soles, some shoes designed for SPD pedals offer more flex.
Giro describes the Petra VR shoes (£76.49), for instance, as “versatile shoes that combine performance riding features like clipless pedal compatibility with the walkability and comfort of light hiking shoes” (the recess for the cleat is covered in the picture below).
When she reviewed them here on road.cc Lara Dunn said, “These are one of very few pairs of cycling shoes of this ilk that I've tried that genuinely don't feel like cycling shoes when you're walking, such is the fine-tuning of the flexibility of the sole. The soles are also grippy enough to be genuinely useful to walk in.”
There are many two-bolt touring shoes out there, like Shimano’s RT5s (£60.99 - £71.99, RT stands for Road Touring).
“There’s no ultra stiff low profile carbon sole with a road-style three-bolt cleat drilling here,” we said. “Instead, it’s a glass fibre sole with a recessed two-bolt drilling that’ll accept Shimano’s mountain bike SPD cleat system with the raised tread sections ensuring you can walk without fear of slippage. It’s not an aggressive sole like you get on a mountain bike shoe – they’re not intended for walking in muddy conditions, but getting around town, the office or cafes without slipping up and spilling your flat white.”
Some two-bolt shoes are designed specifically for urban use, like Shimano’s £66.99 CT5 (CT stands for City Touring) which have a casual trainer style to them along with an EVA mid sole designed to add walking comfort.
The more time you’re likely to spend walking, the more appealing SPDs become.
So why wouldn’t you want the treaded outsole that an SPD system allows? There’s no point for a lot of us. If you get on your bike and ride until you get home again, or you just stop for a coffee or to nip into a garage for an emergency Snickers, you might as well save a little weight by doing without.
If you really don't know whether you'll be better off with a two bolt or a three bolt system, some shoes, such as Shimano's RP2 Women (above) are capable of taking either. Look out for a sole that has a pair of SPD bolt holes nestled among the three spots for SPD-SL cleats
Most SPD-SL pedals are single sided, meaning that you can only clip in to them when they are the right way up. With most of the weight at the back of the pedal, they’ll usually hang with the correct side facing backwards towards your foot, so clipping in is straightforward when you get the hang of it. Occasionally, though, bikes do funny things and you might find yourself trying to engage the wrong side of the pedal. Hopefully, no one will notice!
Some people find it easier to clip into SPD pedals than SPD-SLs. First, most (not all) SPD pedals are double-sided, so you can clip in to either side. There’s no such thing as having those pedals the wrong way up.
Second, the recess in the sole of the shoe can help guide the cleat into the mechanism. In truth, though, you’ll probably soon adapt to whichever system you choose.
Shimano Click’r is essentially a variant of SPD with even easier entry and release. You use the same SPD cleats but clipping in and twisting out of Click’r pedals takes far less effort than with standard SPD pedals. You want figures? Shimano reckons it takes 60% less force to clip in, and 50% less force to release.
Over on the road side, the RS500 pedal is available in a standard model for £42.50 and a Light Action model (about £39.80).
All of these pedals have spring tension adjustment allowing you to alter the force holding the cleat in place. It’s a simple hex key job that takes seconds.
SPD cleats are small and many people find an SPD-SL system more stable, especially when riding out of the saddle. The top-level Dura-Ace 9100 road race pedals (£182), for instance, have a platform that’s 66mm wide.
However, you can buy SPDs that have a cage around the pedal body to increase the size of the contact area with your shoe. Shimano’s PD-M424 pedals (above, £39.56), for instance, features a resin cage that’s designed to increase foot stability while the PD-M324 pedals (below, £43.40) have an SPD mechanism on one side with a steel platform on the other.
Despite being larger, SPD-SLs are a little lighter than SPDs of an equivalent standard. SPD-SLs weigh from 228g (per pair) for race-focused Dura-Ace R9100 up to 330g for R540.
SPDs weigh from 310g for XTR cross-country mountain bike pedals to over 500g. A pair of the M324 SPD/flat pedals (above) just mentioned, for example, weighs 533g.
People often say that SPD-SLs offer more stable attachment of the shoe to the pedal than SPDs. Is that true?
"SPD-SL pedals hold the cleat in three positions whilst the SPD pedal holds the cleat in two positions (fore and aft) to make it easy to unclip in off-road situations." says Shimano's Ben Hillsdon. "With both pedal systems, though, the cleat retention (and therefore the stability of the connection) can be adjusted."
SPD-SL cleats are available with three different amounts of float (the degree to which your feet can rotate while the cleat remains engaged with the pedal). Cleats with red tips are fixed (0°), blue offers 2° of float and yellow gives you 6°.
The fact that they’re made from plastic and they’re exposed (rather than recessed into the sole of your shoe) means that SPD-SL cleats wear out fairly quickly if you walk far in them on a regular basis.
SPD cleats are metal and they’re better protected when you walk so they tend to last much longer. They’re cheaper too – £14.99 rather than the £19.99 you have to pay for SPD-SL cleats.
SH51 SPD cleats allow you to release from the pedal by twisting your heel outwards while SH56 SPD cleats (above) allow you to disengaged by twisting your foot in either direction.
"Common Shimano SPD cleats (like the SH-51) offer at least 6° of float," says Shimano's Ben Hillsdon. "It's worth mentioning that as cleats wear the amount of float increases so it's important to adjust tension on the pedals to reduce unwanted unclipping."
“I find SPDs more practical, particularly for commuting, getting on and off the bike, popping in to Sainsbury's on the way home. They're easier to walk in, and because the cleats are metal they don't wear at anything like the rate of a plastic SPD-SL or my Time road cleats. Even when they do wear, they still work. Also, maybe because I'm more used to them, I find them more comfortable over short to medium distances.”
Tony Farrelly, road.cc editor
“I use SPDs for mixed rides and long rides, and the shoes are better for walking in. Maximal power transfer and platform stiffness aren’t such an issue on a 400km audax as not falling down the steps at the tea rooms. Also, they’re easier to clip in to because they're double sided, and cleats and pedals cost 3 shillings and sixpence and last about 1,000 years. If I'm racing, or on the chaingang, I use road shoes and SPD-SLs because they look more pro. Erm. I mean, they're lighter and stiffer”
Dave Atkinson, road.cc tech guy
“If it has fat tyres and I know I’ll be heading off-road at some point in the ride, I ride SPDs. If I’m staying on the road I’ll always go for a three-bolt system because I know I won't be doing any walking and prefer the lightness and stiffness for maximising every measly watt of power I can output (even if it's only in my head). That and I'm also using PowerTap's excellent power meter pedals that i can easily swap between test bikes for consistent power measurement.”
Dave Arthur, road.cc technical editor
“When I got back into road a few years back I just took the SPDs off my mountain bike and went riding in my carbon soled mountain bike shoes. It was okay but felt wobbly on climbs.
I was then persuaded to buy SPD—SL and some mid range road shoes… The difference in power transfer, and more importantly, foot stability/knee tracking, was night and day different.
I still use SPD on the mountain bike, but for road riding riding, including hill climbing, long distance and even commuting, it’s SPD-SL.”
“The physical benefits of SPD-SL over SPD's are the wider platform of the cleat and pedal means there is more lateral stability for your foot on the pedal.
“The single sided nature of the SL also reduces the profile of the pedal allowing you to pedal marginally deeper into a corner.
A proper road shoe has a stiff sole all the way to the tip of the toe giving a more stable base, whereas in most MTB shoes the carbon or nylon stops just ahead of the cleat to allow the sole to bend slightly at that point, to aid walking as often required in MTBing.
“Road shoes are generally lighter as they don't have tread and reinforcements, so a slight reduction in rotating mass.
“As with all the bike industry claims, none of the above will make the huge difference they would like you to believe, but I do prefer the more stable, lower profile of a proper road shoe/pedal setup.”
“Having learned to ride clipless with SPDs, I thought I should try SPD-SLs on my road bike. I never got on with the clipping in on the SLs. Partly this is because it is much easier clipping in to double-sided pedals, but this is not the only factor - I ride A530 single-sided SPDs on my commuting bike, and even these are much easier than the SPD-SLs, even though they are not double sided.
“I was also really unimpressed with the wear on the plastic SPD-SL cleats. I made a real effort not to walk in them, and they still rapidly wore down such that I think I would have needed to replace them at least twice a year, and they're not cheap.
“If your shoe sole is stiff enough, SPDs are fine.”
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Mat has been in cycling media since 1996, on titles including BikeRadar, Total Bike, Total Mountain Bike, What Mountain Bike and Mountain Biking UK, and he has been editor of 220 Triathlon and Cycling Plus. Mat has been road.cc technical editor for over a decade, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a winner of the Cycling Media Award for Specialist Online Writer. Now pushing 50, he's riding road and gravel bikes most days for fun and fitness rather than training for competitions.