Shimano’s SPD and SPD-SL clipless pedals are a popular choice for bike riders across a range of disciplines.
They’ll hold your feet in contact with the pedals better than a flat pedal, providing a secure connection and potentially improving your pedalling efficiency.
But why are there two different systems for Shimano clipless pedals? And which one is likely to work better for the type of riding that you do? We’ll answer both questions in this article.
We’ll also have a quick look at pedal systems from other manufacturers. While ‘SPD’ and ‘SPD-SL’ refer specifically to Shimano’s road and mountain bike pedal systems, the terms are often used to broadly describe similar systems from other brands, even if they are incompatible with one another.
These pedal systems are referred to as ‘clipless’ because they’ve largely replaced the earlier system of toe clips and straps, used by road racers such as Eddy Merckx. In a clipless pedal system, the pedal has a mechanism that locks it to a cleat screwed into the underside of the shoe.
Read our guide on how to use clipless pedals for more on getting started riding clipless.
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What’s the difference between SPD and SPD-SL?
SPD stands for Shimano Pedalling Dynamics, with the SL standing for SuperLight. That gives a clue as to the intended use of the systems.
SPD has become more-or-less a synonym for mountain bike pedals, while SPD-SL is mainly used for road cycling – that’s where the reduced weight comes in. But there are good reasons why you might choose to use SPD pedals on a drop bar bike.
We’ll come on to the specific differences, and advantages and disadvantages, of the two systems.
SPD cleats (the part of the system which fixes to the bottom of your shoe and ‘clips in’ to the pedal) are made of metal and are smaller than SPD-SL cleats.
SPD cleats use two bolts to fix to the shoe, so they’re often called ‘two-bolt cleats’. SPD-SL cleats have three points of attachment to the shoe, so they are also called ‘three-bolt cleats’. They are made of plastic, to keep their weight down.
The design differences have other consequences – read on.
A bit of history
French brand Look first developed a clipless pedal system, used from 1984 by five-time Tour de France winner Bernard Hinault. With patents on its design, Look initially held a monopoly on road bike clipless pedals – it’s still the main rival to Shimano in this space today.
Shimano’s first clipless pedal, the Dura-Ace 7401, arrived in 1987, with a Look-compatible cleat licensed from the French company. The SPD-R design followed but it wasn’t until the 2003 model year, and the launch of the 7750 Dura-Ace pedal developed with input from Lance Armstrong, that Shimano landed on the SPD-SL.
In the meantime, Shimano had developed the SPD design, based on a smaller metal cleat with two points of attachment to the shoe, and first released in 1990. This was a natural fit for mountain bike riders, but didn’t work so well for performance road use, where pedalling efficiency is paramount.
Why use SPD pedals?
Most SPD pedals are double sided – that means you can clip into either side of the pedal, which makes starting from stationary a lot easier.
You can adjust the release tension of the cleat using the small screw at the rear of the pedal (one each side, because they’re double sided). Some riders prefer the additional security that comes from increased release tension, but if you’re just starting out you may want less tension.
Most cleats will offer some ‘float’ in the shoe to pedal interface, letting your feet rotate about a vertical axis without disengaging, for a more comfortable ride.
All SPD cleats are made of metal, so they are robust, although you may find that wear to the binding surfaces after a few years’ use means that engagement becomes less secure. It’s easy to find replacements and they are inexpensive.
There’s some adjustability in cleat position on the shoe because the mounting hardware is on a separate plate within the shoe’s sole. The bolt holes in the cleat itself are designed to allow a bit of leeway in where you position it.
Shimano sells SPD cleats that only release from the pedal when you twist your heel outwards (SH51/SH52) as well as the SH56 multi-release cleat, which will disengage from the pedal when you twist your heel upward too.
The latter makes disengagement a bit easier, but most riders prefer the more secure design of the former.
The latest deals on Shimano SH51 SPD cleats
The latest deals on Shimano SH56 multi-release SPD cleats
Confusingly, Shimano also sells a few single-sided SPD designs in its Ultegra (PD-ES600) and Tiagra (PD-A530) road pedal ranges, and GRX gravel pedal range (PD-ES600), aimed at riders who want an SPD pedal but with a wider platform.
These, however, are a rarity and the bulk of Shimano’s road pedal range uses the SPD-SL design.
A key advantage of the small SPD cleat is that it is easy to walk in when you’re off the bike.
Most shoes for two-bolt cleats include a tread on the sole, and the cleat is recessed, so you’re walking on a large, grippy area on the bottom of the shoe, not the actual cleat (as is the case with the SPD-SL design).
If you expect to walk a significant amount, SPD pedals are the natural choice. The sole’s tread means that you shouldn’t slip on smooth surfaces and makes for plenty of grip if you have to walk or climb when riding off-road too.
SPD pedals are a good choice for the commuter too, who will typically be putting a foot down at stops and walking to bike sheds at the beginning and end of the ride. They’re also good for touring, when you will want to be able to walk around during stops.
Off-road use also means that SPD pedals are designed to shed mud.
Most SPD pedals have an open construction with a large gap in the centre, so that any mud that accumulates on the bottom of the shoe will fall off and not interfere with pedal engagement or pedalling efficiency.
The resistance to clogging and walkability make SPD pedals the natural choice for cyclocross racing, as well as mountain biking. They are also typically used by gravel bike riders, with the latest gravel-specific shoes offering SPD compatibility.
SPD pedals are a good choice for your first pair of clipless pedals and for casual use, if you’re nervous about making the switch from flat designs.
It’s worth roadies considering buying a set of weatherproof SPD boots and pedals for winter riding, when muddy, wet or icy surfaces are common and there’s more chance of muck being kicked up by your wheels to clog your cleats, or being forced to walk because of road conditions.
Shimano makes some SPD pedals with a very small surface area, to maximise mud-shedding. There are also designs in which there’s more of a platform to the pedal, increasing the size of the interface to the sole of the shoe, upping pedalling efficiency and making it easier to ride with the shoe resting on the pedal without clipping in.
You can add thin shims between the cleat and the shoe, to optimise the connection between the shoe and the pedal surface.
Why use SPD-SL pedals?
Bigger pedal platform
The SPD-SL format is all about low weight and power delivery.
With a wider pedal platform and much larger interface between the pedal and the cleat on your shoe, the foot is held more firmly in place and pedalling efficiency is increased – ideal when sprinting.
The design uses a large plastic cleat, with the three bolts on the underside of the shoe widely spaced, for a secure attachment to the shoe.
The large cleat makes walking in your shoes awkward though. You end up waddling and if a surface is wet, you can easily slip. Plus road cycling shoes have no grip on the soles, except a small pad at the toe and heel to reduce wear.
The cleats tend to wear more quickly than SPD ones too, and need more regular replacement, although again they are not expensive.
If you do walk in any mud, the deeper binding surfaces on SPD-SL pedals tend to get clogged up and your cleats can fail to engage properly with the pedals.
So SPD-SL pedal systems are designed for the rider who wants to cover long distances on the road and doesn’t expect to need to put a foot down or walk too much.
SPD-SL pedals are single sided. They naturally rest pointing obliquely downwards, so clipping in is more of an art than with SPD pedals, involving flipping the pedals over as you start to ride and accurately engaging the cleat with the pedal’s top surface. It’s something that requires practice to get right, but once mastered becomes second-nature.
Some riders find disengagement with SPD-SL cleats slightly harder than with SPD pedals, but tension can be adjusted to suit. Beginners and commuters are also likely to prefer the double-sided design of SPD pedals, particularly when navigating busy junctions and road traffic.
Otherwise, another advantage of SPD-SL pedals for the road rider is their lighter weight – typically between 50g and 100g a pair less than SPD pedals at a similar price. Top-end SPD-SL pedals have carbon fibre bodies.
As with SPD pedals, you can alter the release tension of SPD-SL pedals by tightening or loosening an Allen key bolt in the back of the pedal. You can also select the amount of rotational float between the shoe and the pedal by choosing a different cleat, identifiable by its colour.
The most common yellow Shimano cleats offer 6 degrees of float. For less lateral movement, you can fit blue cleats which have 2 degrees float, while the red bodied cleats have no float for a fixed foot position.
As with the SPD system, you can also shift your cleats back and forth on the shoe to suit your pedalling style and fit preferences. There’s some adjustability in the angle of the cleat and most (but not all) shoes allow you to shift the mounting plate back and forth within the sole.
Latest deals on Shimano SPD-SL cleats
It’s not all about Shimano’s pedals, with other marques selling similar two-bolt and three-bolt systems. Some are compatible with Shimano pedals, others not.
Shimano’s two-bolt pedal patents have now expired, which has opened the way for SPD-compatible pedals to be sold by other makes, including Look.
Other major players in two-bolt pedal systems, with their own incompatible systems, include Crankbrothers, Speedplay and Time. Have a look at our pick of the best flat and clipless mountain bike pedals.
Look’s three-bolt pedals are incompatible with Shimano SPD-SL. Other road-going systems with a three-bolt cleat design include Time’s road pedals, but again there is no cross-compatibility with Shimano SPD-SL pedals.
Speedplay is another of the major players when it comes to road pedals. Its lollipop-shaped Zero pedals fit into a metal cleat with four points of attachment to the shoe. The adjustment mechanism is in the cleat rather than the pedal.
You can either use an adaptor to fix Speedplay cleats to three-bolt shoes, or some shoes are available with four fixing points for in-built Speedplay compatibility.
Read our guide to the best road bike pedals to choose the right system for your riding preferences and budget.
Summary of SPD and SPD-SL advantages and disadvantages
SPD pedals pros and cons
+ Double-sided design for easy engagement
+ Excellent mud-shedding, less prone to clogging
+ Walkable cleats and shoes
+ Suited to a variety of riding disciplines
– Smaller contact area leads to less efficient power delivery
– Greater likelihood of foot ‘hotspots’
– Generally heavier than SPD-SL at a given price point
SPD-SL pedals pros and cons
+ Large contact area for improved power transfer and stability
+ More direct feel
+ Lighter than SPDs
– Single-sided entry
– Difficult to walk in
– Cleats wear more quickly than SPD