Bicycle Pedal Standards: Threads, Clipless Systems & Cleat Compatibility

Also called: Standard pedal thread, ISO pedal thread, 9/16 inch

9/16" (~14.3 mm) diameter, 20 threads per inch; left pedal reverse (left-hand) threaded

The near-universal spindle thread on adult bikes with three-piece cranks — road, mountain, gravel, commuter, and e-bikes alike. The right pedal has a normal right-hand thread; the left pedal is reverse-threaded, so it tightens counterclockwise and loosens clockwise. Pedals are stamped L and R and are not interchangeable side to side.

Why it exists: The left-hand thread on the left pedal solves a real historical problem: left pedals kept unscrewing themselves. A rotating spindle inside a slightly larger hole 'walks' in the opposite direction to its rotation (a physics effect called precession), so a normal thread on the left side would slowly back out under pedaling loads.

Typically found on: Virtually all adult bikes with two- or three-piece cranks, from any era

Also called: One-piece crank thread, BMX pedal thread, 1/2 inch

1/2" (12.7 mm) diameter, 20 threads per inch; left pedal reverse-threaded

The smaller pedal thread used on one-piece ('Ashtabula') cranks, where the crank arms and spindle are a single forged steel piece. A 1/2" pedal will not thread into a 9/16" crank and vice versa — the difference is about 1.6 mm of diameter, enough to feel obviously wrong.

Why it exists: One-piece cranks are cheap and rugged, so they dominated American cruisers, department-store bikes, BMX, and children's bikes. The thinner crank arm cross-section suits a smaller pedal thread. Thread adapters (1/2" to 9/16") exist for fitting modern pedals to these cranks.

Typically found on: BMX, kids' bikes, older cruisers and department-store bikes with one-piece cranks

Also called: Flat pedals, Flats

Typical platform ~90–115 mm long x 90–120 mm wide; body thickness ~11–18 mm; replaceable traction pins on MTB versions

A flat surface for any regular shoe, with no attachment mechanism. Modern mountain-bike flats are thin aluminum or composite platforms with threaded metal pins for grip; commuter and kids' versions use molded plastic or rubber blocks. Toe clips and straps — small cages bolted to the front of a platform pedal — were the standard foot-retention method before clipless arrived, and survive on some touring and track bikes.

Why it exists: Simplicity and freedom: no special shoes, instant foot removal, and easy repositioning. Modern downhill and trail riding drove the development of thin, large, pinned platforms paired with sticky-rubber flat-pedal shoes.

Typically found on: Commuter, kids', BMX, e-bikes, and mountain bikes (downhill/trail riders often prefer flats)

Also called: SPD, Shimano Pedaling Dynamics, 2-bolt Shimano

2-bolt cleat, bolts 14 mm apart side-to-side in fore-aft slots; small stamped-steel cleat (~37 x 20 mm); cleat bolt torque 5–6 Nm

The dominant off-road clipless system since 1990. A small metal cleat bolts into a recessed channel in the shoe sole with two M5 screws, so you can walk normally. The pedal's spring-loaded jaws grab the cleat; a screw adjusts release tension. Two cleat types exist: SH51 (black, releases only by twisting the heel outward) and SH56 (silver, 'multi-release', lets go at multiple angles for beginners).

Why it exists: Shimano designed SPD for mountain biking, where riders need to clip in and out constantly and walk in mud. The recessed 2-bolt cleat made clipless practical off-road, and its walkability later made it the default for commuting, touring, gravel, and spin classes.

Typically found on: Mountain, gravel, commuter, touring, and e-bikes; the most common clipless system overall

Also called: SPD-SL, Shimano road

3-bolt cleat (standard road 3-hole pattern), large plastic cleat; float by color: yellow SM-SH11 = 6°, blue SM-SH12 = 2°, red SM-SH10 = 0°; cleat bolt torque 5–6 Nm; stack ~14.6–16.5 mm

Shimano's road-racing system, introduced in 2003. A wide plastic cleat bolts to a 3-bolt road shoe and clips into a single-sided pedal with an adjustable-tension rear spring. The big cleat spreads pedaling load across the sole but protrudes, so walking is awkward. Cleat color sets float: yellow (6°) is supplied with most pedals, blue (2°) pivots at the front-center, red (0°) is fixed.

Why it exists: Road racers wanted a larger, stiffer shoe-to-pedal interface and lower weight than SPD offers. SPD-SL adopted the 3-bolt hole pattern that Look established, making it compatible with nearly all road shoes — though its cleats remain incompatible with Look pedals.

Typically found on: Road bikes; standard choice for road riders on Shimano groupsets

Also called: Kéo, Look Kéo

3-bolt cleat; float by color: black = 0°, grey = 4.5°, red = 9°; stack ~14.8–17.8 mm depending on model

Look's current road system, launched in 2004 as a smaller, lighter successor to the original Delta pedal. The plastic cleat mounts to any 3-bolt road shoe. Keo pedals come with either a conventional adjustable steel spring or, on Keo Blade models, a carbon leaf spring with fixed tension set by swappable blades. Keo cleats pivot around the toe, which feels different from Shimano's center-pivot float.

Why it exists: Look invented the modern clipless pedal (1984) by adapting its ski-binding technology, and defined the 3-bolt shoe interface the whole road industry uses. Keo shrank the cleat and pedal for weight and cornering clearance while keeping the 3-bolt mount.

Typically found on: Road bikes; second most common road system after SPD-SL

Also called: Eggbeater, Crankbrothers, Candy/Mallet cleats

2-bolt cleat (SPD-pattern shoe holes); float 0° or 6° by cleat choice; release angle 10° (easy) or 15° (standard); brass cleat material

A minimalist open design of four spring-steel wings around a spindle — the 'eggbeater' — that sheds mud better than almost anything and offers four-sided entry. The same mechanism appears with platforms around it (Candy, Mallet, Double Shot). Cleats fit any 2-bolt shoe but only work in Crank Brothers pedals. There is no tension screw; retention feel is fixed, and float/release angle are chosen by which cleat you buy and which shoe it goes on.

Why it exists: Mud clogs conventional clipless mechanisms in cyclocross and wet mountain biking. The open eggbeater geometry has nowhere for mud to pack, and four-sided entry means no fumbling to flip the pedal.

Typically found on: Mountain, cyclocross, and gravel bikes; popular with racers in muddy conditions

Also called: ATAC, Time (SRAM)

2-bolt cleat (SPD-pattern shoe holes); ~5° angular float plus lateral float; 13° or 17° release angle by swapping cleats left-to-right

Time's off-road system (Auto Tension Adjustment Concept) uses two horizontal spring bars that grip a brass cleat, giving generous built-in rotational and side-to-side float that many riders' knees love. Swapping the left and right cleats changes the release angle (13° vs 17°). Time also makes 3-bolt road pedals (Xpresso, formerly RXS/Impact) with their own cleats. The Time brand was acquired by SRAM in 2021.

Why it exists: Time built its reputation on 'bio-position' float — free lateral and angular movement without spring resistance — as a knee-friendly alternative to fixed cleats, plus excellent mud performance from the open two-bar design.

Typically found on: Mountain, cyclocross, and gravel bikes; Time road pedals on road bikes

Also called: Speedplay, Speedplay Zero, lollipop pedals

4-bolt cleat pattern (adapter plate fits standard 3-bolt shoes); float adjustable 0–15° via cleat grub screws; dual-sided entry; very low ~11.5 mm stack with 4-hole shoes

Speedplay inverts the usual design: the retention spring lives in the cleat, and the small round 'lollipop' pedal is essentially a bare engagement dumbbell — so you can clip in on either side. Float is micro-adjustable from 0° to 15° with two screws in each cleat, independently for inward and outward heel movement. Release tension is not adjustable; Wahoo sells standard-tension and easy-tension cleats instead. Wahoo acquired Speedplay in 2019 and relaunched the line in 2021.

Why it exists: Founded 1991 to solve problems single-sided road pedals couldn't: dual-sided entry, ultra-low stack height, huge adjustable float for injury-prone knees, and multiple spindle lengths for fit flexibility.

Typically found on: Road and time-trial/triathlon bikes; riders needing fine-tuned float or stance width

Also called: Dual-sided pedals, Touring pedals, SPD one side, flat the other

One flat platform side + one 2-bolt SPD-mechanism side; 9/16" thread

A pedal category rather than a single standard: one face is a flat platform for street shoes, the other carries an SPD (or compatible) clip-in mechanism. Popular for commuting and e-bikes where riders sometimes clip in and sometimes ride in sneakers.

Why it exists: Commuters and casual riders wanted clipless efficiency on long rides without being locked into cycling shoes for every trip to the store.

Typically found on: Commuter, touring, and e-bikes

By bike and crank type

If your bike is an adult bike with crank arms bolted to a separate axle, the pedals are almost certainly 9/16" x 20 tpi. If it's a BMX, kids' bike, or an older cruiser whose crank is one continuous S-shaped steel piece through the frame, it's 1/2" x 20 tpi. Vintage French bikes (Peugeot, Motobecane) may be 14 mm French thread — don't force pedals into these.

By measuring

Measure the spindle thread diameter with calipers just behind the threads: about 14.2–14.3 mm means 9/16", about 12.7 mm means 1/2", and 13.9–14.0 mm on a vintage French bike suggests French thread. For cleats, measure the bolt spacing on your shoe sole: two slots side by side = 2-bolt; a triangle of three holes = 3-bolt road; four holes in a rectangle = Speedplay 4-bolt. Stack height and spindle length are listed in the pedal's spec sheet rather than measured.

By markings

Pedal spindles are stamped L and R near the wrench flats — and often with the thread size (e.g. '9/16'). Shimano cleats carry model numbers: SM-SH51/SH56 are SPD (2-bolt); SM-SH10 (red), SH11 (yellow), SH12 (blue) are SPD-SL (3-bolt). Look Keo cleats say 'Keo' and use black/grey/red for 0°/4.5°/9° float. Crank Brothers brass cleats and Time ATAC cleats are 2-bolt but shaped nothing like SPD cleats. Speedplay cleats are large round discs covering much of the forefoot.

By the pedal's shape

Flat platform with pins or rubber blocks = platform pedal. Small double-sided metal mechanism = SPD or similar 2-bolt system. Wide single-sided body with a plastic or carbon rear catch = road 3-bolt system (SPD-SL or Keo). Four bare spring wings like a whisk = Crank Brothers Eggbeater. Small round lollipop on a stick = Speedplay. One flat face and one mechanism face = hybrid commuter pedal.