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Shimano Cycle Pedal Foot Cleats
SPD SH51 Versus SH56 Differences.

This page: http://berklix.org/bike/shimano/cleats/

By Julian Stacey

Why Of Interest ?

(Regardless if you remove your toe clips (40+ year old traditional style ), or go from no clips),
If you adopt modern cleats, by buying modern pedals, shoes, & integrated cleats underneath, You Hit This Inadequately Explained Question :

Which SPD Cleats To Choose ?

SH51 (& similar SH52) one directional release, or
SH56 (& similar SH55) Multi directional release

- If you realise you have a choice (not all do) - Its hard to find info. on the difference

  • A choice of Usage, Performance And Safety !
  • Take the cleats that come standard with the shoes ?
  • Or take the other cleats which my shop was willing to swap to at no charge?.
  • With decades of toe clip reflex, in an emergency, one fancies minimising the chance of falling off , feet still locked in with a different mechanism.
  • One also fancies higher performance cleats - but at what if any extra (or possibly lesser!) risk ?
  • I couldn't find detailed analysis, not on wikipedia, not on Shimano web,
    one other web referenced below knew what the usage difference was, but not Why
    another web referenced below only spotted the less important of 2 differences.
  • So I bought both, measured differences, analysed, with both, am free to later choose to install alternate cleats in shoes on different days, for alternate types of forest dirt track & main road tours etc.
  • The 2 (main) Shimano SPD cleat types
    • Require a choice between maximum power Versus easier un-clipping.
    • The minute differences in metal cleats, create differences in release mechanism between rotate only, & {rotate &/or up} to release.
    • SH56 (Silver) would be better on dirt path tour days with other bikers (& tree roots) both doing unexpected things, & for newcomers to SPD cleats;
    • SH51 (Black) better for road racing days & people more experienced with SPD cleats, & people wanting more power by pulling up on pedals as well as pushing down.
    • There'll be less horizontal flex with SH51 (Black).
    • Understanding the differences & commonalities could also help on where to watch for wear etc

From Web & Sales leaflets, Prior To Writing This

http://en.wikipedia.org/wiki/Shimano
"SPD has spawned 2 types of road cleats which are incompatible with standard SPD pedals and some shoes - SPD-R and SPD-SL. SPD-R is a now defunct pedal standard. SPD-SL is basically a copy of the standard Look clip-less pedal system. It has a wide, one-sided platform and a triangular cleat that is Look 3-bolt compatible."

2 DIFFERENT SPD CLEAT SETS: SH51 & SH56
Both embed within shoe tread so one can walk OK, (unlike real race shoes which have a flat sole & have a protruding clip under sole)
Silver:
  • SM-SH56
  • As sold with my shoes @ www.sportscheck.com 2012_07_02
  • Allows horizontal, vertical & diagonal escapement. & slack/ wobble to allow for knees moving etc.

Black: 14.95 EU @ www.sportscheck.com 2012_07_03
SM-SH51 PD-M858 These are for horizontal escapement only, should be no wobble.

http://www.spdshoes.org/spd-cleats/
  • MTB cleat is MUCH smaller than the road cycling cleat
  • SPD is 2 hole
  • SPD-SL is 3 hole
  • SH51 (Black) - single-release
  • SH56 (Silver) - multi-release

Upward as well as sideways escape happens for SH56 (Silver).
http://www.bikepro.com/products/pedals/shimspd.html
"Incidentally, the difference between the two types is the depth of the notches that the clamps grip on the upper side of the cleat. The notches are considerably shallower on the Silver SH55 or SM-SH71 set, making the grip slightly less precise and allowing release at various angles."

Analysis By Julian Stacey

There's no notch on the SH56 (Silver) (just a tiny dot/ pressure mark).

There's a 2nd more important difference, only easily seen by unscrewing cleats from shoes:

The SH56 (Silver) at the back, at the top (when cleat is viewed same way up as it would be cycling), has about (comparing with SH51 (Black), 1.5 mm (measuring horizontally) of metal shaved off at an angle of 45%, each side of the centre. On my new SH51 (Black), moving the spring loaded lever of new pedal with pliers, one can see the lever pulls Very tightly over the top of SH51 (Black), on metal that would be absent on the SH56 (Silver). This locks the cleat tightly on SH51 (Black), no lateral horizontal play, (as felt by hand, maybe some with foot in shoe though) but I imagine over time some wear & slack will return, as at the front the cleat mounts loosely, & does Not have a centre position. (Some cyclists like some slack for knee movement, for racers with another manufacturer Look, there's 3 settings of slack, 0 upward).

It would seem, if ever the cleats screws to shoe became loose, & pedal release lever became distorted & rode up over rear of cleat, you'd be trapped, potentially fatal. Man in shop had said keep them tight. I'd also think: monitor for abrasion on vertical at rear, at top edge, & if you see any, fit new cleats. That goes for both SH51 (Black) & SH56 (Silver)

Back of cleats, looked at horizontally from side:
SH56 (Silver)
______
......\
.......\
......./
______/

SH51 (Black)
_______
.......|
......./
....../
_____/

Wear

Before they start wearing, I measured precise dimensions while brand new, for later reference. (I used an LCD micrometer, but don't let the 2 decimal places fool you, (or minor differences between SH51 (Black) & SH56 (Silver). Measurements did vary, depending precisely where placed, these cleats are not That precisely machined. Of course I took average reading of the cleats. Measurements in millimetres.
SH56 (Silver) KA SH51 (Black) JG Description
34.03 34.0 Length, back to notch near front
36.05 35.93 Length, total
6.12 5.93 Front slot, width
6.87 6.66 Front, length of slot
7.05 6.85 Thickness
6.76 6.65 Rear Thickness
12.11 12.04 Rear, total width
6.11 5.92 Rear slot, width

Environment: Gear I was trying it with:

PEDALS PD-M324
49.95 EU @ www.sportscheck.com 2012_07_02
"Specifications
Model Number PD-M324
Series SHIMANO
Pedal System SPD
SPD Cleat Surfaces one-side
Pop-up Floating Cage -
Spindle Thread BC 9/16" x 20 T.P.I.
Spindle Material chrome-moly
Cartridge Spindle -
Cleat Retention Indicator yes
Cleat Retention Adjuster yes
Mud Shedding Design -
Pedal Body Material aluminum / barrel finish
Cage Material aluminum
Reflector Y41B98010
Average Weight 533g (pair)"
PDF:
"Use only Shimano cleats (SM-SH51/ SM-SH52 / SM-SH55 / SM-SH56)"
Multiple release mode cleats: SM-SH55 (Silver) / SM-SH56 (gold /Silver).
Single release mode cleats: SM-SH51/ SM-SH52 (Black /Optional accessory)

  SHOES SH-M087G

79.95 EU @ www.sportscheck.com 2012_07_02
"Features:
  • UPPER: Tough stretch resistant synthetic leather and mesh
  • Micro-adjust buckle and dual asymmetrical straps
  • Snug, durable and breathable comfort
  • LAST: Close-to-foot fit last
  • SOLE: Fiberglass reinforced polyamide midsole plate
  • Durable rubber tread offers excellent traction and walking comfort"
PDF:
"These SPD shoes cannot be used with SPD/SPD-R/SPD-SL pedals for road riding."
Shimano text in Italics is wrong, misleading, It caused me to waste time going back to shop to check: Shoes cannot be used with [SPD derivatives] SPD-R or SPD-SL, but Can be used with SPD.

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