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Both in discussions among riders and in equipment manufacturers’ marketing discourse, the concept of stack height is now emerging as a new lever for performance optimization. Applied to pedals, this measurement, which corresponds to the distance between the pedal axle and the sole of the foot, is generating increasing interest, both among amateurs and in the professional peloton. Rightly or wrongly? Here’s how to navigate it when fine-tuning your bike’s settings.
By Guillaume Judas – Images: depositphotos.com
Behind this concept lies a simple mechanical reality: the shorter the distance between the foot and the axis of rotation, the more direct the power transfer. Each additional millimeter introduces materials that can deform under stress, thus generating slight energy losses.
Some brands even put forward ambitious figures. Italian manufacturer Q36.5, in partnership with SRM, mentions a potential gain of up to 1% in power for each millimeter reduced. A figure difficult to verify, but consistent with the fundamental principles of biomechanics.
Multiple but Subtle Benefits
Beyond pure efficiency, a reduced stack height offers other advantages. The weight gain, though minimal, is amplified by the position of the pedals, which are rotating elements located at the end of the cranks.
The biomechanical impact is also notable. While the current trend favors shorter cranks, implying an increase in saddle height, reducing the pedal-shoe height partially compensates for this effect and limits aerodynamic drag.
Finally, a reduction in frontal area marginally improves air penetration. A detail that can matter at a high level.
| Pedal + Cleat System | Height |
| Ekoï PW8 | ≈ 8 mm |
| Wahoo Speedplay Zero (4-hole direct) | 8.5 mm |
| Q36.5 x SRM | 9.7 mm |
| Wahoo Speedplay Zero (with adapter) | 11.5 mm |
| Wahoo Powrlink Zero | ≈ 13 mm |
| Shimano SPD-SL (Dura-Ace) | 14.6 mm |
| Time Xpro / Xpresso | 14.7 mm |
| Look Keo Blade | 14.8 mm |
| Favero Assioma PRO RS | 15.8 mm |
| Shimano SPD-SL (Ultegra) | 15.8 mm |
| Shimano SPD-SL (105) | 16.5 mm |
| Favero Assioma Duo | 16.8 mm |
| Garmin Rally (SPD-SL / Look) | 17–18.5 mm |
| Look Keo 2 Max | 17.3 mm |
| Shimano SPD (XC race type M9100) | ≈ 15–16 mm |
| Look X-Track MTB | ≈ 16–17 mm |
| Shimano SPD (PD-M520 etc.) | ≈ 17–18 mm |
| Time ATAC MTB | ≈ 18 mm |
In pink: road systems
In green: MTB/Gravel system
Technical… and Costly Solutions
Current market standards, dominated by Shimano, Look, or Time systems, show heights between 14 and 15 mm for the pedal and cleat assembly. Alternatives like Speedplay allow for significant reduction, provided compatible shoes are used. But beware: to this height, you must add that of the shoe, between the cleat and the foot, which depends on the sole thickness. More recently, innovative systems like the one developed by Q36.5 and SRM push the limits even further, with ultra-compact designs.
But these gains come at a price. Between high-end pedals, specific shoes, and potential modifications, the investment can quickly exceed €1000.
Sole Height Differences Between ShoesMost high-end shoes on the market offer a height between the cleat and the foot of approximately 6 to 7 mm. This is the case for Specialized S-Works, Lake, Giro, or Fizik models. With a height of 5.5 to 6 mm, Shimano S-Phyre are slightly lower. Some brands go further, such as Q36.5 (4.4 mm), Bont (3.6 mm), or Nimbl, which claims barely 2 mm. Contrary to popular belief, stack height differences between high-end shoes remain marginal, often less than a millimeter, whereas the choice of pedal system alone can vary the total height by almost a centimeter. Finally, it is important to reiterate that what must be taken into account is the height of the entire system formed by the pedal, the cleat, and the shoe sole. Specifically, a Shimano Dura-Ace system + S-Phyre shoe is approximately 20.5 mm in height above the axle. A Q36.5 x SRM system with Q36.5 shoes is 14.1 mm, which is a little over 6 mm less in total height. |
A Choice to Put into Perspective
While the technical advantages are undeniable, their real impact remains difficult to quantify on the road. Variations in power meter measurements, combined with the small gains, make any definitive conclusion delicate. For cyclists seeking absolute performance, every detail counts. But for the majority of riders, reducing stack height appears more as a niche optimization than a priority lever.
Regarding the combinations of pedals and shoes, between the most extreme configurations and traditional systems, the height difference can reach nearly a centimeter. This is obviously to be taken into account when adjusting the bike. However, on the road, the best configuration often remains one that balances stiffness, comfort, and stability, much more than the sole pursuit of a gained millimeter.
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