Shimano SPD-SL angled cleat shim

Disclaimer

• I am not a doctor or medical professional or even an athletic trainer

• all claims below are based on my own research & experience

Problem

• cycling athletes may have naturally inverted or everted ankle joints when under no load, or even when standing on your own weight

  • AKA varus versus valgus

• looks like this

  

• this would be rotation about the X axis as shown in this diagram

  

• once under pedaling load, this natural angle is forced flat, which can cause all sorts of various pains & aches

Identifying if this is for you

Read this document from BikeFit.

Solution

• angled insoles can be installed in shoes (another example here)

  • I haven't tried these, but I suspect they could drift over time (especially if stacked to get desired angle) unless adhered in place

• a shim can be installed between the cleat & the bottom of the shoe to create the same effect

  • here are a few examples

  • I've already made a 3DP one a long time ago for Shimano 2 bolt style mountain SPD cleats

  • because they are bolted in place, there is no risk of them drifting over time

• all solutions necessarily add stack height

  

  • this affects your saddle height & is ideally compensated for, especially for large angles which generate large stack heights

• regardless of whether inside or outside the shoe, the wedges should be oriented such that the ankle joint is allowed to rest as it does naturally under no load

  • citation here

  • it is possible to install the wedges mirrored about the sagittal plane which exacerbates the problem

    

Commercial solutions

There exist plenty of solutions out there:

1. BikeFit

2. FitKit

3. Shimano SM-SH20

   1. note these appear to be spacers & not wedges

Limitations

Stacking wedges to achieve greater angles

Commercial solutions generally only exist in 1 or 3 deg increments, & you must stack wedges to achieve greater angles, like so:

Design

Matching the curvature of road shoes

• Road shoes (generally shoes compatible with 3-bolt cleats) are not flat on the bottom where the cleat sits

  • this is in contrast to SPD-only shoes (not the ones that can mount both road & mountain cleats), where the cleat mounting area is flat

• this is apparent when you hold a straight edge across any road shoe

  

  • you can also see this subtle curvature in Shimano cleat spacers

    

• the logical consequence of this is what the shoe-side of the shim must be curved the same to ensure a good fit with the shoe

  • a simply flat-on-curved interface would require a lot of bolt torque to conform the flat surface to the curve, & at worst result in slippage of the cleat position

  • this very reason may be why commercial solutions appear to only supply very thin 1 deg & 3 deg shims so that the bolt torque forces the naturally flat shims into the curved shape

Reverse engineering the curvature

• thankfully the curve is purely cylindrical by all rough indications – the curvature is not the surface of a sphere or some other ellipsoid, which would greatly complicate its measurement without a CMM

• I tried to find this number published somewhere, as it should theoretically be standardized such that road shoes made by everyone are equally suited to take Time, Look, Shimano, Speedplay cleats, but the measurement seems to be unknown

• as such, I used this gauge to measure the curvature

  

• the resulting radius of curvature based on geometry is 330.85/2 = 165.425 mm

  

• it should be obvious that the cleat-side (as opposed to the shoe-side) of the shim must also be curved in a similar way, but I forgot about this for R1 & R1.1

  

  • here is a picture showing the curvature of the SPD-SL cleat against a straight reference

    

• validated the fit on R1.1

  

Minimum edge height

• being a wedge-shaped shim, it is necessary that opposite edges of the angle are of different thicknesses

  • for durability, the thinnest edge should be ~0.5 mm

    

Miscellany

• a shell of 3 mm was added to reduce material usage & allow the wedge to flex to better wrap around bottom of the shoe in case my earlier measurements of the radius of curvature were wrong

  

• SLA printing is best given that there are no flat sides to easily place on an FDM bed

• a key was added to locate inside the hollow cored-out section in the original SPD-SL cleat

  

  • in practice, it doesn't actually seem to contribute anything the way I implemented it

    • this idea came from this product

      

  • here is a view of the cored out hollow section I'm referring to

    

• general 2D profile of the cleat came from this model so I didn't have to re-invent the wheel

  • other useful reference models I found

    • https://www.printables.com/model/225338-spd-sl-compatible-road-cycling-cleat

    • https://grabcad.com/library/schimano-spd-sl-cleat-1
       

Notes on 3DP files provided

• please note for left & right shoes, you'll need to mirror the provided STL to generate a wedge for the opposite side

• R2 has been in use for ~200+ miles without issue

  • printed on a Form 3 in Tough 2k resin

Hardware required

Bolt head style

• adding stack height necessarily means the stock screws (see pictures for dimensions of stock screws) are not long enough

• stock screws appear to be custom by Shimano & therefore hard to find & expensive

  • they probably only offer 10 & 13.5 mm lengths

  

• it turns out that the “washers” that come with SPD-SL cleats are already countersunk slots

  

  • therefore, they seem to work with common 90 deg CSK bolts

  • as an aside, it's kind of odd that there is a CSK slot in the first place; it hurts the clamping area for the stock bolts, but does greatly stiffen the “washers” – if that is even necessary

  • it's not ideal to have only 2 lines of contact with a CSK inside a CSK slot, but after ~200 miles as of 2024-12-01, it seems to be fine at ~6 Nm of torque

  

  • comparison of CSK against stock bolts (qty 2)

    

• the largest flange offered by McMaster is 12.8 mm – I decided against these in favor of CSK bolts I already had

  • stock Shimano one measures 14.2 mm

Screw lengths required

• because the shim is not of a single thickness (see height map found experimentally below), you could get away with using a different screw length for each location

  

Hardware you should collect

for the installation of a single cleat:

1. qty 3 M5 x 16 mm CSK

   

   • these worked well for the provided R2 model at 5 deg angle – different lengths required for different angles

Existing 3DP solutions

Additional possibilities with cleat wedges

Compensating for leg length differences

If it were me though, I would simply make a model that did not have the angled tilt & was a purely parallel spacer.

Further work

• If it were me though, I would simply make a model that did not have the angled tilt & was a purely parallel spacer.

Comparison with 2-bolt mountain SPD cleats

• provided that your riding is equally done with either SPD or SPD-SL cleats, SPD-SL cleats generally offer significantly larger range of adjustment because most shoes uniquely able to mount SPD cleats, do such inside a recessed channel

  • this necessarily limits the mounting distance relative to the sagittal plane, would could be relevant for your body