Bike Fitting at Loue Bicycles - Using Pedal Stack Height to replace Cleat Shims

In the previous bike fitting posts at LOUE Bicycles, I wrote about how there is a need to add shims on the SPD cleats of my shoes, due to the slightly different leg length caused by my swiveling hips during pedaling.

A recommended addition of 1.5 mm was suggested for the left leg, to adjust the leg reach slightly to match the right leg. A 1.5 mm difference is actually quite small, compared to the overall length of the leg. On my road bike, the Focus Paralane which I used for the actual bike fitting, I will try to achieve the ideal bike fit to optimize the power output and pedaling comfort.

Bike fitting on the Focus Paralane, at LOUE Bicycles.

As for the other bikes, such as the folding bikes, it is not so critical, as I will be pedaling leisurely instead of at high power. I will probably switch between flat soled shoes or SPD shoes occasionally, on the dual sided SPD/platform pedals.

I have an idea to adjust the leg length, but not by adjusting the shim on the SPD cleats. Instead, I can use pedals of different stack height, which would have the same effect. If the pedal has a taller stack height (distance from centre of pedal axle to sole of the shoe), it will effectively shorten the distance from the saddle, which has the same effect as adding a shim on the SPD cleat under the shoe.

Measuring the pedal stack height is not easy, as it is difficult to find the centre of the pedal axle. Therefore, to simplify the measurement, I used the pedal thickness instead. Then, I assume that the stack height is just half of the pedal thickness. There might be some inaccuracy here, but I think this is good enough.

The idea is to use a pedal with a taller stack height (thicker) on the left crankarm, and a pedal with a lower stack height (thinner) on the right crankarm. This effectively gives a left leg reach that is shorter, which suits my purpose.

I tried to use the product spec provided by Shimano for the pedal stack height, but it doesn't match what I measure (thickness). I think the difference is what I mentioned above, that the actual stack height is measured from the centre of the pedal axle (virtual point) to the sole of the shoe (another virtual point). I can't measure those points directly or easily, which is why I chose to measure pedal thickness instead.

Moving forward, I will use pedal thickness to approximate the different stack height of the pedals that I have, to find a suitable pedal for the left and right side.

The pedal that is currently on the Focus Paralane is the XTR PD-M9020, which is rather lightweight.

I have an alternative SPD pedal, the new GRX PD-ME700 SPD pedals, which are similar in design to the other trail SPD pedals, but at a lower price point.

I know that the XTR pedal has the lowest stack height, so this will remain on the right side, while I will find a thicker pedal on the left side to reduce the leg reach.

Thickness of XTR PD-M9020 is 17 mm.

Here is the GRX PD-ME700 SPD trail pedals. I will do a separate introduction/comparison post later on.

Thickness of GRX PD-ME700 is 18.7 mm.

From these measurements, we see that between XTR and GRX pedals, there is a 1.7 mm difference in thickness, which works out to about 0.85 mm difference in stack height, theoretically. It is not as much as the 1.5 mm that I was advised to use, but I think it is acceptable, and better than nothing.

Installed the ME700 pedals on the left side of the Focus Paralane.

There is a bigger gap between the spring and the cleat platform on the ME700 pedals on the right side of the picture, versus the XTR pedals on the left of the picture.

Later on, I remembered that I actually have another pair of SPD trail pedals, the Deore XT PD-M8020 which is currently in use on the Cervelo Aspero gravel bike. For a comparison between XTR PD-M9020 and Deore XT PD-M8020 pedals, check out this comparison post.

Deore XT PD-M8020 SPD trail pedals

The M8020 pedals is actually slightly thicker than the ME700 pedals, at 18.8 mm.

With that, I swapped the pedals again, by installing the left side M8020 pedals on the Focus Paralane, and retaining the XTR M9020 pedal on the right side. This gives me a stack height difference of 0.9 mm, which is frankly a small amount.

Can I actually feel this small difference? I am not sure, but I will try it and see since I have the pedals to swap around.

XTR vs Deore XT pedals side by side

There is a small difference in stack height and thickness between these two pedals. I will follow the bike fitting advice to adjust the leg reach.

In the end, I used pedals of different stack height to account for the different leg reach, instead of adding shims under the SPD cleats. Although this means that the pedals on the left and right side don't match, I think it is a more elegant solution than adding shims under the cleats, which comes with other problems.

I think I will only do this pedal stack offset on my Focus Paralane and the Cervelo Aspero, since these two bikes are more sensitive to a bike fit. As for the other bikes, they are ridden more casually with casual shoes, and I don't think a small stack height difference actually matters.

I am glad I did the bike fit at LOUE Bicycles, as I really learnt a lot about myself and also the bike. It will be great to replicate the bike fit on other bikes with the data generated, instead of adjusting it bit by bit using trial and error.