Bike Fit and Wedges and Shims

In the world of bike fit, there is always debate and controversy surrounding one subject or another. One such debate is when it is and when it's not appropriate to shim and/or wedge someones cleats. Ari and I have spent a great deal of time on the subject and we hear quite a bit about it and thought it would be a good time to give our opinion.

First off, There are things that should defined here. Shimming cleats is often used to compensate for leg length discrepancies. This is done by adding plastic pieces (cleat shims) between the riders shoe and cleat. Adding these shims to the shoe effectively makes that leg longer. A leg length discrepancy is just like it sounds, one leg longer than the other, we'll get to that next as it's pretty important to understand in this context.

Wedging is very similar except that the piece on material (shim) is thicker on one side than the other. This effectively cants or tilts the shoe to one side or the other, Varus or Valgus. This is most typically done to help with knee tracking and or knee alignment. It is very important to be able to accurately determine the cause of poor knee tracking and poor lower leg alignment.

Leg length discrepancy is where things get interesting and is very often misdiagnosed. Leg length discrepancy is either functional or structural. Functional leg length discrepancy is caused by muscular inbalance. In other words, your muscles pull your pelvis out of alignment and one leg appears to be longer. A structural leg length discrepancy is when your bones are actually longer. This is important because when it comes to bike fit, we treat them differently. Functional issues can, in most people, be accommodated by working on improving your overall physical alignment. When you shim the cleats of a cyclist with a functional leg length discrepancy, you are treating the symptom, not the cause and their functional issues remain. If you improve your overall physical alignment, you not only overcome the leg length discrepancy but you can avoid other issues with the knees, hips, back, neck and shoulders (basically everything). Structural discrepancies are really the only situation where we go to shims or in some cases a lift inside a shoe. Many fitters are taught to shim everyone before looking into the difference between a functional or structural leg length discrepancy. How can you tell the difference? The most accurate means of determining the difference is by getting a full body xray and literally taking measurements. On the other hand, an experienced, well trained Physical Therapist can do a good job of it. A good bike fitter can also do this. One thing to note is that sometimes people are so functionally off that they can't overcome their alignment issues and a shim can be used as a last resort.

Wedging is often done to accommodate bad knee alignment and knee tracking. The problem here is that we need to know why someone has poor knee tracking or alignment in the first place. Foot and lower leg alignment and proper arch support are all related and are very important. Wedging is sometimes done when what really needs to be addressed is arch support or forefoot (not whole foot) alignment. In fact, there is a lot of marketing out there than tells us that all cyclists need a certain amount of Varus (outward tilting of the foot) correction. First, assigning a physical characteristic to an entire population is...interesting, we'll leave that alone. Here is another case where understanding someone physically is key. If someone is overpronating, they likely need arch support, not a wedge.

The Verdict? Wedging is not a substitute for accurate arch support. Shimming may not be the ideal solution for leg length discrepancy. One very important thing to mention here is that there is really no text book method of fitting that can be universally applied to the masses. There is no perfect, step by step method of fitting that works on every cyclist. Some people can adapt to change where others cannot. Cyclists experience changes to their position in different ways. When I was younger, I could ride any old bike all day and get on a different one the next day and be fine. Not so much these days. The point is that there are plenty of bike fitters out there but experience and the understanding that there are all sorts of different types of cyclists out there makes all the difference. We're not all 23 years old and we're not all 60 either. We work with all kinds of cyclists, we like it this way. That helps us remain at the top of our field, we learn more every time we meet someone, that's how this all works. We've been doing this for a long time, it's safe to say that even I know more about bike fit than most "fitters" out there and I'm just the inventory janitor. We've spent a lot of time researching every method of fit and we've refined our process in a way that allows for the absolute best long term experience any type of cyclist can have. That's why we're here.