Bike Fitting: Proper Pedal-Foot Interface
Hi all – as we head to the riding season I thought it might be helpful to talk about a fundamental element in bike fitting, the interface between your pedals and feet. If you’d like to be more comfortable this season now would be a good time to schedule a bike fitting to address lingering issues from season’s past.
A cyclist contacts her bike in three places, the saddle, the bars and the pedals. How we connect to the bars and pedals is controlled by the reach from where we sit. When we are properly positioned on the bike with our center of gravity correctly located from front to back the rest of a good bike fit will fall easily into place. When we are badly positioned on the saddle, and the center of gravity is not correct the bike fit will be compromised in some fashion. After getting the saddle position right how a cyclist’s feet are positioned on the pedals is the next most important connection point. Why? The pedals provide the power for locomotion! Ideally the balls of the cyclist’s feet are positioned over the pedal spindle, or axle, and an optimum leg extension will yield a knee angle of approximately 25 to 35 degrees at the bottom of the pedal stroke.
In a bike fitting the first thing I look at when the rider is on the bike is how the feet are positioned on the pedals. Next I look at the relationship of foot placement to where the cyclist is sitting on their saddle. The saddle needs to be positioned at plus or minus 2 degrees from level to provide a stable platform, and the rider’s sit bones need to be over the widest part of the saddle. Tilting the saddle nose down more than 2 degrees will cause the rider to slide toward the nose of the saddle with bad consequences. Prolonged riding with your weight on the front of the saddle will result in a painful ride that could cause circulatory and, or nerve damage. Additionally, a saddle tilted too far forward will put stress on the arms and neck resulting in pain, numbness and, or injury from the hands on up if not corrected. In a recent fitting, a client came to me to help solve discomfort concentrated around the saddle. Although the saddle was close enough to level, what I found was that the bike was too big by a full size. The rider was not able to keep her sit bones in the best position and was sitting toward the front of the saddle. This bad position was exacerbated by poor technique – the rider never thought about relieving saddle pressure by standing. After 15 minutes numbness would turn to pain, and the damage done would take days to overcome.
When I measure inseam to get a frame size and set the saddle height I make the calculation, bearing in mind, that the foot will be positioned as I’ve described with the ball of the foot over the pedal spindle. In the case of this fitting, the cyclist was relatively new to road riding and was using flat pedals with toe clips and straps that were left loose. I adjusted the saddle height and showed the cyclist where to position her feet. When the cyclist pedaled her feet slid forward so her toes touched the toe clips. Nothing strange in that, that’s what the toes clips are there to do, but in this case the clips were too large. The cyclist was pressing on the pedals with the middle of her feet rather than with the balls of her feet and effectively shortening her leg length. Even though the saddle was now in place to suit the measured leg length her foot position pulled her forward toward the front of the saddle. I readjusted the saddle lower and forward again to accommodate her foot position. I also shortened the stem and adjusted the handlebar angle to make her reach more comfortable.
The non-thought that went into the original fitting is really upsetting. Not only was the frame too big, but none of the fitting details were looked at and it doesn’t seen that there was any rider education regarding sitting and standing. A women’s model saddle was added, but I’d guess that there was not a lot of thought about it. This rider wants to become a better cyclist so our next steps are a set of clipless pedals which will mean repositioning the saddle again. Eventually a better size frame would be a good thing.
Back about 30 years ago, before clipless pedals proper size toe clips to keep the cyclist’s feet in the best place with the balls of her feet over the pedal spindles would have been the fix. It’s a detail that can still be attended to if you don’t plan to go to clipless pedals, but you probably need to ask for them, don’t expect that they will be offered. Want a bit more on the theory? Check out Keith Bontrager’s article from 1998 offered on Sheldon Brown’s site under http://sheldonbrown.com/kops.html