Initially, I started with a whole Specialized set of new footbeds and six shims. The set normally goes for $50 but I picked up a great deal on a local shop sale. I’d been planning on testing all of this out at some point, but I pretty much had my bikes set up so my shorter left leg really wasn’t much of an issue until late in trainer season. All of that time in the saddle with no out of the saddle adjustments meant a sore spot just in front of my sit bone on the left side.
I tried the shims, first. There are two kinds, a 1mm and a 1.5mm. One deals with pronation and the other with supination. I tried the orange 1.5 first and really couldn’t feel much of a difference. I stacked the 1mm on top of the 1.5 and gave that a whirl. Disco.
I rode with the double shim setup for a few days and liked the feeling – it felt as though I was more centered on the bike and my left side wasn’t bottoming out on the saddle.
However, it wasn’t perfect. I developed a little soreness in my knee that I didn’t like. I decided to take on of my old footbeds and cut it to the shape of the shim to see if I had any more luck with that. The bodged footbed felt amazing when I started riding. I was certain this would be the way to go… right up until I really started smarting on the top of my knee, just behind the kneecap. I knew this was bad, especially after only 20 minutes. I dismounted immediately and put the shims back in place. The pain subsided entirely and I finished my session.
And so now I know what too much shim does!