Over the last year George has observed on many occasions under certain circumstances that my hips rock noticeably and I appear to be over-extending in my pedal stroke when viewed from the side while riding. Since having had the power meter, I have been able to identify a discrepancy in power delivery to the pedals in balance.
We began a few weeks ago with a review of past measurements and current bike setup as well as a discussion of his observations. We decided on a "start from scratch" measurement from the waist down. We found two interesting things. The first thing was that I measured a full centimeter shorter than what we had on record for me from 1991 when George first measured me and also from other measurements that I recorded over the years. The impact of that is that when calculating various components of the bike fit, it alters a few things, most notably, frame size and saddle height. I had been riding at 81.8cm (leg length x .885) and the new calculation puts me at 80.6cm - a full 1.2cm difference and in bike fit terms, that's quite a bit.
We started with adjusting my saddle height and after some discussion about how we would approach adjusting such a large gap along with other adjustments that we suspected would need to be made, we decided to do it in three increments - 4mm at a time. We lowered it to 81.4 and I have been there for two weeks. I immediately noticed the difference as soon as I got on the bike. At first it took some getting used to, but I noticed a couple of things. On the positive side, it is slightly more comfortable and I feel like a get a better pull through the bottom of the stroke, especially in larger gears. On the negative side, my spin (when I "overspin") seems a bit choppy and I felt like I needed to 'push back' in the saddle often - both of which may subside once I am acclimated and in recent days it doesn't seem as noticeable.
The other thing observed was that my left leg is 1.2cm shorter than the right. This somewhat explains the fact that my right-left balance on the power meter has consistently shown averages for all types of rides (recovery, endurance, intervals) to be anywhere from 44% to 48% on the left and 52% to 56% on the right - clearly an imbalance of power input at the crank and it has never been the other way around where the right leg is lower.
In addressing this, we observed a couple of other related issues. First, my cleats were not in an optimal position. I had them set in a neutral position with the line signifying the center of the cleat centered on the ball of my foot. For different riding styles and applications (road, track, TT) this can differ slightly but typically only within a couple of mm either side of center. Historically, I have always used one set of shoes for everything - road racing, track and time-trial. After discussions about how we would approach the series of adjustments required for an optimal cleat position, we decided to set "my good shoes" for a road-race position which is 1 to 3mm behind center. I will acquire a second set of shoes for the track and deal with the setup on those at a later time.
We started with moving the cleats backward 2mm from center which effectively puts the foot deeper into the pedal. The result of this should be that can put more power to the pedals. At the same time we utilized some power shims to alter the angle of the interface to the pedal which adjusts the inherent alignment issues that most all cyclists have.
The plan is to ride with this for a couple of weeks before we begin to work on shimming the short leg. There is a fitting process that details how to deal with this anomaly and interestingly enough most people have it to some extent and mine is not significant. We will shim half the distance of the measured imbalance, but not all at once. In a couple of weeks, we'll do 2mm first (the smallest amount possible with the cleat shims) and after a couple of weeks review how it feels and discuss if I want to go another step and add another 2mm. It so, we'll see how it feels and see if we need to go further to the full 6mm. After that, we will re-observe the saddle height portion to determine if we should drop it another 4mm. We currently are still at the first adjustment of 4mm lower that the original that I started at.
The key part to all this is paying attention to how things feel and my providing feedback to George. He and I both understand that you can't simply take numbers and apply them to someone and say "that's it". We are doing this slowly and methodically to address some specific things. This fitting stuff is not a concrete science. There are a number of methods and calculations to create a baseline starting point for anyone, but from there it's all about the feedback loop and making methodical adjustments because everything on the bike is interrelated and changing one thing often affects something else.
Once I get this all sorted, I can have the piece of mind knowing that my fit is spot-on for my next purchase:
http://www.serotta.com/pages/ottrott.html
Painting titanium and carbon is just plain WRONG. This is the scheme I will be getting...
No comments:
Post a Comment