Lou,
I went and read the article, and I must say that I found the concept intriguing. While in all of my work on fit, I had never considered using that technique, I thought I would use Accufit Designer to see how it worked out.
The actual steering axis, is not the head tube centerline, but the extension of the caster angle. The caster angle is the angle formed by extending a line from the point on the ground where the extended head tube centerline touches the ground, back up through the center of the front axel. This is actually the angular component of trail and on most bikes that tend to have good handling characteristics, is about 81 degrees.
Using Accufit Designer to look at fit vs. steering axis and plotting what I thought was the approximate center of the ear, I found that the center of the ear was always in front of the extended centerline of the head tube unless a very short stem (under 6 cm) was used and the neck was pivoted to a fairly upright position. This was done with the hands positioned on the top of the bars. With a very long stem (12 cm) the ear was about midway between the extended centerline of the head tube and the extension of the caster angle. This of course made it necessary to significantly shorten the top tube to compensate for the change in stem length.
With the hands in the drops, the long stem short top tube combination places the ear very close to the extended caster angle, but still to the rear. With a more normal combination (for me) using a 9 cm stem and 54.8 cm top tube, the ears is a substantial distance behind the extension of the caster angle.
With all due respect to Albert, I just don't see this as something that would provide the consistency of fit that I was looking for when I was building custom frames, nor is it consistent with what I have found while developing Accufit. This would only come close if you could control the length of the top tube as with a custom frame, and even then, I think it is a bit suspect. It is slightly better than the old rule of thumb of sighting the front axel with the bar to determine if the length of the stem is correct. Just in case someone thinks that I am advocating the handlebar front axel method, I am not, as it makes no allowances for head tube angle or top tube length variations.
I would be interested in hearing about your findings. Where were your ears relative to the extended centerline of the head tube?
If you truly want to sort out your fit issues, and try to get all of your bikes adjusted to a good fit, I would suggest that you take a look at Personal Accufit. At $29.95, for two riders, it is far cheaper than even most used stems.
Hope this helps.
Bill Boston
dark in Wilmington, DE
http://www.billbostoncycles.com
> Bradley Woehl sent this link (below) to an article he wrote in the Bicycle
> Trader about Albert Eisentraut. After reading the part about bike fit,
> specifically the comment that the inner ear should be in alignment with
the steering
> axis, I went out with fellow listmembers Brent Harrell and Bess David to
see
> whether it proved true for our bikes. Unfortunately, it became obvious
that we
> don't understand the definition of "steering axis". We started with the
> extended line from the steerer tube. Didn't come close. Does anyone have
a
> definition of this measurement? Lou Deeter, Orlando FL
>
> http://www.bicycletrader.com/