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PostPosted: Tue Feb 23, 2010 7:27 pm 
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Joined: Sun Mar 06, 2005 4:48 pm
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Location: Eugene Oregon
I have my Sport set up so that my hands are every so slightly behind and to the rear of my front axle. If I draw a line from the vertical part my brifter that my hands push against it is almost directly above the front axle, thus my hands fall just to the rear.

So to the fit guru's (Richard and others) is there a guidline that one should use in determining where your hands should fall in relation to the front axle?

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Pat Mc


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PostPosted: Fri Feb 26, 2010 11:03 am 
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There are lots of rules of thumb that have crept into the lore of bike fitting. Some, like the knee of pedal spindle, are better than others, like the bars blocking your view of the front hub. In the case of the bars-to-front hub rule, it probably made more sense for criterium riders when it was popular in the 80's than for other populations, yet for a while it was a widely used rule of thumb. We rarely hear it mentioned these days because we know so much more about bike fit now.

In terms of bar placement, the first priority is to have your bars in a comfortable position for the kind of riding you do. Ideally you will feel comfortable and confident regardless of where you have your hands on your bike. Once you have that relationship down, you want to have a stem reach appropriate for your overall weight distribution. For recreational / distance riders, this can be looser than it would be for stage racers or other competitive riders.

The more your bars are in front of the axle, the more weight is over the rear wheel. On high speed descents, this reduces the threshold where high-speed oscillations can creep in. Many recreational riders never reach that threshold, so it never becomes an issue.

To the extent your bars are behind the axle, you have more steering leverage, which means that it's easier for you make small adjustments to the steering. For most riding, this isn't an issue. Touchy steering is a double edged sword. For crit riders, is means that you get more control, but you also need better handling skills. On high speed decents, it also means that you need a lighter touch on the bars lest you get handling problems from a "death grip".

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PostPosted: Sat Feb 27, 2010 11:27 am 
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Joined: Sun Mar 06, 2005 4:48 pm
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Location: Eugene Oregon
Richard

As always thank you for sharing your wealth of knowledge. So for serious riders that do not race but do want a very good handling bike, what would you recommend as a front/back weight relationship? I have heard 45/55 as the ideal but what latitude is reasonable for a good hadling bike?

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Pat Mc


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PostPosted: Sat Feb 27, 2010 1:25 pm 
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45% front wheel / 55% rear wheel weight distribution: That's another familiar rule of thumb. Actually, the range is (40-45% front and 55-60% rear). While we use this rule of thumb, there has been no systematic research to back it up. Not only that, people rarely actually measure it, let alone testing it against real world experiences.

With all the money spent on wind tunnel testing, structural modeling and other bike performance topics, I'm surprised at how little has come out on this topic. For those who think that the big Tour teams keep it a secret, the fact that race bike weight distribution hasn't changed much in the past 20 years means that either:

a> nobody's studied it.
b> somebody's studied it and found that there aren't any changes worth making.

Here's a fun link to a weight distribution applet: http://www.ibiblio.org/links/devmodules ... heory.html The applet was designed as part of Rensselaer Polytechnic Institute's engineering program - more as an illustration than anything else.

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