Subscribe via iTunesAerodynamics With David Ripley of ZippIn addition to working for Zipp, David is also a bike fitter and consultant for 51 Speed Shop.

Topics discussed include:

The Four restrictive properties working against you on the bike are:

1. Aerodynamics2. Gravity3. Drivetrain Friction4. Road Friction

75-80% of aerodynamic drag comes from the body.  The wheels are the second greatest source of drag.  Components are next, and the frame is last.  Weight doesn't become a significant factor until the grade hits 6% for an extended period of time. A good clincher and latex tube compared to a poor tire and a butyl tube can result in a 10-11 watt difference per tire.  He recommends air pressure of 100psi for a 150 pound rider on a tri bike on a smooth road.  On a rough road a slightly lower tire pressure is recommended. 

Biggest bang for your buck in aerodynamics Vibram Five Finger ShoesA 10 week study published in the July 2013 issue of Medicine & Science in Sports & Exercise compared two groups of runners.  A group of 19 who slowly transitioned to the use of Vibrams over 10 weeks, and 17 who ran in conventional running shoes.

Using MRIs for analysis, 10 of the 19 in the Vibram group were determined to have a foot bone injury by the end of the 10 weeks.  Only 1 of the runners in the control group had a foot bone injury at the end of the study.

Runners in the control group ran an average of 30 miles in their peak week, while those in the Vibram group ran an average of 15-18 miles in their peak week.

This article describes the study in a little more detail.

Based on a lawsuit against Vibram settled in May 2014, Vibram Five Finger users may be entitled to a settlement that will likely be in the range of $20-$50. Details at http://www.fivefingerssettlement.com.

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