On Wednesday, January 11, 2017 at 5:04:57 AM UTC+1, jbeattie wrote:
On Tuesday, January 10, 2017 at 7:28:41 PM UTC-8, Frank Krygowski wrote:
On 1/10/2017 4:11 PM, wrote:
But light bikes do NOT make hard climbs much easier. In fact they add a lot of problems. Once the grade gets up to 18% you can't use low gears because on the light bikes it will lift the front wheel off of the ground. The bike will then pivot around the rear wheel and if you're ready for that you can lay the bike over before it turns down hill.

The way professional climbers get away with this is that they use LARGE gears. Then you don't have the leverage to lift the front wheel.

I think you need to draw a free body diagram of the forces involved.

Sure, you can pop a wheelie on a steep grade if you put too much weight over the rear wheel on a short wheelbase bike in a super-low gear -- but you can do that with a steel bike, too. That's why you move your weight forward a little -- but not so much that you lose rear traction.

Professional climbers do not use LARGE gears. Post-Lance, they spin. My son was on the crew for the Tour of Utah and was surprised that a lot of domestic and Euro pros were using low gears. Here's a photo that he took: http://tinyurl.com/hpztj3o That ride has some staggering climbs with 20% grades.

-- Jay Beattie.

Pro riders use 34-28 regurarly on 14% grades and steeper.

Lou