Wednesday, April 22, 2009

Are You Wasting Power?

Women's Ruby with SRAM Red

Specialized Roubaix with SRAM Red. Note how top of sifters are ~ level with the bar top. This provides the maximum amount of forward reach for climbing

Tarmac racing bike with SRAM shifters and racing handlebars

Looking at the number and size of spacers, do you notice a trend here? Look at where the headtube's bearing race is relative to the top of the top tube on these bikes. With the arched toptube of the Tarmac, the bearing race is actually BELOW the top of the toptube - not sticking up 25mm (1 inch) above it like on the Ruby.

Look at where the top of the handlebar drops are - your drop position - relative to the bottom of the top tube. Now fire up the bike calculator (upper left of the blog) and remember that with 25mm of extra headtube height, a 20mm bearing collar, plus a 10mm and 2 X 5mm spacers, even when riding on the hoods your Ruby's position is "bar tops" for this calculator.

For a 150lb rider putting out 200 watts into a 5mph headwind the difference between "bar tops", and drops that are actually drops, is ~ 3.5 mph, and relative to aerobars, is almost 4.5 mph. Oh, and those aero bars are only actually aerodynamic IF they are mounted on handlebars mounted at a reasonable height. Now enter a speed of 20.07 mph in the Power from Speed calculator and see how much power you are wasting.

To go the same speed as your 200 watts will power you to in properly mounted aerobars, you'd have to generate 349 watts riding on "bar tops" - which is equivalent to riding on the hoods with a big stack of spacers under your stem. That's a 75% increase in required power to produce the same speed.

The best handlebar height is the lowest one your low back will tolerate. That will almost always change in your favor over time as your body adapts to the new position/s. You don't have to go all the way on the first date, you can move spacers from below to on top of the stem over time, but usually it's best to be aggressive as most people underestimate their body's ability to adapt. Ergonomic changes on a bicycle are a convergence process. Body adapts to machine, and then machine to body, and so on and so forth in an endless cycle.

The single most important factor in how comfortable you are on the bike is how much weight your feet are bearing, and thereby, how little your hands and butt are bearing. How will you ever get strong legs riding in a weak, upright position? Marketing departments like to sell plush bikes with seductively comfortable positions to new riders, but any serious rider should look to change such a stock setup ASAP.

So why set up bikes in such an upright position? Maybe so they can solve your speed "problem" with a more expensive bike. I'm guessing. I don't really know. I just know that 4-5mph is a HUGE increase in speed, more than going from a $500 bike to a $10,000 bike, so get out your 5mm hex wrench, maybe your hack saw, and enjoy the fastest ride of your life!

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