Saturday, October 9, 2010

Computrainer Race League

A quick note, for anyone with a Computrainer, there is a Race Series for the next 21 weeks.

The first race (10k TT) must be submitted before Midnight GMT this Sunday.

What price a wheel?

It has been a busy month, trying to get hours in on the bike, get back into track shape, and some paying work done :-)

Last night was the 2nd Friday night race of the year. I'm racing with the A group this year so that I can race in my 93" gearing.

What was interesting about was the difference between the last week and last night. A week ago we did a 40 Lap Scratch race and a 4x10 Points race. In both races I was getting spit out the back, then going up to the blue line and when the pack came around jumping back in. Last night we did a 25 Lap Scratch race and a 6x10 Points race. I managed to stay on the pack for the 25 Lap scratch and didn't get lapped in the points until lap 30, and even then was working well with smaller groups who where also down one lap.

Speedwise last night was about the same as last week. But there was something different about last night. Suddenly I was able to stay on the pack, at the back of pack, not working in the rotation. But still much better than last week where I simply couldn't hold on (in many cases couldn't even get on.)

The difference was the rear wheel. Last week I was on a loaner training wheel with some no-name training tire. This week I had my Zipp 900 with a Vittoria Pista EVO CL 22.  Gearing remained unchanged at 50x14 (about 93.6" for the 700x22 Vittoria.)

If you look at the scatter plot on the right, The green and yellow points are from last weeks race. Blue and Red from this week. This is power at speed. And you can see a clear trend for higher speed at most power levels for the red and blue points.

At a guess, between 2-3 kmh for most power levels. An that makes the difference of hanging in at the back and getting spit out.

So what is the price of a wheel? Call it about 2 kilometers per hour. For whatever power output you have you'll be able to go about 2 kmh faster.

Or more pragmatically, something like an extra 50 watts to push around the training wheel at speeds between 46-52. You'll need to produce those extra watts if you want to use the training wheel.