When you convert to Mph my achievement so far doesn't look so good.

I'm covering
country lanes (wide enough for 2 cars) 70%
Urban dual carrageway with lots of traffic lights (cars have 40mph limit - although its busy so they do 10mph avg) 30%

Over 15.7 miles I'm averaging 20.2mph on a MTB 44 x 11 gearing, with Continental GRand Prix 26 x 1 tyres.

My bike is light - 7,938g (17.50lbs)
Although I dont have aero bars - just flat MTB ones.

I've only been riding for 1 year, but covered between 6k and 7k miles

It a commute to work, but I compete with myself and motor vechicles. Its so busy, I get to work 5 mins fast on the bike than in a car

The calculation of analyticcycling is pretty realistic. I do not know if all people would agree with the wattage for novice/sports/elite level that I supposed, though.
I know, I can pedal around 250 watts for about 40 Minutes (SRM says so)and I think I´m not a novice (11.000 km/year). The 42 km/h on a flat course for 15 miles (~ 23 km) is realistic for me.

Also the elite speed seems to be realistic compared to some ITT´s I´ve seen (mostly they go faster).

Now it´s your decision when you´re a novice

_________________
www.carbonsports.com
www.carbonsports-forum.com

Sounds pretty fast for me.
I don't have a powermeter but at a sporttest in the winter I had 280watt at my MLSS (maximum lacate steady state, anaerobic threshold) level (at 72kg bodyweight). It should be possible to cycle 1 hour at MLSS poweroutput. But I don't think I will make the 42372meter.

Or should the 250watt be 350watt?

Some of the calculations on analyticcycling.com are wrong. He does not calculate the rotational inertia of a wheel correctly.

The definition given here http://www.analyticcycling.com/WheelsConcept_Page.html does not calculate the rotational inertia of a wheel. You can not calculate rotational inertia by swinging an object from a pendulum. The period of the pendulum's swing will not be effected by the mass distribution along the radius of a wheel. In other words analyticcycling calculated the wheels inertia without taking into account whether all the mass was located at the hub or the rim.

In order to calculate rotational inertia you must impart a torque to the spinning axis of the wheel. The acceleration of the wheel in response to a known torque is then used to calculate rotational inertia. A search on Google for Rotational Inertia Calculation will give you many examples such as http://www.physics.capcollege.bc.ca/lab ... nertia.htm and http://www.rowan.edu/colleges/las/physi ... nertia.pdf

Calculating the inertia of a wheel without taking into account the rotation of the wheel will only interest you if you plan on carrying the wheel on your back. As many have discussed before wheel rotational inertia is of paramount importance, especially when hill climbing as all spinning objects are accelerated with each pedel stroke.

Sorry for the long post but I felt since weight weenies spend thousands of dollars on wheels to reduce both overall weight and rim weight I thought it was worth the explanation.