So Why do heavy guys do better on Flats? - Page 3

yeah, i know... i've got some issues i need to work on...

Doc, I don't claim to know much about aerodynamics (or anything else), but I'm always a little suspect when someone quotes the manufacturer's own man. Josh does work for Zipp, right?

From his page you posted, he first says the Tour tests should be taken with a grain of salt, as they were run in zero-yaw (no crosswind) conditions, not real world. He states that in zero-yaw, "most wheels are very similar". But looking at the test data, from 38W saved down to 5W, I don't see very similar results at all. Appears like a huge contradiction to me, but perhaps I'm missing something.

Another small issue turns up in the Wind Tunnel pdf, where Zipp 808s are claimed to save 81 seconds/27 watts (over an unnamed wheel) for a TT rider (eg, Cancellara) putting out 300W.
But then the explanation fine print says slower riders (ie, everyone else in the world) get even more time savings because they are riding longer. That statement just doesn't fit with my limited understanding of how aero drag works.....the part where drag is proportional to the cube of the velocity. Perhaps someone in marketing wrote this burb, thinking that the 27 W savings was a constant regardless of speed

Bicycling Mag had a test report from the Texas A&M wind tunnel a while back. IIRC, they found that a good aero position on the bike was by far the biggest factor. Next was a TT helmet, followed by a tight jersey or skinsuit kept zipped up. The conclusion was that the wheelset was the last thing a TT rider needed to invest in, not the first. Maybe I've got this all wrong; perhaps someone has the issue and can look up the results.

The savings for the slower rider are absolutely bigger, but smaller as % of ride time.

As the finish times at amateur level are also more variable, the equipment savings is doubly important at the higher level.

Chris Boardman would agree with Alberto too...

yes, you need to look at the qualities of each of the wheels listed... the lower ranked ones are tri spokes the perform well in cross winds but not so good at 0 degrees, some like the cormina are only 40mm deep vs 80mm for the 808s and the better performing ones. of the ones with similar characteristics to the 808 they are all in the 25-35 ball park give or take...

you have to remember that the drag of the wheels is not that much to begin (when compared to a persons body.. this is my point that started this tangent by the way) and so the speed differential is not enough to make much of difference in absolute terms (relative to the contribution from the wheel yes) Cancellara speed to normal human speed. secondly you have to remember that an increase of 27 watts at 30km/hr will change ones speed more significantly that a 27 watt increase at say 50km/hr... so as counter intuitive as it sounds, the slower you are the more impact aero equipment will have on your times because the faster you go the more and more incremental power it takes to go even faster...


25-35 watts out of say 300-350 IS peanuts.. damn right! i'd be working on my position.. i have seen a really good article in cyclingnews (can find it now though) that gives a really good analysis of these comparisons and a cost benefit/value analysis too... for the money i think the helmet was the best kit to spend your money on but still position is very most important thing.. was interesting that most road bikes couldn't get riders into an optimal position... and again this is the point i was making... saying that the aerodynamics of big compared to small riders is insignificant just doesn't make any kind of sense... all you have to do is look over at your bigger or smaller buddies power reading as you ride and you'll see this.

Here's one data point in terms of power savings of different components at constant speed for a single rider and single frame tested:

How Aero Is Aero? - BikeRadar

Not exactly an exhaustive test suite, but good food for thought.

-Dave

as swampy said... Chris Boardman (former world hour record holder) 5'9" and 150lbs.. that's not exactly what i'd call a "big" guy and yet in his time he was arguably the best on the flat of anyone on the planet.. kinda blows the big guys do better on the flat theory out of the water.. big guys are really just on an equal footing on the flat.. and maybe very slightly advantaged if any...

also look at the gold medal match in the sprint this year.. Bauge the mountain on the left ended up winning but, Azizulhasni on the right ended up with the silver medal and actually took one of the heats in the final...