Does anybody know where actual scientific data on the benefits of aero wheels is? What is the average speed that that you need to maintain before you overcome the downside of the extra weight? It seems to me that it must be rather high. I wonder if lots of people, even moderately fast people might not be better off with lighter wheels rather than aero wheels?

I recently had a set of light but not especially fancy tubulars built up and I swear, these things changed my bike into an absolute rocket! Granted, I live in a very, very hilly place where you might expect light wheels to be a nice addition to the bike but I didn't expect this.

I had been riding a Campagnolo Chorus with a pretty standard Mavic Aero profile rim. 36 spokes in back and 24 up front (To get a 24 spoke wheel I used a 36 hole rim and hub and skipped every third hole) I replaced this setup with an IDENTICAL set of chorus hubs made in the same year and NOS Mavic GL280 tubular rims and 320 gram tubular tires. Both the front and rear wheel have 32 DB spokes. This setup feels like I have dropped 5 or 6 pounds from the bike.

I don't notice any difference in the time in my training log. Indeed, I have had on average slightly faster times this week. In theory I have gained two spokes and two square rims woth of air-resistence and lost about 1.5 lbs in weight. Am I all alone in this or have others found the same thing to be true?

Check out the tech articles on this site - http://www.bicyclesports.com

In general, aero trumps weight regardless of the speed and regardless of the course profile.

Lightweight mostly helps for accelerating and going up hills. Past that you're MUCH better off having a heavy aero wheel for any kind of "steady state" event. 75% of your power on the bike goes to beating the wind, and you can save a lot more aero "weight" than you can bike weight.

Take a peak at this - http://www.timetrial.org/aerodynamics.htm
The numbers are pretty close there, look at the amount of minutes you can save by going from completely non-aero to completely optimized.

http://www.cervelo.com/tech/articles/article5.html - has some good info as well, and compares a large section of rider ability (because not everybody can rip a 30mph avg 40k).

More information can be found here;
http://www.bsn.com/cycling/WheelAerodynamics.html
http://www.soton.ac.uk/~aijf197/Wheel%20Aerodynamics/Executive%20Summary.htm#top (you can skip to the "results" if you don't want to read all the other junk in there)
http://www.analyticcycling.com/DiffEqWindCourse_Page.html (has some good wheel data)
http://www.analyticcycling.com - just a cool technie cycling site

The difference you are feeling probably comes about by the fact that your old wheelset didn't offer very many aero benefits over what you have now, you need to get into a really DEEP rim section to start seeing the aero differences, so in your case you may very well have made up the slight loss in aero from the savings in weight.

Andrew

I think part of the deal here is that I am riding on terrain similar to San Francisco. Hong Kong Island has extremely steep hills 6:1, 5:1 type slopes and very winding off camber roads that are often wet and clogged with traffic. You cannot ride them fast either up or down. Going up one of hese hills you're a really strong rider if you can make 15 - 20 KPH (6 - 8 MPH) At 45, with tendonitis in my hips I am lucky to stay that fast! The bigger issue for me on Repulse BayRoad or Old Peak Road is brakepads!

I had riden tubulars way back in the late 70's and 80's until I retired from racing. When I picked the bike back up in the late 90's I went with clinchers because they are slightly less trouble to repair. Tubulars have always ridden better but I don't remember the weight feeling like this. However, parts, especially rims, were lighter back then.

I think I'll stay with my tubulars at this point. I'm riding to finish and enjoy the excuse for training. Anyway, if I win I might have to buy a new bike.

Excellent, informative thread. Especially the links. Thanks guys!

Some good articles.

In my fanatic racing days I developed method of testing and analyzing different set ups. For aero effects a cheap and effective "wind tunnel" to measure drag is a long, constant sloped hill where you can reach terminal speed and hold it for several seconds or longer. Simply do a few coasts with your different setups(including position) and use your speedo to determine the terminal speed. If you're fortunate enough to have a hill where terminal is about your TT speed then the difference will be very near any speed improvement measured.

For weight considerations - for steep climbs the only thing that counts is total weight(bike + rider). Lighter is faster by the ratio of the total weight. For accel's it's rider + bike + rotating mass. The key on rotating mass is to keep it away from the rim because the effect is a function of radius squared.

Another issue with wheel aero drag. Many studies I've seen don't include the effect of drag from the fact the wheel is doing more than just rotating. It rotating plus translating. The top of the wheel is moving at 2x ground speed. The bottom of wheel is not moving at all unless you're sliding. Because aero drag is a velocity squared effect simply rotating a wheel does not provide the true drag. The hill test, however, does account for this.

Happy trails.