# What is the average CdA to Weight relationship of a professional Road cyclist?

As Body mass increases so does its volume resulting in a higher CdA causing more drag. However CdA does not increase linearly with mass. Are there any posted weight and CdA comparisons out there for pro riders?

I need an average CdA preferably for a road cyclist of a certain weight although TT data is also welcome.

• As a very rough, zeroth-order guess, you might say that CdA scales as mass^(2/3), assuming the shape of a person on a bike is constant with mass. Would be interesting to test this against some data, though! Commented Dec 2, 2016 at 8:00
• A rider's CdA can vary by more than a factor of 2 depending on position -- so his or her CdA-to-weight will also vary by more than a factor of 2. Commented Dec 3, 2016 at 4:33
• @Will Vousden: Please, how is 62^0.666 = 15.66 a valid CdA value? Commented Dec 3, 2016 at 18:44
• @AzulShiva "Scales as" means "is proportional to", not "is equal to". Commented Dec 3, 2016 at 20:04
• ah yes, apologies. (Why do I keep finding the most useful answer to be only a comment?) Commented Dec 4, 2016 at 22:17

A very brief answer to part of your question. Perhaps you or others can leverage this to produce a more complete answer, unless Alex or Robert chime in :-)

As you probably know, CdA is the product of the frontal area, A, and a coefficient of drag, Cd. It is also known as the "drag area." In most cycling applications, the area is measured in square meters, so a cyclist with a CdA of 0.30 has a drag area of 0.30 m^2.

AFAIK there are few studies that have been released for pro cyclists, although these days several of the pro teams say they do wind tunnel testing. Maybe that's just PR.

There are multiple academic papers that relate to this. Once you have one you can follow the trail of citations to others. Currently the most famous is probably

Martin, Millikan, Cobb, McFadden, and Coggan. Journal of Applied Biomechanics, 1998, 14, 276-291.

A copy can be found here

In their experiments they used six volunteers. Not pro cyclists. The volunteers rode in the time trial position.They say the average drag area was 0.264 m^2 for an average body mass of 71.9 kg. See the paper for more details.

In another post on this site Simmons measures his own CdA at 0.334m^2 on a road bike compared to 0.286m^2 on a TT bike, a 14% reduction.

Alex's post gives some other references that can be followed. Several of his other posts will be helpful also.

So the CdA depends on the cycling position. In my own models, I find a CdA of .3 m^2 gives a good fit for my performance on a road bike. I'm 70 kg.

Andy Coggan has also collected some rough rules of thumb for estimating CdA from anthropometric data like height and weight here.

• Thanks for the edit @R.Chung. My quote from Alex is slightly inaccurate now, but in this context I guess it reads better, but the extra link is valuable. Commented Dec 2, 2016 at 8:20
• Nice answer. The anthropometric scaling formula posted by Andy Coggan are as good as you'll get for an estimation without actually measuring CdA but like many such formula, they apply on average and the individual of course may show some variation from the average. As an example, I had a club mate who was same height, weight and power output as me but his track pursuit position CdA was 23% lower than mine (0.235m^2 v 0.180m^2). The only way to know CdA is to test for it, e.g. via field testing/analysis with a power meter, or in a wind tunnel. Commented Dec 2, 2016 at 19:47