Yes, you read that correctly, and no, I'm not taking crazy pills. Slower wheels can make you faster. To make sure you choose the right wheels the next time you put on a race number, keep reading.
Your Front Wheel Is The Culprit
In this article, we will focus on your front wheel. Your front wheel connects to a steering axis—your fork and handlebars—and as a result, is affected more by crosswind than your rear wheel.
Crosswind not only pushes your front wheel side to side, but it can also turn your wheel left to right just like your handlebars do. You feel the effects of crosswind more intensely the deeper your wheel gets.
Having the wind turn your wheel while descending in the aero bars at 40mph is an unsettling experience. Riders in this predicament often sit up on their hoods to control their bike. Doing so, takes their body from an aerodynamic position and puts it directly in the wind.
You Need To Keep Your Body Out Of The Wind
Your body is the biggest source of drag on your bike. If you are sitting up on your hoods to control your bike, you are losing time. Here's why.
During a 5-hour Ironman Florida bike leg, our front FLO 90 AC will save you roughly 11 seconds more than our front FLO 60 AC. This 11-second separation tells us the difference in drag between a front FLO 60 AC, and a front FLO 90 AC is very small.
CdA is a measure of drag. As CdA increases so does drag.
At 5 degrees of yaw, the CdA of a front FLO 60 AC and front FLO 90 AC is 0.00987 and 0.00962 respectively. That's a CdA difference of 0.00025.
In comparison, the difference in CdA between a rider on the hoods and a rider in the aero bars is roughly 0.3. If we divide 0.3 by 0.00025, we can see that getting out of your aero position and riding on the hoods creates 1,200 times more drag than changing from a front FLO 90 to a front FLO 60.
So What Front Wheel Should I Use?
Based on what we learned above, it's paramount that your front wheel allows you to stay in your aero position.
The FLO 90 is faster on paper than a FLO 60, so most people think they should ride it. But, if the front FLO 90 causes you to come out of your aero position when a front FLO 60 wouldn't, you've lost more time riding the 90.
After selling tens of thousands of wheels over the last few years, our experience tells that a FLO 60 is the best front wheel for the majority of riders. Its depth gives riders a massive aerodynamic advantage and allows them to stay in their aero bars in most wind conditions confidently.
If you are overly sensitive to wind, then we'd suggest the front FLO 45. If you are a very confident bike handler, then take a look at the front FLO 90.
If The Difference Between Wheels Is So Small, Why Do I Need Race Wheels
You see the most significant aerodynamic advantage with cycling wheels when you go from a stock wheel like a Mavic Open Pro to a high-end race wheel like a FLO 60 AC. Once you've gained that large initial advantage, the difference between one high end race wheel and another is much smaller.
As an example, we know from above that the difference in CdA at 5 degrees of yaw between a FLO 60 AC and a FLO 90 AC is 0.00025. However, the difference in CdA between a Mavic Open Pro and a FLO 60 AC is 0.00953. This tells us the difference in CdA between a Mavic Open Pro and a FLO 60 AC is more than 38 times greater than the difference in drag between a FLO 60 AC and a FLO 90 AC.
My advice is, make sure you get the considerable initial advantage of going from a stock wheel to a race wheel, but don't obsess over the minute differences between individual race wheels.
What About My Rear Wheel?
Your rear wheel is fixed in your frame and does not have a steering axis like your front wheel. As a result, it is far less affected by crosswind. For this reason, we always recommend athletes pick the fastest rear wheel they can. If you want more information on selecting rear wheels, check out our guide to buying race wheels.