June 17, 2016
Deciding which race wheels to buy can be a big decision. There are a lot of questions that many athletes have, and we’ve tried to simplify the decision making process as much as possible. Below are some recommendations that we’ve developed over the years for purchasing race wheels. If you have any questions, please ask below.
Let’s start by outlining what we will discuss below.
1. Types of Cyclists/Riding Styles.
2. Aluminum + Carbon wheels vs. Carbon Clincher wheels.
3. Affects of Crosswind.
4. Wheel Selection.
5. Estimated Times Savings for Different Wheel Combinations.
1. Types of Cyclists/Riding Styles
We like to break riding styles down into three groups. These groups are as follows.
Triathletes and Time Trialists
These athletes are most commonly riding a time trial/triathlon bike and concerned with getting from point A to point B as fast as possible. These athletes are typically riding alone, and not in a pack or group.
These athletes ride a road bike and are also concerned with getting from point A to point B as quickly as possible. Unlike triathletes/time trialists, road racers are often riding in a pack, and can experience long sustained steep climbs and frequent accelerations more often.
The recreational rider is most commonly riding a road bike, and typically rides for fitness, pleasure, or a way to spend time with friends and family. These athletes are less concerned with getting from point A to point B as quickly as they can, but are more concerned with optimizing comfort, efficiency, and enjoyment.
2. Aluminum + Carbon vs. Carbon Clincher Wheels
Reasons to Buy Carbon Clincher Wheels
- Lighter Weight. Nearly 1 lb per set.
- Typically Better Aerodynamics.
- Better Compliance/Comfort.
Reasons to Buy Aluminum + Carbon Wheels
- More Affordable.
- Better for Winter Riding with sand, salt, and debris.
Historically, wheels with aluminum rims have had better braking performance. Our new carbon clincher rims, and specially formulated brake pads offer very strong braking. Don't let braking performance deter you from purchasing a carbon clincher wheel.
3. Affects of Crosswind
Front wheels are more affected by cross wind than rear wheels because they have a steering axis. This is a fancy way of saying that a front wheel can be turned clockwise and counter clockwise by your handlebars. Adding this additional steering axis means something else can move when the wind pick up. Wind forces on your front wheel can cause this rotation of the wheel/handlebars, making it more challenging to control your bicycle. The force that causes this movement is known as Yaw Torque. FLO wheels have been designed to limit yaw torque, and when compared to wheels with older technology, the difference is very noticeable. Yaw torque is one of the reasons riders often choose a front wheel that is shallower than their rear wheel.
Since rear wheels do not have a steering axis they are less affected by cross wind. In fact, having a rear wheel that is deeper than your front wheel moves your center of pressure backwards, and helps improve your stability in windy conditions. This is another reason why athletes often choose a rear wheel that is deeper than their front wheel. Most athletes can confidently control any depth of rear wheel.
4. Wheel Selection
Below I’ll give recommendations for both front and rear wheel selection for the three types of cyclists defined above.
Front Wheel Selection
For this group of athletes I recommend that they ride the deepest front wheel they can confidently ride in all wind conditions. What does that mean, and why do I say that? In short, it’s all about drag. The biggest component of drag on your bike is your body. Keeping your body in the aerobars and out of the wind, is much faster than sitting upright with your body in the wind. The increase in drag you will experience by getting out of your aero bars and sitting up in the wind, is much greater than the difference in drag between any of our front FLO wheels.
Knowing this, it’s easy to see that any triathlete or time trialist should aim to stay in the aerobars as much as possible. For this reason we recommend a front wheel that allows you to do this. Our front FLO 90 can be a bit challenging to control in higher wind conditions. It’s increased depth can force all but the most confident riders out of their aerobars when the wind pick up. For 90+% of our customers, the front FLO 60 is the perfect depth for a front wheel. Most athletes can confidently control a front FLO 60 in all wind conditions, and it’s still a very fast wheel. In fact, in low yaw conditions, it’s actually faster than our front FLO 90.
If you are a very timid rider, or riding in extremely high winds, we’d recommend our front FLO 45 as a front wheel.
When riding in road events, you are often riding in packs. Riding in these conditions means that you are very close to the riders beside you, so keeping the ultimate control of your bike at all times is of upmost importance. Like our recommendations above for triathletes and time trialists, a front FLO 90 could be a little too to handle when the winds pick up. If high winds cause your bike to move from side to side, you could collide with another rider. In my opinion, a front FLO 60, FLO 45 or even FLO 30 would be better front wheel choices for this style of riding. By choosing one of these three wheels, you are still getting really great aerodynamics, but you will be able to keep better control of your bike. On top of that, the front FLO 60, 45 and 30 are lighter than the front FLO 90 which will help with climbing, and the frequent accelerations and sprinting road racers often experience.
For this group I often recommend a front FLO 60, 45 or 30. All three of these wheels are easy to control in almost any wind condition, and their aerodynamic efficiency will make riding the same paces easier. Those who are looking for improved comfort and compliance should consider our Carbon Clincher options. The full Carbon Clincher wheels help dampen bumps and road buzz, which is a nice relief, especially on longer rides.
Rear Wheel Selection
Our general recommendation for rear wheels for the triathlete and time trialist is to pick the deepest rear wheel they can. The fastest rear wheel we sell is our FLO DISC. If you are a triathlete or time trialist, and you are looking to get from point A to point B as quickly as possible, then we recommend a FLO DISC wheel. That said, the FLO DISC doesn’t make the best every day training wheel, and is actually illegal at certain events like the Kona Ironman. This often means the FLO DISC is a great second wheel to have for racing. Many of our athletes will chose our next deepest option (our current best selling rear wheel) the rear FLO 90. FLO 90 is also a very fast rear wheel, can can be combined with a wheel cover from wheelbuilder.com if budget is a concern. Having a rear FLO 90 and a wheel cover (which cost about $100) gives an athlete the best of both worlds. Essentially you can have a rear FLO 90, and the closest thing to FLO DISC for a very affordable price. The rear FLO 60 or FLO 45 combined with a wheel cover are also great options for athletes who focus on road racing or recreational riding, and also compete in triathlons or time trial events.
The FLO DISC is illegal in road racing events which leaves the rear FLO 90, 60, 45 or 30. While the rear FLO 90 is our fastest wheel aerodynamically, the time differences (seen below) are quite small for a rear wheel. For this reason, a lot of road riders will prefer the reduced weight of the FLO 60, 45 or 30 for climbs and accelerations. If you are a road rider that is also competing in time trials or triathlons, we’d recommend buying a FLO DISC or matching wheel cover from wheelbuilder.com for improved aerodynamics in those events.
For this group I often recommend a front FLO 60, 45 or 30. The improved aerodynamic efficiency of these wheels will make riding the same paces easier. Those who are looking for improved comfort and compliance should consider our Carbon Clincher options. The full Carbon Clincher wheels help dampen bumps and road buzz, which is a nice relief, especially on longer rides.
5. Estimated Time Savings for Different Wheel Combinations
After finishing the design of our new 2016 wheel line, and visiting the A2 Wind Tunnel, we sent our new aero numbers to Ryan Cooper from Best Bike Split, so he could run our wheels through his math model. For those who don’t know, Ryan Cooper is a PhD optimization mathematician, who has been predicting incredibly accurate bike splits for triathletes, and pro tour riders with his Best Bike Split math model. Below, we have ran multiple wheel combinations over two Ironman courses. You’ll see numbers for our 2012 model wheels, our 2016 Aluminum + Carbon wheels, and our 2016 Carbon Clincher wheels. We chose to model a flat course, Ironman Florida, and a course with a relative amount of climbing, and higher winds, Ironman Kona.
6. What is more Important? Aerodynamics, or Weight?
The short answer is aerodynamics by a long shot. In fact, in an acceleration aerodynamics is nearly 50 times more important than weight. For a full explanation of the importance of Aerodynamics vs. Weight, read the most popular article we've ever written "The Great Debate - Aero vs. Weight"
I hope you have found this article helpful. Please leave your comments and questions below.
June 8, 2016
Posted by FLO Cycling at Wednesday, June 08, 2016 Labels: Aerodynamics , en , FLO Research & Development , Tire Study
In Part 1 of this series, we looked at the aerodynamic drag created by different tires on a front FLO 60 Carbon Clincher wheel. As many of you know, when searching for the fastest tire, aerodynamic drag is only half of the equation. In order to know how much power is required to rotate your tire, you must also consider it's rolling resistance. Only when you combine the wattage required to overcome both the aerodynamic drag and the rolling resistance, can you tell which tire is the fastest.
To calculate the rolling resistance generated by each tire, we sent our box of tires to Tom Anhalt from Blather 'bout Bikes. Tom is a well respected engineer, and a wealth of knowledge on all things cycling. Tom has his own rig for testing rolling resistance, and it was perfect for our application. After Tom was finished calculating the rolling resistance of each tire, he calculated the total wattage each tire consumed.
Let's get to the numbers!
Step 1: Calculating Rolling Resistance
To calculate the rolling resistance values below, we used the following test procedure.
- - Bike Speed 35km/h or 21.75mph
- - Wheel load 45kg or 99.21lbs
- - Rolling resistance numbers were measured on a Mavic Open Pro wheel at 120 psi. *
* Tom noted the following: "I've found that the Crr on the (smooth) rollers of a tire the Mavic Open Pro wheel at 120psi, is approximately equivalent to the Crr on a 21mm internal width wheel at 100psi."
Below are the rolling resistance values and the power to overcome that rolling resistance for each tire. They are listed in order from fastest to slowest.
For each value plotted on the graph, a tire's aero drag and rolling resistance values were converted to Watts and added together. This combined value represents the total wattage required to power the tire.
Note: When combining the both the aerodynamic drag values from Part 1 of this series and the rolling resistance values, it is important to note that beta correction of the data was completed by Tom. Tom's Beta correction calculation assumes that the ambient wind is at 90deg to the direction of travel (pure crosswind) for the resultant yaw angle for a given bike speed.
Because there are so many tires on one chart, we felt is was best to display this data on an Interactive chart.
Step 3: Applying our Net Drag Reduction Value Formula
So what does all of this data mean? Which tire is truly the fastest? At FLO we have developed a Net Drag Reduction Value (NDRV) formula that gives a cyclist a realistic estimate of how much time a wheel will save them in the real world. This formula was developed using the 110,000 real world data points we collected in our 5 step design process. Since we know how much time a cyclist spends at each yaw angle on average, our NDRV formula can calculate a weighted average power value across all yaw angles. In the table below, we have listed the tires from fastest to slowest based on the numbers generated by our NDRV formula. Keep in mind that the lower the power number, the faster the tire. Wattage numbers are for one individual tire.
I hope you have enjoyed this article. Please leave your comments and questions below. I'd like to say a special thank you to Tom for all of his help with the Crr data.
June 3, 2016
The benefit of aero race wheels is that they reduce your overall drag and make you faster. In 2012, I wrote a blog article that discussed how much time you'd save by reducing your drag while traveling at speeds between 1-30mph. In that article I discussed how there is a common misconception that you have to be traveling at a certain speed for race wheels to be of any benefit. The truth is, that is false. In reality, the slower you go, the more time you save over a distance. That's right, if you were to ride 40km at 30mph you would save less time then if you were to ride 40km at 20mph. While counterintuitive, the best explanation I can give is riding at slower speeds allows you to experience the benefits of reduced drag for a longer period of time since it takes you longer to complete the course.
Since I wrote the first article, we've released all of our new wheels and have updated our Net Drag Reduction Value formula based on our Data Collection Project. Today, I wanted to share all of the new time savings charts for each of our new wheels for relative velocities between 1-30mph.
Before We Start
Before we discuss the results, let's first discuss relative velocity, and the math behind the time savings calculated below.
Before we get into the math, there is an important concept you should understand. This is relative velocity. When calculating drag, your speed is not simply the speed at which you are traveling on your bike. Relative velocity is the combination of the speed at which you are traveling on your bike and the velocity of the wind. This combination of velocities are known as the relative velocity. If you are traveling 15mph into a 5mph head wind, your relative velocity would be 20mph. If you were traveling 15mph with a 5mph tail wind, your relative velocity would be 10mph. For a more detailed explanation on relative velocity, you will find this post helpful.
The Math Behind the NumbersIn the original post FLO Cycling - Cycling Wheel Aerodynamics - How Speed, Time, and Power are Affected by Reducing Drag, there is a detailed discussion of the math behind the calculations below. If you are interested please take a look.
FLO Carbon Clincher Wheels
FLO 45 Carbon Clincher - Time Savings between 1-30mph
FLO 90 Carbon Clincher - Time Savings between 1-30mph
FLO DISC Carbon Clincher - Time Savings between 1-30mph
FLO Aluminum + Carbon Wheels
FLO 60 Aluminum + Carbon - Time Savings between 1-30mph
FLO 90 Aluminum + Carbon - Time Savings between 1-30mph
FLO DISC Aluminum + Carbon - Time Savings between 1-30mph
FLO Aluminum + Carbon Wheels
FLO 30 - Time Savings between 1-30mph
I hope you enjoyed this article. If you have any questions or comments, please be sure to let me know.