June 17, 2016
Posted by FLO Cycling at Friday, 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.
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 , 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.
May 29, 2016
Posted by FLO Cycling at Sunday, May 29, 2016 Labels: Aerodynamics , FLO Research & Development , FLO Wheel Development
The first time I heard someone say tire pressure would change aerodynamics, I questioned if this would be true. The more I thought about it, the more I questioned how aerodynamics would be effected by tire pressure. When you change the air pressure in a tire, you change the shape of the tires contact patch, and ultimately the profile of the tire. If tire pressure did make a difference in drag, my guess was that it would be a small change.
To answer this question, Chris and I decided to study the effect tire pressure has on aerodynamics when we visited the A2 Wind Tunnel in November of 2015.
What We Tested
We tested our front FLO 60 Carbon Clincher with a 23mm Continental GP 4000 S II at the tire pressures listed below.
How We Tested the Wheels
It's important to define how a test is performed in a wind tunnel. There are countless variables, and if you are not clear about the test, the results are not very clear. Here is how we tested the wheels at the A2 Wind Tunnel.
1. Tare was calculated and removed from all tests.
2. Each wheel was swept from 0-20 degrees of yaw, in 2.5 degree increments.
3. Each measurement was taken twice and averaged.
4. The same Continental GP 4000 S II tire in a 23mm size was used for each test.
5. The tire pressures were calibrated with a highly accurate digital gauge.
5. The tire pressures were calibrated with a highly accurate digital gauge.
It turns out I was wrong. By changing the tire pressure from 100psi to 95psi, you save 6 seconds over a 40km and 30 seconds over an Ironman. Considering a bike has two wheels, this savings would increase when taking both into consideration. While it won't double, it will increase.
The table below shows the time savings for the psi measurements listed above. Since 100 psi was the worst case, I considered it as the baseline. The time values for the other psi readings show the savings when compared to the 100psi test.
While 30 seconds is not a huge number, I can tell you I'll stop pumping when the gauge reads 95psi.
*UPDATE: If you would like to see the results on an aero graph you can click the links below.
Results in Grams of Drag vs. Yaw
Results in CdA (m^2) vs. Yaw
*UPDATE: If you would like to see the results on an aero graph you can click the links below.
Results in Grams of Drag vs. Yaw
Results in CdA (m^2) vs. Yaw
May 22, 2016
Jon and I recently traveled to Ironman 70.3 St. George to conduct our first Bike for a Kid giveaway of the year. We took 150 bikes to donate to The Learning Center in St. George. We shared booth space at the Ironman expo with our partner, More than Sport. More than Sport have been incredible partners since last year, and are paramount in helping run and organize our Bike for Kid events.
All of the bikes were built over a three day period. We had many volunteers help with building the bikes, and organizing the event. We'd like to extend a huge thank you to all of those who helped make this event possible, and to all of our customers who have made Bike for a Kid a reality.
I have attached a few photos below showing some highlights from the event.
|Linsey Corbin stopped by to build a bike!|
|Behind the scenes.|
|Ironman Foundation CEO Dave Deschenes stopped by to build a bike.|
|These bikes are loaded and ready to go to the donation site.|
|150 bikes lined up and ready to go.|
|Jon and I found some fellow twins.|
|Jon and I with Austin and Jayme from More than Sport.|
|Jayme keeping things under control.|
|Pro Brent McMahon donating his time at our giveaway.|
I hope you have enjoyed this article.
May 12, 2016
Posted by FLO Cycling at Thursday, May 12, 2016
Without a doubt, our most popular blog article to date is our “The Great Debate - Aero vs. Weight” article which is Part 1 of this series. For that article, we sent our aero data to the mad scientist from Best Bike Split, Ryan Cooper, so he could give us a third party estimate of how much time the all new FLO wheels would save you on popular Ironman courses. In Part 2 of this series, we calculated time savings for even more courses and wheel combinations. 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.
After finishing the design of our new 2016 wheel line, and visiting the A2 Wind Tunnel, we sent our new aero numbers to Ryan so he could run our wheels through his 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.
Why Do We Use Best Bike Split?
All of our wind tunnel numbers are calculated using only the wheel in a stand. While studying individual wheels in a wind tunnel is excellent for validating designs, there are better options for calculating how much time you will save with wheels on a bike with a rider. We like to partner with Ryan for this data because his model takes the entire bike, and rider into consideration. This allows us to give our customers a better estimate of how much time a specific wheel set will save them on a course.
Now let's get to the numbers!
We chose a rider with the following characteristics for our model.
FTP: 250 watts
Let’s take a look at the course profiles and times savings for each FLO wheel combination when compared to a Mavic Open Pro wheel set.
After looking at the numbers, there are few things that stuck out to me.
- Our new 2016 wheels were designed after studying real world wind conditions. During that study, we learned that average yaw angles were much lower than we originally thought, and we developed our new wheel line with that in mind. The aero improvements of our 2016 wheels when compared to our 2012 wheels (which were designed for high yaw angles) is considerable. These times savings and average yaw angles calculated by Ryan, line up exactly with all of our real world data, and are in line with our Net Drag Reduction Value Formula.
- When looking at our wind tunnel results, the FLO 60 Carbon Clincher is slightly faster than the FLO 90 Carbon Clincher at low yaw angles. On a lower yaw course like IMFL, the FLO 60 Carbon Clincher actually beats out the deeper FLO 90 Carbon Clincher. However, on a higher yaw course like Kona, the 90 Carbon Clincher is the faster option. This is something that very strong riders or riders who are riding in very low wind condition races should consider.
- Time differences compared to the original study (Part 1 and Part 2) are due to us using real weather data from races as experienced by the athletes on race day.
I hope you have enjoyed this article. Please leave your comments and questions below.
April 27, 2016
Posted by FLO Cycling at Wednesday, April 27, 2016 Labels: FLO Research & Development , FLO Wheel Development
If you've been researching carbon clinchers, you've likely come across a thread on a forum where someone has melted their wheels while braking. That's a scary thought. Do all carbon clinchers melt? The quick answer is no.
We've done a lot a testing to ensure our new Carbon Clinchers pass safety standards so you won't have an issue with your wheels. We've even conducted some of our own testing above and beyond the ISO standards. If you are interested, this article goes over some background on carbon clinchers and then discusses our testing.
A Bit of History and Background
Before we discuss our testing, I think it makes sense to talk about the history of a carbon fiber brake surface.
Thinking about it quickly, it seems like it should be an easy concept. Replace the traditional aluminum brake track with a carbon fiber brake track. Well, it's not that easy. Here's why.
Friction our Friend and Foe
In order to stop when applying the brakes on a bicycle, you need friction between the brake pads and the rim. The force of friction absorbs the bicycles kinetic energy and brings it to a stop. The only down side of this, is that the absorbed kinetic energy is transferred into heat. Stopping when you need to is good, but the resultant heat can be bad.
Aluminum Braking Surface
When using an aluminum rim, we are not concerned about heat because the braking temperatures do not reach the melting point of aluminum. 6061-T6 - a common aluminum used for rims - melts at 652 degrees celsius. Brake heat rarely exceeds 400 degrees celsius.
Carbon Fiber Brake Surface
With a carbon fiber rim things are not so simple. To better understand why, we first have to look at how carbon fiber is made.
Carbon Fiber Material
The first component of carbon fiber is the carbon fiber material. It is similar in structure to fiberglass. It comes in sheets and is woven together. By itself, it not much more than a fancy fabric.
The second component of carbon fiber is the epoxy resin. This is a glue like substance that is used to cover the carbon fiber material. When heat is applied the resin sets and hardens. Combining these two components together, makes the finished carbon fiber used in bicycle wheels.
Carbon fiber material science is an extremely difficult topic. In addition, the number of options that exist when selecting the carbon fiber material, and an epoxy resin, are mind blowing. There are also numerous ways to set carbon fiber. Mold types, ramp cycles, etc., the topic is very diverse.
With all of the options that exist, we can easily get ourselves into trouble if we do not pick the right epoxy resin. Epoxy resins have a Glass Transition Temperature (Tg). The Tg is the temperature where the polymer transitions from a hard glassy material,
to a soft rubbery material. If you reach the Tg of an epoxy resin when braking, you have a big problem.
Early epoxy resins were able to create carbon fiber that was either tough, or good at handling heat. Finding a resin that had both characteristics was very difficult to do. If you've ever seen a melted rim, it's a clear sign that the Tg of the resin was too low. Epoxy resins have advanced a lot since then, and modern resins have the ability to be both tough, and good at handling heat.
These new resins are much more expensive and can be difficult to obtain. This is why you still see rims melting today. Factories looking to cut corners, are still using the old resins. This is the reason why working with reputable factories is critically important.
Once you have selected the correct epoxy resin, the next step is selecting a brake pad that is designed to work with that resin. Using the wrong brake pad with your resin system can damage the brake tracks, or effect the braking performance of the wheel. We supply brake pads with our wheels that must be used to keep your warranty valid. They have been designed to prevent heat build up/damage, and to optimize braking performance. When set up properly, we feel no difference in the braking performance of our carbon wheels when compared to our aluminum rim models.
Our Testing Protocol for our Carbon Clinchers
ISO has a predefined set of tests for bicycle safety. To start our testing, we looked at the most recent ISO standard. The standard states that a wheel should have the brakes cycled 1,000 - 3,000 times in three second intervals. This means the brakes are on for three seconds and then released for three seconds. This process is repeated 1,000 - 3,000 times. We chose to cycle the brakes 3,000 times. Here are the specifics of the test.
- Test Speed: 12.5 km/h ± 5 %
- Test Load: 100 kg, with deceleration efficiency < 2.20 m/s2 ±10 %
- Testing Cycle: 3,000 Cycles of brakes on for three seconds and off for three seconds
- Temperature Measurement Source: Inferred Camera
We passed this test without any issues. We are currently waiting for a video of the test and will have a more thorough walk through of the test soon. The image below is from the test.
We wanted to push the wheels to an unrealistic limit so we decided to lock the brakes on while descending Mount Charleston in Las Vegas. The tests ran for 25 minutes and required an output wattage of over 200 watts for a good portion of the descent. At the end of the test there was no damage to the braking surface.
We hope you have enjoyed this blog article, and that you have a better understanding of our carbon braking system. Stay tuned for the upcoming blog article that discusses our testing in more detail. If you have any questions at all, please do not hesitate to contact us.