Your tires could be keeping you from qualifying for Kona or setting a new PR. Like everything else on the planet, tires are subject to the laws of physics, and it takes energy to move them forward. The wrong tires can cost you more than 7 minutes in an Ironman, so it's essential to pick the right ones.
How Tires Slow You Down
There are two main forces that slow tires down. Those are the aerodynamic drag and rolling resistance. You'll want to make sure your tires are efficient in both categories. Here's a quick explanation of both forces.
If you have ever stuck your hand out of the window of a moving car, you are well on your way to understanding aerodynamic drag. The force you feel pushing on your hand is aerodynamic drag.
The shape of the object in the wind plays a significant role in how high the aerodynamic drag is. If you face your palm towards the wind, you feel a strong force pushing your hand backward. If you turn your hand—like a karate chop— into the wind, you experience a lower force meaning you have lowered your aerodynamic drag.
You go faster on your bike when you lower your aerodynamic drag. For this reason, you'll want to select a tire that has a shape optimized for reducing aerodynamic drag.
Your weight causes the section of your tires in contact with the road to flatten out. When you roll forward, your tires are continually changing shape from round to flat. This process of continual deformation takes energy which slows you down.
Some tires change shape more efficiently than other tires. Tires that use less energy to deform will have a lower rolling resistance and in turn, make you faster. Make sure you pay attention to rolling resistance when selecting your tires.
How We Measure Aerodynamics
We measure the aerodynamic drag of tires in a wind tunnel. A wind tunnel uses giant fans to blow air past an object—in our case a tire on a wheel. A series of highly detailed strain gauges then measure the forces felt by the object.
Our studies have shown that aerodynamics alone can save you up to one minute per tire in an Ironman. For an in-depth look at this study, check out Part 1 of our Tire Study. The following table shows the aerodynamic performance of many popular tires.
|Tire On Front FLO 60 CC||Rank Fastest To Slowest||Time Savings Per Ironman (Sec)|
|Continental GP4000 S II - 23mm||1||59.81|
|Schwalbe Ultremo ZX - 23mm||2||56.46|
|Continental Gator Skin - 23mm||3||51.79|
|Felt TTR1 Aero - 23mm||4||50.24|
|Bontrager AW3 - 23mm||5||46.12|
|Continental Attack - 22mm||6||46.11|
|Specialized S-Works Turbo - 22mm||7||44.20|
|Bontrager R4 - 22mm||8||43.94|
|Schwalbe One - 23mm||9||43.72|
|Continental Gator Skin - 25mm||10||42.03|
|Continental Force - 24mm||11||39.75|
|Continental GP4000 S II - 25mm||12||39.52|
|Zipp Tangente Speed - 23mm||13||38.67|
|Continental GP Supersonic - 23mm||14||37.02|
|Schwalbe One - 25mm||15||32.95|
|Bontrager AW3 - 25mm||16||32.90|
|Hutchison Atom - 23mm||17||31.04|
|Specialized S-Work Turbo - 24mm||18||28.67|
|Zipp Tangente Speed - 25mm||19||18.84|
|Specialized Turbo Cotton - 24mm||20||0.00|
Side Note: Fast tires are only part of the equation. Well-designed aero wheels will make you even faster. Learn about our 5-Step Data Driven Design Process and see how much time FLO wheels can save you.Learn About FLO Wheel Design
How We Measure Rolling Resistance
We measure rolling resistance by riding a bike on a set of steel rollers. During the test ride, we collect many values including power, rear wheel load, and temperature. Those values are then used to calculate the rolling resistance of the tire used during the test.
If you would like a more detailed explanation of this test, I'd highly recommend reading this Blather 'bout Bikes Article by Tom Anhalt, a rolling resistance guru and the creator of the test.
Our studies have shown that the rolling resistance of a single tire can save you up to 3 minutes and 56 seconds. For an in-depth look at this study, check out Part 2 of our Tire Study The following table shows the rolling resistance performance of many popular tires.
|Tire||Rolling Resistance (Car)||Time Savings Per Ironman (Sec)|
|Continental GP Supersonic - 23mm||0.0029||235.62|
|Continental Force - 24mm||0.0029||235.62|
|Specialized Turbo Cotton - 24mm||0.0029||235.62|
|Zipp Tangente Speed - 25mm||0.0030||223.72|
|Continental GP4000 S II - 25mm||0.0031||214.20|
|Continental Attack - 22mm||0.0033||192.78|
|Zipp Tangente Speed - 23mm||0.0033||192.78|
|Continental GP4000 S II - 23mm||0.0034||183.26|
|Bontrager R4 - 22mm||0.0035||173.70|
|Specialized S-Work Turbo - 24mm||0.0036||161.84|
|Schwalbe One - 25mm||0.0037||152.32|
|Specialized S-Works Turbo - 22mm||0.0041||111.86|
|Schwalbe One - 23mm||0.0041||111.86|
|Hutchison Atom - 23mm||0.0046||61.88|
|Felt TTR1 Aero - 23mm||0.0048||40.46|
|Continental Gator Skin - 25mm||0.0048||40.46|
|Continental Gator Skin - 23mm||0.0052||0.00|
Combining The Two
To find the best overall tires, you have to combine aerodynamic drag and rolling resistance values. If your tires perform well in one category but poorly in another,—like the Continental Gator Skin - 23mm—their overall performance will suffer.
Aerodynamically, the Gator Skins are the third best performing tire, but they roll worse than a tank. When you combine their aero performance with their rolling resistance, they end up last.
The million dollar question becomes, which tires should I use during my next Ironman. Below is a list of tires in order from best performing to worst performing. We've included the watts saved if you are interested in power. Times savings listed are for one tire.
|Tire||Watts Saved||Time Savings Per Ironman (Min:Sec)|
|Continental Force - 24mm||9.35||3:43|
|Continental GP Supersonic - 23mm||9.20||3:39|
|Continental GP4000 S II - 25mm||8.47||3:22|
|Continental GP4000 S II - 23mm||8.08||3:12|
|Zipp Tangente Speed - 25mm||7.94||3:09|
|Continental Attack - 22mm||7.88||3:08|
|Specialized Turbo Cotton - 24mm||7.58||3:00|
|Zipp Tangente Speed - 23mm||7.56||3:00|
|Bontrager R4 - 22mm||6.91||2:44|
|Specialized S-Work Turbo - 24mm||5.80||2:18|
|Schwalbe One - 25mm||5.58||2:13|
|Specialized S-Works Turbo - 22mm||4.37||1:44|
|Schwalbe One - 23mm||4.32||1:43|
|Hutchison Atom - 23mm||1.63||0:30|
|Felt TTR1 Aero - 23mm||1.62||0:39|
|Continental Gator Skin - 25mm||1.28||0:30|
|Continental Gator Skin - 23mm||0.00||0:00|
There you have it, folks! That is how you save seven minutes in an Ironman by changing your tires.