Save 7 Minutes In Your Next Ironman By Changing Your Tires

Legacy Article: The data discussed in this article is taken from our previous generation of wheels.

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.

Aerodynamic Drag

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.

Rolling Resistance

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

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.

Results

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

UPDATE: See our new Tri Wheels Guide with charts to help you select the best FLO Wheel for your next race.

There you have it, folks! That is how you save seven minutes in an Ironman by changing your tires.