Austin Tri-Cyclist Blog

Thursday, November 20, 2014

All About Road Bike Tires

by Jack Mott

Cycling lore is a funny thing. Question an accepted principle, and often you will get a "This is just how things are done." Or more often, some vague explanation based on "feel." Intuition plays a large part in racing and is a good basis for some equipment choices—but when it comes to tires, you should set aside the stone tablet and think about the science.  

Josh Poertner of Silca shared a story on Slowtwitch about his experience introducing Zipp 808s to a pro men's team in the 2004 Tour. He describes the scene on the morning of the prologue when he arrived: The pro mechanics and riders were in the midst of a shouting match, unable to figure out why the 808 rims were "blown up like blow-fish" and jamming the forks of the new BMC Time Machine. Nothing was making sense until Poertner discovered the fact that the pro mechanics were inflating 20mm Continental track tires (with helium!) to 280 psi. Team leadership was insistent that their choices were correct; after much argument, Poertner was able to talk them down to "only" 220 psi, but the riders were plagued by punctures and crashes in the TTs and had a near-phobia of their TT bikes by the end of the Tour. "It was ultimately the impetus for us to start a real educational process with the mechanics and directors on not only what wheels for what days, but also tire choice and the importance of pressure," Poertner writes.

Tires are the single most important part of your bike. Whether you're seeking comfort, grip, or pure speed, no single change will make as much of a difference as your tires. We all love to obsess over the latest frames and wheels, but it's the tires that dampen the bumps, hold the bike to the corners, and transmit the power from our legs to the road. While the latest frame or latest wheels might save you one minute or so per 40K thanks to their slippery aerodynamics, a tire with good rolling resistance might save you four or five. Similarly, a frame with a carefully engineered carbon fiber layup might dampen harsh road vibrations a small amount, but a well-chosen tire will have a hundred times more impact on comfort.

What Makes a Tire Fast (And Comfortable!)

It isn't the weight! It's the rolling resistance. As you bike along, your tires are constantly deforming as they come into contact with the road. Each inch you move forward on the road brings another inch of tire to the road, and the rubber has to squish a bit. This process is where energy is lost, and it can be a lot. This is also what makes some tires more comfortable than others. A tire whose material is more supple will waste less energy as it deforms and be more comfortable. These properties can be objectively measured by using a power meter and rollers. Handy tables of rolling resistance results are available online, such as this one from Tom Anhalt.

Another consideration is aerodynamics. While not as important as rolling resistance, the shape and size of a tire can significantly affect the overall performance of your wheel. A wider tire will have less rolling resistance, all else equal, but also more aero drag. So, for instance, for a time trial you wouldn't want a wide tire on the front. Some tires, such as the Continental 4000S, Attack, and Force, also have bonus aero properties due to their textured sidewalls.

What's the Catch?

The downside to fast tires is that they tend to be more delicate. The easiest way to reduce rolling resistance is to remove material from the tire—for example, to use less rubber and remove any tough, puncture-resistant layers. With some options, however, you can find a very effective compromise; some tires offer reasonable durability and puncture resistance along with very good rolling resistance. (See "Suggested Tires" below for specific models.)


The properties of rolling resistance that apply to tires also apply to tubes. Standard butyl tubes soak up significant amounts of energy as they deform along with the tire. Fast tubular tires use latex tubes instead of butyl, which can save as much as two to four watts. This is also why tubulars feel so plush. But you can get latex tubes for clinchers, too, and have just as fast and plush of a ride as any tubular. (ATC stocks Vittoria latex tubes, a good choice.) The only downside is that you must install latex tubes very carefully, as they're not as forgiving as butyl. Read our other posts "Tips to Avoid Flats" and "Living with Latex" to avoid common installation mistakes. Once installed properly, latex tubes are just as durable as a regular tube and work better with sealant.


Proper pressures are the final piece of the speed and comfort puzzle. Many athletes crank their tire pressures up as high as they can, thinking this will reduce rolling resistance. At first glance, it seems to make sense: higher pressure means the tire deforms less, so less energy is wasted. The catch, however, is that the imperfections and rough texture of the pavement mean that at some point higher pressure actually causes more energy to be wasted to vibration than is saved from the tire. Optimum tire pressure will be a function of how heavy the rider is, wide the tire is, and bumpy the road is. This chart by Michelin gives you an easy starting point. Keep in mind, most people find that pressures that are too high feel faster, but that is misleading. Field tests have shown this not to be true. A fast tire at optimum pressure may feel "squishy" or "dead" to riders accustomed to using higher pressures. If that describes you, stick with it and just consider it a sign that you're soon going to notice more grip and more speed.

Some Suggested Tires
  • Continental 4000S II Clincher - The ultimate jack of all trades. Great rolling resistance and great aerodynamics combined with good durability. You can train on this, race on this, time trial on this, anything at all. ATC just received a shipment of these, so they're in stock at both the Barton Springs and 360 locations. 
  • Continental Attack/Force Clincher - This is perhaps the best overall time trial setup. The narrow Attack is used on the front for aerodynamics, while the wider Force is used in the rear, where aerodynamics don't matter as much. These tires still have puncture protection, though not quite as much as the 4000S. This is the tire ATC Racing used to clinch the Texas State Time Trial record.
  • Continental SuperSonic Clincher - For those who need those last few seconds no matter the risk, the Continental SuperSonic is for you. No puncture protection layer is included at all, but rolling resistance is among the best in the world. Available in 20 and 23mm widths, this tire can make the ultimate time trial setup. While the SuperSonic Clinchers aren't suitable for regular training, professional Ironman triathletes like Thomas Gerlach do use them regularly in racing with success. If you find yourself just a few seconds from your goals and road conditions are good, give this option a look.
  • Fortezza Senso (Tubular and Clincher) - Available in Xtreme Weather, All Weather, and Superlight varieties (in increasing order of speed), these are one of ATC's most popular tires and can make a good dual purpose race/training tire and a great winter/rain tire.
  • Michelin Pro4 Clincher - Michelin offers many varieties of the Pro4, most of which have good but not great rolling resistance, falling a few watts short of the 4000S. They do make for a very nice training tire, though, with decent flat protection, comfort, and speed. They also make a "Grip" version intended specifically for wet weather grip.
  • Vittoria EVO Corsa (Tubular and Clincher) - These tires come in a few varieties as well, the CX and CS, and all are very fast. They rank among the very best in rolling resistance, just shy of the SuperSonic but with a little more flat protection. Plenty of people train on them, but they are somewhat delicate and will need to be replaced fairly often. They make a great race tire but don't have the magic aero properties of some of the Continentals, so you might avoid using them on front wheels for time trial purposes. They also tend not to fare well in wet weather chip seal areas. If you have a rainy road race, you might switch to something else.
  • 2015 Zipp Tangente (Tubular and Clincher)- Zipp has a new line of tires, and they offer some excellent choices, in various widths and levels of flat protection. Look for them to be offered in store very soon. They are optimized both for aerodynamics and rolling resistance, as Zipp was squarely targeting tires like the 4000S when they designed them.
  • Continental Gatorskin - While this tire is so slow it will make a Zipp race wheel slower than your training wheel, it does offer incredible flat protection. If you are looking for a training tire that offers flat protection and aren't concerned about comfort or speed, this is a great tire that will last a long time. They also stand up well to trainer duty, so you can use them on the trainer and on the road. Another bonus, if your significant other is faster than you like mine is, you can have her use Gatorskins so that you can ride together!

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