Oversimplified: Rolling Resistance

July 15, 2018

Rolling resistance ostensibly has a short yet boring definition, and doesn't relate exclusively to cycling... 

"The force that resists the motion of a body rolling on a surface."

Ok, we got that out of the way, but how is knowledge of rolling resistance going to help you as someone who is definitely not boring and hopefully also a cyclist? By making your daily ride much more enjoyable and efficient! 

Science or Art:

There is a bunch of science involved but at its core you'll find that dialing in your ideal tire pressure is truly an art. Think of it as an arty science, or rather a sciency art. 

Our goal as cyclists is to minimize rolling resistance while ideally maximizing comfort. This is unfortunately a task easier said than done, as it's directly related to the PSI (pounds per square inch) of air in your tires, and dependent on a multitude of factors relating to the specific bike and its rider. We're talking riding style, bike geometry, tire size, body mass, etc. 

Tire Pressure 101:

Every tire generally lists its minimum and maximum pressure printed right on the sidewall. At the very least, they will list the suggested max. This is a great baseline to pump your tires up to, and usually what we recommend to begin with. Fine tuning within the suggested range is totally up to your preferences and something we urge you to experiment with.

Please, please, (please,) get a floor pump with a pressure gauge if you don’t already have one. You and your bike will be very grateful later on. Once you scrutinizingly decide on your ideal pressure, you can make note of that and use the floor pump to keep your tires inflated at this level regularly. It's a tool no cyclist should be without.

As a general rule, narrower tires need higher pressures than wider ones and heavier riders need higher pressures than lighter ones. Again this is a general rule, but one with merit to it. Narrower tires need higher pressures due to the fact that they have less surface area to distribute your weight across. 

Trending Towards Wide:

For generations the assumption of top tier road cyclists was that a narrower tire (21-23mm) would yeild a faster ride. "It's aerodynamic," they said.  "Pump them up rock hard," they said. Well, over the past several years, this attitude has changed among the majority of cyclists as it's been proven that a slightly wider tire (25-28mm) does actually roll faster than a narrow tire at the same pressure. 

This is due to the wider tire creating a smaller "contact patch" with the road (see illustration above.) Although the tire is indeed wider, it creates much less overall contact with the road. This means less rolling resistance, which leads to a faster rolling tire for the rider. In addition, you realistically don't lose anything to aerodynamics, and the added weight is something you should only be concerned with if you're a world class sprinter or climber.

Bearing this in mind while designing our latest generation of bike, we opened up the clearence on the fork to allow for tires up to 32mm in width. So although the integrated lighting definitely steals the show, the option of running tires wider than our previous max (25mm) is a secondary addition that our customers have been absolutely loving. 

Rolling Resistance:

Harder tire = faster revolutions (in an ideally smooth or lab setting)

But how does that hold up in a real life scenario? Recent studies have shown that in real life, roads can be quite bumpy. Bumpy roads lead to vibrations that will undoubtedly shake your bones, causing fatigue, and ultimately slow you down while riding. 

This means that running your tire at a slightly lower pressure than the recommended max actually absorbs the vibration of said bumpy roads much better and will potentially roll with less resistance albiet a larger contact patch. 

Getting a Grip:

Lower pressure (within reason) = More compression under weight

So what does this mean for you? More compression under weight means your tire will be putting more rubber on the road, which in turn leads to better grip. I know what you're thinking. "But won't this increase my contact patch and slow me down?" Yes, it will unfortunately increase the size of your contact patch, but you'll also be gaining something potentially more valuable than speed as a commuter – comfort. This is something for you to not only ponder on, but to experiment with and consider when finding the ideal tire pressure for your current setup.

Be Careful:

Running a lower pressure absolutely has its limits.

So opening up your valve wide open and dropping pressure sounds like it's gonna be awesome right? Not so much.

What can happen if you run your tire pressure too low?

  • It WILL slow you down - This will be fairly noticeable and an indicator that you need more air. No big issue here, just get to your nearest pump and top those tires up to the level you prefer.

  • Your bike will become unstable when cornering - This will be even more noticeable and a little scary. When we say "unstable," we mean your tire will want to slide out from under you. It could possibly even peel off the rim entirely, which is super-dangerous at speed. Let's avoid this one!

  • Your tires will become very susceptible to pinch flats - This will be extremely noticeable and a real bummer if/when it happens. A pinch flat occurs when your wheel hits an object with a sharp edge (curb, pothole, rock, etc.) while running at an unfavorably low pressure. This causes the tube to get pinched between the object and your rim, often leaving the tube punctured, your tire flat, and your rim bent. You'll need a patch kit or a new tube if this occurs, and a new rim in the worst case scenario.

 

So what’s the “best” pressure to run your tires at?

This is a question not easily answered. It’s different for everyone and factors in what tires your bike is running, your body weight, and the type of ride you are looking to get out of your setup. 

Our best advice is to experiment and find what gives you the best combination of comfort and performance for your individual setup! Start by inflating your tires to the max psi, and deflating them by increments of 5-10 psi at a time until you find your ideal pressure.

 ...now go forth and master the sciency art of finding your ideal tire pressure. 

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Staff Pick: Continental Gatorskins

*Free upgrade with the purchase of any Mission bike this month*

Throughout the years we've ridden our fair share of tires but there's one we always come back to. The Continental Gatorskin encompases a trifecta of grip, speed, and puncture protection that we deem second to none. These are normally sold as a $50.00 upgrade on our bikes, but we're offering them up for $0.00 when you build and purchase a bike with us during the monthe of July 2018.

Just leave us a note in the comments section of your purchase and we'll be sure to knock them off the price of your custom build. Act fast!