You’ll read a whole lot of hoopla about what makes a good bicycle tire…and one consideration is rolling resistance.
So bone up, Mr. Bike Tire Investigator!
1). Let’s Start With The Test Results…
How much are the cycling tires holding you back? This is where the rubber meets the road.
I was just reviewing some results of cycling tire tests and now have a decent understanding of how it shakes out. One of the biggest obstacles for us Yanks is converting the more refined metric system into the cave-speak of the English system.
Here’s the data, put into a paradigm so simple even an caveman American can understand it:
A 187lb (85kg) man/bike combo goes down the road at 21.7mph (35km/h). His expensive tires are inflated to 108.78psi (7.5 bar). How much drag are the tires producing, if the cyclist had two bananas and a bowl of Raisin Bran for breakfast?
Answer: somewhere between 34 and 54 watts, depending on the tire.
But that’s meaningless!!! Unless you know the rider’s overall energy expenditure, which is about 220 watts. The bottom line is that bike-tire-rolling-resistance is in the neighborhood of 20% of the total energy output.
2). Hybridization Of Materials
Bike tire issues are about trade-offs.
If a hard rubber is used, the rolling resistance reduces and the tire lasts a long time, but it won’t grip in the turns. Too much softness in the rubber department causes the tire to wear out too quickly and it ‘sticks’ (surface adhesion) to the road too effectively to let the tire roll well.
The solution for some of the high-end tires (you know they’re high-end when each tire costs $62 (42.90 euros) is to run a stripe of longer lasting/lower rolling resistance rubber around the middle of the tire where it contacts the road, while putting a softer rubber for gripping along the sides for when you really lean that sucker over in a turn.
open for deep bike tire discounts at Bike Nashbar.
There are 10 different tires for 50% or more off.
3). Going Tubeless
Mountain bike tires have been offered in a tubeless version for a while now. Stan’s NoTube was at the forefront.
Tubeless road tires are currently made by Hutchinson, but need a rim that’ll accommodate them. Currently the only rim appropriate for road bike racing is the Shimano Dura-Ace Aluminum rim. Testing done by the German magazine ‘Tour’ demonstrated a significant lower rolling resistance in the tubeless Hutchinson Fusion 2 Tubeless when compared to the Hutchinson Fusion 2. But…
The tread pattern on the tubeless was thinner so they were comparing apples to oranges. And you know what that means…fruit salad for lunch.
There’s friction between the biking tire and the tube, which in theory can rob the rider of power. However, I suspect that eating fewer jelly rolls may have a more direct effect on cycling performance.
4). Tire Pressure And Rolling Resistance
The seemingly obvious solution to reducing rolling resistance is to add as much pressure as you can absorb in your butt as your bike bounces down the road. But obvious isn’t right.
There’s a certain amount of ‘chatter’ where the rubber meets the road when tires are overinflated. On a perfectly smooth surface this wouldn’t be a factor. But most of us aren’t riding in a velodrome. We’re on the road.
When you increase the springiness of your tire with too much pressure, it bounces up over obstructions. It slams down (‘slam’ being used to catch the attention of cage fighting fans) into the next micro-obstruction in a very non zen-like manner. This works against forward momentum.
Dude, there’s no harmonic convergence betwixt tire and pavement. Your bike’s fightin itself.
What you really want to happen is to strike a balance between tire deformation over an obstruction (robs energy) and excessive bounce (robs energy). Tire pressures adjusted for the rider’s weight and the smoothness of the surface are appropriate. For most of us (without an engineering lab next door) this is an art form.
For years I’ve been irritated by authors (like myself) who can’t give me a definitive answer to my question regarding proper tire pressure. Then I realized that we’re splitting hairs. And split ends only look good on rock stars.
So I’ve quit fretting, and if the road is real smooth I’ll increase the tire pressure to about 10 lbs (0.6894740 bars) more than if the pavement is real rough.
If I’m off by 0.01 bars, or so, I think I’ll just try to enjoy the ride anyway.
See you where your costly bike rubber meets the road,
Speaking of costly bike tires…I just looked again and there were ten different road bike tires for 50% off at Bike Nashbar.
There was one for 49% off. I’m sure that tire’s feeling the shame of not making the 50% club.