Tires
Tire choice is based on a relationship between durability, speed and comfort. I rank speed first, durability second and comfort third. I think most riders would like to sacrifice as little durability and comfort to speed as possible.
Tire Construction
My research concerning tire construction and its relationship to speed, durability and comfort has identified the following factors that affect each of these issues.
Slick versus Tread: Slick tires are faster than tires with tread. Unless you ride on dirt, there is no reason to use tires with tread. The relationship of tire width, load and speed for bike tires is not sufficient to make hydroplaning an issue. Finally, if you ride a trike where your ear is near the tire you soon realize that tire tread produces noise and is a signal that energy is being lost.
Puncture Protection Layer: A kevlar or puncture protection layer helps resist puncture flats. It adds some weight but is worth every ounce. Some of the new fabrics are very light and tough as found in the Schwalbe Ultremo.
Weight: As weight goes up, acceleration in a sprint goes down and climbing slows. Tire weight occurs at the perimeter of the wheel and therefore produces a greater affect than simi liar weight added at other points in the bike. Smaller wheels accelerate faster but larger wheels maintain speed better. Weight is a positive in maintaining speed or momentum.
Supple versus Stiff Side Walls: Supple side walls minimize energy loss produced by the tire as it deforms during the rolling process. Supple side walls produce a more comfortable ride. Stiff side walls are generally more durable.
Soft versus Hard Tire Compounds: Hard compounds increase durability while softer ones increase traction. Many road tires have harder centers for durability with soft sides for cornering traction. Hard compounds contribute to a wheel bouncing over small road imperfections with associated loss of energy. Soft compounds deform around small road imperfections and reduces wheel bounce and energy loss.
Tire Inflation: Over inflated tires cause wheels to bounce over road imperfections. The bouncing uses energy and reduces speed. Correctly inflated tires tend to deform around road imperfections reducing energy loss. This leads to the next section on tire inflation.
Tire Versus Wheel Size
I have two wheel sizes on my bikes. The following defines the range of tire sizes that can be used on each wheel based on rim dimensions.
19mm Rims (Velocity Deep V & Fusion) (13mm interior dimension): 18, 20, 23, 24 & 25mm tires. This is the range of tire dimensions that will work on most road bikes. 23mm tires are by far the most common.
24mm Rims (Velocity AeroHeat) (19mm interior dimension): 28, 32, 35, 37, 40 & 44mm tires. This is the rim dimension used on most trikes.
Tire Inflation
The preceding chart, based on information from Frank Berto, was published in an article titled "PSI RX" by Jan Heine in the March 2009 issue of Adventure Cyclist magazine.
In the article, Jan Heine reports that the result of testing by Bicycle Quarterly demonstrated that performance/speed increases with an increase in tire pressure up to the point that corresponds to about a 15 percent tire drop. Tire drop refers to the difference in tire height before and after loading - before and after you sit on the bike. The chart provides a way to determine the tire pressure that will yield a 15% drop for various loads and tire widths. The loads are for each wheel not the entire bike. Use the following link to open a bigger version of the Inflation Chart (gif).
I found the article by Jan Heine very interesting and used it to examine my tire inflation practices that have consisted to this point of just pumping my tires up to their maximum specified pressure. The following provides my systematic identification of tire pressures for my three bikes. I created blocks that were the same thickness as my bathroom scale and put them under the wheels not on the scale to determine wheel loads. In round numbers, I weigh 185 lbs, the T-Bone weighs 30 lbs, the Expedition weigh 40 lbs and the Kettwiesel weighs 45 lbs. All numbers are rounded up to the nearest 5 lbs.
I found that my floor pump was off by 10 plus psi so I would recommend that you test your pump against a digital tire pressure gauge if you are interested in implementing a more precise tire pressure program.
The following provides the tire presures based on the chart that I am going to experiment with on my bikes.
T-Bone High Racer
Rear Wheel Load:
120 lbs (55%)
Front Wheel Load:
95 lbs (45%)
Tire Width: 24 mm (Continental, Grand Prix 24mm, 24-571, 95 - 120 psi, 280g folding)
Rear Tire Pressure:
120 psi
Front Tire Pressure:
110 psi
Tire Width: 35 mm (Schwalbe Kojak, 35-406, 55 - 95 psi, 230g folding)
Rear Tire Pressure (35): 60 psi
Front Tire Pressure (35): (50 psi: below tire minimum) 60 psi
Catrike Expedition
Rear Wheel Load:
55 lbs (1 wheel)
Front Wheel Load:
85 lbs (each for 2 wheels)
Tire Width: 35 mm (Schwalbe Kojak, 35-406, 55 - 95 psi, 230g folding)
Rear Tire Pressure: (30 psi: below tire minimum) 60 psi
Front Tire Pressure: (40 psi: below tire minimum) 60 psi (for both tires)
Tire Width: 28 mm (Schwalbe Durano, 28-406, 85 - 125 psi, 190g folding)
Rear Tire Pressure: (30 psi: below tire minimum) 85 psi
Front Tire Pressure: (65 psi: below tire minimum) 85 psi (for both tires)
This was a big surprise to me. I had been pumping the tires up to their maximum. Since implementing the lower tire pressures I have not experienced a drop in performance but have enjoyed a softer ride.
Hase Kettwiesel
Rear Wheel Load:
100 lbs (each for 2 wheels)
Front Wheel Load:
30 lbs
Tire Width: 35 mm (Schwalbe Kojak, 35-406, 55 - 95 psi, 230g folding)
Rear Tire Pressure: (50 psi: below tire minimum) 60 psi
Front Tire Pressure: (30 psi: below tire minimum) 60 psi