Resistance rolling

Rolling resistance increases markedly with rolling velocity. 

Guanidines. Guanidines (10) were one of the first aniline derivatives used as accelerators. They are formed by reaction of two moles of an aromatic amine with one mole of cyanogen chloride. Diphenylguanidine (DPG) has enjoyed a resurgence ia demand as an activator for sulfenamides and a co-accelerator ia tire tread compounds which employ siUca fillers for low rolling resistance. Guanidines alone show too Htde activity to be extensively used as primary accelerators. There were no U.S. producers as of mid-1996. 

The tread is desigaed and compounded for abrasion resistance, traction, low rolling resistance, and protection of the carcass. It often is divided iato two subcomponents to maximize performance the outer tread for surface contact, and the undertread for tying iato the carcass while reduciag tire rolling resistance through decreased hysteresis. 

Compound Standard High performance Low rolling resistance Medium tmck radial (MTR)... 

Because of demands for improved fuel consumption through reduced rolling resistance, a new series of carbon blacks referred to as LH, ie, N300 with this innovation would be N300 LH. Basically this series of blacks has a wider size range in both the primary particles and primary aggregates in addition to a more chemically active surface area. 

In the same way that natural mbber is predominandy used in blends, it is also predominandy used in tire manufacture. Its excellent building tack, low heat buildup, low rolling resistance, and good low temperature performance make it the polymer of choice for many parts of tire constmction, for both passenger and tmck vehicles. The effects of radiali2ation and demand for low rolling resistance and good low temperature performance have all tended to benefit natural mbber, especially in tmck tire constmction, as shown in Table 9. 

Natural mbber was also used extensively in its oil-extended form in winter tires in the 1970s (57). Use of oil-extended natural mbber treads, found to have excellent traction on ice and snow, superseded studded synthetic mbber treads when studs were banned in certain countries and states owing to the damage they cause to partially cleared roads. This concept has been extended into aH-season tires, which account for over 75% of original equipment and replacement tires in the United States. It has been shown (58) that part replacement of styrene—butadiene mbber (SBR) in the formulation of aH-season tire tread compounds with oil-extended natural mbber increases ice and snow traction, reduces rolling resistance, and has no effect on normal wet grip. Also, there is only a minor trade-off in wear performance, because below a tire surface temperature of approximately 32°C, the wear of natural mbber is superior to SBR, whereas above this temperature the reverse is tme (59). Thus, wear of an aH-season tire ultimately depends on the surface temperature of the tread over its annual cycle of temperatures. 

Requirements for tire cord material will to some extent be driven by new vehicle trends. Eor example, the clean air emphasis in North America places lightweight vehicles and materials at a premium. Eor tire cord the fuel economy or rolling resistance provided by the cord—mbber composite may shift the pattern of usage. A common requirement for all types of tire cord surfaces is a high strength-to-weight ratio. 

The force required to move the vehicle forward is the sum of four components rolling resistance, aerody-... 

The rolling resistance coefficient of a tire depends on the construction of the tire carcass, the elastic characteristics of the tire material, the tread design, and characteristics of the roadbed. It increases with decreasing wheel diameter, tire underinflation, and roadbed compliance. It decreases as the operating temperature of the tire rises. 

Before the 1960s, the bias-ply tire exemplified standard construction. It had a typical rolling resistance coefficient of 0.015 on hard pavement. Since then, the radial-ply tire has emerged, offering a coefficient closer to 0.010. Coefficients as low as 0.008 to 0.009 have been claimed in tires suitable for use on passenger cars. Cutting the coefficient from 0.015 to 0.008 offers the opportunity for about a 10 percent reduction in fuel consumption. 

Other qualities sought in a tire include ride quality, cornering ability, traction characteristics on both dry and slippery roads, tire noise, life, and cost. Addressing these qualities often opposes the objective of lower rolling resistance. 

A corresponding situation occurs at high altitude, where one-third of the sea-level power available has been lost due to low atmospheric pressure. This low air density also reduces aerodynamic drag, but rolling resistance is unaffected by altitude. As a result, power resei"ve is seen to suffer. In fact, at this altitude, the power available in fourth gear is insufficient to operate the vehicle on a 6 percent grade at any speed without downshifting. 

The human engine cannot match this power output, yet the mechanical efficiency of the bicycle helps tremendously because a vei y small amount of horsepower can generate great speed. For example, 0.4 horsepower (298 watts) of output can result in 25 niph (40 kph) speeds or better. One set of calculations shows that if a cyclist rode on level ground, with no rolling resistance, and aided by a 25 mph tailwind, it would require only around 0.2 horsepower (150 watts) to sustain a 25 mph pace. 

Rolling resistance is almost directly proportional to the total weight on the tires. It is the sum of the deformation of the wheel, tire, and road surface at the point of contact. Energy loss occurs when the three do not return all of the energy to the cycle. 

Rolling resistance varies tremendously by tire. Greater air pressure and less contact area is the reason the rolling resistance that a tops of-the-line racing tire encounters on smooth pavement is half or one-third that of a heavily-knobbed mountain bike tire. 

Over rough surfaces, an opposite effect, not easily measured in the laboratoiy, becomes apparent to the rider. A tire inflated to veiy high pressures (for example, 120 pounds) bounces off the peaks of the road surface, making the bike harder to control, and negating any theoretical decrease in rolling resistance. For... 

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