It also accounts for the slightly "low on air" (bulging) look that radial tire sidewalls have, especially when compared to bias-ply tires. With only radial cords, a radial tire would not be sufficiently rigid at the contact with the ground. To add further stiffness, the entire tire is surrounded by additional belts oriented closer to the direction of travel, but usually at some "spiral" angle. These belts can be made of steel (hence the term steel-belted radial), polyester, or Aramid fibers such as Twaron or Kevlar. In this way, low radial tires separate the tire carcass into two separate systems: The radial cords in the sidewall allow it to act like a spring, giving flexibility and ride comfort. The rigid steel belts reinforce the tread region, giving high mileage and performance. Each system can then be individually optimized for best performance. Application Radial tires have different characteristics of springiness from those of bias-ply tires, and a different degree of slip while steering. A benefit was that cars could now be made lighter because they would not have to make up for the deficiencies of bias-ply tires. However, motorists were not accustomed to the feel, hence the suspension systems of cars had to be modified. Ford Motor Company engineer Jack Bajer experimented in the 1960s on a Ford Falcon, by giving it less tight steering, and adding both isolators to the drive shaft and bushings to the suspension, the latter being to absorb the thump of riding over asphalt expansion joints in a concrete roadway. Radial tires have occasionally found application on bicycles, used on the 1980s Miyata touring bicycle; models 1000 and 610, and more recently in 2009 on the Maxxis Radiale. Panaracer radial tires were also standard on the Jamis Gentry model bicycle in 1985. Features The advantages of radial tires over bias ply: Flexible sidewalls Reduced fuel consumption due to less rolling resistance A softer ride because of the layout of the tire's plies and because of the flex of the sidewalls. This assumes equivalent profiles between the two tires (also, as stated above, at lower speeds radial-ply tires will react more harshly to ridges in the road such as expansion joints). More stable contact with the road surface. Steel belted – Results in tougher overall construction Longer tread life Wider footprint Less ground compaction and damage Reduction in tire replacement due to less heat generated by the