disc brake systems..

There are two main types of disc brake: mechanical (cable-actuated) and hydraulic. Mechanical disc brakes are almost always cheaper, but have less modulation, and may accumulate dirt in the cable lines since the cable is usually open to the outside.

Hydraulic disc brakes use fluid from a reservoir, pushed through a hose, to actuate the pistons in the disc calliper, that actuate the pads. They are better at excluding contaminants, but are difficult to repair on the trail, since they require fairly specialized tools. The brake lines occasionally require bleeding to remove air bubbles, whereas mechanical disc brakes rarely fail completely.

Also, the hydraulic fluid may boil on steep, continuous downhills. This is due to heat build up in the disc and pads and can cause the brake to lose its ability to transmit force ("brake fade") through incompressible fluids, since some of it has become a gas, which is compressible. To avoid this problem, 203 mm (8 inch) diameter disc rotors have become common on downhill bikes. Larger rotors require less calliper pressure for equal stopping power, dissipate heat more quickly, and have a larger amount of mass to absorb heat. Two types of brake fluid are used today: mineral oil and DOT fluid. Mineral oil is generally inert, while DOT is corrosive to frame paint but has a higher boiling point. Using the wrong fluid may cause the seals to swell or be corroded.

-wikipedia

saddle tips..

adjusting the rear derailleur..

world's most expensive bike wheel..

Lew Racing proudly trumpets their Pro VT-1 as “the strongest 880 gram wheel set in the world PERIOD.” The laminate is created through a born and carbon combination process called DEX-LCM, developed by Lew Aerospace for the Department of Defense. Even the spokes are aerodynamic, using a NACA (National Advisory Committee for Aeronautics) airfoil design. Despite weighing only 3 grams apiece, the Pro VT-1’s spokes are actually stronger than those of a normal bicycle wheel.

An 8-spoke version of the VT-1 was ridden to 4th place by French cyclist Jeannie Longo-Ciprelli in the 2008 Olympics. While this set could only support a rider up to 165 lbs, a standard set of Pro VT-1 wheels can support up to 185 lbs.

The world’s most expensive bicycle wheels can be purchased for $5,495. The wheels can be customized, however, up to $15,292. Options include the ability to support up to 500 lbs and an extended 4 year warranty.

- most-expensive.net

world's most expensive bike..

Aurumania’s Gold Bike Crystal edition is almost entirely plated with 24 karat gold—even the spokes. The seat is a Brooks saddle made of the finest leather while the handlebars have grips made with hand-sewn, chocolate brown leather. Even the numbered badge is made of leather. Of course, the bike isn’t called “Crystal edition” for nothing. It’s decorated with over 600 Swarovski crystals—including the Aurumania name written in Braille along the crossbar.

The world’s most expensive bicycle is a limited edition item—only ten will be made. They can be purchased and delivered to anywhere in the world for €80,000 (US $114,464).

- most-expensive.net