2008年11月3日星期一

Mountain bikes


Many newer mountain bikes have a full suspension design. In the past, mountain bikes had a rigid frame and a rigid fork. In the early 1990s, mountain bikes started to have front suspension forks. This made riding on rough terrain easier on a rider's arms. The first suspension forks had about 1½ to 2 inches (38 to 50 mm) of suspension travel. Soon after, some frame designers came out with a full suspension frame which gave riders a smoother ride throughout the ride.

Newer suspension frame and fork designs have reduced weight, increased amount of suspension travel, and improved feel. Many lock out the rear suspension while the rider is pedaling hard or climbing, in order to improve pedaling efficiency. Most suspension frames and forks have about 4 inches (100 mm) of suspension travel. More aggressive suspension frames and forks made for downhill racing and freeriding have as much as 8 or 9 inches (200 or 230 mm) of suspension travel.

Many riders still prefer to ride a hardtail frame, and almost all mountain bicycle riders use a suspension fork. Well-known suspension fork manufacturers include Manitou, Marzocchi, Fox Racing Shox, Rock Shox, Suntour, RST and (to a lesser extent) Magura, White Brothers and Maverick. Some Cycle manufacturers also make their own suspension systems to fully complement the bike set-up.

Although much less common, some road bicycles do incorporate suspensions, particularly the Soft Tail variety mentioned above. One example is Trek Bicycle Corporation's s.p.a (Suspension Performance Advantage) rear suspension, offered on some of their Pilot models, but the system was removed for the 2008 model year. Virtually all bicycles produced by Alex Moulton bicycles also have very effective full suspension, due to the low unsuspended mass of the small wheels and high pressure tires, a characteristic of the unconventional design of these bicycles.

Many recumbent bicycles have at least a rear suspension because the rider is usually unable to lift themselves off of the seat while riding. Single pivot is usually adequate when the pedaling thrust is horizontal - that is, forwards rather than downwards. This is usually the case provided the bottom bracket is higher than the seat's base height. Where the bottom bracket is significantly lower than the seat base, there may still be some pedalling-induced bounce.

Short-wheelbase recumbents benefit from front suspension, because the front wheel is often smaller than the rear wheel and bumps are unduly felt without it.

The Softride Suspension System was launched at the Interbike 1989 bike show. The original SRS systems consisted of two foam filled fiberglass boxes bonded together with a viscoelastic layer. Originally intended for the use in mountain bikes, Softride produced its first full-fledged mountain bike, the PowerCurve, in 1991. During 1996 Softride released its first aluminum frame road bike, the Classic TT. The Softride Suspension System is used almost exclusively for triathlon racing. Softride ceased bicycle production in 2007. [8]

A very closely related suspension design to the Softride is the Zipp 2001, a contemporary competing beam bicycle, where the suspension was in the hinge, rather than in flex of the beam itself.


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