Dirt jumping bikes are really starting to take off as a popular alternative to BMX’s. Their sleek look combined with their tough appearance has many people suddenly interested in owning one.
What parts make up a good jump bike however?
1) Gears (or lack of them) – A lot of jump bikes emulate the single speed design, similar to the system used on BMX’s. A high gear ratio of XXX is frequently used, which gives the rider just the right amount of torque to instantly shift the bike when required. Lack of gears also means that there are fewer moving parts to go wrong, making the bike more reliable. Some jump bikes, such as the Specialized P2, do offer a choice of a gear, but they also usually have the option to convert quickly into a single speed as well. Horizontal dropouts on the rear of the frame allow the chain tension to be set perfectly.
2) An ultra-strong, lightweight frame – Jump bikes need to go high up in the air, and the best way to make this easier is to make the frame as light as possible . Common materials used in the frame construction are chromoly (Cro Mo) or 7005 aluminium. The geometry of a typical dirt jumping frame tends to be very squashed, with a very low seat post to give the rider maximum range of motion.
3) Wide treaded tyres – The tyres on a jump bike tend to be very broad, and are deliberately underinflated to cushion landings in addition to the suspension. Slicks are out, since the tyres need all the grip they can get!
4) Tough wheel rims – The wheels of a jump bike need to undergo some intense pressures form repeated high-impact landings. Reinforced rims prevent buckling when springing some massive hucks (high drops off objects).
5) Mechanical disc brakes – These kind of bikes need some serious stopping power, so they almost always come fitted with disc brakes. The best dj bikes come with hydraulic versions, which prevents any dirt from interfering with the brake mechanism.
6) Awesome suspension – The vast majority of jump bikes have front shock suspension only. Really high quality absorbers tend to be used, with adjustable travel to get just right amount of firmness to suit the terrain.
All of the above combine to form one mean dirt jumping bike machine!
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