<P> Trials bikes are set up very specifically for the purpose of bicycle trials . Two varieties of trials bike exist, those with 26" wheels (referred to as' stock') and those with 20" wheels (referred to as' mod' because historically they were modified BMX bikes). They typically have no suspension at all, though some still make use of some form of it . Competition rules require stock bikes to have multiple gears for competition, but most riders never use their shifters . Competition rules do not require mod bikes to have any gears . Many non-competitive riders run single - speed, choosing a fairly low - speed, high - torque gear . Most modern trials bikes have no seat at all, as the rider spends all of his time out of the saddle, and trials riding is not conducive to the use of the saddle as a control interface as in normal mountain biking . These bikes are significantly lighter than almost all other mountain bikes, ranging from 7 to 11 kilograms (15 to 24 lb). This makes maneuvering the bike much easier . </P> <P> Single - speed (SS) mountain bikes have one set gear ratio . The gear ratio chosen depends on the terrain being ridden, the strength and skill of the rider, and the size of the bike (a bike with 29" wheels often requires a different gearing than a bike with 26" wheels). Often single - speeds are fully rigid, steel - framed bikes . These are typically ridden by very fit individuals on mild to moderate cross country terrain . </P> <P> Mountain cross or "Four - cross" (4X) is a type of racing in which four bikers race downhill on a prepared, BMX style track . These bikes generally fall under the categories of Dirt Jump or Slopestyle designs, with the main distinctions being the use of a derailleur rather than a single speed setup, or slightly slacker head angles than ordinary Dirt Jump bikes for increased stability at race speeds . Four - Cross racing has fallen in popularity recently, with the UCI removing Four - Cross from the World Cup due to excessive erosion and inconvenience caused by the purpose - built race tracks . </P> <P> Dual slalom (DS) is similar to Four - cross, but instead of four competing cyclists during a race, there are only two, racing in parallel lanes . The courses are in general more technical with smaller jumps than Four - cross courses . Dual Slalom races originally took place on grass slopes with gates and minimal jumps, but are now held on man - made courses . Dual slalom racers will usually use Dirt Jump, Slopestyle, or Dirt Jump bikes . </P>

Is there a difference between men's and women's mountain bikes