LONDON , England ( CNN ) -- There is a mathematical reason why the French Open is so different to any other of the Grand Slam tennis tournaments . Clay courts require a different type of game to grass and hard court surfaces . The Roland Garros tournament is currently being contested , with Rafael Nadal looking for his fifth win in a row , and world number two Roger Federer searching for his first ever French Open title . • Get the latest French Open news . What has brought problems to Federer , and to other greats like Pete Sampras and Boris Becker -- who never won a French Open , is the clay surface on which it is contested . The maths of the clay surface are distinctly different to grass or hard-court surfaces . All officially recognized courts have a court pace rating ( CPR ) , which rates the `` speed '' of the court -- and clay courts are at the bottom . The crushed-brick mixture that constitutes the base of a clay court produces a the highest bounce and most friction of the three surfaces , meaning they have the lowest CPR of all three surface types and are considered as the `` slowest '' . Grass courts are generally have the highest CPR numbers , and are the `` fastest '' courts . The CPR numbers give a hint as to whether a ball will bounce higher or lower on a specific surface , and how much friction there is to either slow the ball or allow it to skid on . An example court pace rating for each surface may be 23 for a clay court , 35 for a hard court and 46 for a grass court . • Try our special interactive to see how tennis ball bounce on different surfaces » . This number is calculated by considering both horizontal speed and vertical bounce of a tennis ball off a court . The equation used is CPR = SPR + 150 x ( 0.81-e ) . To make more sense of this , the International Tennis Federation , the game 's law-makers , have produced a chart which simply matches the coefficient of friction ( friction ) and coefficient of restitution ( bounce ) to produce a court pace rating . But it 's not just the bounce and speed of the ball off the clay surface that sets it apart from other courts , and makes the French Open an elusive tournament for some players . Head of women 's tennis at Britain 's Lawn Tennis Association ( LTA ) , Nigel Sears , told CNN the slippery nature of the clay surface also set it apart from other types of court . `` The main factor that makes it different is that it 's a loose surface . That allows players to slide on it . '' The loose surface and different clay characteristics meant the crushed-brick surface required a different game plan , he said . `` Players are a lot further back on the clay surface . If you look at Nadal , his return of service points of contact are different to other surfaces ... on clay he can sit back . '' The slower pace and higher bounce also meant big servers like Sampras were negated on clay and certain types of players were better suited to it , Sears said . `` Clay magnifies spin . So the slice is effective on clay ... and you can also produce a lot of top spin . One of the problems Federer has on clay is that he has a single-handed backhand , and Nadal can get so much spin -- so Federer is trying to hit single-handed shots up around his shoulder . '' The clay approach was slightly different in women 's tennis , however , as some players tended to approach clay matches similar to hard-court games , he said . Sears said endurance was also a crucial advantage on clay , particularly at Roland Garros . `` You tend to have longer rallies on clay . The French Open is so physical with five-set matches . When somebody faces Nadal to five sets no-one can compete with him physically , '' he said .
Clay , grass and hard tennis court surfaces all produce different bounces . The speed and bounce of certain courts can adversely affect a player 's game . Use the CNN interactive to see how the bounce differs on each surface .