Tour de France champion Alberto Contador has admitted to uncertainty over his form ahead of this year\'s race, but warned it won\'t stop him attacking key rivals if he finds his \"good legs\". Contador, who won his third yellow jersey in 2010 only to reveal a positive test for clenbuterol less than a month after the finish, heads into the July 2-24 race as the overall favourite for cycling\'s biggest prize. After a gruelling three weeks at the Giro d\'Italia, which ended with victory for Contador on May 29, experts remain divided over whether he has enough in the tank for the crucial mountain stages in the Tour\'s last two weeks. The last rider to achieve the feat was now deceased Italian climber Marco Pantani in 1998. Since then, many have tried and failed. Contador said he will need to assess his form after a hectic first week which includes flat and undulating stages and a team time trial. But the Spaniard warned that if he comes good for the first high mountain stages in the Pyrenees, his racing instincts could supercede worries about the energy he left behind at the Giro. \"Of course I will have some doubts (about his form), and I will need to gauge things after the first few stages and see how my body recovers,\" Contador said here Thursday. \"But you know me, it\'s hard for me to be conservative when I\'m racing. If I have good legs, I find it hard not to attack.\" Despite owning three Tour de France yellow jerseys, two Giro d\'Italia pink jerseys, a Tour of Spain crown and numerous other stage race wins, controversy shrouds Contador\'s presence this year. After his positive test Contador claimed he had ingested clenbuterol, a banned substance, by eating a contaminated steak. He was cleared of any wrongdoing by the Spanish authorities, leading the International Cycling Union (UCI) and the World Anti-Doping Agency (WADA) to appeal the Court of Arbitration for Sport (CAS) to have the decision overturned. After announcing it would make a final ruling on the case before the start of the Tour, the CAS has postponed the decision until August. If means Contador still risks losing his 2010 title to rival Andy Schleck, the Luxemburger who has finished runner-up the past two years.Leopard-Trek climbing specialist Schleck, however, would rather beat Contador on the road. \"I\'m happy that he\'s here, for another reason: I want to beat him on the road. I want the challenge and the duel,\" said Schleck. On the 98th edition there is something for everyone, from the sprinters like Britain\'s Mark Cavendish, the winner of 15 stages in three editions, to the \'punchers\' like Belgian Philippe Gilbert who are at home on the undulating stages that finish with an uphill sprint. Yet it\'s to the climbers that the race has most in store. Featuring only one individual time trial, a 42.5 km ride around Grenoble on the 20th and penultimate stage, the 21-stage race has nine days in which at least one categorised climb appears. The opening salvos could come as early as eight and nine in the Massif Central, or the powder kept dry for any one of a trilogy of Pyreneean stages which feature the race\'s first summit finishes (stages 12 and 14). If the yellow jersey is still undecided after two hard days in the Alps, it almost certainly will be on stage 19. Over 42 km of climbing features as the peloton tackles the legendary Telegraphe and Galibier mountain passes before finishing on the summit of Alpe d\'Huez. Australian Cadel Evans, Italian Ivan Basso, Dutchman Robert Gesink, Belgian Jurgen van den Broeck and Britain\'s Bradley Wiggins also have the tools to play a leading role in the yellow jersey battle. BMC team leader Evans, a two-time runner-up in 2007 and 2008, said he\'s not racing to make up the numbers: \"I\'m not going to ride for second place. You don’t win by starting off looking for second place.\"