NURBURGRING, Germany - Lewis Hamilton's hopes of a first win for his new Mercedes Formula 1 team were hit by revised tyre regulations introduced for the 2013 German GP.Mercedes' team chief Ross Brawn confirmed this on Monday when he admitted that the ban on swopping rear tyres wheel-to-wheel combined with hot weather led to the team's weaknesses being exposed again.Hamilton battled to finish fifth after starting from pole and his problems were a reminder of the team's early-season struggles with the fast-wearing Pirellis.WISHING FOR A WINHamilton said: "It would be good to get a win but at the moment it really doesn't feel like it's going to happen. At some stage it's got to come."The 2008 champion also started from pole in England a week earlier where he led but then suffered the first of the four tyre blowouts that caused the crisis which ushered in a change of tyres and revised rules for using them.Brawn said: "The construction of the tyre has changed and I think the ability to swop tyres was a good way of off-setting stress on the tyres. You could use it in qualifying and then swop it and have it in a different condition for the race.GETTING IT RIGHT"You cannot do it with these (new) tyres and I think we were back into going over the limit of the temperature of the tyres and suffering from it. The first half of the race was pretty horrible for us but in the second half the fuel weight was down, it got a touch cooler, and we got back in the window again."The times were respectable, so it shows how critical we are. On high fuel (load) at the beginning of a race when we were trying to push we overstressed the tyre and we need to overcome that."As Brawn and his boffins work on the car, the team's motorsport chief Toto Wolff said he was talking to the sport's rulers about allowing Mercedes to take some part in the upcoming young drivers' test at Silverstone. The team was banned for taking part in a tyre test in Spain.He said it was not about performance gain but safety, especially now that teams were allowed to run their senior drivers at the test."When it is about safety," Wolff said, "it would be good if all teams are clear whether the tyres work on their cars but it is up to the IAF to decide. Safety is the priority." Stay with Wheels24 for the 2013 F1 season – fresh reports every day.