ive had my road bike a couple of weeks now and enjoying it but ive had 2 punctures, the first one i had just pumped up the tyres to the correct pressure of 120 psi and about 3 minutes later i was sitting down (not on the bike) and the tyre just popped without anyone even touching it ,the other puncture i noticed this morning before i was just to go out for a ride (same tyre) but it was fine when i got home on it from a ride,could it be something im doing wrong? thanks