Last weekend I replaced my folder with a pair of new Schwalbe tyres (28-406) and tubes (SV6A). The tube are Presta valve and lightweight. I pumped them up to 60psi but they both leaked in 24 hour and before I had a ride yet. The front dropped to 45 and the rear to 30. Then (2 days ago) I pumped again but to 90psi just above the min. tyre pressure 85psi. They both seem okay to keep the air pressure. It really puzzled me. Would it be 60psi not enough to shut the valve completely and thus cause the leak? Does a tube have a recommended pressure range? I have already tightened the valve lock nuts properly and replaced the dust covers. I even had a under-water check of the front tube and no leaking was found. Thanks
Franky