Presta valve problem new to the Presta valve game, I just replaced my tube and the valve tore in less than 10 mins of riding. My bike tire is 26x1.9 the tube the got was 1.7-2.4. I have both the same rims and the front is also running a Presta valve. Not sure if I did something wrong or just a faulty tube.
A picture of the damage would tell for sure but 90% of the time tearing a valve - presta or schrader - is due to under inflation.
Low inflation pressure allows the tire to slip (during acceleration and/or braking on the rear, braking on the front) on the rim. The slipping tire rotates the tube. As the tube moves the valve is torn off as it moves against the valve hole in the rim.
It is possible to have a faulty tube. Usually defects (imperfections in molding etc.)look very different than forcibly tearing or cutting the valve on a tube.