First of all, to me, 1900 calories as a BMR seems high.

Secondly, how long does 30-40 miles take you? If you estimate 500 calories per hour, you'll be much closer to the correct calories burned. So if 30 miles takes you 2 hours, chances are you will have burned 1000 calories.

Thirdly, on a 2+ hour ride, you will probably want to eat something while riding anyway. A recommendation is approx. half of the 500 calories you're burning per hour ... so in other words, on rides over 2 hours, eat approx. 250 calories per hour.

Fourthly, try riding the amount you do, and eating whatever you normally eat (plus a bit extra while you ride) for about 3 weeks. If you are losing weight, add a few more calories. If your weight remains the same, you've got it about right.