you mean hydraulic discs ?
WHo put in the new pads, and did they do anything else to the brakes, like letting a bit of fluid out maybe ?
How would you describe the problem:
1) loads of travel & then good braking with your levers quite close to the bars but not touching ?
2) loads of travel, levers resch the bars before braking starts to happen
3) braking starts early but spongy & lever continues to pull inwards ?
If it's 1, rejoice – your hands will get less tired on long downhills this way (move the levers inwards a bit away from the grips & use 1 or maybe 2 fingers to brake if you're not already – this'll stop you crushing other fingers under the lever). Whoever did you brakes for you might have altered a reach-adjuster (not all brakes have one)
if it's 2, it may just be that the pistons need to reset (they auto-adjust as the pads wear – pistons push a bit further out through the seals) bit of lever pulling might sort this or you could try CAREFULLY pulling lever with something a little thinner than your rotor between the pads to make the resetting easier. You can go too far & find it hard to get the rotor back into the gap so be careful (do not pull lever when there's nothing between the pads or you'll end up shoving pistons back in and maybe damaging stuff)
if it's 3 – maybe need a bleed (but hard to see why a pad change would cause this)
