New pads aren't fully effective until the "fur" is worn off the surface. This doesn't take long.

You did clean all the cosmoline off the new rotors didn't you?

You may also need to bleed some air out if you opened the bleeder valve or brake line at any point.

I'm not sure exactly what calipers you have, but I expect the newer "floating" type -- make SURE the little "ears" (springs" are under the sliding portion and not sticking up out of the slot, and that the outer pad is seated correctly in the caliper. If it is sitting sideways with one end out of the carrier, you won't have much in the way of brakes!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!