Strange brake behavior?

[Martin Suryadarma]

Hi listers,

My 89 Audi 100's brakes are kinda weird lately. Bomb is less than a year
old. During city driving, the brake pedal feels firm and nice, with not
too much travel. But after I drive on the highway, I need to press the
pedal so far down before I can feel the brake engaging. Any ideas? It just
started happening quite recently. Is it dangerous? To be honest with you,
sometimes I feel like I don't have brake in the highway, even though I
always do, I just have to press deep enough. Thanks in advance.

Regards,

Martin