Under heavy braking the pedal seems to travel excessively?
 

When I'm driving my car, I've noticed that under heavy braking, the pedal goes pretty far down. Fluid level is fine, pads are fine, and the rotors are new. Is this just something that occurs on the stock brakes? I don't think its fade because its not like I overuse the brake. Perhaps the 25 year old rubber brake lines are a little worn. Are SS lines a good upgrade?

Does it engage normally then as you keep the same pressure slowly begin to sink? It could either be that you just need to flush out the lines with some new fluid or your master is beginning to leak back into the resivoir. Check all the rubber lines for any leaks or buldging as that is a sign of some real wear and tear and could possibly rupture.

Mine used to do that and it did turn out to be the brake master cylinder. So that is my guess. I don't think that bulging brake lines would cause THAT much extra pedal travel, I may be wrong.

Anyway to check the master cylinder?

1) Pull the master cylinder and check for leakage at the back.

2). If you are parked with the engine running and you apply pressure to the brake pedal and keep the pressure there, if the pedal starts to slowly go down towards the floor board then the master is failing.

I would absolutely recommend upgrading your lines to braided ss. They do wonders for pedal feel. No more mushy inconsistent pedal travel, and it will hold the brake pedal in the perfect spot for heel toe downshifting. Will definitely improve your confidence in your car's braking ability.

How about a master cylinder brace? Ask hyper4mance2k. He said it made the biggest difference.

I'm going to check the brakes tomorrow. If it was just air in the lines, that would make the pedal feel spongy, no? There is no spongyness, just a little soft under heavy braking.

I did the 'driveway test' with the car running and firm pressure on the brakes. Pedal stayed solid. When it does it during braking, its not excessive, just a little longer than usual. I think its the lines.