brake pad change issue

[pkjense]

I have an issue I find odd. I run cool carbon pads for the track on my 73 911 with Carrerra calipers. They are terrific. To save the expensive pads, I changed them out for metal master pads for the street. The metal masters are almost new, and thus are thicker. However when I put them in my pedal travel is about an inch farther down, in relation to the gas pedal, and it feels mushy. yes brakes are bleed etc.
I expect less initial bite from these pads, but more travel before I even get resistance (sitting still) from a thicker pad? How is that possible? It feels like the metal masters are made of sponge compared to the cool carbons. Can the pad material actually be compressing??

TIA Paul

[Quicksilver]

If they are mushy then the only option is air in the system.

As to how the air got there...
It is possible you have a caliper seal problem from having to retract the pistons farther for the thicker pad. It isn't likely because most people retract the pistons flush to the caliper instead of just far enough for the pads.

Either way you need to pressure bleed and be ready to run as much as 2 quarts through to get them really good.

[pkjense]

I bled, to no avail. I tried another set of metal master pads I had and still no go. I put the cool carbons back in, pedal height is back up, and no more mushy brakes. So I am leaving them in.
hard to believe the pads could make that much difference in pedal feel but they do. And when I say they were mushy with the metal masters, I mean foot to the floor, and pray the car will stop. Now I hardly need any pressure to reach threshold braking.

Go figure...