brake systems

I have a question about the brakes on my 1999 Suburban 4x4. The brakes seem spongie. They go about half way to the floor before they start to grab. Then they will not stop the truck when they should or at least with in the time and distance that I think they should. What is my problem and how hard is it to fix?

The rear brakes have a tendency to get out of adjustment (and dirty) and then the front brakes are left trying to do a higher percent of the
braking than they were designed to, (the front brakes could have overheated and glazed also). Just remove the rear brake drums and clean the brake shoes (brake cleaner in a spray can) and then adjust the brakes out until the drum just goes on.
Good luck.

Almost immediately after buying our Suburban new, we had the experience of the brake going almost to the floor before stopping.
Then last spring it went all the way to the floor and would not stop. I ended up running a red light and hitting another car. The person behind me in traffic said he could see I was trying to stop. We contacted Chevy at the time and told them about it. They said there were no recalls or issues with the brakes and after inspecting it did not think the brakes had failed. Additionally, we had the parking brake issue that some have posted. Has anyone else had this experience?