After the winter I took the stud tires off and got some summer rubber. Took it for a hard drive and while breaking hard the pedal becomes soft. I started braking from 100 and then it became soft and would not even lock. Is that normal? Also when I was breaking really hard the other day this cracking noise came from the pedal. Any ideas?

 

First, check for any evidence of leaking around each of the calipers. Is your master cylinder still filled to the proper level?

If you're low on brake fluid, you need to repair whatever's leaking, then fill & bleed your brakes.

If you're still full, try bleeding the brakes until you have good clean fluid at all four corners. Brake fluid is hygroscopic, and once it absorbs a lot of water, you'll have a spongy pedal.

If neither of those fix your problem, the most likely problem is that the master cylinder is bypassing. If it is, just replace it, then do the bleed and fill routine.

 

Bet your fluid is boiling...it is waterlogged.....lowers the boiling point.
Brake fluid absorbs moisture...gets in around the seals in the caliper mostly.
Get a full flush...
You pads may also be not up to the task and overheating...but they will usually smell pretty bad or smoke...first step bleeds the brakes, but while there, a upgraded pad would be a good idea if you regulay stomp on the brakes from high speed.

 

I was actually just braking hard after the winter to clean the brakes. I just had the brake fluid changed 2 years ago with dot4.
Maybe its time.