SR-22 pilot reported the loss of directional control resulting in a taxiway excursion due to the brake system failure. Aircraft was towed to hanger for maintenance.

Narrative

Airplane had just completed Annual including replacing the brakes. This was the first flight post annual. I completed a very thorough pre-flight check; pulled the airplane out of the hanger and started it without problem. I did note the brakes felt 'stiff'; but it held the plane for warmup while completing pre-taxi checklist. I taxi'd to the run-up area and did note I had to apply more force on the brakes to turn. Run-up indicated no problems and the brakes held; all engine indicators were good. Because of the brakes being very firm I requested from ZZZ ground for a high speed taxi on the non-active runway (XX-XY) informing them it was a post maintenance test. The first high speed taxi (Runway XY) went up to about 45kts and brakes felt stiff but maybe getting better. I exited the runway without problems and was offered and accepted a run in the other direction (Runway XX; still not the active). I had to hold position several minutes for landing traffic on intersecting runway. When cleared by ground for second taxi I got up to about 50-55kts. This time however the brakes were even 'stiffer' and I was unable to get turned at the end of the runway and got two tires into the mud off of the taxiway. I did not hit anything; and informed Ground that I had run-off and needed assistance getting back onto the taxiway. I shut the engine down and they were able to get a tug to pull me back to hanger. The A&P was on site and said he'd look at it in the morning. So as for the causes - something wasn't right with the brakes. Someone told me later the brakes should have been bedded in and that was the likely cause. I pushed as hard as I could and it didn't stop. As for how I could have prevented it; I should have stopped with the first indication the brakes weren't as I expected. Interestingly I had just listened to a webinar on post-annual testing period. I am super glad there was no equipment damage and that I didn't just fly off somewhere.