I had that problem with an old Murray here. I got it from my Bro-in-law, then gave it to my son, who gave it back 5 years later, saying the tranny won't shift and the handle came off. So, out came the tranny, i took out the broken handle bolt, fixed it right, reinstalled the tranny, started it up, and went to mow. Tried to stop it, and it wouldn't stop, stayed in gear, i could not find neutral, and cutch didn't have any effect! Well, the engine now reposes in another tractor, and the rest is in line for the junk yard! Its a shame, because the body parts and tires are really good, but---alas and alack--its time!

Rotor thickness variation is a condition that can be imagined as the two sides of the rotor not being parrallel to each other. This can be caused by a "crushing" of the rotor by the brakes. It can be caused by uneven wear. Or it simply could have developed over time from a combination of forces. This problem is normally felt in the brake pedal by it pushing back at you with a rythm consistent with the current wheel speed. Rotor run-out is often caused by debris (rust) being caught between the new rotor and the old wheel hub, or by improperlly torquing the wheels, which can bend the hub, rotor and wheel. There is always a chance that excessive heat build up from heavy braking without sufficient time for the system components to cool is playing a role as well. This by the way is the most common cause for the report that we often see where a new car keeps having to get the rotors machined. It's not the cars fault, it is how the driver is using the brakes in heavy traffic! We also have rotor delamination, or rusting if you will. This causes a combination of runout and thickness variation issues. Typically rotor thickness variation of .002" is plenty to feel when driving. Otherwise you would have to use a dial indicator, and mark the high and low points on both sides of the rotor to see it. Rotor runout's of .005 or less will normally give no real signs they are present as the calipers of today have sufficient movement built into the system to "follow" the rotor. Between .005, and about .009 you will often feel the pulsation, but quite often you will hear the brake pads "saw" on the caliper supports as they get pushed back and forth. This "saw" is the grunting sound you get on a light brake pedal application as the car moves slowly such as 15mph or less. As I alluded to in the beginning of this response, a good technician does not even need to put a dial indicator on a car where the problem is rotor thickness variation. He/she will feel that right from the drivers seat. However, the technician DOES need to use a dial indicator, and measure wheel runout, then remove the wheel and (for most cars) put the lugnuts back on and measure rotor runout, then measure the front hub runout so that this problem is repaired the first time. Sadly this is one of the times where the good technician that does the job correctly needs to be paid to do so, yet the allure of the "free" brake inspection often prevents them from getting good at it because many are rewarded for being fast and getting the work in and out and as "cheap as possible" which in some occasions turns around and bites them for the effort. For the record, don't do "free" brake inspections, but I fix them.

Regenerative breaking has nothing at all to do with the brakes themselves. That is actually accomplished through the "transmission", and the "generator" for lack of better terms. As far as it having disc/drum, well first that just goes to show that we aren't seeing any of these in for any services at all. Virtually everything that needs done on these so far is being done at the dealerships that I know of. Brakes can grab, or be noisey, especially during the first one or two applications each day, and not be anything really wrong other that the moisture content of the surface of the lining. In order for them to even verify this problem, you really should drop the car off today, for Monday, so that it sits and recreates the same conditions you encounter. I know thats not always convienent, but it can really help in the verification of the issue. From there in order for the shop to test and verify a repair has been made, they actually need to allow the car to sit and try it again after a sufficient amount of time, which means a Tuesday pick-up at the earliest is in order IMO.

I can only guess about your brake problem. You have not reported any loss of braking effort, just a momentary change of pedal height when the brakes begin to act, so there may not be any serious problem. Consider this: Your car probably has an ABS (or anti-skid) system. For some ABS systems, these are not active immediately following a cold engine start, but will check out and prime themselves a few seconds after the transmission had been engaged and the vehicle moved a few feet. In my jeep, I detect this by a pulsing sensation in the brake pedal and a rise of pedal height while backing up from a parked location. The pulse motor can be heard faintly inside the cabin. It lasts for only a second or two. This checkout and priming only happens after the vehicle has been parked for a time. The degree of sensation depends on how much pressue is being applied to the brake pedal during this period. Could this be what you are detecting?