Assist: brake sound check

OK, I tested too. My finding is basically similar to @m8547 result.

While Parking, with a hard press all the way to the floor, it came on every time. But with lighter push did not trigger as often as @m8547. Certainly, it was not every other time. I could go on without triggering it for quite some time. On my way home I was paying attention to the "whirr" sound as I apply the brake, but the only time I noticed the sound was when I had to come to a complete stop at a traffic light and when I reached home and came to a complete stop. All other brakings were very light mostly regenerative and did not cause the sound.

 

My post above was testing while parked. I hear it less often while I'm driving because I'm careful to use light braking to maximize regen. Usually if I hear it, it's as I'm just coming to a stop at a few mph. Or if I needed to stop faster than expected and the friction brakes come on earlier.

 

Interesting. The PiP doesn't behave this way. There are a couple of issues related to how the electric motor system interacts with other systems in the Prime. It seems like maybe Toyota didn't have access to engineers of the same caliber as those that designed the PiP when they designed the Prime.

 

Yap, that sounds like my experience too. To be honest, I have not paid much attention to the sound, for my commuting of 18 miles has only 3 traffic lights with very light traffic most of the time. Sometimes, I can drive the entire 18 miles without applying any braking.

 

I don't have a Prime, but if its brake ECU has a "linear solenoid learning" routine as in the earlier generations, it might not be a total waste of time to go through it and see what happens.

 

The Prime can brake itself for the radar cruise control. I wonder if that has anything to do with the brake weirdness compared to older models. I don't know anything about the PIP, so I don't know if it can brake like that. I know older Toyotas have brake assist where they can slam on the ABS if it thinks you are doing a fast stop, but that's different than being able to smoothly modulate the brakes.

 

I tested in neutral facing downhill: it still happens. Definitely the brakes.

 

Interesting. I've noticed that sometimes the brakes in mine get "notch-y", where it feels like the pedal almost clicks into a few different levels of braking. It happened this morning, and it usually happens after harder than normal braking, and then goes away after some time. I think it's the same thing you're talking about. But for me 90% of the time the brakes are very smooth, and I have good control even inching forward at low speed. The vast majority of my braking is very gentle to maximize efficiency.

 

A build up of corrosion on the rotors from light use do to regen braking will make the brakes grabby.

 

The pedal itself becomes grabby. There is a light clicking sound as it moves.

I've noticed corrosion on the rotors, but only at the beginning of a drive. The brakes sound rougher and louder when it happens. It goes away pretty quickly, after 1-2 stops, since the friction brakes always activate at low speed as I'm coming to a stop.

This grabby brake pedal feeling can happen at any point in the drive when there's clearly no corrosion. I haven't tried to trigger it, but I'm pretty sure I could on demand by just pressing moderately hard on the brakes while stopped.

 

I don't think it's the pads. It's the brake system. You can hear the pedal clicking with each slight change in pedal pressure and hear the noise of hydraulics.