Ubering with a Prius C and poor braking, including fade

i don't recall anyone ever having had this problem. have you done a thorough brake inspection?

i don't see how unerring would have anything to do with it, compared to a fully loaded private vehicle, do you have to speed or drive recklessly in some way when unerring due to customer request?

 

Our c requires very little pedal effort to get a lot of braking force. I don't know if they changed anything over the years- I've only driven 2017 & 2018 models.

Get it checked out before changing parts. If you're getting a lot of brake fade, that says to me that the friction brakes are being used more than expected. Maybe something is up with the regen system?

 

Maybe not.
Stop following so close and SLOW DOWN.
Really. Honestly.

"Performance oriented" pads will just make the stops even MORE abrupt and they likely will wear out much faster.

This is not a sports car; stop driving it like one.

That probably will make your passengers happier too.

 

Prius brakes above 6mph is mostly a function of your electric motor generating electricity... The control that shifts between mechanical braking and regenerative breaking is an expensive part to replace. I'd recommend finding someone with a Prius C similar to yours and driving their car to see if you notice a difference.

Historically these types of brake issues happen when someone switches from a car with a manual transmission to a car with an automatic transmission, which have much more forceful brakes with less push of the pedal compared to standard manual clutch design. In a Prius it's even more pronounced.. It takes a while to get good at barely hitting the brake pedal, but seems like you'd be already at that point, so I'd compare your experience with a similar Prius C to see if there's a difference.

 

Keep in mind you've got two brake systems on board, and a computer programmed to prevent you from knowing which one is in use at any given time.

The regen brakes are always used first and most. If they aren't right* for the situation, the system "seamlessly" substitutes the friction brakes.

* not right can be anything on this list:

1. Pedal travel is extremely rapid - computer interprets this as a panic stop
2. regenerative ABS controller can't figure out what's going on as in a front wheel skid
3. very high pedal force applied - same panic stop as above
4. battery level too high, too warm or HV electric fault- no place to put the electricity
5. Speed too low - friction brakes become primary below 6mph.

There are probably other things to put on that list, but that covers a lot of it.

I wonder if you are feeling the difference between the two systems and writing it off to thermal fade?

I also wondered if the battery is just getting a bit too hot, causing more use of friction brakes, and then even more usage eventually results in bona fide thermal fade.

I understand that you can read the data stream in real time and see which system is in use and get notification of cutover to the friction system. The car doesn't have a built-in display that I'm aware of, but people are doing it with Scangauges, smartphone apps and similar gadgetry. Maybe look into that, maybe read your rotor temps with an IR gun? I feel like some inexpensive tools and a few days of measurements & observations would shed a lot of light on this.

 

If the brakes get worse with each application sounds like you are experiencing a classic case of brake fade. After a long bad stop park the car and put your hand carefully on each wheel and see if they are hot. I'm surprised you don't notice the smell of brakes too.
It's time to get the brakes inspected, you could be liable because you know there is something wrong and still haul people for hire.

 

I had been using my C for commercial driving (deliveries), and noticed a similar thing, but it wasn't as bad as other cars I used that had the brakes trashed by constant stop-go city driving.

Things I would consider here:

1. Brakes, obviously. Unfortunately I don't think there are aftermarket rotors available for the C that will have better metallurgy and cooling than the OE rotors (the cheap drilled and slotted rotors are junk).

2. Transaxle / transmission fluid. Old fluid that gets hot (e.g. in extended city driving) makes the vehicle feel wonky slowing and accelerating, for lack of a better term.

3. Changing driving habits. Use the brakes less with predictive coasting. Even if you don't care about max fuel economy (more rides pays more $), driving faster does, of course, increase wear and tear.

4. As a commercial driver, you are more sensitive to changes in vehicle performance that most drivers, or at least I noticed that I was hyper-sensitive about things with my cars. Sometimes this serves you well detecting problems early, other times, it's just normal things that you're overthinking being in the car so much.

 

This is great... You make the Prius braking system sound like a conspiracy theory... You got style, my man. Great style with your words! Much appreciated!

 

Could it possibly be related to tires? How is the condition of the tires, and has the air pressure been increased to compensate for the extra passenger weight?

On the other hand, it may very well be related to the regen system. My 2016 Gen4 also has that unexplained brake fading issue. It comes and goes, ever since the car was new. I describe it as being very "mushy" brakes, which requires a much firmer push on the pedal to stop the car. It was really bad yesterday, just driving normally in city traffic. (Dealer has not mentioned any unusual wear -- they are 8mm.) I don't like it. It's a very uncomfortable feeling. And I'm the only one in the car.

 

Sorry. But by necessity "we" need to fill in the blanks with some guesses because we can't hope to know ALL the facts of the real story just from your brief description.

And we need to eliminate the most obvious and likely possibilities first.

So.....I have only 2 suggestions:
Find another C and drive it to compare.
Take it in and have your brakes checked; there could be something worn out or sticking.

There have been 3 C's in my family and none of the drivers has had that complaint.

P.S. Speed and following distance are two DIFFERENT things, although often related.
You mentioned speed but not following distance.
Do you maybe have a tendency to leave too small of a gap to the car ahead ??

 

During any range of "normal" braking, one should NOT notice any difference in braking efficiency as the brakes heat up a little.

NOW.......if you use the brakes a LOT more than "normal", then maybe they would heat up enough to notice a little fade.

 

Don't know about the 'c,' but in the 'v', using the most aggressive engine mode ('PWR', presumably for POWER, in the v) also increases the aggressiveness of regenerative kinetic energy harvesting and braking.

 

What does that mean?

The maintenance schedule from Toyota recommends an in-depth brake inspection every 30K miles or 36 months, whichever comes first. Yeah, I would get that done; you're likely looking at $300~400, for a proper job.