The brake problem is back (or did it never go away?)

The "fix" reduced it but it can't eliminate it. Otherwise you would eventually destroy the HSD.

It was always there, it didn't "come back". You just finally noticed it again.

 

Could you please elaborate?

 

Yep, the brake "problem" still there. I encounter it from time to time.

 

It's simple.

Regen braking uses the front wheels!!!!!! The prius has small tires!!. The car is front wheel drive so it uses the front wheels to slow the car down in regen, if the front wheels loose traction the car lets off the regen(so you don't loose steering control just like abs) and then applies the friction brakes to all 4 wheels. There is less braking force for less than a second(this feels like the car is moving faster or you lost all brakes, but is normal) now it stops just like a normal car. If it really bothers you there's nothing you can do.

 

Its normal for all hybrids that use regen to recover wasted braking energy .

 

This "problem" has been here all along, even before the Gen III. It's an issue with ABS exacerbated by regenerative braking. The OP's sudden recurrence is coincidental.

Tom

 

Hi XVS,

Has it been rainy there lately? My guess is your brakes are a little rusty, and when the car switches to friction brakes, the rust dust is lubricating the braking action. Do the brake cleaning maneuver and report back....

 

Yep, as gbee42 states the seemingly problematic brake function can be explained by three letters: A B S. I also own an Envoy. The braking functions exactly the same when combined with a bump or pot hole in the road. It may feel strange but its only normal antislip action happening.

 

Yeah I find the 'problem' to still be there - its called ABS braking. All cars with ABS have it - some better, some worse - its not just a Toyota thing.

 

I had my prius for just 2 weeks, too short to comment on the specific issue, but it was my understanding from the day one of my car driving that one is not supposed to brake hard over potholes, bumps, or other road irregularities or loss of braking or suspension damage would ensue. Isn't that correct?

In case of emergency, I would combine braking AND swerving to avoid obstacles, as ABS will not always provide enough braking force in low friction conditions.

 

I am not an explainer... lol

But the way I understand it, the problem comes from the combination of ABS and the regenerative(braking caused by drag of the Motor/Generator). When the ABS is triggered (rough/slippery surface), it causes the regenerative braking to stop and the friction braking to kick in. That transition is what people are feeling. Toyota shortened that time with the update.

 

I think they've shortened it very well - infact I think it is over keen if anything.

 

Regenerative braking exacerbates the problem, but doesn't cause it. The current Toyota FJ has the same issue, without any regenerative braking. It does use electrically assisted power brakes, as does the Prius, so that may be the common component.

Tom

 

it is just abs... i wonder how these people survived driving cars 7-8 years ago when abs was much worse when it comes to the "feel"... current gen abs is much better and you rarely feel like something is wrong... i remember with 2002 Corolla, dear god if you pressed brakes over the bump abs would come on so forcefully, you would think your front wheels are gone

 

Perhaps that is the real problem. When ABS used to go "THUNKTHUNKTHUNKTHUNK" you knew that ABS had kicked in. Now it does it without fuss, so some driver's might think they are experiencing brake failure as opposed to ABS.

Tom

 

Right... I wasn't meaning to implying that that the regen was the cause but rather the combination. Even though the ECUs might be responding at the speed of light or close to it, there are still mechanical processes involved that slow things down. It would seem if they could apply the rear brakes slightly at all braking requests that might help eliminate the sensation and only slightly effect that regen advantage.?

 

I know from experience that you Prius Chatters get real touchy when you start talking about the brakes....

What I'm wondering is since my understanding was that the software flash update primarily was simply changing the split second reaction time between regenerative and standard brakes...to provide a more "standard" feel, I'm wondering if the perceived lag or difference doesn't begin to once again manifest more strongly as the brake pads themselves start to wear?

I've just noticed with my new (non-prius) new car, over the past few months and about 7000 miles...as the standard ABS brakes (break in) the brakes feel smoother to stops, but the pedal feel is slightly more spongey and I'm wondering if given the duality and complexity of The Prius system..what you have is a normal condition, being adjusted by the software update, and then a different calibrated feel as the regular brakes themselves become used.....

But don't jump all over me...just speculation....

 

Ive experienced this before a few times. I dont really see it as being a dangerous problem, as its only for a split second and if thats all the margin you leave yourself you cant really blame the car.

In a panic stop this car is the best braking car I have driven. I had a deer run out in front of my car about 4-6 car lengths away and i was going about 55 and I was at a dead stop by the time I crossed his path.

There is alot going on in regenerative braking mode, the computer is trying to make the pedal act and feel like brakes you are used to on every car you have ever driven. About 99% of the time its seamless and linear, but it seems like the bump under light braking is still an issue. Ill take that quirk over Toyota re-flashing it to make it foolproof by having the rear brakes react under light braking. Any day. Im looking forward to replacing my first brake pads somewhere north of 100k.

This is a well known quirk, so its pretty easy to account for and anticipate. If someone is unwilling to accept slight differences between the Prius and a standard car, they probably should have got a Corolla. Its not about being touchy, its just not that big a deal, its not really a safety issue, and anyone who gets in an accident and blames it on .2 seconds of braking inconsistency needs to re-evaluate their driving abilities. It would be one thing if it did this kind of thing under hard/panic braking, but it doesn't, its only in the regen zone, at least it always has been for me.