Prius Brakes

[steve9999]

Had the upgrade done but still concerned that when braking on a rough surface the brakes lose their feel/effectiveness and have to be let off and on again..... Has anyone else still experienced this "problem"....or is it just me imagining it?

[kithmo]

What you're describing is the normal behaviour of ABS, if you're having a problem braking on a rough surface you're driving too fast, common sense says don't drive fast on a loose/rough surface unless you're a rally driver.

[kithmo]

Skidding on Ice next ?

[flow]

What you're describing is the normal behaviour of ABS, if you're having a problem braking on a rough surface you're driving too fast, common sense says don't drive fast on a loose/rough surface unless you're a rally driver.

Not true - Its the change from regen to normal braking (i think) that causes the 'sensation' and is only noticable at very slow speeds.

I had mine updated back in March. I still notice it but not as much as before.

Its not dangerous as you are never without brakes, its just how the Hybrid braking system works.

[kevin h]

What you're describing is the normal behaviour of ABS, if you're having a problem braking on a rough surface you're driving too fast, common sense says don't drive fast on a loose/rough surface unless you're a rally driver.

Not true - Its the change from regen to normal braking (i think) that causes the 'sensation' and is only noticable at very slow speeds.

I had mine updated back in March. I still notice it but not as much as before.

Its not dangerous as you are never without brakes, its just how the Hybrid braking system works.

Totally agree, just get used to the Hybrid system

[steve9999]

What you're describing is the normal behaviour of ABS, if you're having a problem braking on a rough surface you're driving too fast, common sense says don't drive fast on a loose/rough surface unless you're a rally driver.

[steve9999]

What you're describing is the normal behaviour of ABS, if you're having a problem braking on a rough surface you're driving too fast, common sense says don't drive fast on a loose/rough surface unless you're a rally driver.

Living in London it's quite difficult to drive over 20mph so your comment not very helpful, but thanks anyway for taking the time.

I disagree that it is normal behaviour of ABS having driven ABS fitted cars for the last 20 years or so. Anyway the car is going back into the Toyota dealer

[kithmo]

What you're describing is the normal behaviour of ABS, if you're having a problem braking on a rough surface you're driving too fast, common sense says don't drive fast on a loose/rough surface unless you're a rally driver.

Living in London it's quite difficult to drive over 20mph so your comment not very helpful, but thanks anyway for taking the time.

I disagree that it is normal behaviour of ABS having driven ABS fitted cars for the last 20 years or so. Anyway the car is going back into the Toyota dealer

Apologies steve for the "not very helpful" comments, now you mention that it happens at low speeds, it throws new light on the subject and I would not have made the above comments if you had mentioned below 20 mph in your original post.

You are correct, ABS does not behave in this way at low speeds (unless on a very slippery surface, like ice) so it is a problem. I hope you get it sorted.

I have only had my prius for 5 weeks now but I have not experienced this "sensation" when the car goes from regen to normal braking that some people mention, mine just feels the same as all the other ABS equipped cars I've owned and brakes smoothly and evenly from light to heavy braking on normal road surfaces. I suggest to the other posters on here that if they are experiencing a strange feeling with the brakes on a normal road surface then they may have a problem too.

[Parts-King]

Of course you should have it checked, but it is probably NOT a problem, just the "Feel" that you get with this type of braking system, the system is working as it was designed to do. There was concern that the brakes were not working and this mod somehow "fixed" a problem, all that happened was a new flash file was loaded into the ABS ECU to change some of the parameters. You should have it looked at to ensure the ECU does indeed have the correct file in it

Kingo

[timberwolf]

Had the upgrade done but still concerned that when braking on a rough surface the brakes lose their feel/effectiveness and have to be let off and on again..... Has anyone else still experienced this "problem"....or is it just me imagining it?

When the feel of the braking force on your body (and the car) goes light (a sort of floaty feeling, or some people describe it as the brakes letting go), are you saying that to fix this you have been releasing your foot pressure off the brake pedal and then pressing back down again?

[Dave R.]

Had the upgrade done but still concerned that when braking on a rough surface the brakes lose their feel/effectiveness and have to be let off and on again..... Has anyone else still experienced this "problem"....or is it just me imagining it?

When the feel of the braking force on your body (and the car) goes light (a sort of floaty feeling, or some people describe it as the brakes letting go), are you saying that to fix this you have been releasing your foot pressure off the brake pedal and then pressing back down again?

Building further on the advice - the "problem" wasn't actually a problem, as if you continue to apply pressure to the brakes, the ABS will decide it has grip, put the brakes back on and the car will stop (hence the brake recall wasn't a mandatory safety recall - it was just to stop customers complaining that it felt strange!) If this isn't happening (and as Timberwolf is asking) and you have to release the brakes and reapply them, then something else is wrong!

[Parts-King]

No you dont have to let the brakes off and re-apply them, the original "Feel" was that you needed to apply more pressure than you anticipated, the upgrage just altered the parameters so that you did not have to apply as much pressure

Kingo

[DrCez]

Had the upgrade done but still concerned that when braking on a rough surface the brakes lose their feel/effectiveness and have to be let off and on again..... Has anyone else still experienced this "problem"....or is it just me imagining it?

You might want to try this: (N.B. it goes without saying to find a safe place / time - which may not be so easy in London ) while under braking put the car into neutral, and observe what kind of 'feel' you get from the brakes. My understanding is that the Prius doesn't use the electric motor/regen in neutral so you will be forcing it to go from regenerative to mechanical braking. I find there is a very slight change in brake responsiveness - I feel I need to press the pedal a little harder, which was unsettling the first time but I don't notice it now (plus the software fix may have lessened the sensation). I think that the ABS system also uses mechanical braking without regen in which case the change over from regen to mechanical braking could be what feels strange to you. Certainly the putting-it-in-neutral exercise helped me to get a better idea of a Prius-specific characteristic.

Normally my car switches to mechanical braking somewhere below 10 mph (in quiet conditions you can actually hear it) which is why I presume some folk say the braking issue only applies at low speeds, but my impression is that you do feel it if ABS kicks in at higher speeds - e.g braking and running over a drain cover, loose gravel, pothole etc. I have a Gen 3 Prius BTW.

HTH

[DrCez]

Had the upgrade done but still concerned that when braking on a rough surface the brakes lose their feel/effectiveness and have to be let off and on again..... Has anyone else still experienced this "problem"....or is it just me imagining it?

You might want to try this: (N.B. it goes without saying to find a safe place / time - which may not be so easy in London ) while under braking put the car into neutral, and observe what kind of 'feel' you get from the brakes. My understanding is that the Prius doesn't use the electric motor/regen in neutral so you will be forcing it to go from regenerative to mechanical braking. I find there is a very slight change in brake responsiveness - I feel I need to press the pedal a little harder, which was unsettling the first time but I don't notice it now (plus the software fix may have lessened the sensation). I think that the ABS system also uses mechanical braking without regen in which case the change over from regen to mechanical braking could be what feels strange to you. Certainly the putting-it-in-neutral exercise helped me to get a better idea of a Prius-specific characteristic.

Normally my car switches to mechanical braking somewhere below 10 mph (in quiet conditions you can actually hear it) which is why I presume some folk say the braking issue only applies at low speeds, but my impression is that you do feel it if ABS kicks in at higher speeds - e.g braking and running over a drain cover, loose gravel, pothole etc. I have a Gen 3 Prius BTW.

HTH

[timberwolf]

Yes, I was thinking it wasn't a good ides to ease off the brake pedal. Instinctively, pressing harder on the brake pedal seemed to be the right thing to do when it has happened on my gen 2. Read somewhere of one driver so freaked out that they let go of steering wheel.

[Ancient Nerd]

Yes, I was thinking it wasn't a good ides to ease off the brake pedal. Instinctively, pressing harder on the brake pedal seemed to be the right thing to do when it has happened on my gen 2. Read somewhere of one driver so freaked out that they let go of steering wheel.

And put their hands over their eyes? Seems an effective way to stop the car. I must try it!

[Grumpy Cabbie]

Had the upgrade done but still concerned that when braking on a rough surface the brakes lose their feel/effectiveness and have to be let off and on again..... Has anyone else still experienced this "problem"....or is it just me imagining it?

Hmmm, are you sure they actually did the update/recall?

Just that I had the brake feel 'issue' a couple of times before the recall and indeed it was rather scary, almost like being rear ended by someone and completely different to the ABS sensation (I have driven many many different cars). Since the update I have found the Prius to be completely normal. Yes it has a bit of a skip sometimes when the ABS kicks in, but no different to many other cars out there. In fact some are much worse.

I had the recall done at about 5k miles and am now upto 23k miles and haven't had an issue with the brakes since.

Is there a way of getting another dealer to check that the update was installed correctly on your vehicle?

[timberwolf]

The switch from regenerative to friction braking when the traction is briefly lost is unique to cars with regenerative technology and quite possibly specific to the Prius design. Both the 2nd and 3rd Gen Prius can exhibit this behaviour in the appropriate circumstances and it does not IMHO feel like ABS braking.

The 3rd Gen got bad press because Toyota did not do their sums correctly and they then had to tweak some values in the braking ECU. I do wonder why and how Toyota got it wrong?

With increased use of the fly-by-wire and intelligent systems able to "take over", I think drivers are going to have to get used to the idea that the systems will sometimes make unexpected decisions in circumstances that their designers had not foreseen.

[Jolly English Gentleman]

The switch from regenerative to friction braking when the traction is briefly lost is unique to cars with regenerative technology and quite possibly specific to the Prius design. Both the 2nd and 3rd Gen Prius can exhibit this behaviour in the appropriate circumstances and it does not IMHO feel like ABS braking.

Indeed I think I have have experienced this when slowing down for a roundabout and finding a :censor: great big pothole. Found it twice! On each occasion I felt a decided wobble come up the steering wheel and one of the amber warning lights flashed briefly (probably ABS but it was so quick I did not take it in). Since then I know to avoid that pothole.

The 3rd Gen got bad press because Toyota did not do their sums correctly and they then had to tweak some values in the braking ECU. I do wonder why and how Toyota got it wrong?

For the same reason that many software programmers get things wrong. There has to be a fine line between testing and getting a product out before a competitor - in this case probably Honda's Civic which has always seem to have been playing catchup.

With increased use of the fly-by-wire and intelligent systems able to "take over", I think drivers are going to have to get used to the idea that the systems will sometimes make unexpected decisions in circumstances that their designers had not foreseen.

Indeed. The car that drives itself is many years ahead.