Transition from Regen Braking to Normal Braking

[Bozz]

I mentioned this in a post a couple of weeks ago and must say of all the positives and negatives this is the one feature of the car that is the most worrying / disconcerting. 

On the motorway this week going from braking under ACC control and then changing lanes to find that the ACC braking hadn't picked up that the car in front is now braking hard I braked manually to find that there was the sensation of no increased retardation even if the pressure on the brake pedal was increased. It was only by pushing really hard that the braking effort was sufficient to avoid a collision. It was almost like the discs and pads were soaking wet and there was no friction. The conditions were dry btw.

I've also experienced this when trail braking into a bend (not using ACC) where initially the car appears to be regen braking but then I need to slow down quicker but pushing the brake pedal has little effect unless pushed really hard.

Is this a feature of the product or a fault?

 

 

 

[TonyHSD]

1 hour ago, Bozz said:

I mentioned this in a post a couple of weeks ago and must say of all the positives and negatives this is the one feature of the car that is the most worrying / disconcerting. 

On the motorway this week going from braking under ACC control and then changing lanes to find that the ACC braking hadn't picked up that the car in front is now braking hard I braked manually to find that there was the sensation of no increased retardation even if the pressure on the brake pedal was increased. It was only by pushing really hard that the braking effort was sufficient to avoid a collision. It was almost like the discs and pads were soaking wet and there was no friction. The conditions were dry btw.

I've also experienced this when trail braking into a bend (not using ACC) where initially the car appears to be regen braking but then I need to slow down quicker but pushing the brake pedal has little effect unless pushed really hard.

Is this a feature of the product or a fault?

 

 

 

Hi, 

what you have experienced  it is a typical for all Toyota hybrids but does not or perhaps should not have happened in normal conditions but only when ABS has been activated due to a slippery roads or emergency braking or hitting a pothole.
To regain normal brake operation you need to release the brake pedal completely and depress again then the system will operate as normal and the brakes will work as they should and be good.
If no ABS was activated the transition between regenerative braking and disc brakes should be seamless and when the actual brakes kick in you should feel really good stopping power.
If unsure or thinking something is not right better to check brake system physically and with a diagnostic for stored faults, but that’s not usual for these cars. 👍

[Bozz]

1 minute ago, TonyHSD said:

Hi, 

what you have experienced  it is a typical for all Toyota hybrids but does not or perhaps should not have happened in normal conditions but only when ABS has been activated due to a slippery roads or emergency braking or hitting a pothole.
To regain normal brake operation you need to release the brake pedal completely and depress again then the system will operate as normal and the brakes will work as they should and be good.
If no ABS was activated the transition between regenerative braking and disc brakes should be seamless and when the actual brakes kick in you should feel really good stopping power.
If unsure or thinking something is not right better to check brake system physically and with a diagnostic for stored faults, but that’s not usual for these cars. 👍

Hi Tony, There was no ABS activation in either situation. 

[Bozz]

7 minutes ago, TonyHSD said:

Hi, 

what you have experienced  it is a typical for all Toyota hybrids but does not or perhaps should not have happened in normal conditions but only when ABS has been activated due to a slippery roads or emergency braking or hitting a pothole.
To regain normal brake operation you need to release the brake pedal completely and depress again then the system will operate as normal and the brakes will work as they should and be good.
If no ABS was activated the transition between regenerative braking and disc brakes should be seamless and when the actual brakes kick in you should feel really good stopping power.
If unsure or thinking something is not right better to check brake system physically and with a diagnostic for stored faults, but that’s not usual for these cars. 👍

Or pothholes involved but it did nearly become emergency braking 

[Cyker]

It might be worth getting the dealer to have a look if it's reproducible, but it may also just be getting used to the brake-by-wire - The brakes in the hybrid are completely computer controlled, like the accelerator is, and it takes some getting used to in edge-cases.

It's one of the things I dislike about my Mk4, that the feedback from the brake pedal is artificially generated and doesn't always match what the brakes are doing, and occasionally I find I have to brake harder than the feedback from the pedal suggests in order to brake enough.

 

[TonyHSD]

Just now, Bozz said:

Hi Tony, There was no ABS activation in either situation. 

100% sure there wasn’t? , Any chances you went over a pothole, a large cracks on the roads , anything that can upset the suspension and make the tyre loose even the slightest contact with the road while stopping and the brake pedal will become rock hard and brakes very weak. This is happening because rear brakes got stopping power cut off and front ones only work as manual even not brake bolstered brakes, all that happens for a second, time enough to make your hair stand on end. When this is happening pumping noises from the electronic brake booster can be heard in the next few brake uses. To confirm we are talking about the same thing and your particular case is exactly that you may want to try my suggestion to fully release brake pedal and immediately depress again. 

[TonyHSD]

Toyota hybrids does not like two things: 

1. Emergency or hard braking while driving over potholes, cracks or bumps - the feeling of loosing your brakes will happen 

2. Hard acceleration in similar road conditions- on full power going over cracks or potholes and the car detects wheel slips while on full throttle may cut all power,  set the car into N neutral and trigger fault -“ hybrid system malfunction “.  
I am thinking  you guess how I know 😂, I have  learned the hard way 👌👍

[Bozz]

2 minutes ago, TonyHSD said:

100% sure there wasn’t? , Any chances you went over a pothole, a large cracks on the roads , anything that can upset the suspension and make the tyre loose even the slightest contact with the road while stopping and the brake pedal will become rock hard and brakes very weak. This is happening because rear brakes got stopping power cut off and front ones only work as manual even not brake bolstered brakes, all that happens for a second, time enough to make your hair stand on end. When this is happening pumping noises from the electronic brake booster can be heard in the next few brake uses. To confirm we are talking about the same thing and your particular case is exactly that you may want to try my suggestion to fully release brake pedal and immediately depress again. 

This is a bit like braking so hard in a non ABS equipped car that the front tyres lose adhesion and in order to increase the retardation you have to quickly lift off the pedal before reapplying and repeat. 

[TonyHSD]

1 minute ago, Bozz said:

This is a bit like braking so hard in a non ABS equipped car that the front tyres lose adhesion and in order to increase the retardation you have to quickly lift off the pedal before reapplying and repeat. 

Indeed 👍

[Cyker]

It's not just hybrids - Even my Mk1 would freak out if I was braking firmly and went over a drain cover and instantly cut in the ABS, cutting my braking power in half! Quickly learned to not brake firmly over anything that looked slippery  

That said, I don't think it'd be the ABS as the ABS is very noticeable - The car feels like it's driving over gravel and you can feel the brake pedal pulsing (Compared to my Mk1 and Mk2, the Mk4's brake-by-wire gives even more noticeable pulsing!)

 

[TonyHSD]

3 minutes ago, Cyker said:

It's not just hybrids - Even my Mk1 would freak out if I was braking firmly and went over a drain cover and instantly cut in the ABS, cutting my braking power in half! Quickly learned to not brake firmly over anything that looked slippery  

That said, I don't think it'd be the ABS as the ABS is very noticeable - The car feels like it's driving over gravel and you can feel the brake pedal pulsing (Compared to my Mk1 and Mk2, the Mk4's brake-by-wire gives even more noticeable pulsing!)

 

I mean it’s the abs + the vsc that causes the issue. But in hybrids because of the rear brakes are entirely brake by wire and electronically operated the stopping power complete lost is very noticeable. 

[Cyker]

It was worse on the Mk1 - rear brakes were drums so they'd lock up really easy if one wheel went over something slippy, and that would trigger the ABS and bam 50% braking force gone!

What do you mean by the rears are electronically operated? AFAIK the whole system is hydraulic and brake-by-wire

[TonyHSD]

3 hours ago, Cyker said:

It was worse on the Mk1 - rear brakes were drums so they'd lock up really easy if one wheel went over something slippy, and that would trigger the ABS and bam 50% braking force gone!

What do you mean by the rears are electronically operated? AFAIK the whole system is hydraulic and brake-by-wire

The front brakes are driven directly by the brake fluid from the brake master cylinder and electronically controlled via abs pump same as on the non hybrid cars.
 Rear brakes are exclusively operated via an electric pump and often can be heard as pumping noise. In an event of system malfunction you can still apply stopping power to the front wheels only by forcing the hydraulic brakes pressing the brake pedal harder. This is likely what happened to the op when the car most likely has detected a wheel slip or jump off the ground and had its abs+vsc activated. Here a videos that can help understand how the system works. 

 

[frizzbee30]

To be honest, I've found the brakes to be outstanding. 

 

Yes, it can be slow on ACC, but it doesn't have the processing speed or situational awareness if the human CNS, and if you ' hold your nerve' it actually kicks in and slams on

 

I always brake easy, but on one occasion on an unfamiliar,  shockingly bad motorway  to motorway merge, with a giveaway and no acc lane, it stopped as if suddenly it had hit a wall!

[Cyker]

The stopping power of the brakes isn't in question - I think all owners will agree if you brake hard it will stop so fast it's actually a bit painful!

The problem is more the car not always doing what you want or expect.

I've always been a bit wary of things that abstract out controls and put layers between the control and the driver, as it takes away feedback from the driver, and it's certainly something I've noticed with things like power steering and now the brake-by-wire.

95% of the time it's fine; Feels good, brakes how it should, regen and friction brakes blended in seamlessly. But occasionally it doesn't and I'll find the pedal is giving me a lot of resistance, providing feedback that I'm braking strongly, when I'm actually not - I've been caught out twice by it and both times was only saved by the auto brake system (Which is why I don't want to turn it off despite it displaying false alerts most of the time and occasionally trying to make other people rear-end me  ).

Now I've learned not to trust the brake pedal force feedback (Esp. since I've discovered it is completely artificial) and to just keep pushing if the car isn't slowing as much as I'd thought it would, rather than waiting for the brake force to build as the car slows down like I'd normally do, because it doesn't in this car!

 

[Bozz]

12 hours ago, Cyker said:

The stopping power of the brakes isn't in question - I think all owners will agree if you brake hard it will stop so fast it's actually a bit painful!

The problem is more the car not always doing what you want or expect.

I've always been a bit wary of things that abstract out controls and put layers between the control and the driver, as it takes away feedback from the driver, and it's certainly something I've noticed with things like power steering and now the brake-by-wire.

95% of the time it's fine; Feels good, brakes how it should, regen and friction brakes blended in seamlessly. But occasionally it doesn't and I'll find the pedal is giving me a lot of resistance, providing feedback that I'm braking strongly, when I'm actually not - I've been caught out twice by it and both times was only saved by the auto brake system (Which is why I don't want to turn it off despite it displaying false alerts most of the time and occasionally trying to make other people rear-end me  ).

Now I've learned not to trust the brake pedal force feedback (Esp. since I've discovered it is completely artificial) and to just keep pushing if the car isn't slowing as much as I'd thought it would, rather than waiting for the brake force to build as the car slows down like I'd normally do, because it doesn't in this car!

 

Exactly 

[Gerhard_Corolla]

On 7/4/2022 at 7:46 PM, Cyker said:

The stopping power of the brakes isn't in question - I think all owners will agree if you brake hard it will stop so fast it's actually a bit painful!

The problem is more the car not always doing what you want or expect.

I've always been a bit wary of things that abstract out controls and put layers between the control and the driver, as it takes away feedback from the driver, and it's certainly something I've noticed with things like power steering and now the brake-by-wire.

95% of the time it's fine; Feels good, brakes how it should, regen and friction brakes blended in seamlessly. But occasionally it doesn't and I'll find the pedal is giving me a lot of resistance, providing feedback that I'm braking strongly, when I'm actually not - I've been caught out twice by it and both times was only saved by the auto brake system (Which is why I don't want to turn it off despite it displaying false alerts most of the time and occasionally trying to make other people rear-end me  ).

Now I've learned not to trust the brake pedal force feedback (Esp. since I've discovered it is completely artificial) and to just keep pushing if the car isn't slowing as much as I'd thought it would, rather than waiting for the brake force to build as the car slows down like I'd normally do, because it doesn't in this car!

 

I took the TS for her first long highway drive through the Alps, and two things were difficult to adapt to: engine revolutions management on ascending bits of road, and hard/at high speed braking. The most disturbing of the two was the braking part! 

 

I understand that regenerative braking initiate the phase of braking, then the front brakes takes the main task of decelerating the vehicle, while the rear brakes appear just as an accessory waiting to intervene only if needed. But the case is that I felt that the rear brakes almost didn't participated at all in any important braking. Now I know that the rears are brake by wire and maybe that has something to do with the feeling, but I thought that the rear disks would clean a little bit better after so many km on the road for the first time...

 

... and believe me, I used the brakes a lot driving among thousands and thousands of crazy Italians!

[TonyHSD]

2 hours ago, Gerhard_Corolla said:

I took the TS for her first long highway drive through the Alps, and two things were difficult to adapt to: engine revolutions management on ascending bits of road, and hard/at high speed braking. The most disturbing of the two was the braking part! 

 

I understand that regenerative braking initiate the phase of braking, then the front brakes takes the main task of decelerating the vehicle, while the rear brakes appear just as an accessory waiting to intervene only if needed. But the case is that I felt that the rear brakes almost didn't participated at all in any important braking. Now I know that the rears are brake by wire and maybe that has something to do with the feeling, but I thought that the rear disks would clean a little bit better after so many km on the road for the first time...

 

... and believe me, I used the brakes a lot driving among thousands and thousands of crazy Italians!

If your rear brakes didn’t clear off after some miles traveled it most likely mean that they require a service - cleaning and lubricating the slider pins. Rear brakes do get to work as much as front ones or even more. Rear brake pads on Toyota hybrids wear out  first and it will be first reported for change by the mechanics who work on your car. Rear brakes may engage early before the front ones when car used normally. 

[Cyker]

Yeah I remember someone saying that before (Might have been you!  ), i.e. that the brake engagement order is front regen -> +lightly rear disc -> stronger front+rear disc+max regen

One downside with having the steelies on is it's much harder to see the condition of the brakes so not sure how they've worn so far!

[TonyHSD]

44 minutes ago, Cyker said:

Yeah I remember someone saying that before (Might have been you!  ), i.e. that the brake engagement order is front regen -> +lightly rear disc -> stronger front+rear disc+max regen

One downside with having the steelies on is it's much harder to see the condition of the brakes so not sure how they've worn so far!

Don’t worry, Toyota technicians will look for it when you take the car for a service. Roughly around 50k miles rear brakes will be wearing thin and they will offer a replacement. 👍

[Cyker]

The same technicians that failed to diagnose a failing gearbox, and ac system properly, and also sent me out with tyres at 20psi...?   

 

[TonyHSD]

24 minutes ago, Cyker said:

The same technicians that failed to diagnose a failing gearbox, and ac system properly, and also sent me out with tyres at 20psi...?   

 

If it’s me I will change the dealership then. 👍 

[Gerhard_Corolla]

15 hours ago, TonyHSD said:

If your rear brakes didn’t clear off after some miles traveled it most likely mean that they require a service - cleaning and lubricating the slider pins. Rear brakes do get to work as much as front ones or even more. Rear brake pads on Toyota hybrids wear out  first and it will be first reported for change by the mechanics who work on your car. Rear brakes may engage early before the front ones when car used normally. 

There's a considerable chunk of owners that needed to change their rear disks on their 45,000 km service, because they were practically in 'new' condition but extremely rust due to the low activity of the rear brakes...

 

I thought that with a few hard brakes at speed, the rear disks would drop a little bit of that rust, but it's still visible. Of course less than before, but still present.

[TonyHSD]

3 hours ago, Gerhard_Corolla said:

There's a considerable chunk of owners that needed to change their rear disks on their 45,000 km service, because they were practically in 'new' condition but extremely rust due to the low activity of the rear brakes...

 

I thought that with a few hard brakes at speed, the rear disks would drop a little bit of that rust, but it's still visible. Of course less than before, but still present.

The trick to get rear brakes clean is to use the brakes continuously, like slowing down from 60 to 30 mph with moderate stopping power , so you can go pass regenerative braking and engage the real brakes or perhaps set the car in N neutral and slow down with the actual brakes only.
Few hard brakes will not clean them, but will score the discs only.
The reason why hybrids get rear disc rusty its because of plus the regenerative braking of the car the brakes are always cold and the  slider pins get stuck.  When this is happened rear brakes operate at half., only inner pad presses the disc and outer pad does not provide stopping power. No matter how hard you press the brakes the disc will not clean without lube service. 

[Cyker]

21 hours ago, TonyHSD said:

If it’s me I will change the dealership then. 👍 

Sadly they all seem to be like that around here... must be the London curse!

Honestly, dealing with them sometimes almost makes me tempted to drive the 4 hours to PartsKing's dealership!!  

To be fair, they've not had any major muckups on the service so far (Although many minor ones); I've just learned not to give them anything more taxing than that, or try to buy parts in the case of the Jemca one!