Random braking

[drmotorsport]

Having racked up a few more motorway miles that usual recently i've observed what seems to be a strange new phenomenon. Driver/cars brakelights showing for no apparent reason. All appear to be newer cars both ICE and leccy powered, not a specific manufacturer and even seems to occur when they badly attempt to overtake someone, I thought it may be some be some kinda cruse control thing, but for the love of god it makes people look like incompetent morons trundling along riding the brake pedal. Any ideas?

[Hoofy]

Yes, no idea why. Not just on motorways but empty, straight urban roads. Just lift off the throttle ffs. Maybe they're on their phones.

[Gericho]

Isn't it due to the new one-pedal driving? When you lift off the accelerator the car automatically brakes.

[AmosMoses]

Gericho said:

Isn't it due to the new one-pedal driving? When you lift off the accelerator the car automatically brakes.

Yep its this the majority of the time.

[SmithCorona]

I think it's adaptive cruise tbh, many of them aren't predictive so seem to surge then brake.

Some systems are much better than others.

[Hoofy]

Learn something new everyday. Makes the driver look like an idiot.

[xx99xx]

This is a bit old and may have changed since, but helps to explain why/when brake lights come on under regeneration.



Source: https://unece.org/fileadmin/DAM/trans/main/wp29/wp...

[Roger Irrelevant]

SmithCorona said:

I think it's adaptive cruise tbh, many of them aren't predictive so seem to surge then brake.

Some systems are much better than others.

I have to say the few times I've experienced adaptive cruise control it did do an uncanny job of replicating the (st) driving of my father in-law. After ten minutes as his passenger I'm usually chewing the internal fixings with frustration and suppressing the urge to shout FFS MR MAGOO JUST LOOK FURTHER THAN FIVE METRES IN FRONT OF YOU AND YOU WON'T NEED TO BRAKE EVERY TEN SECONDS FOR NO EARTHLY REASON. I haven't been in a car with ACC for a while though so newer systems are likely much better.

[mac96]

Another possibility is hybrids; our X3 has no engine braking initially because as you take your foot off the gas it just maintains speed on the electric motor. You have to tap the brake to tell it you want to cut electric power as well as the ice.

[Whataguy]

Quite a few normal petrol VW's I've driven have eco coasting on as default with their auto gearboxes.

Lift off and you have no engine braking until you touch the brake, when the gearbox reconnects and you do.

It means you have to constantly dab the brake just to get normal engine braking - unless you drive all the time in sport mode, which disables the system.

Fine idea on paper, except it's not that great to drive and doesn't actually save fuel - I could get 1mpg better in sport mode than in normal drive mode with the eco coasting function.

[Vipers]

SmithCorona said:

I think it's adaptive cruise tbh, many of them aren't predictive so seem to surge then brake.

Some systems are much better than others.

From what my guru tells me, some cars so, and some dont. But I often wondered why some cars seem to brake on open roads.

[croyde]

Before all these new fangled machines it was usually autos and idiots.

I was driving on holiday up in the mountains, almost everyone on the road were in tiny manual hire cars, including me.

The speed limit was only 50kmh and you just did not need the brakes on the numerous curves, especially going up but that didn't stop a lot of the others constantly lighting up their brake lights and in some cases slowing to walking pace.......for every feking corner.

[Pica-Pica]

Whataguy said:

Quite a few normal petrol VW's I've driven have eco coasting on as default with their auto gearboxes.

Lift off and you have no engine braking until you touch the brake, when the gearbox reconnects and you do.

It means you have to constantly dab the brake just to get normal engine braking - unless you drive all the time in sport mode, which disables the system.

Fine idea on paper, except it's not that great to drive and doesn't actually save fuel - I could get 1mpg better in sport mode than in normal drive mode with the eco coasting function.

My 335d has that, when in eco-mode. It is on by default, but it annoys me, I prefer to have engine braking. Luckily, you can switch it off (and it will stay off, that is it does not come on again when you restart). The problem with default settings, people are not sufficiently interested to read the handbook and understand all these switchable modes of operation.

[Zarco]

mac96 said:

Another possibility is hybrids; our X3 has no engine braking initially because as you take your foot off the gas it just maintains speed on the electric motor. You have to tap the brake to tell it you want to cut electric power as well as the ice.

Our 2021 X3 PHEV doesn't act like that. It does vary the amount of regeneration if you lift off and coast. It's much more pronounced around town /sub 30mph where you can feel it slowing the car more, than on the motorway. It never maintains speed.

Perhaps there are different settings. Eco vs normal or whatever.

[Pica-Pica]

Zarco said:

mac96 said:

Another possibility is hybrids; our X3 has no engine braking initially because as you take your foot off the gas it just maintains speed on the electric motor. You have to tap the brake to tell it you want to cut electric power as well as the ice.

Our 2021 X3 PHEV doesn't act like that. It does vary the amount of regeneration if you lift off and coast. It's much more pronounced around town /sub 30mph where you can feel it slowing the car more, than on the motorway. It never maintains speed.

Perhaps there are different settings. Eco vs normal or whatever.

Some hybrids have a brake (B) mode just rear of drive (D) mode, and you can use regenerative braking (so you can drive in D or B). Honda iMMD e-HEV have this, and when I drove a Jazz with it on, it was quite effective, slightly stronger than ‘engine braking’ but not aggressive. Useful for town or long downhills.

[Sigmamark7]

My BMW 340i adaptive cruise control will do this if it thinks that I’m too close to the car in front. The faster I’m going, the greater the distance it wants before banging the brakes on. I don’t believe that I’m guilty of getting too close to the car in front before moving out to overtake, but my car thinks I am!

[garypotter]

agreed with the above re Hybrid, a colleague had one of the first outlanders and every time he stopped accelerating the car would recharge the battery like putting the brake on but NO brake lights, this was then updated approx 6m into ownership so some do out on the brake light even tho not braking

tbh numpty friver s on the motorway love sitting in the middle lane braking for no reason, must be time that after passing a test it should be mandatory to have a M/way lesson?

[Panamax]

One of my cars has a form of cruise control which drives me nuts.
Steady speed cruising - fine.
Accelerate and drive more quickly for a while - fine. But lift off the throttle and the car will appliy the brakes to get back to the previously set cruise speed rather than just coasting down - infuriating.
Find yourself going down hill and the car applies the brakes - infuriating.

Having said that, some drivers seem to have a habit of touching the brake from time to time with absolutely no necessity. It's particularly noticeable at night when you're behind a car that brakes every time a car comes the other way. I think it must be a "confidence" thing.

[xx99xx]

Whataguy said:

Quite a few normal petrol VW's I've driven have eco coasting on as default with their auto gearboxes.

Lift off and you have no engine braking until you touch the brake, when the gearbox reconnects and you do.

It means you have to constantly dab the brake just to get normal engine braking - unless you drive all the time in sport mode, which disables the system.

Fine idea on paper, except it's not that great to drive and doesn't actually save fuel - I could get 1mpg better in sport mode than in normal drive mode with the eco coasting function.

Worked great for me, once you get used to it. Lift off in plenty of time and it will maintain momentum on a flat road for quite a while. Surely coasting at zero consumption is more efficient than accelerating until the point of needing to brake?

[Robertb]

SmithCorona said:

I think it's adaptive cruise tbh, many of them aren't predictive so seem to surge then brake.

Some systems are much better than others.

The problem is that no system as far as I know can see much further ahead than the cars in front and adjacent.

The distronic in my CLS is brilliant in 95% of situations but you still have to pay attention and react for best results.