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Discussion Starter · #1 ·
Hi, two questions related to the Smart Cruise Control:

- When the car slows, does it use the brake discs, or does it just ease off and let the recuperation slow it down? Assuming that if sharper slowing was required that it would definitely use the brakes, but wondered if engine braking was the first choice or not.
Why? Using brakes obviously wears them faster, and emits particulate matter into atmosphere, and of course no recuperation.

Second question;
Is SCC likely to drive more or less efficiently than me? Obviously you don't know how I drive, so I guess the question is: is it trying to drive efficiently, or does it just care about keeping up with the car in front?
 

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It mostly uses regen - not sure if it progresses to brakes if it needs to stop hard. SCC is probably more efficiient than you most of the time, though it can't anticipate thinks like cars moving into your lane which you can probably predict better and slow at a more appropriate rate
 

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If you look below the speed setting for the SCC, you will see the regen report pop up when the car is slowing down. Hard and soft deceleration is handled by regenerative braking. Braking which makes you jerk forward in your seat will be the normal brakes. I've found SCC acceleration to be much efficient than my right foot as there is a great temptaion to experience the instant torque if you do it yourself. :)
 

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You can definitely drive more efficiently manually than the SCC manages, but that requires active decision making, allowing speed to drop slightly on uphills and increase on downhills, choosing between coasting and braking, knowing that you won't hit the car in front as you will change lane when the car next to you has finished overtaking etc. SCC can't do those things it will prioritize maintaining speed if it doesn't detect an obstacle, it's not stupid enough to use the friction brakes for gentle slowing down though.
 

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You can change the speed of response of the CC in the settings. I imagine slower will be more efficient and faster less, but slower will also probably let bigger gaps occur in front which other cars will happily fill.
 

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2020 Hyundai Kona Premium SE 64kWh, Ceramic Blue
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My car brake pad now squeak a bit when used, so I can confirm that scc never seems to use them.

Incidentally I have found that stopping using the left paddle, outside scc, doesn't seem to use the brake pads either.

Putting foot on brake pedal at slow speeds does use the brake pads, as does reversing when controlling speed with foot on brake pedal.
 

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Hi, two questions related to the Smart Cruise Control:
1. When the car slows, does it use the brake discs, or does it just ease off and let the recuperation slow it down?
2. Is it trying to drive efficiently, or does it just care about keeping up with the car in front?
I'm fairly certain that SCC uses just the motor to control the velocity of the Kona right down to zero, just like the left paddle hold, but it's doing that for smoothness. It's not necessarily more efficient from an academic point of view as slow motor speeds require power going in to maintain precise control and hold a position.
 

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My car had its 30k service this week. Pads and discs only 20% worn. Further evidence that its the regen that does most of the braking. On the downside there is some minor corrosion on the rear discs. So whilst they might not wear out till past 100,000 miles they might need replacing before then due to corrosion.

The rear discs will never have to do as much work as the front so at risk of corrosion , I understand the VW ID3 has gone back to drum brakes on the rear, is that why?
 

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The rear discs will never have to do as much work as the front so at risk of corrosion , I understand the VW ID3 has gone back to drum brakes on the rear, is that why?
That is the most common theory, but including cost. Drum brakes are cheaper than disks.
 

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As is the case at similar speeds in Drive using the brake pedal.

There's already been one report of pad wear of "50% used after 33k miles" which IMO may be due to disk rust wearing them down.
 

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There's already been one report of pad wear of "50% used after 33k miles" which IMO may be due to disk rust wearing them down.
We had a Honda Civic (about 15 years ago) which we bought used from a Honda dealer, a couple of years old and with 4000 miles on it. Previous owner an 'older lady' it appeared.
Had to have 4 new discs within a year - lack of use (and probably kept outside) had rusted them down to minimum thickness.

It's not a new problem
139339
 

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Discussion Starter · #14 ·
Wow. Never even considered brake discs suffering because of lack of use. When my old diesel sat out during lockdown they rusted up, but scrubbed up bright the moment they were used again.

I love stopping on the left paddle - takes a bit of judgment to know exactly when to start pulling on it though, and I may have got it wrong a few times and had to dab the foot pedal at the last second!

Thanks all. Good discussion.
 

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2020 Kona EV, Red, 230.4MJ (64kWh) Premium SE (10.5kW OBC)
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I tend to pull the left paddle as soon as I know I'm likely to need to slow to a stop, before I move my right foot at all. I can then modulate the position of my foot on the right pedal to bring the car to a smooth halt exactly where I want it. Generally I find this is both smoother and more precise than lifting off the pedal completely and then judging when to pull on the paddle - YMMV of course.
 

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Braking while reversing always uses brake pads, probably to prevent rust. So I should probably do some spirited reversing every time and then :)
My drive is on a steep slope and I reverse off so using the disc brakes. That helps keep the discs clean but the lack of use off the car is most of the problem.
 

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That is the most common theory, but including cost. Drum brakes are cheaper than disks.
The VW accountants would no doubt have been looking at ways of mitigating the increased cost of the EV package. Having said that drum brakes on the back may prove to be the the optimal solution.
 
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