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Cruise control braking

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Old 05-23-2014, 07:11 PM   #1
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Default Cruise control braking

Going down a hill, if the cruise is on, it applies the brakes. I can't stand this. Is there a way to disable cruise control braking?
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Old 05-23-2014, 08:38 PM   #2
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I don't think it is applying brakes but rather engine braking alone.
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Old 05-24-2014, 01:10 AM   #3
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I have experienced this as well. I can't say with certainty that the brakes are applied, but it sure feels like it, and I have noticed the brake lights come on as well. No idea how to disable it, although that would defeat the purpose of having cruise control.
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Old 05-24-2014, 04:12 AM   #4
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Brakes definately applied, you can see the brake lights go on at night. Would be nice to be able to turn that off with VCDS. I asked them years ago about it and they knew nothing about it back them. I toggle the cruise off on the downhills to save my brakes. Our 2008 does not apply the brakes.
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Old 05-24-2014, 07:13 AM   #5
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Quote:
Originally Posted by rdA4WtQ5 View Post
Brakes definately applied, you can see the brake lights go on at night. Would be nice to be able to turn that off with VCDS. I asked them years ago about it and they knew nothing about it back them. I toggle the cruise off on the downhills to save my brakes. Our 2008 does not apply the brakes.
Since I have a 011' mine may not come on.
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Old 05-24-2014, 08:31 AM   #6
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From the 2013 Owners Manual page 95, "the speed is kept constant by modifying engine power or through an active brake intervention".
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Old 05-24-2014, 08:50 AM   #7
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Default It does use car's brakes; related aspects...

It uses the brakes too. My 2006 A8 w/ adaptive cruise is the same. So was my 2004 Toyota Sienna.

It will actually apply them fairly aggressively if another vehicle pulls into your lane in less than the pre set following distance. Or very rarely, on winding multilane freeways (like Interstate 80 in the CA Sierras) if it misreads a slow vehicle in a different lane as being in yours. Typically very good at tracking--better than my Toyota Sienna was--but in weird situations like changing radius curves it can't really perform the calculations correctly using a combination of the forward radar and the angle sensor. Where a curve tightens up it can misread a semi struggling up a grade in the tighter part of the curve in the slow/truck lane and can get on the brakes aggressively. Thus, a situation to avoid using it, or know the issue in sweeping multilane decreasing radius curves and be ready to disengage quickly or put foot on gas to override.

Meanwhile to OP's post, no known way I have heard of to turn off that element, nor have I seen that on other vehicles w/ adaptive. What I find you can do is to marginally bump the pre-set speed up if you want when coasting downhill, sometimes a few times, and then bring it back down once the downgrade is over. W/in the first few MPH of speed over the setting it doesn't immediately intervene w/ the brakes, and the added speed bump up timed correctly keeps it so without accelerating either. Once you do it a few times, you find the pattern w/out much hassle.
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Old 05-24-2014, 11:03 AM   #8
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I like the braking feature most of the time, but if I want to coast I just bump the cruise control stick forward to cancel and then pull it back to resume the cruise after I've coasted. The Q seems to be pretty forgiving with the resume speed, so I just resume the cruise within +/- 3 MPH of the set speed. I've driven a Toyota and a Buick that both go crazy if they aren't resumed on exactly the set speed. The Toyota would basically floor the accelerator if it was resumed from 1 MPH below the set speed.
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Old 05-24-2014, 06:45 PM   #9
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I really dislike this "feature" and I hope someone figures out a way to disable it.
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Old 05-25-2014, 06:53 AM   #10
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You do realize that the purpose of cruise control is to control/maintain a single, driver determined speed, right? Well, gravity and going downhill tends to cause the vehicle to speed up, above that set speed. Brakes are the only way to fix that issue. If you're not on cruise control you can see the hill coming and lift in advance to maintain speed. I'm sure some day that sort of "smart car" will exist, but until then you're gonna have to either turn the CC off or raise the speed a bit on the hill to allow the car to coast and the computer not to see a speed that is out of the allowable range.
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Old 05-25-2014, 09:52 AM   #11
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Quote:
Originally Posted by gtwagon941 View Post
You do realize that the purpose of cruise control is to control/maintain a single, driver determined speed, right? Well, gravity and going downhill tends to cause the vehicle to speed up, above that set speed. Brakes are the only way to fix that issue. If you're not on cruise control you can see the hill coming and lift in advance to maintain speed. I'm sure some day that sort of "smart car" will exist, but until then you're gonna have to either turn the CC off or raise the speed a bit on the hill to allow the car to coast and the computer not to see a speed that is out of the allowable range.
I must admit I was a bit puzzled by the question as well - I just assumed the OP was saying he would prefer that the speed be reduced solely by engine braking versus the actual brakes.

Not sure I understand the concept of raising the cruise speed when going downhill, either .. I mean, if you want your max speed to be 80, raising it to 90 going downhill is ... going to make you go 90.

The best bet is to do what the one other member said - flick your cruise control off when going downhill, then pull to resume at the bottom.
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Old 05-25-2014, 10:41 AM   #12
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Default In the real world, these things are still comparative aero bricks...

It takes a very slight bump up on the cruise control on most downgrades at highway to get downhill momentum offset by aero drag. It's just another way/style to use the vehicle controls if desired. Relative to "older" vehicles, the 8 speed tranny means there is little engine drag, and even less if it has a "sailing function" (the Hybrid), so those are no longer particularly effective to slow the vehicle in som everyday downhill scenarios. Nor even the first gear (7th) stepdown or two as another potential highway technique; TDI's w/ the higher baseline diesel compression may have a bit more drivetrain effect though when off throttle.

Back to OP's question, from a safety perspective, I think the manufacturer would have to be out of their collective engineering minds to let speed go up meaningfully without volitional control by driver. Similarly, why you don't tend to find this stuff as a hack or mod somewhere in the electronics w/ VAG COM. The whole purpose of the adaptive overlay on old fashioned cruise is to deal w/ changing road and traffic conditions. Letting it go up unnecessarily by remote control invites blaming the statistically occasional accident on "the car" or the speeding ticket on the same.

When you actually "want it," it may also save an occasional ticket. Here in CA traversing the Sierra's a good number of times per year, I have become familiar w/ true downhill cruise effects (including areas steep and sustained enough to have runaway truck gravel offramps), Hybrid sailing function and the like. And no surprise that on I-80 through the Sierra's you predictably find more CHP hiding in the weeds, on overpasses (literally) and around ramps with their now laser and sometimes still radar either where the road opens up or along the downhill stretches.
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helpful cross reference to a C6 post with MMI and other TSB's that also cover D3 A8's.


Last edited by MP4.2+6.0; 05-25-2014 at 01:00 PM.
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Old 05-25-2014, 12:01 PM   #13
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I would rather have the brakes applied versus getting a speeding ticket :-)
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Old 05-25-2014, 03:05 PM   #14
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My SQ5 is different. I know about the braking. The A4 loaner did it, as does my wife's Toyota. The SQ5 however, works like no other cruise-control I've had before. I can set the speed to whatever I want while it is disengaged. Then, I can engage it with resume and it will match that speed quite gradually. I have dropped it 30 MPH quickly and did not notice any braking. If it did, it was very casual, unlike the Toyota and the A4.

An example would be cruising at 80 and about to come into a town that is posted 50. I can hold down the decel and it shows 79, 75, 70, 65, 60, 55, and I let off at 50. It slows down so gradually that I really don't think it uses the brakes. Same going down hill. BTW, I do NOT have the adaptive CC.
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Old 05-25-2014, 03:05 PM
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