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Discussion Starter #1
When setting my cruise control, I find that it almost always sets the speed to 1 MPH higher than displayed on the speedometer. Example, I'm going a steady 50 MPH, press "Set-" and the cruise says it is set at 51 MPH.

Has anyone else noticed this (2017 LT)? I can get it to set at 50 but I have to accelerate VERY slowly and watch: 48, 49, 50 and press "Set" the instant it hits 50. Then it'll hold 50. But if I hold it at 50 for a few seconds and then press set, it'll invariably pick 51. It's like the cruise set is maybe a half MPH high... or it rounds "up" or something?

That said, it's pretty awesome that I have to nit pick at that level to find something to "complain" about. But hey... thought I'd ask. :)

Mike
 

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I suspect the system is based on a metric conversion and fractions are rounded up. That said, my 2011 Volt and my 2017 Bolt only rarely encounter this. It does happen, but rare. I suspect there is a range of slightly different speeds that will display as 50 mph (maybe 49.9-50.8 let's say) depending on EXACTLY how fast you are going, you'll see cruise choose 50 or 51.
 

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I suspect the system is based on a metric conversion and fractions are rounded up. That said, my 2011 Volt and my 2017 Bolt only rarely encounter this. It does happen, but rare. I suspect there is a range of slightly different speeds that will display as 50 mph (maybe 49.9-50.8 let's say) depending on EXACTLY how fast you are going, you'll see cruise choose 50 or 51.
Yes, everything in these vehicles is in correct :))) units and converted to US.
There is also wiggle in the cruise @ +/- 1km/h

So if you set it at 80km/h (49.7mph = 50 rounded on your display) you might also see 79km/h (49mph)
or if it was set at 81km/h (50.3mph = 50 rounded on your display) you might also see 82km/h (50.9mph = 51 rounded)
 

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Discussion Starter #4
If that's what is happening, I'd call that a "bug". I wouldn't care whether it uses kph internally and then converts: the same conversion should be used on the speedometer and the cruise control. So if you are going 82 Km/h and you set the cruise, both the speedometer and the cruise control should convert to 51 MPH. One shouldn't say 50 and the other 51.

Mike
 

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Yes, everything in these vehicles is in correct :))) units and converted to US.
There is also wiggle in the cruise @ +/- 1km/h
Yes, that's my recollection. My experience is every so often I'll see a 1 MPH difference in the cruise setting. Most of the time not. It doesn't mean much in the scheme of things. More of a small oddity, like using miles, inches, feet when the rest of the world has gone metric.

"Let's use archaic units of measure" as a policy has consequences. In this case cruise control anomalies. In other cases, a lost multi-million dollar Mars spacecraft when someone converts from one unit to another and creates a navigation error.

 

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If that's what is happening, I'd call that a "bug". I wouldn't care whether it uses kph internally and then converts: the same conversion should be used on the speedometer and the cruise control. So if you are going 82 Km/h and you set the cruise, both the speedometer and the cruise control should convert to 51 MPH. One shouldn't say 50 and the other 51.

Mike
If you read my explanation again, it is holding the same setpoint. But the system does not hold it on that number 100% of the time. It has some wiggle room for efficiency.
It just happens that sometimes that wiggle room results in rounding to the same number, and other times it rounds to the next one up.
If it was natively programmed in mph you'd see 49-51mph at any given time depending on the terrain you're on.
 

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You have entered the digital world and your OCD has been exposed. What would you have done with an analog speed display?

VIN # B0985
 

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Discussion Starter #8
If you read my explanation again, it is holding the same setpoint. But the system does not hold it on that number 100% of the time. It has some wiggle room for efficiency.
It just happens that sometimes that wiggle room results in rounding to the same number, and other times it rounds to the next one up.
If it was natively programmed in mph you'd see 49-51mph at any given time depending on the terrain you're on.
I understand it won't/can't hold an exact speed over different terrain over time. But we're talking about a readout of current speed in MPH and a setpoint in MPH. It's not rocket science (even for Nasa). ;) Km/h * 0.621371 = MPH. Always. It's not Km/h * 0.62 when displaying current speed and Km/h * 0.63 when setting the cruise value.

So if you are holding 50 MPH and set the cruise, it shouldn't still say 50 for current speed and "Cruise set to 51 MPH" right underneath it. Which is what is happening. Sometimes.

Mike
 

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Stop defending this problem. LOL

Mine does this, too, and all I can say is that it's an annoying issue that should not happen. My old Chrysler 300C had an amazing Mercedes-Benz cruise control (all metric) with a little stalk to the left of the steering wheel. I never had this issue with it. It's sloppy engineering; simple as that.

Also, the position of the CC buttons on the steering wheel requires an unnatural change of grip to use.

Don't get me wrong... I love my Volt, but this has been a bee in my bonnet since day 1.
 

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Note: Lightly tap the RESUME and it will climb 1 mph.
Lightly tap SET and it will drop 1 mph.
Push RESUME hard and it bumps 5 mph.
Push SET hard and it will set at your current speed.
So you can jump from a 55 to a 75 mph setting with 4 shots.
 

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As above. Don't lose sleep over it. Just press set when you're in the ballpark, then nudge it up or down until you've reached your desired speed.
 

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Discussion Starter #12
As above. Don't lose sleep over it. Just press set when you're in the ballpark, then nudge it up or down until you've reached your desired speed.
That's what I've been doing. I press set and when I see 50 up top and "Cruise set to 51" underneath it, I just press set again and the cruise changes down to 50. But that's just so much more effort to press it a second time. Plus I'm afraid I'll wear out the button prematurely. :D

Mike
 

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OMG. This is really a thing?

I bump mine up and down in 5mph increments. Since I drive mostly using ACC, my set point is 5 to 10mph above the speed limit. Somebody poking along at 50 (or 51) would start to invoke road rage unless we were in a 35mph speed zone.

We have some of ‘those people ‘ that drive 5mph under the speed limit in the center lane. Not pretty when dealing with commuters.

Don’t be the rock in the stream. Be the leaf.
 

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I understand it won't/can't hold an exact speed over different terrain over time. But we're talking about a readout of current speed in MPH and a setpoint in MPH. It's not rocket science (even for Nasa). ;) Km/h * 0.621371 = MPH. Always. It's not Km/h * 0.62 when displaying current speed and Km/h * 0.63 when setting the cruise value.

So if you are holding 50 MPH and set the cruise, it shouldn't still say 50 for current speed and "Cruise set to 51 MPH" right underneath it. Which is what is happening. Sometimes.

Mike
All I can tell you is this doesn't happen in metric. I'm not defending it, I'm trying to determine a reasonable mathematical scenario in which it happens.
If you've been holding at 50 and it still does that, I have no theory.
I'd understand if you were accelerating and it did that as there's a lag in the display where you might see 50 but actually be reading 51 behind the scenes. Of course, if it's only sometimes, this could still apply as your speed changes micro amounts in the time before the display updates. Is it "almost always", or "sometimes"? That makes a big difference in determining the cause behind the scenes.
Almost always suggests a systemic error, while sometimes suggests a situational circumstance.
 

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Mine does this, too, and all I can say is that it's an annoying issue that should not happen. My old Chrysler 300C had an amazing Mercedes-Benz cruise control (all metric) with a little stalk to the left of the steering wheel. I never had this issue with it. It's sloppy engineering; simple as that.
I think the MB implementation is horrible. I hate the stalk. Why should you have to take your hands off the wheel to control the cruise control? I'm not a big fan of many aspects of the Chevy ACC, but the ergonomics of the button configuration and position are spot on.
 

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That's what I've been doing. I press set and when I see 50 up top and "Cruise set to 51" underneath it, I just press set again and the cruise changes down to 50. But that's just so much more effort to press it a second time. Plus I'm afraid I'll wear out the button prematurely. :D

Mike
I have bad news for you. When you set the CC to 50, the car will continue to vary it's speed up and down around 50 depending on the terrain and power needs. You should take it into the dealer tell them the CC won't hold EXACTLY at 50 and see what they tell you :)

And while you're at it, let us know the next time you get a ticket for doing 51 in a 50 ;)
 

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When setting my cruise control, I find that it almost always sets the speed to 1 MPH higher than displayed on the speedometer. Example, I'm going a steady 50 MPH, press "Set-" and the cruise says it is set at 51 MPH.

Has anyone else noticed this (2017 LT)? I can get it to set at 50 but I have to accelerate VERY slowly and watch: 48, 49, 50 and press "Set" the instant it hits 50. Then it'll hold 50. But if I hold it at 50 for a few seconds and then press set, it'll invariably pick 51. It's like the cruise set is maybe a half MPH high... or it rounds "up" or something?
It'll tend to roll down if you're coasting while setting.

Mostly I don't even up caring about a MPH or two here and there. My sensitivity to speed is more "am I too close to the car in front?" than anything else, and I know very few cops are gonna care if you're going 57 in a 55 zone. A tap up or down adjusts by 1 MPH anyway, so if not-round numbers are irksome, it's easy to fix.
 

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Is it "almost always", or "sometimes"? That makes a big difference in determining the cause behind the scenes.
Almost always suggests a systemic error, while sometimes suggests a situational circumstance.
My experience is: sometimes.

That's why I think it's the micro speed differences within the range that are converted from metric and displayed as "50" that are at play here. Terrain, foot pressure, wind could all cause slight speed variations. Depending on when the Set button is pressed, you could be on the edge where the conversion drops you into the next MPH.

It's also possible that the speed display is using a few more or less decimal points than the cruise, both within GM's acceptable accuracy range, but yet not the same.

The cruise control system is likely widely used within GM (off the self). The Volt's speed display may have been built for the Volt by a different group. Again, both systems comply with whatever the +/- accuracy specs GM has, but it's the spread between the two system's +/- that can, at certain times, cause the resulting conversion calculation to bump the cruise display by 1 MPH. This would account for the fact that those using metric never see this issue. There is no conversion rounding up/down going on where the result is being exaggerated by the +/- accuracy range between tow systems.

I also see something similar with my tire pressure.

Even though my tire gauge reads 40 on all 4, a slight difference in what constitutes 40 results in 3 tires displaying as 40 in my TPMS and one displaying as 39. Two different systems with different sensitivities that occasionally have a crossover point difference.
 

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I think the MB implementation is horrible. I hate the stalk. Why should you have to take your hands off the wheel to control the cruise control? I'm not a big fan of many aspects of the Chevy ACC, but the ergonomics of the button configuration and position are spot on.
Maybe my fingers are longer, but on my 300 I could control the CC stalk while holding the wheel at 10 and 2 by just moving my middle finger (don't go there LOL). I loved it.

Perhaps I will get used to the GM buttons with time. I assume I will, and perhaps I'll be able to tune myself in to when to push the CC set button to get it just right.

On the positive side. electric car cruise control with the amazing torque is great. Going over the mountain passes it's like having that big Hemi 8 under the hood, but quieter. No downshifting in the steeps. No engine RPMs revving. Just a steady solid "go" from valley to pass. Amazing! How will I ever be able to go back to ICE again? Probably won't happen.
 
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