Cruise Control speed setting 1 mph out.

[st3v3cx-3]

Perhaps it's to do with the HUD now needing the SD card navigation data in order to pick up and display the speed limit when a suitable roadside speed limit sign isn't available or recognised by the appropriate camera?

[alanandlyn]

The difference in readings is probably due to the variation in tyre circumference which will be affected by tyre wear and tyre pressure.

Mine has been 1mph out since it was brand new and has never changed in nearly 3 years, so I don't think this is true at all. I just live with it.

[santa]

The difference in readings is probably due to the variation in tyre circumference which will be affected by tyre wear and tyre pressure.

Mine has been 1mph out since it was brand new and has never changed in nearly 3 years, so I don't think this is true at all. I just live with it.

Can You change from mph to kmh and see if that fixes it?
Maybe it's something in the conversion going wrong.

[Handy Andy]

The difference in readings is probably due to the variation in tyre circumference which will be affected by tyre wear and tyre pressure.

Mine has been 1mph out since it was brand new and has never changed in nearly 3 years, so I don't think this is true at all. I just live with it.

Can You change from mph to kmh and see if that fixes it?
Maybe it's something in the conversion going wrong.

Tried that, no difference, I treat it as a feature now.

[SoonerV8]

My CC also sets higher, so I set it lower, it also creeps higher when going down hill. The speed limit display must always favour GPS information, which as we know is often not that up to date. When another limit has been set on a stretch of road, the old limit still shows, obviously the camera information (if indeed there is any) is ignored.

[santa]

Mine has been 1mph out since it was brand new and has never changed in nearly 3 years, so I don't think this is true at all. I just live with it.

Can You change from mph to kmh and see if that fixes it?
Maybe it's something in the conversion going wrong.

Tried that, no difference, I treat it as a feature now.

That's so weird.
Mine has always been spot on, except when going downhill or uphill, then it can go over or under by 1-3 kmh, until it hits the mark gain.
And I don't envy that feature, by the way

[Strangways]

Santa, I don't know what spec the Optimum is, but I would guess it has 16" wheels. All the people who say there HUD is showing 1mph faster have 18" wheels. The difference in the overall circumference is 1" bigger on an 18" wheel. If the speedo has been based on revolutions of the 16" wheel then the car will actually be travelling faster if it is on 18" wheels. 70 mph on the 16" wheels will equate to 70.8 mph on 18" wheels.
Has that solved it or did I guess wrong on your wheel size?

[st3v3cx-3]

Can You change from mph to kmh and see if that fixes it?
Maybe it's something in the conversion going wrong.

Tried that, no difference, I treat it as a feature now.

That's so weird.
Mine has always been spot on, except when going downhill or uphill, then it can go over or under by 1-3 kmh, until it hits the mark gain.
And I don't envy that feature, by the way

That is my experience too. I can't see how it could keep the mph exactly on the cruise control setting when there is a slight downhill or uphill. When the hill is steeper mine will often go 2 or even 3 mph over or under depending on the steepness until the cruise kicks in and slowly brings the mph back in line with the cruise control setting. My wheels are the 18" ones.

[santa]

Santa, I don't know what spec the Optimum is, but I would guess it has 16" wheels. All the people who say there HUD is showing 1mph faster have 18" wheels. The difference in the overall circumference is 1" bigger on an 18" wheel. If the speedo has been based on revolutions of the 16" wheel then the car will actually be travelling faster if it is on 18" wheels. 70 mph on the 16" wheels will equate to 70.8 mph on 18" wheels.
Has that solved it or did I guess wrong on your wheel size?

The Optimum here in Scandinavia is the top spec with 18" wheels and there is No difference with My 16" winter wheels.
My Cruise control is spot on, only going up and down hills, will the speedo go over or under the set speed and pretty quickly find the correct speed again.
That's why I thought it might be the miles conversion that does it.
And the speedo is quite precise compared to the gps: 80 kmh on GPS is 82 kmh on the speedo/HUD on 18" wheels, on My 16" wheels it's more like 83/84 on speedo is 80 kmh on GPS.

[Strangways]

Okay so I guessed wrong but it does make sense for those who are getting a higher reading on the HUD.
For those of you with 18" wheels and matching readings I suggest you check your tyre pressures