W209 Cruise Control - Cutting Out above 70mph

[ChrisCLK240]

Hi - I recently changed the wheels on my CLK W209 Facelift. I believe it is since then that I have had issues with the Cruise Control. It works fine up to around 75MPH but fails to hold the speed if set above this.
It almost as if the car is running at a slightly faster speed than the Cruise is set at, and it flashes, cancels itself and decellarates.
It been like it for sometime now, because as I am sure you can imagine I never need to exceed 70mph . Does the diagnostic system need to have the new wheel size programed into it ? If not can anyone suggest a cure ?
Also worth noting - before the wheel upgrade, if for instance I set the cruise to 70mph the speedo would read about 68/69mph. Now since the wheel upgrade it reads identicle to the cruise setting.

Many Thanks,
Chris.

 

[Mad4Coupes]

have you checked to see if the speed limiter is set around that speed?

 

[moonloops]

Are the new tyre sizes all correct to merc spec ?

 

[BlackC55]

This problem will be down to the tyre sizes

 

[Stratman]

If your tyres aren't the same size as before, especially if the fronts and rears are now different, the wheels will be rotating at different speeds on the road. The faster you go the bigger the difference, and eventually the CC will interpret this as loss of traction such as aquaplaning. As a safety measure the CC will then disengage.

 

[kwakdonut]

What are the tyres like? If the tread on one pair is much lower than the other, the CC will again cut-out above certain speeds

 

[Mercington]

You can enter the tyre info into the sat nav system somewhere I believe? Not sure if you can actually specify the sizes however, but I know you need to update it when replacing tyres.

Try that. (this assumes you have sat nav of course)....

 

[x332race]

Check you have reset "tyre pressure loss warning" (if fitted). Dont know if this affects cruise though.

 

[BTB 500]

What Stratman said.

Put your front/rear wheel & tyre details into the 'tyre size calculator' on this page (you have to scroll down a bit to get to it):

Car Bibles : The Wheel and Tyre Bible Page 3 of 4