[jvelecky]

I have recently read many articles suggesting a relationship between the wrong tire size and a cruise control that kicks out at higher speeds. After a recent tire change I began having this issue around the 105 KPH mark. On checking my tires I discovered that my front tire size was 225/50r/16 NOT the recommended size of 205?55R/16. Before I start changing tires again is this the source of my cruise control problems. There was a great online tire comparison chart but since I need it I am unable to find it. Thanks.

 

[bryantmoll]

I have recently read many articles suggesting a relationship between the wrong tire size and a cruise control that kicks out at higher speeds. After a recent tire change I began having this issue around the 105 KPH mark. On checking my tires I discovered that my front tire size was 225/50r/16 NOT the recommended size of 205?55R/16. Before I start changing tires again is this the source of my cruise control problems. There was a great online tire comparison chart but since I need it I am unable to find it. Thanks.

In my humble opinion "not a Mercedes tech, just enthusiast" that said, you do realize the front wheel size compared to rear wheel size has only a width variance? I couldn't imagine a small hight variance would causing a partial failure. I would be interrogating the wheel sensors. ie: rear right sensor and front left, for a partial failure. Does the yellow triangle flash when the cruise control fails? Or any other indicators?

Sent from my Nexus 9 using Tapatalk

 

[jvelecky]

No sensor or warning lights of any kind. The cruise works flawlessly at speeds under 105KPH, even when going up a steep hill. Going down however when the speed reaches that threshold of 105 then cuts out. The speed sensors were next on my list. Thanks

 

[jvelecky]

Someone was kind enough to point me to an online tire comparison table and just by using the profile of 50 for the front, I was at a -3.17% variance which I believe is too much for cruise to work properly. Then I used the 205/55/16 numbers and had only a .08% variance. I never would have figured that a little change in the profile of a tire can make such a difference.

Tire Size Calculator - Tire & Wheel Plus Sizing

 

[bryantmoll]

I'm quickly arriving to the same conclusion. A partial failure of one or both wheel sensors would trip the ESP warning lamp. My car has the 722.6 electronic gear box which has a speed sensor internally, I just don't know if the cruise operates in relation to that sensor or what!? In all honesty, I've never heard of a circumstances like this happening. Let's hope others can chime in on this topic.

Sent from my Nexus 9 using Tapatalk