Strange chassis vibration when I hit about 85mph
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Member
Joined: Oct 2007
Posts: 82
Likes: 7
2012 CLS63, 2009 Scud, 1978 930 Turbo
Strange chassis vibration when I hit about 85mph
Greetings to all. I have a 2016 CLS63S. Bone stock except an ECU flash.
I like the car, but I have noticed a strange vibration that only happens when I hit about 85mph. The vibration feels mechanical, or almost as though it is coming from the engine. However, if it is indeed engine related and I am feeling it at the 3K RPM's that my engine is turning in 7th gear when I am doing 85mph, wouldn't I also feel it at the same RPM's in lower gears? So that may be one strike against my theory that this is engine related.
I am confident that it has nothing to do with the balance or alignment of my front wheels, since I am not getting any kind of vibration in the steering wheel.
This leaves the alignment/balancing of my rear wheels as a possible culprit, especially since the vibration seems to be speed related. I have also gone to great lengths to make sure the tire pressure is dead nuts equal in both rear tires. I am running about 37psi in the rear tires btw.
One final theory: could my engine be misfiring or detonating? I remember the guy who flashed my car saying sometimes the flash will throw a check engine light, in which case he recommends swapping to a different spark plug with a different gap.
However, my car has never thrown a CEL and if it was detonating, wouldn't it do so at the same rpm in all gears? Again, I only have this problem when hitting about 85mph+.
Any armchair mechanics out there care to offer a theory here?!?!?!
Best regards to all. Stay safe out there!
Rob
I like the car, but I have noticed a strange vibration that only happens when I hit about 85mph. The vibration feels mechanical, or almost as though it is coming from the engine. However, if it is indeed engine related and I am feeling it at the 3K RPM's that my engine is turning in 7th gear when I am doing 85mph, wouldn't I also feel it at the same RPM's in lower gears? So that may be one strike against my theory that this is engine related.
I am confident that it has nothing to do with the balance or alignment of my front wheels, since I am not getting any kind of vibration in the steering wheel.
This leaves the alignment/balancing of my rear wheels as a possible culprit, especially since the vibration seems to be speed related. I have also gone to great lengths to make sure the tire pressure is dead nuts equal in both rear tires. I am running about 37psi in the rear tires btw.
One final theory: could my engine be misfiring or detonating? I remember the guy who flashed my car saying sometimes the flash will throw a check engine light, in which case he recommends swapping to a different spark plug with a different gap.
However, my car has never thrown a CEL and if it was detonating, wouldn't it do so at the same rpm in all gears? Again, I only have this problem when hitting about 85mph+.
Any armchair mechanics out there care to offer a theory here?!?!?!
Best regards to all. Stay safe out there!
Rob
Super Member
Joined: Jan 2007
Posts: 979
Likes: 38
From: South Africa
2018 E63s AMG (Current) 2011 CL63 AMG (Sold) 2005 CLS55 AMG (Sold) 2004 C32 AMG (Sold)
I would definitely go have all tyres / rims balanced and have alignment done. Relatively cheap for piece of mind before tackling engine/drivetrain hardware. I reckon it's in the wheels
