4 replies to this topic

[J Blair]

We took the new car on its first road trip this weekend, doing over 500 highway miles (all with the top up!) and we heard a noise that we did not hear at test drive that I would characterize as a “knocking” (like someone knocking once or twice on on the back fender). I first heard this knocking noise on Friday when we were stopped at an exit ramp and then turned right to go find a gas station. The pavement was deeply rutted and when I turned right, (thanks to the lovely pavement) the driver's side of the car moved up and down while the passengers side did not (pavement on the passenger's side was more smooth). The knokcing occurred going over the first couple of ruts and my first thought was a bad stut as the noise seemed to conincide with the up and down force on the suspension.

However, if all 4 wheels hit the same bump (like a raised expansion joint in the road), the roof is quiet and we also heard the noise on the passenger’s rear side as well (when the uneven pavement is on that side of the car).

I don’t know much about physics but it seems to me that when there is more force (or torquing) on one side of the car than the other, this knocking sound is the result of the roof flexing to compensate. In the case of the rough pavement, if it causes the driver's side to move more than the passenger's side then the noise is on the drivers side rear. If the opposite is true then the noise is on the passenger's side.

We have never heard any such noise when driving with the top down - regardless of the speed or pavement quality.

Is this normal of do I take it in to the dealer?

Thanks for your advice!

[downunder_slangin]

Hi mate, take it to the dealer under warranty and get them to check but it prolly is just the normal sound, from what i've seen on the slightly earlier model they can be noisy. I was advised to stay away from them, other than that they are sexy as hell in my opinion. Hope you stay on the forum, there's alot to learn.

[VTT5]

Your diagnosis sounds right -- chassis flex causing the roof to make some noise. That's a common issue with convertibles, since there's no fixed roof to help control body flex. Don't know if anyone offers chassis bracing for the P1 models which could help minimize it.

[FCPGroton]

Could it be possible that your just hearing the noise with the Top up? Some 2011 C70's came with sway bar link nuts loose, There's a bulletin out for it. Just check and re-torque the Rear sway bar link nuts. This could be your problem.

[smokin' T5M]

Common adjustment to the rear panel for the convertible top. Hope it all worked out well for ya since this post is about 1.5 yrs to late