[DFW_Muscle]

Has anyone experienced increase in NVH from installing aftermarket suspension components / bushings? I have a relatively small...but annoying high frequency vibration that I am interested in reversing.

I installed BMR front and rear swaybar endlinks, rear lower trailing arm (non-adjustable with poly bushing) and rear cradle lockout inserts (BK063).

The NVH is felt as a vibration throughout the entire car (seats, panels, mirrors etc) as the car is moving. It does not seem to be speed dependent, remains relatively constant at all speeds over ~20mph. And before it's suggested, it is not wheel / tire / alignment related, as all of those have been replaced as part of initial diagnosis.

I am not sure if the endlinks would have any NVH effect or not?
I would think the trailing arms could...since they are directly connected to the chassis with poly bushings.
I am hoping it's not the rear cradle lockout as that is one item that makes a significant improvement, and, I haven't seen others complain of a NVH issue resulting from it.

Thanks in advance for any insight.

[arpad_m]

Unless you got defective parts, I think the rear cradle lockout kit (BK063) can be eliminated, as it had zero impact on NVH with my car, or at least less than what I am able to distinguish.

Granted, my car is a 2SS, but both the kit and the suspension components it mounts into are the same as far as I know.

[Scargoes]

Do you have chassis ears? They could help pin down a location.
What kind of vibration is it, steady state or cyclical? How does it change with speed? What about throttle, or brake application? Steering input? What kind of road surface are you noticing it on the most? Did you change anything else on the car at the same time, like tires or wheels?

[DFW_Muscle]

Originally Posted by arpad_m

Unless you got defective parts, I think the rear cradle lockout kit (BK063) can be eliminated, as it had zero impact on NVH with my car, or at least less than what I am able to distinguish.

Granted, my car is a 2SS, but both the kit and the suspension components it mounts into are the same as far as I know.

I tend to agree with that. I haven't heard of others complaining of any NVH from the cradle lockout alone.

Originally Posted by Scargoes

Do you have chassis ears? They could help pin down a location.
What kind of vibration is it, steady state or cyclical? How does it change with speed? What about throttle, or brake application? Steering input? What kind of road surface are you noticing it on the most? Did you change anything else on the car at the same time, like tires or wheels?

No on the chassis ears.

Steady state, unrelated to engine RPM or vehicle speed. Anything over about 20 mph and I can feel it. It's partially masked when on rough roads as I obviously am feeling more input from the road surface than anything else, however, on smooth roads I can still feel it. I got rid of the stock GY's and now have Michelin PS4S thinking the tires may have been the issue. Didn't change. I'm honestly hoping it is the lower trailing arms, may swap back to the stock ones and see if it changes.

[Scargoes]

I would check the rear wheel balance and make sure when it's mounted on the car that it is done in the proper sequence with a clean mating surface. A friend just had the same problem on his S550. Brand new wheels and tires installed with a few other chassis stiffening parts and he developed a vibration like you describe.

[Msquared]

If it were the tires, it would probably come and go within a certain speed range. If it's constant in both volume and pitch, that leads me to think it's something at the transmission for forward of that, since everything after the tailshaft varies its rpm with road speed. The cradle bushings are intended to isolate the chassis from NVH form the rear gear and driveshafts, so you could possibly have increased that with the lockout kit. But most people don't report any changes in NVH with that mod. I'd tell you that a poly bushing anywhere in the rear suspension links is a bad idea anyway because they introduce bind. So if I were you I'd put the stock trailing links back in and see if that solves it.

[DFW_Muscle]

Originally Posted by Scargoes

I would check the rear wheel balance and make sure when it's mounted on the car that it is done in the proper sequence with a clean mating surface. A friend just had the same problem on his S550. Brand new wheels and tires installed with a few other chassis stiffening parts and he developed a vibration like you describe.

I am highly confident it is not wheel or tire related. Those have all been changed, balanced, rebalanced, rotated, remounted etc etc.

Originally Posted by Msquared

If it were the tires, it would probably come and go within a certain speed range. If it's constant in both volume and pitch, that leads me to think it's something at the transmission for forward of that, since everything after the tailshaft varies its rpm with road speed. The cradle bushings are intended to isolate the chassis from NVH form the rear gear and driveshafts, so you could possibly have increased that with the lockout kit. But most people don't report any changes in NVH with that mod. I'd tell you that a poly bushing anywhere in the rear suspension links is a bad idea anyway because they introduce bind. So if I were you I'd put the stock trailing links back in and see if that solves it.

I am planning on doing that this weekend and see if it solves it. Oddly, I haven't seen or heard any feedback from folks running these lower trailing arms.

[Scargoes]

Originally Posted by DFW_Muscle

I am highly confident it is not wheel or tire related. Those have all been changed, balanced, rebalanced, rotated, remounted etc etc.

It was just an idea. As I said , my friend had a very slight steady vibration from 30 to 100+ that freaked him out. They measured the wheels on the balancer and it showed the weight was off. The marked the position of the weight and the total weight added then stripped the weights off. When they did the balance, the total weight was the same but the original installer had the weights clocked 15-20* off. Essentially, instead of putting the weight center on the mark, they put the weight edge on the mark.

Another thought is that you are more in tune to some NVH items. I used to not be, but after my last two jobs working in vehicle testing for manufacturers I have picked up on many of these things. To me, I noticed a huge change in NVH when I installed new wheels that were 7.5lbs lighter at each corner. I noticed another huge change in NVH after installing camber plates. Sometimes it really bugs me and I consider taking the camber plates back off.

[Stephen12ZL1]

NVH not affected by my lockout and I have the differential lockout (front bolt locations) as well. With the rear seat delete, it is noisier for sure.