Someone mentioned having a flat spot on a tire would cause such a sound. Sounds logical to me.

Another note:

When I was doing some research on wheel fitment. I followed a link to hubcentric rings. Check if your wheel fits snugly on the hub. If there is some play I think it would cause a vibration you can feel.

 

The wheels and tires are A-1. Had it on a lift today and spun them. Nice. Easier since they're so clean.
When I bought the spacers, I put them on a lathe and checked tham with a dial indicator. <.001" eccentricity and flatness. Tight fit in the wheels and snug over the hubs too. I did think ahead, for once!

Keep thinkin'!

 

I was referring to the hub center bore. I checked the stock size and its 66.5mm in diameter. Since we have the same wheels I searched the spec on those and it is a 72.6mm in diameter. (I would call the company to make sure)

Since you have hub centric spacers the lip should fit snugly within the wheel. Since you have a 6.1mm difference there is some play.

 

I'm sorry, but I think your research is in error. The Stern ST-1's come with a true Mercedes fitment -5 X 112, 66.56 mm center bore. When I bought them, Elites-Wholesale.com listed them as having a 73.1 mm (BMW) center bore. I even bought the poly fiber centering rings at the same time anticipating this issue. All for naught as it turned out. I also bought the Mercedes fitment hub-centric spacers to sandwich this all together. Those were the only bits I needed. And they have, as I said, a very nice, snug fit to the ID of the wheels. And a nice snug fit over the hub on the car.

Please don't take this response the wrong way!

I'm a machinist and have been building machinery for 30 years.

Keep thinkin'!

I'm at a loss. I just wish someone else could drive my car for 5 minutes. They would probably say "It's this, idiot!"

 

Max,

I occasionally have a similar sound and it is odd because it is not in line with the rotation of the wheels. I also did the coast at 70 in neutral and it does that uneven sound. I am assuming that It may be an alignment issue but like your car it tracks right and straight. THe only difference are my tires which are needing replacement for the fronts.

I am not sure but it definitely is an odd vibration that is not easily defined. I figured that with new rubber my problems may be solved but then again we seem to have a similar issue.

I have not figured anything out as of yet.

THanks.

 

Re-reading my response I understand now. Your right the INSIDE diameter is a mercedes fit. The OUTSIDE diameter is what I was stuck on.

Back to the drawing board...

 

The latest step I've taken, while helping another member with some meaurements of the spacer mods for the front grease caps, was to really clean and inspect the fitment of the aftermarket spacers. In the 8 (?) months since installation there has been some electrolysis between the zinc coating of the rotors and the aluminum of the spacers. I removed the crud and took the spacers to my lab for measurement. I used a granite surface plate and a height guage to determine the uniformity of the thickness. It showed <.0003" uniformity on all 4.
While removing them from the front hubs, I felt that they were VERY tight on the grease caps. The spacers need to be machined a little bit to accomodate the larger diameter of these. I did the machining 8 months ago, but just handed them to the tire installer for the assembly job. I wish I had done the work. It seemed that they were not fully flat on the hub face. And when I used a feeler guage, I found a .005" space behind them both. They were hanging up on the grease caps and were being pulled down flat by the lug bolts when the wheels were installed. I don't know yet if this is the problem, but I'll give it a test drive when the weather clears. I just detailed it for the Dragon GTG and don't want to waste the shine just for a test drive!

Thanks everyone for the ideas and suggestions!

Keep 'em coming-I'm not out of the woods yet.

BTW-I coated the mating surfaces with LPS 3. A waxy spray-on grease for corrosion control. Good stuff.

 

Ok, I finished with the inspection and cleaning. After a short test drive on a road surface I have always had the "thrum" on, it appears to be fixed. The front spacers have to be machined to fit the OD of the grease cap and I made them too tight. This prevented the spacer from fully seating on the rotor face/contact surface. The tightening of the lug bolts pulled them down to make contact, but it seems to have done so by crowning the spacers. I also found that the last place to balance all 4 wheels, a "performance shop" did a really pi$$-poor job of torquing the lugs. All over the map.
In essence I cleaned all of the mounting surfaces, shaved off a bunch of little burrs and rough spots and properly mounted and torqued the lugs.
I haven't really driven it far enough to make a solid conclusion, but one thing I re-confirmed:

If you want it done right, do it yourself.

I guess we'll see on the way to the Dragon Friday morning.

 

I have just noticed the same issue in my 2005. I wanted to try to track it down but it is a constant, rythmic vibration. It is felt in the driver seat and it doesn't increase with speed. I feel it mostly in 5th and 6th gear when cruising. I have 144K and I haven't done motor/trans mounts yet or the drive disks.

I did just change tires, I do have spacers, I have KYB shocks and Eibach springs. It's time to do the mounts and the disks anyway, but I was concerned that it might be a more serious problem, perhaps with the transmission. Also, I was concerned that it might be some wheel bearings? Do we grease and repack these, or just replace?

 

Ill be cleaning the spacers and re-torquing this week. I will also drive without spacers to see if seating is a culprit.

 

After doing this car feels amazing! no vibrations, no thrumming sound. A little rust and debris on the spacers and I re torqued my brake disks while I was there. There used to be a bit of a brake pulsation as well and that is gone too. Perhaps one of my rotors was not tightened down all the way and created all of the vibrations, thrumming, and pulsing I was experiencing. Car feels like a $1000000.

After 2 days of driving, I had a little vibration back at the steering wheel, I am wondering if my cheap aftermarket spacers came with bolts that are not holding their torque spec over time. Maybe some thread lock or higher quality bolts might do the trick.

 

So, I still hunt this noise from time to time.

I notice a rythmic vibration that can be seen in the side view mirrors. It's alway with the top up and it's always when it's windy.

I thought maybe the fin needed to be locked down because it wasn't all that snug, but I think my top is contributing to this sensation I can't seem to really track down.

Any thoughts on the top being a source of vibration over time, shaking the entire frame at 70mph plus.

 

Curious if a failing motor mount could cause a rhythmic vibration that can't be linked directly to the suspension. Also, my custom exhaust has not resonator, I wonder if the exhaust pipe needs to be anchored down to keep from vibrating under the car at certain speeds now.