I had all tires replaced two months ago on my 06 CLK350 with new old stock OEM 18" CLK wheels. I think these wheels were CLK dealer upgrades. Nice.

Anyway, about every other 20 minutes of actual driving I will brake and hear a GRINDING sound that sounds exactly like I am grinding down a brake caliper.

Took it to the dealer three times. They heard the sound only once on a test drive. It is not the brakes. Plenty of pad left on the brakes.

What is this noise? It sounds related to the brakes. It only happened after the tires were changed.

Not sure what to do! Dealer says it could be a suspension spring?

Backing plate rubbing totor?

Or lug bolts that are slightly too long?

Lug bolts sound most logical to me. If so, the tire place owes me a new brake job... will have it checked out.

Not sure what the backplate rubbing is?

There is a shield on the inside of the rotor. Sometimes they get bent and rub the rotor

lug bolts would be my bet too. but i dont see how the tyre shop would owe you a new brake job for that. nothing to do with the brakes whatsoever. lug bolts dont even touch the brake pads or the discs itself.

Well the dealer has had the car three times and no satisfaction. I took an off ramp with a deep curve yesterday and braking while turning seems to trigger the problem. Then it seems to taper off the more I brake while wheels are straight?

Very strange.

i still say its the backing plate.
get the car off the ground and remove the tire and see if you can see anything, spin the tire and listen for it, also get someone in the car and repeat with putting slight pressure on brake and turning the steering

I had a similar issue in my car, every time i would turn my car i would hear ga grinding sound as if it was from the brakes, modulating the brake pedal would affect the sound. eventually a friend and I figured out it was the metal clips that hold the brake pad. I only buy OEM brake pads from the stealership and I was surprised that they would have a manufacturing defect like that. Anyway i went ahead and bought another set of brakes and compared the metal clips; the ones that were on my car were shorter and they were hitting the front discs causing a "brake pad" sound. just changed the clips and good to go. Dont know if it helps you out. But it was damn impossible to diagnose.