Low Speed Scraping Sound.... need help VERY STRANGE
 

I've got a 1990 Miata and its making a metal on metal scraping sound from the front drivers side at low speeds 25-30 and on decel from those speeds while in neutral. Braking sometimes affects the sound and can sometimes induce it.

Driving over smooth bumps or hills will sometimes cause an increase in noise.

At first I thought it was simply a rock stuck in the brake shield but they are clean. My next thought was a front hub so that was replaced with no change. i have tried swapping both the front rotors and pads (left to right side) one item at a time still with no change.

At this point I figured it had to be the caliper dragging so it was also replaced.

As a last resort I tried swapping wheels with no change...

I am open to absolutely ANY input from ANYONE! Someone please sweet F*!@$ jesus!

Did you replace the bearings with the new hub?

Yes the bearing was replaced. It was an entire assembly.

Check all suspension bolts and control arm bushings too.

Everything was nice and snug, the bushings have some wear but dont look as bad as i'd expect 240k miles on what i assume are OEM bushings (just recently got the car) but nothing too bad.

Tied to vehicle speed? Might look for something falling down or blowing against the tire. I have had that happen a couple times with a liner/cover and thought the truck was coming apart. Would think it obvious, but have had some blow bad pretty far at speed. just a shot in the dark for ya.

The other thing might be a bearing in a accessory? or a pulley rubbing something.

jack car up, spin wheel. get a couple feet of vacuum hose and stick one end in your ear and the other end various places with the wheel spinning to see if you can pinpoint the sound.

Its wheel speed based, independent of gear. there really isnt anything in that area of his car that would fall down, or bow into contact at those speeds, let alone any other speed.

Y8's great idea, but with the car jacked up, we cannot replicate the noise.

yeah, something rubbing out there was slim. Bearing like others said is most common. Brake pad squealer maybe? Pads? sounds different than you described but... Might pull the the caliper and look for tight clearance around the rotor. And your backplate clearance. If there is any movement in the bearing assembly it might shift just enough under load to cause your problem.

Jack the car up and put a jack stand under the control arm and gently lower the car to compress the suspension and then turn the wheel?

OP - re-read your original post. Appears you covered the bases pretty well. Going to be a tuff one. Any luck yet?

I had something just like this recently. Turned out to be the brake shield was slightly bent, probably from when I did a lot of suspension work over the winter. I went through the trouble of switching out brake pads and clips/hardware, but no luck. Then I decided to give the brake shield a little more clearance just to be sure, even though it didn't appear to be rubbing when moving the wheel with the car on jack stands. I wedged a screwdriver in between the rotor and shield to bend it out just a couple more mm all around (I think underneath is where my problem was). I haven't heard the sound since.

Don't know if this is your problem since you say you already checked the brake shield, but if you haven't tried bending it just a touch, it might be worth it since it's quick and easy.

The ironic thing is that off all the things we tried. A 0-90 pull down the onramp and highway ended up fixing it :dunno: Oh well, its fixed! lol