Hi I recently purchased the "cheap" copy of 3M backing plate some Meguiars M80 and I started polishing my car 
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Elite Car Care - Elite 123mm Ultra Soft M14 Backing Plate
But I have experienced something strange. I spread the product at 600 rpm and then rev it up to 1500 to work it. After the first or second pass (at 1500) many times I get some strange noise and the rotary vibrate a lot.
Check the video for more info. The vibrate noise starts at 12 to 11 sec of the video. (I edit the video so it is small enough for everyone to see it quickly)
and another video
I get this vibrate-noise to both cars I have made (a PUG 106 and a MG) even I use a meguiars polishing pad (PUG) or a meguiars finishing pad (MG). I never get the vibrate when I use my smaller 4" pads (different backing plate)
Trying to stop the vibrate I found out that if I tilt the rotary a little everything gets better.
After priming the pad I use two drops of polish (this is the max amount, most of the times the drops are a little smaller)
P.S. even when the rotary vibrates (and do nothing to stop it (even it creeps me out) I get decent results.
unpolished
polished
.Elite Car Care - Elite 123mm Ultra Soft M14 Backing Plate
But I have experienced something strange. I spread the product at 600 rpm and then rev it up to 1500 to work it. After the first or second pass (at 1500) many times I get some strange noise and the rotary vibrate a lot.
Check the video for more info. The vibrate noise starts at 12 to 11 sec of the video. (I edit the video so it is small enough for everyone to see it quickly)
and another video
I get this vibrate-noise to both cars I have made (a PUG 106 and a MG) even I use a meguiars polishing pad (PUG) or a meguiars finishing pad (MG). I never get the vibrate when I use my smaller 4" pads (different backing plate)
Trying to stop the vibrate I found out that if I tilt the rotary a little everything gets better.
After priming the pad I use two drops of polish (this is the max amount, most of the times the drops are a little smaller)
P.S. even when the rotary vibrates (and do nothing to stop it (even it creeps me out) I get decent results.
unpolished
polished