My passenger front wheel is making a "nails on a chalkboard" type squeak/squeal while driving, not while applying braking.
In other cars I've had stones lodged between the pad and rotor and this is not nearly that loud.

Do the pads have some sort of squeaker mechanism to warn when they are low? Rotors look good, no rust.
LS460L with 30k miles.

 

No, but if they did, you would be hearing the sound when braking not while driving. Check your wheel bearings.

 

Once a stone got lodged between my RR rotor and shield. Oh my, I got real spooked. 4 hours later (first I checked pads etc, then parking brake - nothing) when I took the rotor off it fell out. Phew, dodged that one.

 

Does the sound change once the brakes are warmed up? If it does then its probably your brake pads... The brand, not necessarily the pad thickness. Although worn out pads could be the problem too, of course, but the only way to find out for sure is remove the wheel to check things. Once I had the wheel off the ground I'd spin it and listen, if the noise is constant and not effected by much of anything, then as another poster commented, probably wheel bearings, although some other causes could be, rotor finish, or a real long shot, a sticky caliper piston. If just one piston is sticking it'll be a lot hotter than the one on the other side, and a digital thermometer might indicate that. And if it's the piston sticking, you definitely want to find out if that's really the problem and get that sorted out right away.

 

Just had it fixed today. The brake pads were low and they were making noise to indicate that. Tech said it wasn't quite at the point where the electronic sensor would turn on, but close.

When I had a stone in the rotor of my other car the noise was shockingly loud. Seemed to wake up all of the dogs in a 3 mile radius.

 

Is that normal though, that your pads were pressing up against the rotors with enough pressure to set off the noise? I once went on a day trip in hot weather with my car and when I got home i realized the rear pads were getting pressed against the rotors so hard they were worn down to bare metal, I assume the heat had something to do with it. It hasn't happened again.

 

The tech said it was something similar to a squeaker, where the pad was design to make noise when it was low by rubbing against the rotor. He said that it worked because tolerances in Lexus brakes were so tight. I didn’t actually see it, but braking sucked before getting new pads and it solved the whining sound.

The whine almost sounded like a bad pump, compared to brake squeal/grinding sounds.

 

I call bs on that techs explanation, there used to be metal wear indicators clipped on one tab on each pad that would squeal when pads were low but you have a copper sensor on an LS that will wear through almost silently and create an open between the two wires and generate a light on the dash. I had a 96 ls400 that even had these sensors...first time they wore through I just connected the wires to eliminate the light.

 

Mine does this when cold goes away when i prees the brakes ,Good pads .Just normal stuff, 2013 LS