Wheel making whistling noise but not when car is in reverse

A whistling noise is coming from the area of my right rear wheel when the car (Elantra 2015) is in motion. But only in forward gear. When the car is in reverse - no noise. It started suddenly today. It only sounds when the car is in motion and it seems to be associated with the speed of the wheel rotation. But again, only in forward gear. Sometimes, sound will go away for a bit - it went away once when I hit a small bump in the road, and another time for no apparent reason - and then will come back when I hit the brakes. So it has something to do with the brakes too, but it doesn’t go away when I let go of the brakes.

(Edited) It’s connected to the brakes in another way as well. The sound stops eventually, when I go about 1/4 mile without touching the brakes. Then when I touch the brakes - while I’m pressing them - it becomes a constant noise, which then becomes a non-constant noise (with noise volume going up and down, up and down very quickly as the wheels turn) when I let go of the brakes until it stops after about 1/4 mile.

Similar posts to this one suggest it may be a faulty wheel bearing or debris on the brake pads. But then it would make the noise when in reverse as well, wouldn’t it?

Probably the wear sendor on a front brake pad. Have someone check your brakes.

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+1 for your brakes are probably worn and in need of replacement. There’s a little noisemaker that’s installed on the brake pads so that when they get to a certain point they squeal, alerting you that it’s time for brake service. You can verify this by looking at your brake fluid reservoir; if it’s low, then you know the pads have worn significantly since your brake system was last serviced. Also, if the sound goes away on it’s own, that doesn’t mean you don’t need brake service anymore.

Hmm… the question is whether it’s safe to put another 100-200 miles on the car before taking it to the mechanic. Are worn brake pads a clear and present danger, and if not, are you sure it’s not a bearing/debris? Is the car safe to drive? It would be much more convenient for me to take it to the mechanic in another day or two, and I drive a lot (uber) so that could be up to 200 miles.

PS i added more details to my original post.

You are responsible for evaluating your own safety and risk assessment. If it were me, and the noise just started very recently, I would be comfortable with putting a couple hundred more miles on my car before a scheduled service. This would be assuming that I have not noticed any other performance or safety issue with the car’s braking system. The brakes will typically continue working even when the pads are worn well beyond their indicator point. The problem is that once they are excessively worn, brake performance will decline rapidly and other components that are not designed to wear out as quickly (namely the rotor and calipers) will begin to wear prematurely, making what would normally be a quick/routine maintenance issue into a far more expensive system overhaul. I’ve seen standard brake service packages run anywhere from $300-$3000 for all four wheels. If you wreck your rotors and calipers because you waited too long, you can double those numbers. Shop around.

If it is the wear indicator, it is safe to go another 100 miles or more. Somebody has to check it to make sure that it is the wear indicator and not a fully worn out brake pad.

You’re an Uber driver and you want to carry passengers around with possibly worn brakes or wheel bearings?

I can see the lawsuit now if you have an accident.

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I have seen wheel bearing and brakes go bad prematurely on these cars. Take it to a reputable mechanic for an inspection.

At least jack up the car, remove the wheel, and inspect the brakes carefully from all angles with good lighting. It’s usually possible doing that to determine the remaining thickness on at last one of the brake pads. And you might find some road debris has accumulated against the brake pad. Or there’s something stuck in the wheel, etc.