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I have a mysterious squeak, coming from the rear axle/suspension area on my car (2016 Toyota RAV4 hybrid) on speed bumps. The squeak started when I used the car very little over several months due to primarily using my bicycle. It clearly comes from the rear, since when I go over a speed bump, when the front suspension is compressed, nothing is heard, but when the rear suspension is compressed, the squeak occurs. The shock absorbers work just fine (apart from the squeak if it's coming from the shock absorbers).

I mentioned this in the annual service, where they didn't see anything wrong in the rear suspension, but noticed the rear brake discs are rusty, which I noticed too when I looked at the discs, I just hadn't noticed this prior to the service because I didn't think that rusty rear brake discs could cause squeak on speed bumps. The rusty discs is a continuous problem for me, since I use the car so little during summer periods, primarily using the bicycle. They recommended replacement of the brake discs, which I'm going to do in the next service, since they are not only rusty but so worn that eliminating the rust by an Italian tune-up would just remove so much material that they would need changing nevertheless. Despite the rust, braking works just fine so no dangerous brake problems there.

When I recently had a bike accident and had to use the car far more often than usual at this time of the year, the squeak started to go away. Now the squeak in speed bumps is so minor that often times I don't hear it, and when I hear it, it's only very momentary and not as loud as it used to be.

So this sounds like maybe the brake discs were the cause, since starting to use a car more often than usual could remove surface rust from the discs due to braking.

However, this theory about the brake discs has two suspicious features:

Firstly, can rusty brake discs actually cause squeaks on speed bumps? I brake prior to the speed bump, not during the speed bump, so during the speed bump, the brake isn't compressed at all, and the squeak occurs then.

Secondly, the rear brake discs are still somewhat rusty. So the frequent usage didn't eliminate all rust.

Pᴀᴜʟsᴛᴇʀ2
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juhist
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1 Answers1

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Brakes can squeak, but you'd hear it every time you brake and not just when you go over speed bumps. Squeaking when going over speed bumps is almost always due to worn suspension components, a bushing or a ball joint has deteriorated. My money would be on a ball joint.

However, sometimes your suspension may still be in fair shape but just develops a squeak, in which case a few shots of silicone lubricant spray in the right places may cure it for you, namely the ball joints and bushings. Even if it doesn't help you aren't going to hurt anything by trying. Just make absolutely sure not to get any on the brake rotor or disks, and if you do clean it off thoroughly with brake cleaner.

GdD
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