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Discussion Starter #1 (Edited)
There are a "thud - thud - thud - thud" coming from what seems to be my right left tire somewhere.
It increases in frequency and loudness the faster i drive, but if i just slightly presses the brake its gone, and if i break hard, its gone for a while before the sound comes back. which brings me to believe its something with the brake.

It starts at about 40km/h, but after a hard brake i can drive in 100km/h with no problem, for a while before returning.

Anyone have any idea what the problem might be? sliders?
There are new brake pads all around, I had an issue with squealing noise from the brake a while after i change them, i have no idea if its related, but the sound went away about a week ago.
 

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There are a "thud - thud - thud - thud" coming from what seems to be my right front tire somewhere.
It increases in frequency and loudness the faster i drive, but if i just slightly presses the brake its gone, and if i break hard, its gone for a while before the sound comes back. which brings me to believe its something with the brake.

It starts at about 40km/h, but after a hard brake i can drive in 100km/h with no problem, for a while before returning.

Anyone have any idea what the problem might be? sliders?
There are new brake pads all around, I had an issue with squealing noise from the brake a while after i change them, i have no idea if its related, but the sound went away about a week ago.

My money is on a bent rotor. They can distort under heavy braking when they get down to minimum thickness. Also some folks thing turning them to reface them is a cheap way to avoid replacing them and a couple of things can happen.
First they get turned past the minimum and hence warp under heavy braking because of the heat.
They also can be cut too hard and fast when being refaced and the heat generated is enough to change the metal characteristics and they warp the first time they are used in heavy braking.
New OEM rotors area available at reasonable prices.
 

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Discussion Starter #3
With rotor, you mean brake disc, right?
I think it sounds a bit weird, as it just suddenly happened with no hard brake or anything like that.
Secondly, why does the sound go away for a while after i brake hard? Shouldn't it be there constantly?
 

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This is interesting. I have had 'bent' rotors (discs) fairly often, on a variety of cars. I always get them machined but over here no brake shop will take them below the minimum thickness - it's illegal and they won't do it.


Warped discs produce a vibration under light braking. Easily diagnosed. If you don't have this, then I doubt it's warped discs.


Having said that, I can't offer any other explanation. I assume your wheel nuts are tight!!
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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Warped discs produce a vibration under light braking. Easily diagnosed. If you don't have this, then I doubt it's warped discs.

Having said that, I can't offer any other explanation. I assume your wheel nuts are tight!!
Rotor: Can feel it under light/medium braking (and heavy as well but I rarely have the need for heavy braking--safe distance and all you know:tu: ) and can also hear it. On my wagon.

It's not a serious issue, more of an annoyance.

If nuts are loose, you'll notice it (slight feel--a wobble and it is noticeable) and you can tell which wheel but can also hear it) under heavy acceleration.

Once at a steady speed, it disappears (in my experience anyways, again on my wagon). Obviously, that IS an issue :surprise: .
 

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Registered 2012 SLK 55 w/P30
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This happened to me once another car many years ago. I had belt separation and the braking caused the belt to wedge up against the tire carcass. So the sound would go away after I braked, but would come back shortly afterwards. The tire shop told me they saw this rarely, but it did happen occasionally. I believe this was back in the mid-1970s. Something to consider if there is no pedal modulation. Just a quick brainstorm.
 

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Discussion Starter #7
I still cant understand the symptoms.
I started with the bolts, kinda just to confirm that they were tight, because I didnt have any wobble or unstability, just the sound. And i cant understand why it went away after a hard brake or at a slight brake. Driving with the brakes just barely touching on shuldnt have any effect on the bolts, right?



But 4 out of 5 bolts om my front left wheel were a bit loose, I tighten them all and the problem seems to be gone.
Weird.
 

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Super Moderator CA 2012 SLK55 AMG w/P30
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But 4 out of 5 bolts om my front left wheel were a bit loose, I tighten them all and the problem seems to be gone.
Weird.
Why weird? Apparently not tightened properly in the past. Using a torque wrench? 80 lb ./110 NM. Check them monthly if not. Also tire pressures should be checked regularly (at gas fill up is when I check: keep the gauge in the glove box).
 

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Discussion Starter #9
I always use a 110nm torque stick on my impact wrench to not overtighten.



What was weird is the symptoms, not that they came loose, I know that can happen :)
 
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