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Discussion Starter #1
Coming from the right side rear end tire area I think. It isn't all the time but noticed it this morning pretty bad on my way to work. It's like a knocking sound that gets worse on acceleration then can't really hear it at like 60 but you know it's definitely still there. I have a short vid I can post but you can't really hear it well in it from my cellphone. Anyone else have this or experience it before? It's like the 3rd time hearing it I though it was the wheel bearing or something?
 

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Discussion Starter #3
Nah I checked for that no nail that I can see
 

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Being that it changes with speed you have a couple options.

1. Tire issues
2. Bearing issue
3. Under car heat shielding or aero pieces coming loose
 

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Rotate tire to front, see if noise follows.
This is an easy to do test that can help you instantly narrow it down or cross tires/wheels off the list. If it does nothing, oh well you rotated your tires which is good for them anyway.

Check your belly pan under the car and see if you're missing any screws. I'm missing 2 now apparently so I have to decide which ones to screw in because if I don't do it right it'll flap slightly at speed
 

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Discussion Starter #7
Ok thanks guys I thought about the shield but it is weird like sounds like the tore is hitting something but it's not accurate to the speed of the tire like if you had a card in a bike tire it flaps super fast but in my situation, it's like a slower thunk thats progressive but not as fast as the tire if you know what I'm trying to say haha.
 

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Ok thanks guys I thought about the shield but it is weird like sounds like the tore is hitting something but it's not accurate to the speed of the tire like if you had a card in a bike tire it flaps super fast but in my situation, it's like a slower thunk thats progressive but not as fast as the tire if you know what I'm trying to say haha.
At what speed do you start to hear it?

If it's not tied specifically to a once per revolution thing that might single out a tire or bearing issue. But I would still rotate that side and see if it changes to eliminate the tire end of it. If it only happens at slightly higher speeds it might be the air buffeting against a belly pan or fender well. Alternatively it could be the wing, just stretching for a solution here. But I would check out this article to be on the safe side as it seems just about every ST has had this issue.

https://www.focusst.org/forum/focus-st-appearance/39258-check-your-hatch-screws-pics-inside-4.html
 

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Discussion Starter #9
It basically does it right off the start at like 5mph then it just levels out and is part of the engine sound at crusing speed but you can still hear it there just not unless you're looking for it or know it's happening when you first start rolling. It hasn't done it today but I do have a thump back there on certain bumps and turns could be the same part doing it. I looked under there I don't see anything out of the ordinary like the sway bar links and bushings but maybe I should grease them up ? It's not a huge bother until it's all the time but maybe it'll show it's ugly face full time and I can figure it out lol. Rather not bring it in for a tech to say nope it's fine and I have mods now they can contribute to it and bs me about those lol.
 

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It basically does it right off the start at like 5mph then it just levels out and is part of the engine sound at crusing speed but you can still hear it there just not unless you're looking for it or know it's happening when you first start rolling. It hasn't done it today but I do have a thump back there on certain bumps and turns could be the same part doing it. I looked under there I don't see anything out of the ordinary like the sway bar links and bushings but maybe I should grease them up ? It's not a huge bother until it's all the time but maybe it'll show it's ugly face full time and I can figure it out lol. Rather not bring it in for a tech to say nope it's fine and I have mods now they can contribute to it and bs me about those lol.
So being that it starts so soon, I'd say it's not aero related. Which brings us back to a tire/wheel or bearing issue. Rotate that side of the car, if it moves it's a tire issue, if it stays it's a bearing issue.

Being that it's so low speed, the tire is massively flat spotted or cupped or it's a bearing issue.

My money is on a bearing issue.
 

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Discussion Starter #11
Yeah I'll try to rotate it and see what happens I'mma bet it's bearing too but at 40k miles? How hard are they to replace as a hub and not a bearing as I'm assuming that's a pain in the a** to do as a bearing alone.
 

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Yeah I'll try to rotate it and see what happens I'mma bet it's bearing too but at 40k miles? How hard are they to replace as a hub and not a bearing as I'm assuming that's a pain in the a** to do as a bearing alone.
I think the whole hub is relatively easy to do, should be like 6 bolts (includes the caliper bracket bolts). But with that being said I have not personally done it yet. Price wise they range from $100-$200. So nothing to bad to be honest, then say about an hour worth of work.
 

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Discussion Starter #13
Ok not bad at all actually
 

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Ok not bad at all actually
The bearing comes as a bolt in assembly. Its 4 E-torx.

A worn bearing doesnt make thuds though. It grinds, whines, or hums.

You would be looking at the wheel/tire, upper strut mount, lower strut mount, swaybar endlinks, and swaybar mounts.
 

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Discussion Starter #16
Thanks guys but wouldn't it do it all the time ? It's just super strange lol.
 

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Thanks guys but wouldn't it do it all the time ? It's just super strange lol.
Rotate the tire to the front. Inspect all the parts we informed you to. This is what you need to do. After all this is done, come back for debriefing. We need more data at this point, you have all the speculation you will ever need.
 

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Discussion Starter #18
Got it I'll keep you guys posted.
 

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I don't know if it is the same sound, but in my case, the car made a noise as if it were something loose in the trunk and it was hitting the walls. Then, I realized that the car gave small pulls especially when I was going fast on curvy roads and it was in high temperature.

Finally I discovered that it is due to false explosions in one of the cylinders because of dirty valves, that can't close properly (because of the vapors that are sent to burn through the admission).

I have installed the Mountune's breather plate and soon the Mishimoto's oil catch can to prevent this, while using cleaners.
 

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Coming from the right side rear end tire area I think. It isn't all the time but noticed it this morning pretty bad on my way to work. It's like a knocking sound that gets worse on acceleration then can't really hear it at like 60 but you know it's definitely still there. I have a short vid I can post but you can't really hear it well in it from my cellphone. Anyone else have this or experience it before? It's like the 3rd time hearing it I though it was the wheel bearing or something?
OK, now I've experienced something similar to this, and it took me ages to try and describe the sound but "thump thump thump thump" perfectly described what I was hearing, and the location. It turn out that I needed to replace my back tyres and yes it stopped straight away once the new tyres were on.
 
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