Anyone ever hear knocking from the rear?

Bocifus

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mazda7
Knocks like the spare tire is loose and jumping around on small bumps in the road. Looked underneath, nothing. nothing broke or unbolted. Struts are fine, spare tire isnt loose. Car has 103k and stock struts. are they bad and would it sound like that? Car rides fine and doesnt bounce around at all. Doesnt have any other problems. Thx
 
Front and/or rear sway bar bushings are known for this. A little work getting them installed but definitely a cheap bet.
 
Since we are hearing it from the rear... here is my list in order of likeliness

1. Sway bar bushings (sometimes called anti-roll bar, stabilizer bar)... and sway bar links.
2. Lower shock bolts not at correct torque (this would usually happen after new shock install)
3. Upper shock mounts
 
Sway bar bushings and sway bar was the first thing we looked for. Didnt see anything. I will check if shock bolts are tight tho.
 
Sway bar bushings and sway bar was the first thing we looked for. Didnt see anything. I will check if shock bolts are tight tho.

They will look fine. They can only be tested for play with the torsion removed from the bar by disconnecting the end links and allowing the swaybar to be free.

If they are over 5 yrs old or have more than 50k on them, they will most likely need replacement. I went thru it a few times on our Mazda5 that we put 100k on, and the Mazdaspeed3.

Another test that I always used to confirm the sway bar bushings or links is to find a SPEEDBUMP.

Go over the speedbump so the tires on each side of the axle hit the speedbump squarely at the same time... usual 5-10 mph is just fine...

now try going over the speed bump diagonally so that the tires on each end of the axle DO NOT hit the speed bump at the same time.

this diagonal test is the one that will be working and testing the sway bar bushings and end links.
 
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Oh ya, most people on this site will attest to the bushings looking fine, then upon replacement the knocks miraculously disappearing.
 
*UPDATE*

Just did the speed bump test. Straight away no knocking
At an angle. Knocking.
If these are sway bar bushings, which ones and is there a video changing them.
THX
 
*UPDATE*

Just did the speed bump test. Straight away no knocking
At an angle. Knocking.
If these are sway bar bushings, which ones and is there a video changing them.
THX

Yes, you have now narrowed it down to the sway bar bushings / and/or sway bar endlinks.

If you want to be frugal, just do the bushings. The end links seem to last thru a few sets of bushing replacements.

The OEM Mazda ones are the only ones I have used to replace.

If you are looking for a video, and do not see a mazda5 one, the 04-09 Mazda 3 is the same setup and suspension.
 
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