Popping noises and wheel shudder under hard braking

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  • agent
    Vice Grand Pubaa
    • Mar 2010
    • 7960

    #1

    Popping noises and wheel shudder under hard braking

    Over the course of the last several days, on my latest acquisition I have replaced the following:
    • new Brembo blanks at all four corners
    • new Hawk HPS pads front and rear
    • new H&R Race springs at all four corners
    • new Bilstein Sports at all four corners
    • new Bimmerworld "Lifetime" RSMs; new RSM gaskets
    • new Bimmerworld rear shock tower reinforcement plates
    • pre-owned RUFF camber plates that I purchased from a forum member
    • pre-owned Borbet Type Cs (that I refinished) with serviceable Nitto Neogens - tires were re-mounted and balanced with new stems at Discount Tire
    • pre-owned 20mm spacers (which are not on the rears until I can get the fenders rolled)
    • new 90mm studs and lugs from Motorsport Hardware


    The front upper and lower spring pads were re-used, the rear upper spring pads were re-used, and I put thicker (5mm) pads - also used - under the rear springs.

    We gave up trying to get the collar nut out of the passenger strut housing since it was rusted fast to it. My buddy's car is on stands in his garage getting a swap, so we used the passenger strut housing he happened to have available. On the initial test drive I noticed a popping noise coming from the passenger front under braking, so my thinking was a bad wheel bearing in his strut and we would replace it with mine once I got the collar nut out of it.

    I got the collar nut out Monday at another friend's shop and set out to do the strut replacement last night. After swapping struts the popping noise is still there on the passenger front, although now it seems to be a little less pronounced in the front than it was previously, and it sounds like it's also coming from the driver side rear.

    Under gentle braking the noise is imperceptible. The harder I brake, the more pronounced the popping noise is, and the more vibration I feel in the steering wheel. We have checked and rechecked to ensure everything is tight and secure. The outer ball joints appear to be okay (no play using the 12 and 6 shake test), though the sway bar links and CABs could probably stand to be replaced. The frequency of the popping is greater than once per wheel/tire revolution, so I'd like to think I can rule out the rotors/pads/wheels/spacers/studs. The studs and lugs are torqued as tightly as I dare until I am ready to Loctite the studs into the hubs.


    I spent about an hour searching for "popping noise," though out of the dozen or so threads I read in their entirety, none specifically mentioned the issue under braking and/or it increasing with more brake pressure. Any suggestions on what else to look for or check would be most appreciated.



    Cliffs:
    New and used parts installed, some worn parts that should probably be replaced have not been (yet), new popping noises emanating from front and rear under braking. Noise and chassis vibrations increase accordingly with the amount of brake pressure used.
    Originally posted by kronus
    would be in depending on tip slant and tube size
  • Mr. Tasty
    No R3VLimiter
    • Jul 2011
    • 3421

    #2
    caliper bolts backing out. Happened on my car
    2014 Alpine White 335i MSport
    (Daily Driver)
    Full Mperformance Aero

    2007 Black Sapphire Metallic E92 335i (6MT)
    KW V2 Coilovers
    VRSF Catless Downpipes

    Comment

    • agent
      Vice Grand Pubaa
      • Mar 2010
      • 7960

      #3
      Do you mean the bolts holding the caliper to the strut, or the ones holding the halves of the caliper together?
      Originally posted by kronus
      would be in depending on tip slant and tube size

      Comment

      • Asbradley21
        E30 Mastermind
        • Jun 2008
        • 1938

        #4
        The ones holding the caliper to the strut. I've had these back out too when I wasn't careful putting them in.

        S54B32 swap in progress. Status: Getting There

        Comment

        • agent
          Vice Grand Pubaa
          • Mar 2010
          • 7960

          #5
          I'll recheck them, though I'm 1000% sure those are tight. The last thing I did was torque them with a long handle wrench before putting the tie rod back on, then the wheel.
          Originally posted by kronus
          would be in depending on tip slant and tube size

          Comment

          • agent
            Vice Grand Pubaa
            • Mar 2010
            • 7960

            #6
            Last night the caliper bolts were verified as still tight.

            Still looking for ideas.
            Originally posted by kronus
            would be in depending on tip slant and tube size

            Comment

            • Mr. Tasty
              No R3VLimiter
              • Jul 2011
              • 3421

              #7
              I would just make a list and go through everything

              CAB bolts
              Ball Joint nuts (1 on sub frame and one on shock housing)
              Tie Rod nuts (outer and inner)
              strut mounts nuts (3 on top and one shock)
              2014 Alpine White 335i MSport
              (Daily Driver)
              Full Mperformance Aero

              2007 Black Sapphire Metallic E92 335i (6MT)
              KW V2 Coilovers
              VRSF Catless Downpipes

              Comment

              • vpilarrt
                R3VLimited
                • Jun 2006
                • 2096

                #8
                You might also want to check the threaded inserts in the frame rail that the CAB bolts into.

                Comment

                • RobertK
                  Kicked cancer's ASS.
                  • Jun 2005
                  • 5864

                  #9
                  Sure you didn't put a brake pad on backwards? ;)

                  Check the bolts holding the caliper brackets to the struts.

                  Comment

                  • agent
                    Vice Grand Pubaa
                    • Mar 2010
                    • 7960

                    #10
                    After driving the car a little more this evening, I'm of the opinion it's drive train related. I'm going to try to get the car up on stands this weekend so I can have an extended look underneath, and see if there are any obvious signs of CSB and/or giubo failure, or possibly an issue with the half shafts.
                    Originally posted by kronus
                    would be in depending on tip slant and tube size

                    Comment

                    • carlb
                      Grease Monkey
                      • Feb 2011
                      • 359

                      #11
                      Originally posted by agent
                      After driving the car a little more this evening, I'm of the opinion it's drive train related. I'm going to try to get the car up on stands this weekend so I can have an extended look underneath, and see if there are any obvious signs of CSB and/or giubo failure, or possibly an issue with the half shafts.
                      Did you figure this out? Experiencing a similar problem.
                      1985 M635csi Black on Buffalo
                      1985 535is Zinno on Black
                      1985 M635csi White on Pacific Blue
                      1988 M3 Lachssilber on Black (sold)
                      1987 M3 Zinno on Black (totaled)

                      Comment

                      • agent
                        Vice Grand Pubaa
                        • Mar 2010
                        • 7960

                        #12
                        Nope, not yet. It's still doing it on the driver's rear. RobertK ran into a similar issue on a car he was working on, and replacing the studs with lug bolts resolved it for him. I just bought some extended bolts and plan to try them this weekend.
                        Originally posted by kronus
                        would be in depending on tip slant and tube size

                        Comment

                        • RobertK
                          Kicked cancer's ASS.
                          • Jun 2005
                          • 5864

                          #13
                          That was on Dwayne's vert. He had some spacers and longer lug bolts, longer than they needed to be. They were clicking on the rear ebrakes. Steve and I swapped them for some lugs that were just a tad shorter, no more noise.

                          If you're running studs and they've been screwed in to far into the hub then the same thing can occur.

                          Comment

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