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Broken Pivot Bolt - Reese Hitch

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  • #1

    Broken Pivot Bolt - Reese Hitch

    Regular pre-tow hitch inspection . . . and one of the two main pivot bolts in my Reese 5th wheel hitch comes out in my hand Yikes!!

    What looks to be a fatigue break in this Grade 8 bolt where it threads into the cast head. Luckily this was a pre-tow inspection and not a towing disaster. How we got here on one pivot bolt is another question . . .

    The cast head was threaded all the way through so I was able to thread another bolt in from the other side to push the end of the broken bolt out. Tractor Supply (5 minutes away) had 5/8" Grade 8 bolts of the correct length. Yes . . . I replaced both .

    Bottom line . . . check every bolt on your hitch . . . every time. This hitch is 6 years old with perhaps 20,000 towing miles.

    Rob
    Attached Files
    Cate & Rob
    (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
    2015 Reflection 303RLS
    2022 F350 Diesel CC SB SRW Lariat
    Bayham, Ontario, Canada
    Tags: None
    • Likes 1
  • #2
    Wow Rob - Great catch! You certainly may have avoided a catastrophic failure on the road. If it were me, I'd contact Reese and show them this information. In the missile manufacturing business, we were always concerned with conterfeit bolts that were marked for one hardness, but tested to another.

    Jim
    Jim and Ginnie
    2024 Solitude 310GK - 2020 F350 Dually
    GDRV Technical Forum Moderator
    GDRV Rally Support Coordinator
    • Likes 1

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    • #3
      Yikes!
      Glad you found that one Rob!
      Reminds me of being told why they use grade 5 in automobiles. They bend rather than break like a grade 8. It looks like that reasoning could apply here?
      You know something about building cars I hear....
      Last edited by Scott'n'Wendy; 03-27-2022, 07:04 PM. Reason: spelling
      2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
      2021 303RLS
      Electricians were created because engineers need heroes too...

      Comment

      • #4
        Scott'n'Wendy
        Hi Scott,

        That exact thought went through my mind. I decided to go with Grade 8 because that was how the hitch was built by Reese . . . but, I will try contacting them. I have not had much luck with replies from Reese, but we will see.

        Rob
        Cate & Rob
        (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
        2015 Reflection 303RLS
        2022 F350 Diesel CC SB SRW Lariat
        Bayham, Ontario, Canada

        Comment

        • #5
          Rob, is that bolt more of a threaded pin? Hard to tell if the bolt is actually carrying load, possibly a picture from the tailgate of cab may help.

          If the bolt is more of a threaded pin, the threads could be just to hold in in place. By the looks lf the break, it's recent (no rush in the break)
          Joseph
          Tow           Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
          Coach: 303RLS Delivered March 5, 2021
          South of Houston Texas

          Comment

          • #6
            Jlawles2
            Hi Joseph,

            These bolts are the means of fastening the upper plate of the hitch to the lower frame. Without these (part #5 in the drawings) the top plate (and attached trailer) would have separated from the lower frame and the truck. These are 5/8" Grade 8 bolts. Many other retainers on this hitch are 1/2" mild steel pins. I am wondering if Scott's supposition is the correct. Perhaps Grade 8 bolts are too brittle for this application?

            Rob
            Attached Files
            Cate & Rob
            (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
            2015 Reflection 303RLS
            2022 F350 Diesel CC SB SRW Lariat
            Bayham, Ontario, Canada

            Comment

            • #7
              Thank's Rob. The diagram helps. Grade 5 bolts are soft and ductile yes, but they may lack the required shear strength needed for the connection.

              I'm not a fan of single shear connections like that. Too easy to put the bolts in bending and since the head has to pivot, not possible to help the bolt by use of friction.
              Joseph
              Tow               Vehicle: 2024 GMC K3500 Denali Ultimate Diesel
              Coach: 303RLS Delivered March 5, 2021
              South of Houston Texas

              Comment

              • #8
                Does that 5/8 bolt thread into the pivoting head? When the head pivots, does the bolt rotate with it?
                2018 Dodge 3500 6.7 Cummins w Aisin and 9 cup holders
                2021 303RLS
                Electricians were created because engineers need heroes too...

                Comment

                • #9
                  Cate&Rob Rob is there any noticeable wear on the isolators that would create additional clearance there? Wondering about impact loading. Not sure of the detail in this design but a bolt in shear across the threads is not a good. I looks like they may have moved to a hardened pin design with a clevis?

                  Nice that you caught this.

                  Jim
                  Last edited by Guest; 03-28-2022, 12:05 PM.

                  Comment

                  • #10
                    Wow, good catch! I agree with Guest regarding bolt loading of any sort other than tension in the thread area. I cannot tell from the exploded views just what the geometry of the part into which the subject bolts go, but it appears that even worse than shear, as they might be loaded in bending also. Are the "isolators" some sort of rubber part? If so, then the bolts most certainly are loaded in bending. I know you have reassembled the hitch, but some pictures showing detail of the part(s) into which the bolts thread would be really good to see.

                    If someone is able to take some pictures of this hitch dis-assembled, including some with a ruler for approximate dimensions, I'm happy to do some basic analysis on the system.

                    I'm not a fifth wheel guy, but if I had a hitch of this design, I'd think about pro-actively changing the bolts every season or sooner, depending on how many miles and how bumpy the roads are.
                    Ottertail, Minnesota
                    2022 Imagine 2500RL VIN 573TE3029N6637046
                    2022 Ford F-150 Lariat, SuperCrew, long box, max tow

                    Comment

                    • #11
                      Originally posted by AlexPeterson View Post
                      Wow, good catch! I agree with Guest regarding bolt loading of any sort other than tension in the thread area. I cannot tell from the exploded views just what the geometry of the part into which the subject bolts go, but it appears that even worse than shear, as they might be loaded in bending also. Are the "isolators" some sort of rubber part? If so, then the bolts most certainly are loaded in bending. I know you have reassembled the hitch, but some pictures showing detail of the part(s) into which the bolts thread would be really good to see.

                      If someone is able to take some pictures of this hitch dis-assembled, including some with a ruler for approximate dimensions, I'm happy to do some basic analysis on the system.

                      I'm not a fifth wheel guy, but if I had a hitch of this design, I'd think about pro-actively changing the bolts every season or sooner, depending on how many miles and how bumpy the roads are.
                      Alex,

                      Agree bending is not good as well but I do not know how the inner part of this is made up where it looks like they have moved to a hardened pin design. A bracket that captures the isolator on both sides with the use of a pin would be best. Rob is an engineer as well and will certainly get to the root cause.

                      Jim

                      Comment

                      • #12
                        The bolt in question is definitely being uses as an "axle" for the isolator. It threads into the cast head plate. There is no perceptible wear in the cushion (shock absorbing bushing) that sits in a bore in the carrier. We are travelling at the moment . . . I will disassemble and take pictures when we get home later this week.

                        Thanks for all the thoughtful input!

                        Rob
                        Cate & Rob
                        (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
                        2015 Reflection 303RLS
                        2022 F350 Diesel CC SB SRW Lariat
                        Bayham, Ontario, Canada

                        Comment

                        • #13
                          From my perspective the small part that broke off of the end is taking the most abuse, from the head receiving all of the input from the RV. I wonder if possible to use a longer bolt to get a little more engagement. That sure seems like a small bit to hold that much.

                          Brian
                          Brian & Michelle
                          2018 Reflection 29RS
                          2022 Chevy 3500HD

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                          • #14
                            Originally posted by Country Campers View Post
                            From my perspective the small part that broke off of the end is taking the most abuse, from the head receiving all of the input from the RV. I wonder if possible to use a longer bolt to get a little more engagement. That sure seems like a small bit to hold that much.

                            Brian
                            The fracture point was right at the face of the cast boss that the bolt was threaded into. The rather short section threaded into the hole came out easily . . . no deformation to the threads. The new bolts are about 1/4" longer so have better engagement . . . but I don't think this will make any difference to the loads where it fractured.

                            Rob
                            Cate & Rob
                            (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
                            2015 Reflection 303RLS
                            2022 F350 Diesel CC SB SRW Lariat
                            Bayham, Ontario, Canada
                            • Likes 1

                            Comment

                            • #15
                              Originally posted by Cate&Rob View Post

                              The fracture point was right at the face of the cast boss that the bolt was threaded into. The rather short section threaded into the hole came out easily . . . no deformation to the threads. The new bolts are about 1/4" longer so have better engagement . . . but I don't think this will make any difference to the loads where it fractured.

                              Rob
                              Rob,

                              Would there be room to drill out the threads and size a bolt where the shank is supported by the bracket and a lock nut installed to retain the bolt? This would take the stress off the thread. It would be interesting to know what Reese says about this.

                              Jim

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