Posted 24th January 2013 at 09:55 PM by Burmo
Sorry I haven't been back to answer your questions earlier as I have been trying to resolve what may have caused this incident.Yes it was the top 12mm bolt that snapped (
still held on by the 2 bottom bolts although considerably bent). There are many reasons why this may have happened keeping in mind our 21 ft off road van weight aprox 3.2 t, ball weight approx 330kg.
(1) The hitch I was using was second hand so I have no idea weather it was the original bolt and nut. Word is the bolts and nuts should only be used once, if not the nylon nut could have become loose. I was surprised to find out from one of your blogs that an upgrade of this bolt is available.
(2) The tongue I was using was a Hayman Reece with the WDH head (i was NOT using the WD bars) as i required extra height for our van. This tongue as standard put the ball a long way out from the hitch, hence giving it a larger amount of leverage on the top bolt (although it allowed the tailgate to be lowered). There does not appear to be a specific tongue to suite this hitch although now I are trying to get MB to recommend me one.
(3) I am not an engineer but I feel the bolt used should have been longer so that the thread was outside the hitch and washers used to tighten it up. This would allow for a solid section of bolt through all pulling points. My bolt snapped where the thread ended.
After extensive calls to MB they have assured me the bolt on the latest hitch has been increased both in size and length. They have recommended a Combination Pintal Hook and Tow Ball. We are in the process of getting a new MB hitch and possibly this tow ball arrangement.
The guys at MB have been very helpful and great to talk to. I feel very confident they will get the correct assembly for us in the end. I will have more information when we get the final fitments to our vehicle.
Burmo.
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