Forum Discussion

SH's avatar
SH
Explorer
Jul 29, 2015

Pinbox Flex

Is there a figure used for "acceptable" pin box flex? Doesn't seem like with the amounts of weight involved there could be zero flex. Anyone know of a tolerance figure (e.g. 3/8, 1/2 etc.)?
  • When I questioned NUWA about pin box flex answer was 1/4" to 3/8" normal depending on pin box length
  • You failed to mention how much flex you are experiencing. Given the age of your rig, I would remove the lower cover surrounding your pin box and check for stress cracks in the frame. Move it up and down and put it under load, either with a forklift or just lowering onto your hitch.
  • The question had nothing to do with my rig! Just wondering!
  • SH wrote:
    Is there a figure used for "acceptable" pin box flex? Doesn't seem like with the amounts of weight involved there could be zero flex. Anyone know of a tolerance figure (e.g. 3/8, 1/2 etc.)?


    Not sure what the norm is but as look back through my rear view mirror, I can see the top gap between the pinbox and the trailer flex 1/4' - 3/8". I do have the extended pinbox which probably does flex more.
  • ckwizard777 wrote:
    As far as I am concerned zero flex is the only answer.


    That would be ideal but highly unlikely!
  • SH wrote:
    ckwizard777 wrote:
    As far as I am concerned zero flex is the only answer.


    That would be ideal but highly unlikely!


    And not good...just like airplane wings flex...look it up. :)
  • I measured the flex on our new Mobile Suite and it was 3/8 to 7/16 and Lippard maintained that to be the norm. I suppose with 3500 lbs. or so of pin weight maybe that's why. In 20,000 miles nothing has changed.
  • On my Cameo I really don't notice any. I have a Mor Ride pin box. I know the rubber in the box flexes some but not much when hooking up. I've had problem with too much flex with a Lippert frame, and had to have repairs.
  • Learjet wrote:
    SH wrote:
    ckwizard777 wrote:
    As far as I am concerned zero flex is the only answer.


    That would be ideal but highly unlikely!


    And not good...just like airplane wings flex...look it up. :)


    My old Sunnybrook I never visualy noticed pin flex, Same with my Montana that I have now I can not visualy detect movement while im going down the road and I really try to look for it while goin over bumps so in my mind if I can see it it's too much.