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Passin_Thru's avatar
Passin_Thru
Explorer
Aug 08, 2017

Need engineers thoughts on wheel offset

Travel trailer wheels have either a centered or outside offset. My question is this. I have outside offset wheels and have sheared off wheel bolts on 2 different wheels I have weighed everything and I am 500 Lb/axle below MGWR on each axle. If I move to a centered offset, how will it change the torque and shear on the bolts. I believe that it is being caused by too high a torque load when cornering to the outside at higher road speeds on I 81 in Pa and NY. Will this drop the torque on the bolts and tire? Thanks I am an A&P Mechanic but havent worked much with shear forces.

28 Replies

  • j-d's avatar
    j-d
    Explorer II
    What is the Country of Origin for your Hubs/Studs? Things are getting progressively cheaper, and I wonder if you could replace those studs with Made in USA stuff that might be of better quality and uniformity. NAPA or such a place, and ask to See The Box.
  • How much offset are you talking about? If it is only a few mm there is no way it will make any difference. Even large offset(>20mm) mainly affect bearing loads not bolt loads. As said before broken studs are usually caused by either loose lugs or streched lugs from a previous over tight lugs.
  • pickjare wrote:
    Consider how many cars and trucks on the road have wheels with all sorts of different offsets. I am not an engineer, but if wheel offset caused, or cured, wheel studs from breaking, I think we would have learned this from them. look at your wheel lug holes real close. If any one is elongated or worn, the wheel needs replaced. If every hole is good you might try retorquing the nuts after towing 10 miles--or 100 miles or both.


    well...... virtually all cars and light trucks on the road today have hub centric wheels. that is the wheel hub is a very tight fit to the axle hub. So..... the hub takes ALL the vertical load on the axle, the lugs keep it from sliding off and take any horizontal load.

    Virtually all utility and travel trailers (U-haul is one exception, most or all uhaul trailers have hub centric wheels) have LUG centric wheels, so the center is a loose fit on the hub so the lugs must take ALL the vertical AND horizontal forces on the wheel. Big difference.

    that's one reason retorquing is so important on trailers. And the OP isn't the first person to have problems with lugs shearing on trailer axles. if lug nuts get loose it doesn't take long for the lug centric wheel to beat the **** out of the lugs.

    I suspect any non zero offset puts even more force on the lugs.
  • Consider how many cars and trucks on the road have wheels with all sorts of different offsets. I am not an engineer, but if wheel offset caused, or cured, wheel studs from breaking, I think we would have learned this from them. look at your wheel lug holes real close. If any one is elongated or worn, the wheel needs replaced. If every hole is good you might try retorquing the nuts after towing 10 miles--or 100 miles or both.
  • If some shop over tightened the lugs, they will eventually break off as you describe.
    When you put lugs on does the nut get tight in the middle of the threads, loosen and then tight again as they make contact with the wheel?
    If so then the studs are stretched.
  • Do you torque your lug nuts?

    How fast are you towing that would cause "too high a torque load when cornering to the outside at higher road speeds on I 81 in Pa and NY."?


    Sorry ...I was only a Stationary Engineer
    But lug studs shearing are due to Loose lug nuts OR stretched studs due to over torquing lugs.

    Don't think changing wheel offset will be the cure.
    Might affect wheel bearing thrust loads.
  • Loose or stud weakened by too much torque. Must say when I switched to disk brakes the studs seem very firm as compared to the OEM drums were a bit stretchy. Mine have always been tightened by a torque wrench only.

    If you are buying wheels I would go with zero offset. Make sure you have inside clearance.

    Sorry only three years of engineering before I switched to business.

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