Need engineers thoughts on wheel offset

hotpepperkid wrote:
I think the OP was asking about off sets on the rims not hub or lug centering. You want 0 offset on you trailer

He asked about torque and shear on studs as well. There has been some good discussion, and it is all part of the big picture.

Have you checked the taper on the nuts? Not all nuts have the same taper. Another issue I had was installing acorn nuts that did not clear the bore of the hole. By that I mean the edge of the hex on the nut contacted the side countersink of the hub. That did not allow the taper of the nut to contact the area of the hub that it should have.
Heard a noise when slowing down. Found that 3 studs had broke and wheel was wobbling. Lucky I caught it before the wheel came off.

I know it seems counter intuitive, but cornering loads or offset wheels DO NOT increase the loads on properly torqued wheel studs until they become so substantial that the wheel deforms/deflects enough to cause it to lose contact with the hub. That will add tensile forces to the stud. Think about it. Suppose each stud provides 1000 lbs. of clamping force when properly torqued. That's what puts tension in the stud. The only way to add more tension to the stud is to deflect (stretch) it more. You could do that by adding torque to the lug or by pulling the wheel away from the hub which would increase the tensile force on the lug. (very difficult to do) Each lug would need more than 1000 lbs. of force (in this example) to counter the load all ready on it and stretch it further.

As correctly previously mentioned, the clamping force between the wheel/hub creates static friction which clamps/holds the wheel to the hub. Hub centric hub/wheel designs or conical lugs are only there to provide locating action. That's why everything goes bad when the lugs become loose or become over stressed due to being loaded (over torqued) beyond their yield strength.

Overly offset wheels will substantially add loads to wheel bearings though. Especially double row ball bearings typically used in front wheel drive cars. Trailer wheels less so but it does effect them. It also changes the vehicles stability concerning its center of gravity.

Chum lee

I tightened mine according to A&P Mechanics training. You loosen everyone and retighten with a Calibrated Torque Wrench. Mine is a Snap-On and I torqued to 90 ft lbs.I was doing 65 through Scranton when it sheared off on a curve to the right. I had been on Rt 11 from NY line to 20 N of Scranton, rough twisty windy. My lug bolts came form Dexter Axle, on the trailer. Knew about the L and Right hand threads. Chrysler had them for a long time. will call Dexter tomorrow and talk with their engineers. I may buy titanium bolts.

What size studs? Seems a little light on torques values. Does the nut screw on freely to the stud?

Chum lee, Thanks for the insight. Understand it. Correct taper according to Dexter. They carry the axle, wheel, bolts and nuts installed. 1/2 in Dia. bolts.
Screwed on freely. Dexter says 90 to 120 ft lb is adequate torque.
http://www.dexteraxle.com/docs/default-source/default-document-library/light-duty-wheels-and-tires.pdf?sfvrsn=2
Waiting on Aluminum wheels to arrive. Will try them as they have a 0-Offset. Thanks again to all of you who answered. Its neat to pick others noggins for ideas when one gets stuck and I worked with Engineers at Flight Test for years.

The title is misleading as OP talks about wheel centering.
Centering is determinate by hub design and you can't change it other than changing the hub.
In case of lug shearing, when they were torqued to 90 ft-lb I can only guess they were over-torqued in the past and now break with metal fatigue.
Would order quality bolt and that should solve the issue.
Wheel bolts usually have safety factor about 5, so it takes a lot to have one broken.

Good picture....shows how the wrong offset can contribute to sheared or broken lugs. Some where on Dexters old website they had the same wheel pictures but showed the inner and outer bearing placement located between them.

I've seen several haulers use GM 6 lug std steel automotive wheels on 6 lug trailer axles. After many miles lugs would start to break or shear off at the wheel/hub interface.