Almost lost a wheel

[floyd]

Originally Posted by redbarron55

Steel wheels have that set of ridges around the bolt circle that sets through actual holes slightly away from the hub. This gives the wheel a space to "set" the clamping torque by flexing the wheel center.
Because of this the lugs are less likely to back off after torquing.
The aluminum wheels cannot do this and you have to re torque them to make sure that they are tight.


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I "retorque" every time I rotate tires.
Purpose made trailer wheels are flat across the bolt circle and lay flat against the hub.
They are no more likely to work loose than an old school steel wheel which you describe. Same goes for aluminum wheels.

Sorry,I really don't buy the flex clamping theory.

Also...Trailer wheels, like most automotive wheels, have tapered lug seats which obviates the hubcentric concerns.
There are exceptions of course, like light Ford pickups a few years ago.

[redbarron55]

If you really look at the typical steel wheel you will see the raised porting and the "coined" raised part the lug fits into.
Look at the hub and you will also see the marks are not flat all around the hub.
The raised area acts as bellville washers to load the fastener and to help keep the clamping force on the wheel.
Almost all steel wheels have this feature since WWII. Very heavy steel wheels with more lugs do not have this since the wheel center is very much thicker.

Look carefully at the back of this wheel.



Here is a cross section drawing where you can see the part more clearly



Without this small offset the wheels would loosen easily and fail.
This was discovered during WW 2 and almost all stamped drop center steel wheels since have this feature

[Paul O.]

Nice explanation, Redbaron, thanks. This mechanical engineer was taught many years ago that all bolted connections rely on the elasticity of the components involved. Sometimes the elasticity in increased by making the bolts longer, e.g. the connecting rods. Some instructions may say: tighten to the point of solid contact, then some fraction of a turn, unless a torque value is given.

[David Tilston]

Well, to make this story a bit more complex, I had to grind about a 1/8" around the centre hole to make the ranger rims fit.

[redbarron55]

Any time the clamping pressure in insufficient to keep parts from moving in relation to each other the result will eventually be fatigue fracture of the bolts.
If the hole in the center located the wheel and the bolts did not have a locating cone then this could have been the problem.


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[David Tilston]

The bolts used, and the bolt holes in the rim were both conical. I have been using Ranger rims from Calgary to Northern Ontario, (and back, eventually). When they are torqued sufficiently, I have had no problem. I do check the torque fairly regularly now.

[ruscal]

I have found what JD described to be true. Factory steel wheels have built in resiliency that make them much more resistant to loosening. Wheels that have thicker centers, whether they be cast aluminum or steel plate require re-torquing after driving 50-100 miles, and frequently rechecked periodically. For those wheels the lug studs are stretched during torquing and provide some resistance to loosening. I think the reason they loosen at first is the lug nuts tend to need to bed into the tapered holes a bit. After a while they hold pretty well. Powder coated wheels will need re-torquing a few times at first to bed in.
Hub centric wheels are desirable due to the added shear provided by the hub. However many wheels that are sold are non-hubcentric. There are companies that can machine hub centric adaptors which will work in some cases.
Russ