Looking to buy rims, they are 8-lugs and I have 6, is it as simple as just buying an 8-lug hub and switching the hubs out?

Tiny
JACOB MARINO
  • MEMBER
  • 2003 GMC SIERRA
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 250,000 MILES
So not really any issues going on today but I saw these really nice rims for sale, but they are 8 lug and I have 6. Is it as simple as just buying an 8-lug hub and switching the hubs out?
Wednesday, December 13th, 2023 AT 10:35 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,752 POSTS
No. It would be considerably easier to put the Space Shuttle engine into an airplane. The hub with the wheel studs is part of the wheel bearing assembly which must match the splines on the outer CV joint and fit into the opening on the spindle. The holes on top and bottom of the spindle must match the size and taper of the studs on the ball joints. Pretty soon you'll have the entire suspension system involved in the changeover. The far better solution is to buy the exact truck you want as it was designed and built, then put on the wheels you like that were designed for the application.

The still better solution is to find the same wheels, but in the six-bolt pattern for your truck. Besides the number of wheel studs, you also must consider the diameter and depth of the center hole. Many aftermarket wheels are made with center holes large enough to allow them to fit onto many brands and models of truck. That eliminates the purpose of that hole which is to hold the wheel centered. When the hub doesn't do that, it's up to the lug nuts to keep the wheel centered. They will do that, but it's not what they're designed for. The studs will have to hold up the vehicle's weight and withstand the additional forces from hitting pot holes and other bumps in the road. Steel wheels will do a better job of that, but the stresses can lead to early failure.

Cast wheels will do a much worse job if the center hole doesn't keep the wheel centered. The pounding wheels take will put sideways forces on the lug nuts. As the holes in the wheel become deformed, the pounding action becomes greater and greater. Think of dropping a hammer one inch onto your hand resting on a table. That won't hurt, but as the hammering action on metal car parts continues, the effect becomes greater, as in now you're dropping the hammer onto your hand from two inches, then three inches. The more wear takes place, the more effect it has which causes the wear to increase at a faster and faster rate. Eventually the holes in the wheel become wobbled out. At that point it will be impossible to keep the lug nuts tight. They rely on the tapered surface to match the surface of the nut so the friction holds the nuts tight. (That's why we never put grease on them too). Once the wheel becomes loose in service, it's too late. Nothing will keep the nuts tight because they are not turning to become loose. The surfaces are wearing away creating the looseness. The only solution for that is to replace the wheel and the lug nuts.

The tightness of the lug nuts is also important. Professionals always use a click-type torque wrench when tightening them. This step is usually overlooked by competent do-it-yourselfers. The nuts must be tight enough to develop the required clamping forces, but not so tight that the holes in the wheel become deformed or the friction surfaces are damaged. Torque specs for cast wheels are lower than for steel wheels. That's because it's too easy to deform aluminum. Overtightening the nuts leads to deforming the friction surfaces around the holes. As the nuts are turned more and more, they do not develop higher clamping forces. Rather, the nuts just push the aluminum aside as they go deeper and deeper.

Therre's a lot more to selecting a replacement wheel than most of us are aware of. Your best bet is to find an original wheel that was available for your truck. There are a lot of nice designs that have been around for some time. They tend to hold up better than aftermarket replacements if you live in states where they use a lot of salt in winter. Up in Wisconsin, where I am, they throw a pound of salt on an ounce of snow. Many owners have one set of wheels and tires they put on for winter, then they put the nice stuff on for summer driving.

Let me know if that helps or if there's other questions I can answer.
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Wednesday, December 13th, 2023 AT 2:19 PM

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