Why so many wheel studs? 1

[dadof275103]

What is the driving force in the increase number of wheel studs a car or truck has? I have seen single lug racing wheels (for speed in changing),a three lug, 4 lug, 5 lug, now the migration is to 6 lug wheels. Why ? or is this just a "fashion" trend.

Thanks

Michael

 

[CoryPad]

Higher vehicle mass requires more fasteners to connect the wheels and brake rotors to the hubs. Wheel attachments for passenger vehicles are overdesigned because they are a safety-critical joint that the customer actually touches. The clamp force generated by modern wheel fasteners is quite low compared to other joints. The conical or spherical seats allow force/torque transfer even if there is essentially zero clamping force.

Regards,

Cory

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[dadof275103]

Cory

Thank you for the prompt reply. It just seemed odd to me the big Lincolns, BMW, MB, etc, having 5 lugs then the smaller 1/2 ton trucks having 6wheel lugs.

Michael

 

[BobM3]

I'm not in the automotive field but I'll venture a guess that if the wheel makers are trying to get every little bit of weight out of the wheels then the resulting thinner sections might require more evenly distributed loads (more bolts).

 

[carnage1]

most of the small trucks being manufactured now are based on Asian company designs who have predominately used 6 lug wheels for some time. 4 lug wheels have always been a sign of a "low performance" car, so 5 lugs on the smaller cars that want to look "sporty" has become common. Five lugs have been around the longest / have historically been most common. eight lugs and more are only on 3/4 ton trucks and vans, those have a real reason. Personally having had lugs shear off before (on two different rigs) I am partial to having a few spare ones per wheel.

Luck is a difficult thing to verify and therefore should be tested often. - Me

 

[Silverbullet86]

the rotating hub has a torque force. The wheels in contact with the road bolted to the hub are exposed to a bearing stress where there is a shear force present on the wheel studs and the face of the wheel. The more studs there are, the less shear force on each of the studs. It is just an increase in factory of safety. Ideally, it is not needed. If the car were to produce so much torque, the tires would break loose first.

 

[GregLocock]

Well, speaking as an ex wheel designer, that is a rather curious description. The wheel/hub interface will work perfectly well even if there is no shear in the bolts.



Cheers

Greg Locock

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[evelrod]

Greg, would I be correct in assuming, as I have always done, that the inner wheel and outer hub surface plays a significant role in the amount of shear applied to the wheel studs. I have always gone the extra little bit to machine these surfaces to an nice even finish. I started this procedure in the early 1960's when I was racing a Austin-Healy Sprite that would, on occasion, rip the center out of the wheels. Very disconcerting at speed. Even the slightest failure to re torque the wheels after a run would result in failure. However, never lost a stud!
On subsequent race cars, bigger, heavier, more powerful, an improperly tightened wheel would end up pulling over the nuts but, never breaking a stud. I have broken studs, for sure, but only from over torquing them.
I'm not convinced about the "spreading the shear" theory, as the Roger Penske Trans Am team of AMC Javalins used only FOUR studs---At least until the SCCA made them go back to five. They never had a failure.

Rod

 

[GregLocock]

My word picture is that the wheel studs are in tension, the torque is reacted by the friction between the wheel and the hub.

Evidence in favour of this is that the driven wheels are subject to frequent torque reversals yet the wheel/hub interface shows no sign of scuffing. If there is no relative motion between the two then no shear can be generated in the studs.





Cheers

Greg Locock

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