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history of tapered lug nuts/bolts/screws

history of tapered lug nuts/bolts/screws

history of tapered lug nuts/bolts/screws

My question is if anyone has solid info whether the tapered nuts were initially used for some reason ( either common knowledge belief, superstition, or SAE or ASME spec or ??) beyond centering.

In my limited experience with post WW2 vehicles to the modern era it seems like tapered seats in the wheels and on the nuts have always been standard on stamped steel wheels. And, the evolution from lug centered to hub centered wheels is now just about 100%. For a while US alloy aftermarket (mag) wheels used flat washers, but some OEM alloy wheels have used tapered seats, some (notably Volvo in the 70s and 80s) using cast in tapered steel inserts.

Some folks have suggested that the tapered seat resists loosening better, but my experience and observations suggest that springiness in the raised area around each bolt in most stamped wheels is what is really effective in preserving preload, as it simulates the stretchiness (elongation) of a long bolt or a stout belleville washer.

The difficulties maintaining preload with a 100% clamped metal joint using a relatively short fastener are clearly reported in MIL specs and Holokrome literature.
Similarly it is standard practice for tire shops to document on the invoice that a lug titeness check is required a few hundred miles after installing new tires on cars with alloy wheels.
Similarly II, and an engineer acquaintance whose family manufactured very successful alloy wheels for big rigs mentioned lug loosening was a common issue requiring tightening as maintenance.

RE: history of tapered lug nuts/bolts/screws

Knowledge within GM Fastener Engineering was that wheel fasteners (nuts or bolts) with spherical or conical seats provided resistance to torsional and lateral forces even if there was high preload variation.

Preload variation has many sources, including short clamp length. For wheels produced in 2000 (relatively "modern" in my opinion), the allowable thickness variation on one wheel seat was 1 mm, which was quite large. For five fasteners on one wheel, the accumulated tolerances were substantial. Hence, the need for the "star pattern" tightening sequence, which is common knowledge in industries using bolted flanges.

There are so many SAE standards that touch on wheels and wheel fasteners:

J267, J328, J694, J851, J995, J1102, J1835, J1842, J1965, J2283, J2315, J2316...

RE: history of tapered lug nuts/bolts/screws

Tapered nuts will help to distribute force due to wheel torque evenly among the studs. If flat nuts were used the torque would tend to be carried by the first stud that hit the side of the bolt hole in the wheel.

RE: history of tapered lug nuts/bolts/screws

I'm sure that the "coin" effect of having the contact area of the lug nut raised above the mounting surface of the wheel to hub is an important consideration for steel wheels. I suspect the effect is much less pronounced with alloy wheels.

I am sure that the reason why OE's used tapered seats for alloy wheels is commonality. Further, the use of tapered lug nut seats was carried over when hub centric wheel were introduced.

RE: history of tapered lug nuts/bolts/screws


Have just joined this forum and this is hopefully still be a useful response to your earlier post. I've designed a lot of wheels with conical and flat nut seats over the last 35+ years and I was part of the SAE subcommittee that created SAE standards 2315 and 2316. In answer to your question:

* Conical nut seats are typically set in a Belleville washer boss that greatly facilitates stress distribution and torque retention. Steel wheels also have a secondary Belleville washer effect as the entire mounting pad is lifted in the center.
* Conical nut seats also provide a mechanical stop to wheel rotation during severe vehicle handling maneuvers. Required wheel clamp load is typically defined by using a "clutch theory" where clamp load keeps the wheel from rotating. In the real world, applied torques and corresponding clamp loads are often not controlled, any wheel slip is a failure, and this can be a very real concern.
* The actual wheel to hub joint is far less robust than most people think. Actual stud stretch is only approx .05mm (.002") and any amount of dirt, etc that interferes can cause real concerns very quickly if the wheel is loaded aggressively.
* Because of the limited stud stretch, any paint on the nut seats of aluminum wheels is a serious no-no an must be avoided. This is also very true of nut seats on the class 8 and 9 heavy commercial vehicles.
* Steel inserts were mostly seen on early aluminum wheels that generally weren't heat treated and use a hypo eutectic alloy. Most current cast wheels use A356 heat treated to T6 and the only issue is getting sufficient bearing area.
* Hub-centric is dominant to reduce installed assembly runout. You would be correct in noting a potential centering conflict with the conical nut seats. This is a secondary concern that most people just tolerate. Some European designs us a bolt with a spherical nut seat to potentiall minimize this effect.
* For class 9 commercial vehicle, many users ahve adopted the "Pac-nut" which gives a beneficial Belleville washer effect.

I don't know when conical seats appeared in steel wheels, but I'm certain it was pre-1950s, and for the torque retention and stress distribution benefits that the design offers.

Hope this helps

RE: history of tapered lug nuts/bolts/screws

thanks Popeye427.

Now risking dredging up an old debate, how do you prepare and tighten lug nuts OEM, on that two year old car, and when swapping over the old Volvo's snow tires in crusty-rusty New England?
clean, lube/ no lube, max torquage, adjusted for lube if any, etc.
Olden 60 to 80 lb-ft days, not the modern ones used on Ford Pickups with torque ( and maybe even angle tightening?) so high they seem to be approaching stud yield.

RE: history of tapered lug nuts/bolts/screws

A lot of the old practice has to be set aside as times really have hanged for wheels and tires. I started out as a tire engr in the 70s, working in R&D on the original high performance radial 50 and 60 series tires. In skidpad testing we could easily pull the lug nuts through a standard wheel bolt boss. We always specified police or a heavy duty wheel as aluminum wheels then weren't OEM, and we generally were required to use OEM and report back to them if there were issues.
What you have now are tires that easily surpass those old performance tires and a even more load on the wheel ends. Torques and clamp loads need to generally be higher and bolt circle diameters are increasing. Not sure where you found those old torque specs but we set Fords at 100 ft-lbs +-15 for M12 and 1/2" studs and 150 ft-lbs +-15 for the 10.9 M14s that we changed to around 2002MY. Don't worry about breaking the M14s as min yields are around 27,000psi min tensile, and you'll have a hard time hitting 9,000 lbs tensile with the standard thread coatings at 150 ft-lbs. Remember that T= kFd for threaded fasteners and you need more torque to get the same clamp load for the larger diameter fastener. And yes, that M14 stud is super strong.

For the wheel mounting, I never did get a greased pilot recommendation in the shop manuals, even though, every almost every Ford wheel pilot is greased on the assembly line. What I do for my own wheel mounting surfaces at home is:
* Anti-sieze on the stud threads and either calcium grease or anti-sieze at the wheel pilot. You don't want to be on the roadside trying to pry off a
corrosion locked wheel.
* Wire brush the rotor and wheel mounting surfaces to minimize any corrosion buildup. If I'm seeing heavy corrosion on these surface, and its generally a given here in Detroit area, I'll take a chip brush and smear a very thin film of calcium grease on those surfaces. No, its not in the shop manual, but it works for me if not done to excess.
* Keep the grease and antisieze OFF the nut seats. Any grease on the wheel nut seats will just about double the stud tension.
* If you have an aftermarket wheels and they have left any paint on the nut seats, run the nuts on and off to full torque three of four times to abrade away the paint, Brush away the dust and make sure the nut seats are clean before final install.
* Use a torque wrench for assembly. It may seem overkill, but Harbor freight sells a cheap 1/2" clicker for around $10 and consistent torques are essential to minimize any effects on brake roughness.

RE: history of tapered lug nuts/bolts/screws

Additionally, no excessive lubricant on the stud threads, for the same reason as the wheel seats.

RE: history of tapered lug nuts/bolts/screws

The oldest drawing for which I was design engineer was wheelnut B60. Drawn and released in 1928, scarcely modified since. Still in use in the 90s on steel wheels at Ford Australia. It had a tapered seat.


Greg Locock

New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: history of tapered lug nuts/bolts/screws

Very interesting.
On a number of vehicles with over 100k miles, I see wear on the wheel's nut seats.
The nuts were worn too, and when they look too ugly I replace them.

But I've been using anti-seize on threads and seats to avoid the thread and seat damage.
I've gotten away with it so far, but it seems that I'm doing it wrong.

What do you recommend to avoid nut face and seat wear/damage?
What about thread damage? Is that just from the animals at commercial shops blasting them off fast with air wrenches?

Jay Maechtlen

RE: history of tapered lug nuts/bolts/screws

I don't think it is possible for a vehicle to get to 100K miles and the wheels not to show some wear on the lug nut seats. So I wouldn't worry about that. What you should worry about is if there is DAMAGE - that is, the seats are distorted or scoured or something like that. Even then, so long as one can get a good solid tightening to the lug nut, I think it is good to go.

Thread damage? I think that what we are really talking about is cross threading. Even resting the wheel on the lug studs is going to damage the threads on the studs.

- And, yes, using an impact wrench without hand starting the lug nut is much more prone to cross threading.

RE: history of tapered lug nuts/bolts/screws

I haven't seen actual cross threading - and that would have very obvious.
But I have seen threads that had wear, with shavings of metal coming off of them.
Generally I clean them up, use a wire brush and compressed air to get the debris out of there, then lube it going together.
The treads need to work freely (by hand) before I'll put it together.

Jay Maechtlen

RE: history of tapered lug nuts/bolts/screws

Tapered bolts in V grade were used to bolt the crown wheel to its carrier on the British made Triumph GT6. Provided that Loctite thread lock was used and providing that the bolts were torqued-up properly the crown wheel would never come loose again. Whilst one was in there it was a good idea to use a Swiss file to clean up the oiling slot as often casting "fraze" would reduce the size of the aperture that was intended to oil the pinion bearings. In fact some final drive units used to seize. It was also important to have the upgraded crown wheel carrier as the early type that resembled the letter U stuck onto the letter O was rather weak. The later type resembled a top hat that had little oval windows for fitting the planet gears. This type was awesome and a car fitted with such a hypoid unit could cross The Alps with ease.

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