TECH Stuff # 13 – ET Lug Nuts. What are they, and why?

Within the Aftermarket Wheel Industry, a controversy began during a meeting of the Wheel & Tire Industry Council meeting at the 2008 SEMA Show. A presentation was being done by some of the members regarding Fitments and Applications. It was suggested that ET lug nuts are recommended in cases where questionable thread engagement was present. A statement came from the audience, that ET lug nuts did nothing for thread engagement and had no usable purpose. I took exception to that statement and argued that ET lug nuts are all about thread engagement. Since that meeting there has been a lot of discussion in regards to the true purpose of ET lug nuts, why they were developed and a lot of other hog wash about technical aspects of lug nuts in general. I’d like to add my 2 cents to this discussion. I’ll start by giving my recollection of why ET lug nuts were developed.

Going back to the 50′s and early 60′s, the Aftermarket Wheel Industry was born because of the desire of car guys that wanted something other than stock painted wheels in stock sizes. These cars guys wanted chrome wheels and they wanted them wider so they could use bigger tires. At that time, the OEM’s didn’t offer aluminum wheels. As a result the stud length was shorter on the vehicles. The average stud length was about 3/4″ to 7/8″. This was adequate for steel wheels and there were no thread engagement issues. Then in the early 60′s, the Aftermarket Wheel Industry started offering aluminum alloy wheels. The developers of these wheels solved the thread engagement problem by coming up with the Mag Type lug nut. Since the mounting pad thickness was about the same thickness as the stud length on the vehicles, which left little or no threads on the stud to attach a standard conical seat lug nut, they came up with a lug nut that had a shank that went into the wheel lug hole enough to accomplish proper thread engagement (see illustration). This system was adequate but left a lot to be desired. In order to assure that the wheel was attached to the vehicle with good alignment and acceptable runout, the diameter of the lug hole had to be drilled with a minimum of clearance for the lug nut. After the vehicle was driven enough to heat up the brakes and wheels, the aluminum wheel expanded, thus shrinking the diameter of the lug nut hole. It was then very difficult to remove the lug nuts when the wheel was hot, in order to change a flat tire or what ever.

Now moving forward in time, the OEM’s began offering aluminum alloy wheels on new vehicles. They determined that the use of Mag Type lug nuts was not the best system. They began to offer their aluminum wheels with conical seat lug nuts. They did however lengthen the studs on the vehicles that were offered with aluminum wheels so there was adequate thread engagement. This prompted the Aftermarket Industry to adjust their offering so they could keep up with the OEM’s. In the late 80′s, the Aftermarket Industry began drilling their lug holes with a conical seat instead of the Mag Type lug hole. It was then discovered that the use of a standard lug nut (Acorn Type) was causing problems with the seating area of the wheel. Steel inserts was a solution, but it was soon discovered that the OEM’s were using a Bulged Type lug nut which eliminated the problem with the seating area. So the Aftermarket lug nut manufacturers started offering Bulged Type lug nuts. At that point it seemed that all was well in the Aftermarket Wheel Industry. Not so.

The problem of thread engagement became an issue when a conversion from steel to alloy wheels was made on vehicles that had short studs and were never intended to have alloy wheels. The Aftermarket again responded by developing a Bulged Type lug nut with an extension that would go into the lug hole enough so that proper thread engagement could be accomplished. This lug nut was called the ET (extended thread). Combined with the bulged seat area, the extended thread provides the best attachment that is currently offered.

I have recently observed another problem. In my illustration I show examples of wheels with mounting pad thicknesses from .390″(10mm) to .630″(16mm). I do not recommend a mounting pad thickness to be greater than .390″(10mm). I have done extensive testing on wheels produced in China since 1993 using a .390″(10mm) mounting pad thickness. I have sold in excess of 750,000 wheels and never experienced any failures. Using a Std. Bulged Type lug nut in a wheel with a .390″(10mm) pad thickness on a vehicle with short studs (.800″) (see illustration) is still under the minimum thread engagement recommendation of SAE. And using an ET Bulged Type lug nut in a wheel with a .630″(16mm) pad thickness on a vehicle with short studs (.800″) (again see illustration) is also under the minimum thread engagement recommendation of SAE. In my opinion, ET lug nuts should be used on all aluminum wheels. In summary, what does an ET Type lug nut do? It provides a method to assure proper thread engagement. What is proper thread engagement? Proper thread engagement is defined as engaging the threads onto the bolt or stud by at least the diameter of the bolt or stud. Prior to mounting a wheel on a vehicle, the length of the stud should be checked against the thickness of the mounting pad below the bottom of the conical or spherical seat. Another way to check is to mount the wheel and check how many turns the fastener makes before it reaches the seating area. An example is if using a ½”-20 nut, then there should be at least 10 complete turns.

31 Responses to “TECH Stuff # 13 – ET Lug Nuts. What are they, and why?”

  1. David Says:

    Thanks for this TECH information we have been sure to pass it on to all of our wheel distributors.
    Keep the info coming. See you at SEMA 09
    David

  2. Larry Says:

    David,

    Thanks for the response. If you haven’t read the other TECH Stuff articles, please do. I think there is some useful info in them. I’ll be at SEMA 09. Hope to see you then.

    Larry

  3. Brian Boley Says:

    Larry,
    Some additional points on the ET style lugs nut. When used make sure the shank of the lug nut enters the wheel freely, although I can’t remember specific applications on some wheels the tolerances can be so tight you will not get correct torque on the stud. We used to remedy this by using a drill bit to enlarge the hole slightly, the metal removed was so minimual it did not contact the seat of the wheel. Secondly I used to distribute the ET style nuts with two seperate washers one with an offset conical seat and the other with a centered conical seat. This allowed the installer to convert a mag style wheel to a acorn the washers were used (offset 5×4.5, 5×5) centered (5×4.75). Not exactly remembering but I believe anson and ET both used this set up as the mounting pad was tinner. Glad I found your site been in the wheel industry since 1989.
    Brian

  4. Pete Says:

    Good info. Benn having trouble with some old wheels that use the mag type nuts and have considered machining them for the ET or at least tapered nuts.

    Since you have been around tis industry so long, perhaps you have knowledge of this outfit, couldn’t find any info myself.
    “Wheel Distributers Inc” Ontario CA is cast into the backside.
    Thanks
    Pete

  5. Larry Says:

    Pete,
    If you machine your wheels with a conical seat, make sure you are getting the seat concentric with the existing hole. This will assure you that your bolt hole pattern will remain concentric with the centerbore of the wheel. Also make your lug seat as large as possible (at least as large as the lug nuts you choose.

    And remember to make sure that when you put your lug nuts on that you have at least minimum thread engagement (diameter of the stud). Check out TECH Stuff #4, “A Few Facts About Lug Nuts”.

    Also, use a Bulged type lug nut.

    As for info on Wheel Distributers Inc, I don’t recall that name, but I’ll do a little research and send you an email.

    Thanks for the comments.

    Larry

  6. Mike Says:

    Larry-

    I have a question you might be able to help me with. I’m installing some 5mm spacers to fit some wheels so they don’t rub my calibers. The ET type lug nut seems to be the right solution but will definately require drilling out existing hole in wheel to fit the .62 diameter shank portion of the nut. I’ll be using 1/2×20 ET bulged sytle lug nuts. I’m curious why we don’t here more about the need to drill (like brian’s post)? I would think that this is what most all who use ET sytle type lug nuts will have to do because typically the hole in the wheel is just slightly bigger than the stud? Having said that, my plan is to drill the existing hole of around 9/16 to a larger size of 11/16 in order for the ET sytle lug nuts to fit through past the 60 degree beveled seat. I was going to drill out with 5/8 bit but thought .005 (ET shank portion of lug nut is .62 and 5/8 is equal to .625) of play may not be enough if the drill didn’t cut perfectly in line with existing hole and bind like the old long shank Mag Nuts you talked about in your informative article. Anyway, my only concern over doing what I’d layed out is a bulge lug nut is 3/16 wider (7/8) at it’s broadest point of the bulge than the 11/16 hole I’m about to drill. Is there enough meat still left in the beveled seat to support the 100 foot pounds of torque of a 5×5 pattern? Thanks for your help.

    -Mike LaLonde

  7. Larry Says:

    Mike,

    It’s great to see that you are aware that just putting spacers on to clear brakes is not a good idea. The use of ET lug nuts is a perfect solution. I think that the reason you don’t hear more about drilling out the existing lug holes to accommodate ET nuts is there are a wheels that come from the factory with a .625 dia. hole. The wheel companies that understand the thread engagement problems offer the .625 dia. lug hole. However there are many companies that just copy everything and don’t do much engineering so they aren’t even aware of such problems.

    As for drilling out your holes, I would recommend using a 5/8″ (.625) drill bit. Normally the diameter will end up a little larger unless you are using a milling machine or large drill press with the wheel clamped tightly and the hole perfectly aligned with the drill bit before you drill. By using a 11/16″ drill you will lose some of the seating area of the wheel. The minimum seating area that is safe is .175 (.800-.625). The more seating area the better. The dia. at the top of the conical seat in the wheel should not be less than .800″.
    You mentioned that 100 ft. lbs. was the torgue you were using. The torque requirement is based on the diameter of the stud not the bolt pattern. The recommended torque for a 1/2×20 stud is 85 ft. lbs. Over torqueing will fatigue the studs, and that’s not good. Check out Tech Stuff #4, A Few Facts About Lug Nuts.

    Thanks for checking out my blog and good luck with your project.

    Larry

  8. Roddy Says:

    Hi Larry, I have a similar problem to Mike and was planning on drilling out the holes on my mags. i have a 16mm drill bit. is this too large or should i get hold of a 5/8 one instead? My mags have a steel insert and i don’t want to remove too much of that or the tapered seat!

    Thanks,
    Roddy

  9. Larry Says:

    Roddy,

    16mm is slightly larger than 5/8′ (only .0049″). There is no problem using 16mm. Be sure the drill is good and sharp. Be careful not to catch the drill in the insert and cause it to spin in the wheel. It could cause the hole to open up in the wheel and then the insert might not center proberly and you’d lose concentricity of the bolt pattern to the wheel. If you’re using a spacer, make sure you use ET lug nuts.

    Good luck,
    Larry

  10. Van Says:

    Larry,
    I just came across this article and would like to make a few comments. I have a 1979 Corvette and purchased a set of 15″ Cragar Pro 390 wheels. They use the bulge acorn lug nuts. I have to use spacers to clear the calipers and there are not enough threads to safely use this setup. If mag-style lug nuts were used, I could have used longer lug nuts and would have no problem (it’s how I got a wider track using the stock wheels). So one person’s solution is another person’s nightmare. In my opinion, if it’s a mag-style wheel is should use a mag-style lug nut. When the playing field rules are changed it affects the field of play.
    Regards,
    Van

  11. ben Says:

    hi just to ask a question i have a set of merc amg wheels is it ok to enlarge the bolt holes by 2mm thanks ben

  12. Larry Says:

    Van,
    E.T. lug Nuts were developed for situations such as yours. I’m not a fan of Mag-style lug nuts. Some OEM’s (Toyota) use them, but their OEM wheel has the center bore that is sized to the hub so they can maintain concentricity. Aftermarket wheels that use Mag-style lug nuts have large center bores to fit multiple vehicles. In order to prevent the lug nuts from seizing up on the wheel after the wheel heats up from driving, the lug hole has to be made oversize. Thus concentricity is compromised and excesive runout occurs which causes a 1st harmonic runout (wheel vibration at 55 – 65 MPH). I suggest using ET lug nuts. You’ll solve your thread engagement problem.

  13. Larry Says:

    Ben,

    I would need more information before I could give you my opinion on opening up your lug holes 2mm.

    What type of lug nut or lug bolt are you using?

    What is the current size of your lug holes?

    When enlarging the size of a lug hole that has a conical or spherical seat, the area of the seat is decreased which can cause a problem. Check out my Tech Stuff #4 – A few facts about lug nuts.

  14. ray simpson Says:

    I have some old Halibrand magansuim wheels. They dont excatly fit my studs, they are off about a 1/8″ or less . What is the best way to fix this problem? Lug nuts of what style? I have a 5/8″ hub thickness.

  15. Larry Says:

    Ray,

    I’m assuming that the lug hole you have is to small for the studs on your vehicle. If that’s the problem, you’ll need to open the lug hole. I believe the old Halibrand magnesium wheels used a Mag type lug nut. Check out my TECH Stuff #4 – A few facts about lug nuts, and you’ll see how the Mag type works. Locate a source for lug nuts and check to make sure they can accomodate your 5/8″ hub thickness. Measure the diameter of the lug nuts and drill your lug holes accordingly. In TECH Stuff 13 I discuss the mag type lug nut and the problems associated with it. Make sure you have a little clearance between the lug hole and the lug nut. Good luck and let me know how it worked out.

    Larry

  16. ray simpson Says:

    Larry: The rims are not fitting do to the fact the lugs and the wheel drilling are different. Can i enlarge the wheel holes? Will this work? I have rimmed them out so they will fit but I don’t feel good with the fit.
    Tahnks
    Ray

  17. Larry Says:

    Ray,
    Sorry I misread your problem. It appears that you have a situation of 2 different bolt patterns. Enlarging the holes is not a good idea. You’d have to use some very large washers with Mag type lug nuts. I don’t recommend doing that because you would have problems maintaining lug nut torque. There are wheels that are manufactured with elongated lug holes that could cover 2 or even 3 different bolt patterns. Crager SS’s are a good example. They can offer a 5×4.5 or 5×4.75 bolt pattern in the same wheel. They use a Mag type lug nut.

    If you have already elongated your lug holes, and I think you have, I hope you did it in a milling machine so you could maintain the necessary concentricity so you won’t have balancing or vibration problems. At this point I would suggest you send me a photo of the wheel and give me the original bolt pattern of both the vehicle and the wheels. Send it to my email address wheelprofessor@sbcglobal.net.

    I’m looking forward to hearing from you.
    Larry

  18. Joel Says:

    Hi, I’m late to this discussion, but wanted to ask a question. I work for a gentleman who’s been in the wheel industry for years. He feels that the ET was never designed for thread engagement but rather to assist in vibration problems and make the wheel lug centric. He states that assertion that they were designed to help with thread engagement is false and that they were originally designed by a company called E-T wheel. Any help in clarification would be greatly appreciated.

  19. Roger Says:

    Larry,

    I am wanting to use 1/2″ spacers to get my custom front wheels out where I want them on an 1982 corvette. I am planning on using longer grade 8 studs and e-t nuts. Is a 1/2″ spacer safe for this application? The studs are 7/16 dia.

    Thanks!

    Roger

  20. Larry Says:

    Roger, In my TECH Stuff #6, I don’t recommend using any spacers over 5/16″ thick. However on my own vechicle I’m using a 7/16″ spacer. I made the spacers myself and made the holes for the studs only .010″ larger than the studs. I am also using 1/2″ studs. The material is 6061-T6 aluminum. My vehicle is a 1954 Olds which is at least 4,000 Lbs. I don’t drive the car on an everyday basis, mostly cruises and a few road trips. With your Corvette, which is much lighter, you could probably get away with a 1/2″ spacer making sure you followed the same proceedures I did with my spacers. Another thing to make sure of is not over torquing the lug nuts. That will stress the studs and you could get fatigue cracks. 85 ft. lbs is max for a 7/16″ stud. Good luck

  21. Larry Says:

    Joel, since you’re late to the discussion, I thought I’d be late to respond. I’d be interested to know who you work for. Sounds like he’s been around the industry for awhile. In response to his assertion, he could be right. I think my assertion sounds better, but then it really doesn’t matter. The ET type lug nut works great for thread engagement, so there you have it. As for the term “lug centric”, that was created by the aftermarket wheel industry to justify the fact that their wheels were not centerbore specific to the hub. I also question the effectiveness of the ET extension assisting in vibration problems since the tapered seat of the lug hole and lug nut would over ride the ET extension. I’d welcome any comments you or the gentleman you work for would have.

  22. Joe Says:

    Larry, If my studs are long enough to support a conical nut, do I need to run an ET style. I have upgraded axles and studs on my truck, but wish to run an older mag slot style wheel. The wheel is .500 thick, and set up for a conical style ET I just prefer the regular conical. Thanks

  23. John Woods Says:

    Hey Guys thanks for the great info. I am using aftermarket 17×9 Pontiac Rally II cast aluminum wheels on my 1970 Trans Am. I upgraded the front brakes during the upgrade had some 1/2 inch studs installed. I noticed the studs and lug nut engagement was ok but not as much as it should be. I ordered a set of ET lug nuts to resolve the issue and get some extra thread engagement. Thank you!

  24. EVO 8 MR BBS wheels? - Page 3 Says:

    [...] developed really has no bearing on this particular application. Everyone can read a decent article here for some history on them. They would be relevant here if the wheels were compromising the wheel [...]

  25. Wheel Studs or shanked/tapered nuts - Dodge Cummins Diesel Forum Says:

    [...] [...]

  26. Ernest Says:

    Will a .62″ diameter shanked lug nut fit into 5/8″ hole?
    The fuel wheels I purchased have 5/8″ holes
    The gorilla lugs I want to order are .62″ shank diameter
    Thanks for any info

  27. PMR radios Says:

    One of the better items i have read this week.

  28. Dan Says:

    Hi, I’m running a set of VW ball seat wheels from a Jetta on my neon. I need to run a 5/16 spacer to clear the excellent tread tires until they are worn out. I’ve got some ball seat lug nuts already from doing this on our old neon, but without the spacers (proper tire size) do they make an ET ball seat lug nut? I’m only getting about 1/3 of the threads of my current lug nuts engaged to the lug studs. I feel like that really isn’t enough engagement. I’d love to be able to just go buy the proper size tires but I don’t currently have that kind of funds. Any help is greatly appreciated!

  29. Lug nut question Says:

    [...] [...]

  30. Larry Says:

    Tye, I don’t have a copy of the SAE recommended practice for thread engagement with me I’m traveling. However the standard is very basic. The amount of thread engagement is the diameter of the stud is the minimum amount of engagement. In other words, a 1/2″ stud would need a 1/2″ of engagement or a 1/2″-20 would be 10 threads.

  31. Liam Russell Says:

    One of the better items i have read this week.

Leave a Reply