I just got a new set of aftermarket wheels for my box and thought it was odd that Tire Rack included these odd looking (to me) lug nuts. Since they are el cheapo zinc plated nuts I started looking for replacements which led to learning about ET lug nuts (extended thread). Apparently Scion installed short length wheel studs designed for the oem steelies and the oem alloys use mag style shank bolts to acheive sufficient thread engagement between the studs and nuts.

Anyway, long story shorter, minimum safe thread engagement is the threaded width of the stud. In our case, 12mm or 1/2". I measured 3/4" TE with the ET lug nuts. If I subtract the ET shank length of 7mm from that I have less than 1/2" of TE which is not safe.

If you are running aftermarket alloys on your XB with standard conical seat lug nuts and aren't sure if you have full thread engagement, it is probably a good idea to check. I'm sticking with ET lug nuts even though they're harder to find and I haven't found any ET lug nuts or locks in black. I wouldn't even consider aluminum lug nuts without installing longer wheel studs. Longer studs are always an option but ET lug nuts are easier and less expensive. Gorilla has ET lug nuts, tuner lugs and locks but only in chrome.

 

could explain why i lost 2 of my muteki lugs on my old wheels, on two separate occasions when they were torqued to spec.

good to know!

 

Very likely. I'm not taking any chances. I still remember when a front wheel almost came off my 68 Camaro SS396 way back when because some ignorant wrench monkey forgot to tighten my lug nuts. By the time I felt something wrong and stopped to check, 3 of 5 studs were broken off and only 2 studs and 2 loose nuts were keeping the wheel on. It happened suprisingly quickly.

I don't know how long TC studs are but if my XB studs are so short that I only have 7/16" thread engagement with MSW wheels, chances are that many XBs with aftermarket wheels are running around with less than full thread engagement. 7/16" might be enough in most cases but why risk it?

 

I have no idea what thread engagement is, but with an auto trans & low hp n/a engine, I'm not worried. I've had my wheels & lugs on for over 18k, and they were rotated almost 10k ago with no issues. Time to cross my fingers?

 

It's not really a hp/performance exclusive issue. Lack of adequate lug nut thread engagement could cause the nuts to loosen or even fail due to the lack of sufficient thread to thread contact between stud and nut just from normal day to day driving.

Since all XB2s presumably have the same length wheel studs, the key here is the wheel thickness between disc hub mating surface and lug seat. In the case of my MSW wheels, that part of the wheel is thick enough to necessitate ET lug nuts, according to OZ/MSW, Tire Rack and my own measurements

Luckily it's pretty easy to check. Put a socket on one lug nut and make a reference mark on it at the wheel surface. Loosen the lug nut to where you could remove it and make another reference mark. Measure the distance between the marks and you have your thread engagement. For 12mm studs it should be 12mm or more.

Another method is to count the number of full turns from first thread engagement to fully torqued but I haven't measured that yet.

 

Nuts/bolts rely on friction and very slight stretching of the threads to stay tight. When you reduce the number of threads that are in contact, you reduce the friction between the two parts, allowing them to come loose more easily. Its always a good idea to check nut/lug torque some miles after you tighten them up after mounting/rotating.

 

I meant to say I have no idea what my thread engagement is.

I guess I'll be measuring it, thanks for the heads-up Fred.

 

Is anyone running longer studs?

 

Good info Buickid.

Cionide, it can't hurt to check. 11mm might be fine but I'll feel a lot better with 18mm. Oem's certainly don't go with the minimum 12mm. My oem wheel nuts had at least 18mm.

 

I hear ya. Like buickid referenced, I have had my lug nuts checked & retightened (for free) 80-100 miles after every rotation... gotta luv America's Tire Company (Discount Tire). Each time there was really no tightening necessary, but I feel safer knowing they checked it.

BTW, it's 3am in MD, do you ever sleep, Fred?

 

After 18k miles and no issues, you should be fine. I do however think it wise for XB owners with aftermarket wheels to check their thread engagement since our short wheel studs are borderline safe for aftermarket wheels. After reading a few on-line articles on the subject, I'm a believer in ET lug nuts. Now if only Gorilla, McGard, Muteki, et al would get on board and make them in diferent colors and styles.

I'll get plenty of sleep when I'm dead.

It also helps when you work 2P to 2A...

 

I like your thought process.

 

Thought process? More like random neural synapses firing, fingers twitching and words appearing on the cyber-life optical interface...

Ignore me, it's 5am and past my bed time. G'nite.

 

I seem to remember plenty of nut spinning to tighten my Koenigs (DiscountTireDirect), but it probably is worth checking -- thanks !

 

It might just be that my MSWs are a little thicker at the studs than most wheels but I thought it important enough to pass on to others. If I've only got 11mm thread engagement, I doubt that other brand alloy wheels have much more than the min 12mm with the short oem studs.

Here are some pics of ET vs std lug nuts for anyone who isn't familiar with them already:

 

I spoke with Tire Rack again today and it appears that MSW uses a thicker mounting pad than most wheels. This is not to say that other wheels all have thinner mounting pads so check your thread engagement accordingly. Anyway it means that I should be running ET lug nuts but I'm gonna risk it with Gorilla black chrome locking nuts instead. I've got 6.5 turns on them and Tire Rack says 6.5 turns is the bare minimum for 12x1.5 studs.

I couldn't use the small dia. tuner lugs with my wheels. The tapered seat on them is way too small for the conical seat in my wheels. The Gorilla ET locks fit well but I'd need 20 of them all keyed alike. Or I could get chrome ET 13/16" hex lugs from Gorilla and use 1 lock per wheel. However black looks much better with my wheels.

ET lug nuts offer nothing but advantages. They provide extra thread engagement and the shank helps to center the wheel better. All in all, ET lug nuts are by far the best way to secure aftermarket wheels to oem studs yet none of the companies producing lug nuts offer them in anything but chrome. I strongly suggested to Gorilla that they are leaving a potential market untapped. I hope they listen.

Anyway, more lessons learned and since everyone likes pics, here's one:



Left to right: Gorilla black chrome locking lug, Tire Rack ET bulge lug, Gorilla ET locking lug, Gorilla ET SD tuner lug

 

Bottom line here is this:

http://www.tirerack.com/wheels/tech/...jsp?techid=107

All Scions use 12 x 1.5 mm wheel studs so all Scions need at least 6.5 turns on the lug nuts. If you're not sure, just remove one lug nut and count the number of turns until it's tight.

Edit: I'm an idiot. Every expert source agrees that minimum lug nut thread engagement is equal to the threaded width of the stud, in our case 12mm. 6.5 turns on a 1.5 thread pitch wheel nut is only 9.75mm of TE, 7 turns is 10.5 mm and 8 turns equals the minimum TE of 12mm.

So the bottom line is that you need 8 full turns on your 12x1.5mm lug nuts to acheive safe thread engagement. I guess I have to settle for silver chrome plated ET hex lug nuts, longer studs or new wheels...

 

Well, I finally found suitable lug nuts to replace the zinc-plated crap that Tire Rack supplied with my wheels/tires. They're available from Gorilla as a custom order, but only through an authorized retailer (PITA). Gorilla dropped them as a stock item due to lack of demand.

It came down to these or longer wheel studs. I found one set of 20 in stock at Brandsport and also custom ordered a set of 24 through a source recommended by Gorilla. If anyone needs a set, let me know. The additional stud-centric wheel centering provided helps minimize vibration, the extra thread engagement keeps them from loosening, the case hardening makes them stronger than conventional lug nuts and each lug being a lock makes them very theft-deterrent. Win-win-win-win.

Gorilla part # 68633N

 

Do those come in open ended ones? If so I'm interested...

 

Interesting thread, good info. With my aftermarket wheels and gorilla tuner lug nuts I get about 8 1/2 turns before I torque them down.