Four lug vs. 5 lug vs. 6 lug vs. 8 lug pattens...
I figure for large loads...most 3/4 and above P/U trucks have at least an 8 lug design(strictly for weight). But older Mustang GTs had 4 lug pattern, and don't seem to suffer too much from that design over a 5 lug design. From an engineering standpoint, how much stronger is the same size lug in 4 vs. 5?...Is 5 really "overkill"?...
Where is the "cutoff point" in reference to torque?...

 

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and my 10 second f-body all have studly axles with 5 lugs.

Dia of stud used is where they differ.

 

5 lug is about 25% more strength than a 4 lug assuming the studs are the same diameter. You are concerned with shear strength, meaning shearing the studs off at the wheel or axle flange due to torque. Shear strength should be proportional to cross sectional area of the studs. Five 12 mm studs have .88 square inches of area, while five 1/2 inch studs have .98 square inches or about 22% more. Obviously 8 lugs have 8/5 or 160% more than 5 or 200% more than 4 lugs.

Four lug Mustangs were mostly 6 cylinder cars. If you convert to an V8, it would be wise to convert to 5 lug. The bolt circle diameter also plays a part since torque is force x distance. 4-3/4 diam (GM) bolt circle is only about 5.5% stronger than 4.5 (Ford).

5 studs 12mm are about 17% stronger than the old GM 7/16 studs. I'd use 5 for any performance application, either 7/16, 12 mm (.472) or 1/2 (my preference).

FWIW, Five 5/8 studs on a 5 inch dia. bolt circle (Nextel Cup) are about twice the shear strength of five 12 mm studs. Makes sense to me.

 

Actually 5.0 V8's up till 93 had 4 lugs.

 

Yeah, but they were pretty wussy!

 

Most drag racers use a 1/2" wheel stud while most high HP cars use a 5/8" wheel stud. I haven't broken any myself but I have seen a few break. When wheel stud(s) break, it happens within the first 20 feet of the start line. I was told that a drag car should replace the wheel studs every few years depending on how many passes it does in a season.

 

Yeah,...even the Cobras...
Thanks for the replies. Just wondering why Ford would put an 8.8 4-lug in a '93 down V-8 Mustang when they build a sweet 9" used in other applications. Actually, my cousin has two Ford Diesels...one with 426K miles on it and the other with 364K. Neither rear end has been serviced whatsoever. They are 3/4 ton trucks with 9300 tow ratings and must be pretty darn good. You don't hear of a lot of 8.8's blowing...even with the 4-lug spindles. I figured that they must have been almost as strong as a 5-lug...or Ford wouldn't have done it!...I can't remember if the 429 Cobra Jet Mustangs (and Torinos, etc.) had a stronger rear end with 5 lugs. Maybe it was 4 with a larger dia. lug...

 

On my wussy 1.65 60ft times I was folding stock 5 lugg's in my stock axles on my 7.5. My Moser has 1/2inch 5 lugs

BTW I thought the Cobra(all Fox) got the 5 lugs disks? Guess all the ones we have here are converted

 

7.5's are the 4-lug 1-legged 4 and 6cyl. rear. A bud of mine has a '93 Cobra that he did the swap on...

 

The 7.5 I was refering to used to sit under my 95 Z28 and chevy never did v8 and four lug

 

I would almost agree with the replacing the studs per miles used on a drag car but I'd think a R & R cycle that track's the number of tightening cycles would be a better indicator of "when" to replace. If I was swaping out rims and tire with track tires cause I drive the car I'd be changing studs every two seasons!
Think of them as a teched / SFI numbered part like seat belts or fly wheels, or bellhousings that are to be used for two years then replaced!
I've always felt wheel studs on aftermarket axles should be treated as such.

....don't get me going on driveshafts
thats a whole nother item that should be SFI.

 

LOL You Breaking parts again Jeff?

 

Thats LOTS of cash for people with 12 bolts to replace the studs. New axle bearings, seals, and then the bolts themselves. Hopefully mine hold up, eeek

 

Good points, Hawk.

If the studs are used correctly, that is, not used with spacers that put them in bending instead of shear when they take the torque loads, and if they are not yielded when tightened, I don't see the need for a time change.

Realistically however, sometimes we use spacers, and we may occasionally overtorque the nuts, so changing the studs every so often is good insurance. You do use a torque wrench EVERY time you change wheels, right? It only takes one time with a 200 lb-ft hit with the impact gun to screw the pooch.

 

Ewww, that made me cringe!

-Mindgame