Something else I always wondered about...

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?...

Top fuel
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superstock
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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.

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.

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

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

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.

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.

It only takes one time with a 200 lb-ft hit with the impact gun to screw the pooch.

Ewww, that made me cringe! :eek:

-Mindgame

New Viper has 6 lugs, that many on a sports car has to be a first.

Given that spacers aren't used...and sticky tires aren't used...are the 8.8 Ford 4-lug rears at any disadvantage over a street-driven 5 or 6-lug design? I figure with autocrossing, an advantage may exist (side-force)...but I haven't (in my experience) noticed a lot of lug failures due to "shearing" forces. How much torque does it take to "snap" a set of 4, 5 or even 6 -lugs of the same dia.? (engineering question)...assuming that no spacers are used, that lug nuts are torqued properly...and that the rear rims would be "locked-down". Also, increasing tire height and rim size has to have a negative influence on lug integrety...but is there a formula for this?...
Sorry to be so long-winded, but I'm curious how this all ties in together....

Given that spacers aren't used...and sticky tires aren't used...are the 8.8 Ford 4-lug rears at any disadvantage over a street-driven 5 or 6-lug design? I figure with autocrossing, an advantage may exist (side-force)...but I haven't (in my experience) noticed a lot of lug failures due to "shearing" forces. How much torque does it take to "snap" a set of 4, 5 or even 6 -lugs of the same dia.? (engineering question)...assuming that no spacers are used, that lug nuts are torqued properly...and that the rear rims would be "locked-down". Also, increasing tire height and rim size has to have a negative influence on lug integrety...but is there a formula for this?...
Sorry to be so long-winded, but I'm curious how this all ties in together....

The studs only get as much torque load as the tire grip allows. That's the thing that saves parts and allows OEM 7.5 rear ends, etc. Remember that every extra pound of mass, say in a larger axle, needs to be shlepped around by the car it's whole life. That slows it down and uses more fuel throughout the life of the car. When you put sticky tires on it, and increase the power, you can expect to overstress some parts. Obviously the weakest link should fail first.

5 or 6 studs spreads out the load (vs. 4) so they could be smaller. If one fails say due to overtorqing during installation, you lose a greater percentage with four than 5 or 6. This could lead to heavily overloading the other 3 and subsequent catastrophic failure.

OEM designs are usually overkill for normally driven cars. You rarely hear of a wheel shearing off the studs in a production car that's never raced with sticky tires.

Cornering loads put tension loads on the studs which is what they are good at resisting. Tire traction still determines the max loads the studs receive.

Look closely at the rear of some of those 8/9 sec stangs, a few of them still sport a 4 lug 8.8 rear, I could see where they would live in a non transbrake or manual trans car with 4 lug.


David

Good info. so far. I'm still curious about rim dia./tire height. Seems more leverage would occur b/c of increased rim/tire size. Comments?...

Good info. so far. I'm still curious about rim dia./tire height. Seems more leverage would occur b/c of increased rim/tire size. Comments?...

The shear forces in the wheel studs are determined from the torque at the axle divided by the distance from the center of the axle to the stud, or 2.25 inches on a 4.5 bolt circle. This doesn't change with tire diameter, but it changes with overall gear ratio. Tires are "gears" too, as we know, so shorter tires generally mean lower numerical gears in the rear to get the same carspeed for a given engine rpm. That means less axle torque but the same driving force at the wheels at a given rpm. Of course that's power, which we know doesn't change with gears (except for friction and inertia losses).

Cornering loads are a little more complex, but they are tension/compression loads where the studs are very strong.

Anytime the bolted wheel connecton is not tight, and anything can move, it gets to be a real problem.

A buddy has a 5.0 that runs high 8's at >150mph. He is using the 8.8 with 4 lugs (aftermarket axles and studs though). However, he changes the studs every season and is thinking about upgrading to a 5 lug setup.

Rich Krause

A buddy has a 5.0 that runs high 8's at >150mph. He is using the 8.8 with 4 lugs (aftermarket axles and studs though). However, he changes the studs every season and is thinking about upgrading to a 5 lug setup.

Rich Krause

Did he ever have any failures durning the season? Does he magnaflux to see if stress cracks are developing? I'm starting to think that maybe an upgraded onstuds on a 4-lug set-up is all one would require. I was wondering what IHRA or NHRA rules say about axle/no. of studs requirements...if any. Any thoughts...

Something I have seen, Shearing off the lugs. I dont know the story but this video fits this topic perfect!
http://www.smallblockposse.com/images/forsale/OnABudget_SalemNSCA.wmv

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


Vega / Monza came with V8, no?

What I wanna see is a wheel that's installed on the hub like a balancer. Keyed. Now that would be a strong setup.

Vega / Monza came with V8, no?

What I wanna see is a wheel that's installed on the hub like a balancer. Keyed. Now that would be a strong setup.

Well, maybe not. Keys generally are for location, not for taking shear loads. If they are used for that in high torque or cyclic loads they often fail either by shearing or wearing out the keyway when they move slightly as loads are applied and released. Balancers are often pressed on. That press fit takes the loads. Some balancers don't even have locating keys. Not trying to rag on you, jmd. I've just seen too many keys fail due to folks trying to use them to drive not locate.

Perhaps the best way we have for wheels is the pin drive with one center nut. Open wheel cars like F1, IRL, CART and most sports racing cars use this. The 4-6 pins don't clamp and are used only for location and to take shear loads, and the center nut does all the clamping but doesn't take any shear loads from driving or braking. Eureka! What a smart design! Of course the center nut needs a couple hundred lb-ft of torque, so it's not very practical for a normal OEM street car.

My $.02