17 replies to this topic

[Stix37867]

After installing the new studs, went to torque everything back down and noticed there is no new torque spec given. We tried to do the math ourselves for bolt stretch and were coming up with just shy of 120 ft/lbs. Anyone happen to know what is recommended? I got the ARP studs with the KJZ lug nuts from saferacer.

[Glenn]

After installing the new studs, went to torque everything back down and noticed there is no new torque spec given. We tried to do the math ourselves for bolt stretch and were coming up with just shy of 120 ft/lbs. Anyone happen to know what is recommended? I got the ARP studs with the KJZ lug nuts from saferacer.

Torque at 75 MAX. Will have to check a few times to make sure the stud is seated properly too. Also new wheels need to be retorqued until the powder coat is worn off.....dont ask how I know

[Jim Boemler]

Use your normal torque setting (I use 70, but others use different values). The studs aren't intended to stretch, unless you plan to replace them each time you change tires.

[davew]

We use 65 pounds. Makes the electric impact batteries last longer.

New wheels should have each nut run on and off about 10 times. This is much easier with the long studs. This will wear away the powder coating from the nut surface on the wheel. Otherwise, when the wheel gets hot, the powder will get soft, the nut will come loose and can fall off.

New studs shoulkd also be checked for torque after every session, just to make sure they got seated good on initial install.

Dave

[FTodaro]

Wow I have tight nuts I use 85ft lbs.

[HoneyBadger - BrianW]

I have always torqued to 90... guess it looks like I can back off that a bit.

[Stix37867]

I guess I am not understanding why we are torquing the lug nuts to spec, or even less, when we are installing a higher grade stud. I understand the new wheels and wearing off the powdercoating part which I agree with. The part I necessarily don't agree with is the low torque spec. When installing any bolt or nut, the desired torque is when the bolt or stud begins to stretch depending on the size and grade. I agree that overstretching will fatigue the stud and cause it not to return to its original length. Maybe I'm looking into this too much but I just don't want any problems over something so simple.

Out of curiousity, has anyone tried to contact ARP with their recommended torque rating?

[davew]

You could get into all kinds of engineering/physics/metalurgy etc.

OR

You can just believe the guys who do this for 12 cars 20 weekends a year for the last 10 years. 65 is enough

Dave

[Stix37867]

I guess I just like doing the engineering is all. Called ARP and was told to use factory specs anyways so everyone was pretty much right....well except me

[Keith Novak]

I guess I am not understanding why we are torquing the lug nuts to spec, or even less, when we are installing a higher grade stud. I understand the new wheels and wearing off the powdercoating part which I agree with. The part I necessarily don't agree with is the low torque spec. When installing any bolt or nut, the desired torque is when the bolt or stud begins to stretch depending on the size and grade. I agree that overstretching will fatigue the stud and cause it not to return to its original length. Maybe I'm looking into this too much but I just don't want any problems over something so simple.

The spec is written around street use, not racing. In racing, we put a lot higher side loads on the car that go into the studs. Torque them too close to the yield point and then flog them around a race track where you're increasing the stress significantly over what it is sitting still and you've got potential problems. Torque them to the point where you know the wheels won't fall off (sounds like 65 works, I use 80 but I like the battery life aspect) and your studs will never fatigue.

[Randy Thieme]

Keith makes a great point on the added stress from racing, especially from cornering. The stud is being stretched by the wheel trying to bend away from the hub. Longitudinal loads on the studs are almost certainly more than twice what would ever be seen in normal driving. It's the same stretching load as when torqueing the nut. Interestingly though there is a counter-argument, which is, since the stretching forces are higher more tension is needed to hold the wheel snug to the hub.

Yes, you have "overthought" the issue. But at the risk of encouraging such overthinking it would be an interesting thing to model using a CAD program as a static load on the wheel. There was a recent article in Grass Roots Motorsports on the use of CAD programs at the club racing level. Not a critical thing to model, but an interesting problem as a way of learning a new CAD program.

I've run into one person who varies their torque based on if there's fresh anti-seize goop on the studs. Sort of a wet vs. dry torque setting.

[Keith Novak]

Interestingly though there is a counter-argument, which is, since the stretching forces are higher more tension is needed to hold the wheel snug to the hub.

I don't know that's true. Stress (force) and strain (stretch) are proportional up to yield (load where it never returns to quite the original length) Once you reach yield, quickly less and less force is required to make the bolt stretch. Torque it to 60 or 80 and the initial stretch will be different but add in the same cornering forces and exactly the same additional stretching will occur unless you reached the yield point. Torquing the nut, you're just applying enough tensions so that it's always preloaded whether you're pushing or pulling it in order to to keep the nut from falling off. Overtighten and you limit the additional force you can put in before the bugger snaps. Interesting though. Something that someone with more free time than me to model.

[davew]

I understand 65 foot pounds. I can even understand 80 foot pounds.

But you guys are WAY above my pay grade.

Dave

[Bench Racer]

When your torque the Ba Zinga out of those aluminum wheels check & see if your wheels have steel inserts for nut seats or if your Ba Zinga torque is rapidly wearing out your aluminum nut seats.

[Jim Boemler]

As I mentioned, I go for low torque. I will mention, however, that the Corvette uses the same size studs as our cars, and the factory recommends 100 ft-lbs! It seems like there's really quite a wide range of acceptable torque.

[davew]

My head hurts

I am sticking to 65

[pitbull113]

My head hurts

I am sticking to 65

lol

[Jim Boemler]

My head hurts

I am sticking to 65

Perfect for those AARP studs.