Spacers and Lugs and Nuts, Oh My.

[Orkboyz]

Like most folks, I am looking at wider rubber under the car. However, I'm not going to ask the typical "will this size wheel/tire fit" question. Through experimenting and such I pretty much know what will fit and what I must do to get it to fit. My question has to do with the lug nuts and bolts.

A 5/16" spacer (about 8mm) behind the stock 18" wheels with stock studs results in the lug nuts turning about five and a half to six revolutions before reaching 90ft-lb of torque. That is about half the normal revolutions without the spacer.

The question comes down whether this is enough bite on the stock bolts for "very spirited" driving.

I'm not sure I'd do a HPDE with this set up but I am wondering if it might be too much stress on bolts to AutoX on them. I've already considered getting some ARP studs just to be safe.

Of course I can always just bite the bullet and put some 265 up front with the Skulte (http://www.skulte.com/product_info.php/cPath/21/p roducts_id/84) .75" adapters.

[PreludetoaGTO]

What size are our studs? 3/8-16 or something like that?

There's actually a pretty easy formula for figuring it out.

Each revolution is 1 thread of engagement. Let's say you have 5 revolutions, so you have 5 threads worth of engagement.

The -16 is the number of threads per inch. 5 threads of engagement means you have roughly 1/3 of an inch of engagement.

If you have more than .5*diameter of the threads worth of engagement, the thread strip strength will exceed the tensile strength of the bolt (which is independent of thread engagement).

So in this example, you would be fine.

[Gears for Brains]

Studs are M12 x 1.5

One diameter's worth of thread engagement is what I go by.

I think JusticePete has said stock studs are good up to 6mm spacer?

ARP thread, I added some neat removal/installation suggestions at the end:
http://www.ls1gto.com/forums/showthread.php?t=7326 1&highlight=arp

[Scooter70]

I just got an e-mail from Andris at Skulte today regarding spacers though my question was slightly different than yours. Is 8mm enough for your application? If so, they can make spacers for you, you don't need to jump up to the ($200) 3/4" adapters. As far as your thread engagement question, I would fell better myself with more engagement. Based on G4B's one diameter criteria, it's close but not enough.

1.5mm/thread *5 threads = 7.5mm of engagement. That makes sense since you said that the spacer is 8mm and it takes half of the rotations to torque the nut.

Do you not want to put the ARP studs on the car?

[Orkboyz]

I just got an e-mail from Andris at Skulte today regarding spacers though my question was slightly different than yours. Is 8mm enough for your application? If so, they can make spacers for you, you don't need to jump up to the ($200) 3/4" adapters. As far as your thread engagement question, I would fell better myself with more engagement. Based on G4B's one diameter criteria, it's close but not enough.

1.5mm/thread *5 threads = 7.5mm of engagement. That makes sense since you said that the spacer is 8mm and it takes half of the rotations to torque the nut.

Do you not want to put the ARP studs on the car?

8mm is what is on it right now. That is what I was using to test some fitments. With the suspension the way it is, 6mm would be enough and would give me about an extra 1.5 to 2 rotations which would make me feel better. I used an 8mm because it was readily available.

I was looking at having Skulte build some 6mm spacers since they will make them with the right center bore so the spacers are hubcentric. I figure if I need anything larger than 8mm up front I might as well have them build the .75" adapters so I can get some 265 or 275 on the front. AT that point, though, the tire extends past the lip of the front fender.

As for getting some longer ARP studs, I was going to do that in case I needed a 10-12mm spacer. I'm still considering a set of four just to have them.

[Black Devil]

No it is not. I made 4 passes at a drag strip slipping the clutch for a decent (trying not to spin the tires) lanch. And found that I actually twisted all 5 studs on both sides. These spaces were only 5mm thick, and I was sure I had at least 6 threads of tourqe being used. And call me a bit crazy, but I always TQ my wheels to 100 ft-lbs each time. Get a set of ARP wheel studs and do it right.

[Orkboyz]

No it is not. I made 4 passes at a drag strip slipping the clutch for a decent (trying not to spin the tires) lanch. And found that I actually twisted all 5 studs on both sides. These spaces were only 5mm thick, and I was sure I had at least 6 threads of tourqe being used. And call me a bit crazy, but I always TQ my wheels to 100 ft-lbs each time. Get a set of ARP wheel studs and do it right.

Were those the front or rear studs that were twisted?

[Evil LS1]

Get the EVO ARP studs and do it right. Cheap insurance to keep from trashing your car. I run c5 vette wheels and have a BAER billet spacer up front with the longer ARP studs. I took my die grinder and buzzed the non threaded portion off of the studs because they were too long for the stock caps to fit back on with the stock wheels in the winter. I popped the hubs off, pressed the old ones out and press the new ones in. Took a couple hours, but never had an issue and have no vibration even at 145 mph. Key to this I think is to only have just enough weight on the wheel to keep it from turning when you torque the lugs. Centers just fine. I paid $50 for the pair of spacers last year.

[Black Devil]

The rears. And that was caused by grip, and tourqe from the driveline.

[Orkboyz]

It turns out I do not need more than a 3mm spacer. After putting on the 245/40R18 up front that is all I need to maintain the same clearance the 235/40 tires had. Seems the KDW2 section width in the 245 is a bit on the narrow side.

I've still ordered the ARP studs, however.