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Discussion Starter · #1 ·
Here's something for you to think about, especially if you race your Impala.

Do you know anyone like that? :)

Most of you are probably reasonably comfortable with the stock wheel studs and lug nuts--not the "security" nuts, of course!

Still, when you start racing the car, whether drag or autocross/road racing, there are some conditions imposed on the vehicle that it never was "expected" to endure. One of those is the load on the wheel studs.

If you do race, and regardless of the type you engage in, you may find that you remove and install wheels far more often than the average person. The chance for a wheel stud or lug nut problem goes up with this process.

First, considering the weight of the B-body, and what the "real" racers do on cars that weigh far less than ours, the wheel studs are probably too small, at 12mm.

I am not sounding an alarm here, but in the context of racing our beloved "tanks", a stronger wheel fastener is something that needs to be given due consideration. True, GM built alot of cars with that size fasteners and similar over the years. When I installed the Baer GT system on my car, I converted to 14mm studs, just for peace of mind. Since I'm using wheels that require spacers & adapters, I also have 14mm studs for the rear wheels, even though the adapters attach to the axle flange with 12mm--I'll change that someday.

For most of you--racers, that is, I don't mean to suggest you need to do what I did, but you should think about slightly longer studs and better lug nuts that provide a little more thread contact, or, if nothing else, consider periodic replacement of both the studs and lug nuts. If you get new rotors for the front, it's true that you will typically get new studs, so take that into consideration as you think about this.

I'll admit I haven't found the perfect replacement open-end lug nut yet, but maybe some of you have some suggestions. It seems that racing and metric fasteners don't mix, as most of the HD stuff available for cars similar to the Impala & B-body in the racing community is HUGE--5/8" diameter--about half again larger than stock B-body fasteners.

As for stud recommendations, if you are staying with 12mm, there are a few choices:

22551491 GM Rocketparts 68mm (2.68") long, 12mm direct-fit for GM metric applications. This stud should fit without a problem behind stock wheel center caps, even though the stud is a full inch longer than stock. It will probably be necessary to remove the ABS reluctor on the front hubs to install these, but that is just a matter of some careful use of a press to remove and install the reluctor. Cost about $1.50 each at the "good guy" price.

100-7708 ARP racing studs, 12mm. These studs are supposedly stronger by far than what the factory offers, so its a matter how much you want to spend. They are not as long as the GM racing studs, and the knurl press dimension is just slightly larger. I don't know if they will require any machining to fit, but if not, they will definitely fit "tight". These studs currently cost $11.95 for a card of 5, so they run a little bit more than the GM parts.

610-323 is the third choice, a Dorman item, and it is 54mm long, approximately 1/2" longer than stock, I recall--shortest of the 3 I've mentioned. Like the GM stud, it is a direct fit replacement. These typically cost under $1 each.

Stock studs are about 40mm long--sorry I don't have the part number, but if you want to know, I'll get it.

Another area to consider--perhaps even more important than stud size--is "what is the proper torque on these fasteners". I don't have any recommendations beyond what the owners manual and FSM say--100 lb/ft, and NO lubricant on the threads. Doing otherwise, as far as lubricant on the studs, can give false torque readings--resulting in a stud that is far beyond its design stretch limit. That is why they break, most of the time--and use of a torque tool that has not been calibrated is also a big contributor, too.

Many of you will have suggestions as far as the topic of lubrication of the studs. I'll only suggest that if you do put something on the studs, remove as much of the excess as possible--a very light coat is more than enough to help them release, and the torque reading should be adjusted slightly (less) if you do--say 85-90# instead of 100. I'm not an engineer, but I'm just using a reasonable approach to keep from inadvertantly snapping studs.

I realize that some of you using aftermarket wheels are probably obliged to follow the wheel manufacturer's recommendations and/or specs, which often differ from the factory specs.

Here's a link to an interesting discussion on the SCCA Forum about this entire subject:
http://www.sccaforums.com/ubb/Forum7/HTML/000079.html

Feedback welcome!

Updated 6-4-03 to cross link lugnut info:
http://www.impalassforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=22&t=001952
 
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