The SL-C was designed to fit the stock Corvette C6 Z06 wheel sizes. This assures a wide range of available wheel sizes, both from GM, and aftermarket sources, and also makes for a reliable tire supply, as the number of Corvettes in use is thought to be sufficient to incent tire makers to supply tires in the sizes we need for the long term. Before you order custom wheels, please confirm the actual offsets and sizes, as "stock Z06" isn't always the same as "Fits Z06" or "Z06 fitment".
Recently, the range of wheels for the SL-C has expanded. As such, you should pay special attention to wheel sizes, as they affect tire selection. See the Wheel and Tire page on the Superlite website.
Weight is the enemy of performance, and wheel weights are even more important, because they are unsprung weight, as well as rotational weight. Choose wheels carefully, as there can easily be a real 100 lb difference between a set of wheels and tires from the lightest to the heaviest. This is an area where you want to be sure, and to insist on more than just an assurance that the wheels are "light'.
Fitting wheels to the car is more complex than most people think. There are several aspects to correctly fitting wheels, including a detailed understanding of of the wheel profile and offset, tire, suspension, and caliper clearance, as well as the interplay between studs and nuts.
Another issue to manage is hub concentricity. This refers to the idea that the hub of the wheel should be centered on the bearing hub (either naturally because of the way the wheel is machined, or with an adapter), so that the wheel is always perfectly centered on the mounting hub, reducing the chance for an out-of-round condition due solely to the way the wheel is mounted. While it is possible to mount wheels on the car with just the wheel studs centering the wheel to the hub, this is not optimal. The hubs have a specific taper to them, and the use of hub-centric wheels, or wheels with hub-centering adapters is recommended.
The Forgestar wheels have hub-centric adapters included with each set that adapt the different hub sizes on the car and wheel (but do not add any offset).
The Corvette is a popular car, and the SL-C inherits much from the Corvette aftermarket. One example is wheel adapters. There is a wide range of adapters for the Corvette and most all of them can work with the SL-C. In most cases, adapters are a fix for not having the correct offset on the wheels in question, so often the best adapter is no adapter at all: it's almost always a better solution to have your wheels modified, or just to get different wheels with the correct offset. Some racing sanctioning bodies prohibit the use of wheel adapters, or allow them only in very thin sizes, so if you are building a track or race car, it's doubly important to make sure you have the right offset wheels from the beginning. Here's an example of a relatively slim spacer-type adapter:
Note the lip and corresponding recess on these spacers that account for the hub size, making these an example of being hub-centric. When you see a spacer that is entirely flat, it isn't hub-centric, but depends on centering the wheel on the studs, a good way to introduce vibration on otherwise perfectly balanced wheels.
But when simple, thin spacer-type adapters aren't feasible, a different kind of adapter is a low-cost way to move the wheel and tire assembly out a bit (or a lot, with the right adapter). When you are looking at adapters, think about more than just the thickness and bolt pattern needed. You also need to consider the hub size of the wheel you are using, the hub size on the hub (the car itself), whether or not the wheels are hubcentric, and whether the studs you have are sufficiently long to accommodate the adapters you are contemplating.
Very large offset changes are often made with special adapters that are different from the common spacer type of adapter; these thicker ones actually have a set of studs in the adapters themselves, and a separate set of nuts to hold the adapter to the hub. These are less desirable from the safety perspective, as there are twice as many bolts or nuts to come loose, and this type is typically banned in racing. Here is an example of this type:
If you use other than the standard wheels, it is likely that you will find that the wheel studs need to be longer, especially in the rear. ARP makes a set of longer studs that can be used to replace the stock ones that come installed in the hubs from the OE suppliers. The longest stud they supply for our cars is part number 100-7708 and is available from Summit and others. Recently, Moroso has come out with a metric stud in our sizes with a bull-nose already machined. As of early 2012, they are hard to obtain, but are listed in Jegs here and Summit. GMPP also sells a bull-nosed stud for our cars, though curiously it is labeled as an Oldsmobile Rocket (!) part. Use part number 22551491.
The old studs should be pressed out and the new ones pressed in. Most builders remove the hubs to do this, as getting sufficient purchase from a press is almost impossible when they are mounted on the car. Some builders have reported success installing the studs by putting a wheel nut on them and running them in with an impact gun, but the preferred method is to press them in with a vise or a press.
The 01 race car uses these ARP studs, and the factory has machined a bull nose on the end. That may be a consideration for other builders as well, as it tends to protect the stud ends, and makes starting the nuts somewhat easier, especially under pressure. You'll need to find a local machine shop to machine the studs if you want that.
Doug Rippie Motorsports has made up a great graphic to show the differences in the wheel studs available for our cars:
Many aftermarket wheels are designed for proprietary nuts. You should validate that the wheels you are assessing for your car can be mounted using regular tools and equipment. For example, the Forgestar series of wheels for the C6 Z06 have openings that will fit a 17mm socket, but not a 19 mm one, which is the standard size for the default wheel nuts. Thus, users of these wheels need to find a nut solution that permits thinner sockets to be used in order to install and remove the wheel nuts. One solution for these is the Muteki line of nuts. These are normally targeted at the tuner crowd, but they make a version that is narrow, open, and available in a wide range of finishes. A set in black in the SR48 series fits most aftermarket (and stock) wheels perfectly, and comes with a thin socket to fit in the tight wheel stud openings that some aftermarket wheels have. They are available at Amazon here and many other web sites.
The topic of open or closed nuts is also important to understand. 'Open' nuts are those that are open on both ends. This allows them to install on long studs of any length. Closed nuts, on the other hand, have a closed end, and so can be installed only on a very narrow range of stud lengths before bottoming out, or not having enough threads to engage. Before you order your wheels, be sure you understand the relationship between the openings on the wheels, the length of the wheel studs, and the kind of nuts you will be using- they all have to work together as a system. Unless you cut the studs to length on your car, you will most likely want to use open nuts.
Nuts can be made of steel, aluminum or titanium. Some people have reported good experiences with aluminum nuts, as are often found on eBay, and they have been standard on Porsche cars for a long time. Lately, titanium nuts have begun to appear. They are typically more expensive than the aluminum nuts, but offer still lighter weight for their strength. These Ti nuts for the C6 Corvette are relatively inexpensive for the material, and can fit many wheels and stud combos as they have an open design. Since they use a 16mm socket, they also fit in small wheel nut openings as is common on aftermarket wheels.
The Titanium wheel nuts weigh about .66 lbs for a set (of 20), compared to a little over 2 lbs for a set of the regular chrome acorn nuts in steel. Aluminum nuts are somewhere in the middle, depending on the size and style. The Muteki SR48 nuts weigh about 2 oz each, or about 2.5 lbs for a set.
Locks may be used to reduce the risk of theft of expensive wheels and tires.They have the same constraints as the nuts, so think about them as part of the system of attaching them to your car. Note that some nuts, like the Muteki ones, are not removable without a special socket (included with the nuts) so this makes them harder to steal, and offers some greater theft protection than just the regular nuts alone.
Center Lock Wheels
Superlite Cars now offers center lock wheels as an option. These wheels attach to a hub-mounted adapter with a single large nut used to attach to the wheel. This approach makes changing the wheel faster, as in an enduro race. They also look cool, with a genuine motorsports flavor.
The factory offers one-piece forged center lock wheels from http://www.forgestar.com/v2/ and multi-piece centerlocks are available from Jongbloed wheels . Center locks tend to be very expensive, as they are usually a forged or three-piece wheel, and the cost of the adapters has to be added to their total cost. They are also typically heavier because of the required adapters for the SL-C.
Note that centerlocks are not available from Forgestar, as they just don't make them. Instead, they actually supply blanks to Superlite, who performs final machining to the specific offsets needed to fit on an SL-C with their adapters. Because they are blanks, the finishes are pretty much limited only by what powdercoaters or other coaters can apply to the wheels.
The adapters bolt to the hubs, and provide pins, which slot into machined holes in the back of the wheels. The single large nut holds the wheel on. This is standard motorsports practice, as seen on all Formula 1 cars.
Special tools are required to tighten the massive nuts on these wheels. You'll need a 1" or 3/4" torque wrench that can apply about 350 lbs ft in the middle of the range, and a 3" socket for the nut. That's not a typo, and it's a big, expensive socket! You'll also need special aluminum paste to keep the spindle and nut happy together. The preferred stuff is hard to get, but look for Castrol "Molub-Alloy Paste TA". You'll find it at motorcycle shops and at 5150 Motorsports.