I've been looking in the used market at OEM wheels from other auto manufacturers and discovered quite a bit about which might fit my 2007 SX4 Crossover. I found a valuable post by Tire_Guy on a Mazda 6 Forum and have integrated it with information found on Tire Rack's site and elsewhere as best I can for our use.
There are several parameters that apply to wheel fitment. The first is the Bolt Pattern. The Bolt Pattern, or Bolt Circle, is the diameter of an imaginary circle formed by the centers of the wheel lugs. Bolt patterns can be 4-, 5-, 6-, or 8-lug holes. A bolt circle of 5x114.3 would indicate a 5-lug pattern on a circle with a diameter of 114.3mm. The SX4 bolt pattern is 5x114.3, often referred to as 5x114. Note that GM's 5x115 is NOT the same; it is slightly larger. Most Japanese car companies use this pattern for their 5-lug applications. Most German manufacturers use 5-110 (VW), 5-112 (Audi and VW) and 5x120 (BMW and Mercedes). There are currently 17 different 4- to 5-lug bolt-lug patterns.
The second parameter is Offset (also identified by ET). The offset of a wheel is the distance from its hub mounting surface to the center-line of the wheel, measured in millimeters. Backspacing, similar to offset, is the distance from the hub mounting surface to the inside lip of the wheel, measured in inches.
The offset can be one of three types. A Positive offset indicates that the hub mounting surface is toward the front or wheel side of the wheel. A Negative offset indicates that the hub mounting surface is toward the back or brake side of the wheel's center-line (e.g., a "deep dish" wheel). A Zero offset indicates that the hub mounting surface is even with the center-line of the wheel. High positive offset wheels (+35, +40, +45 or more depending on wheel size) are generally found on Front Wheel Drive (FWD) cars and some newer Rear Wheel Drive (RWD) cars. Medium positive offset wheels (+20) and Low offset (i.e., Zero offset) are generally found on RWD cars.
If the offset of the wheel is not correct for the car, the handling and durability of suspension components can be adversely affected. When the width of the wheel changes, the offset also changes numerically. If the offset were to stay the same while you added width, the additional width would be split evenly between the inside and outside. Increased wheel width also increases tire width and tread contact. So offset must account for additional wheel width to ensure that the wheel and tire clear and not interfere with any of the suspension components and their operation as well as any body components on the vehicle. The SX4 accommodates a rather large range of wheel sizes and widths. The typical offset for the SX4 ranges between +42 and +48mm depending on wheel width, and is usually +45mm.
The third parameter is Bore, also known as Center Bore or Hub Bore. The Bore of a wheel is the machined opening on the back of the wheel that centers the wheel properly on the hub of a vehicle. Original equipment wheels are bored out to the exact size of the hub diameter of the vehicle so the wheels are precisely positioned as the lug hardware is torqued down. These stock wheels are called Hub-Centric Wheels since the center bore matches the car's hub size exactly. Keeping the wheel precisely centered on the hub when it is mounted minimizes the chance of a vibration.
Some aftermarket wheels are vehicle model specific and come from the factory with a hub-centric bore machined to match that vehicle. However, most aftermarket wheels are designed to fit multiple vehicle models and use a centering ring system in order to reduce the bore size to match the hubs of different vehicles. These wheels tend to have a relatively large, standard bore of 73.1 (or sometimes 67.1). So, even though the lug pattern matches the destination vehicle, hub rings need to be installed inside the wheel's bore to match the smaller hub diameter of the vehicle. These rings keep the wheel precisely positioned (hub-centric) as the lug hardware is torqued down.
(Technically, there are wheels that are Non-Hubcentric by design, known as Lug-Centric wheels. With these wheels it is critical to torque the lug hardware with the vehicle on jack stands, off the ground. This allows the nuts or bolts to center the wheel and torque down without the weight of the vehicle pushing them off center. However, it may be possible to use hub rings on these wheels to make them easier to install and center.)
Another parameter pertains to Lug Hardware. Aftermarket alloy wheels or wheels from another vehicle may require new hardware. The lug nuts must match the size and pitch of the SX4, but they must also match the seat design of the wheel. The Suzuki OEM SX4 alloy wheels take conical lug nuts with size and pitch defined as M12 x P1.25 and a 60 degree tapered seat. So, it is critical to obtain lug nuts to account for differences in the wheel's lug seat design (e.g., Flat or Ball/Radius vs. Conical/Tapered) while maintaining the SX4 size and threading pitch. Selecting lug nuts of proper length can also make a difference, e.g., using shorter lug heads to allow center caps to fit.
There are other issues that are much less likely to prevent proper fit on the SX4, including Hub Interference and Load Capacity. Hub interference can occur on vehicles that have additional items on the mounting surface area, which must be considered for wheel applications, including locating pins and rotor mounting hardware. The SX4 does not appear to have any hub interference problems. The new wheel must have enough load capacity when compared to the gross axle weight rating of the SX4. One should only consider OEM wheels from other manufacturers for vehicles that are comparable in weight to or heavier than the SX4.
Manufacturers of aftermarket wheels identify all of the applications for their wheels so that bolt pattern, offset, bore (either precisely matched or via hub rings), and lug hardware are compatible with those vehicles. However, fitting original equipment wheels from another vehicle manufacturer poses problems not usually associated with aftermarket wheels. Although bolt pattern and offset are fairly available and understandable, hub diameter can be a little more confusing.
For example, the SX4 has a hub diameter of 60.1mm. Fortunately, there are very few automobiles with smaller hubs, e.g., 54.1 (generally 4-bolt patterns). If such a wheel were available with a 5-114.3 pattern, while the bolt pattern and offset might be satisfactory, such a wheel wouldn't fit over the SX4 hub because the opening would be too small. Many Toyota FWD vehicles have a center bore of 60.1, which matches the SX4. Regardless, ultimately the question is, where do you go to find information on other vehicle's bolt patterns, offsets, and center bores to increase the likelihood of a good cross-fit?
I can suggest two sources. There is a website that provides this information. Although it is by no means complete, it contains a lot of vehicles. Please reference this link if you are considering buying original equipment wheels from another vehicle manufacturer.
Another reliable source for finding out basic information is TireRack.com. By searching on wheels by vehicle, you can obtain bolt pattern and offset based on wheel size and width for both the originating vehicle and the SX4. If you can find an aftermarket wheel that is comparable to the other manufacturer's OEM wheel, you should be able to determine fairly well if it will fit on the SX4.