Weight
The Mazda RX8's fine handling and ride quality is very sensitive to what is called "unsprung" weight (which can best be understood as what hangs off the RX8 suspension rather than what sits on it). More than most automakers, Mazda tunes and equips its sports cars with very light wheels and owners should be very careful about keeping the weight down when they select replacement RX8 rims. Most RX8 owners can feel a deterioration of ride quality from a gain of as little as 3 pounds per corner in unsprung weight. We therefore strongly recommend that you use only light weight wheels for your RX8 like those we sell here. Unlike other vendors who rely on overly optimistic wheel weights as listed by the wheel manufacturers, we weigh each wheel that we sell to verify the lightness. For that reason, many of our listed weights here are slightly higher than the marketing weight listed on the wheel manufacturers' websites.
Offset and Size
RX8 wheel offset causes a lot of confusion. Here is a simple explanation. If the rim is 8 inches wide, and the mounting surface of that rim (backside of the bolt holes), is 4 inches from either outside edge, that rim has a 0 offset. To the extent that a rim's mounting plane is offset from that zero position, that offset is measured in millimeters for Japanese cars. The Mazda RX8 factory 18x8 inch wheel has an offset of 50mm. A 40mm offset choice is moving the track wider by 10mm per side. RX8 owners looking to stick to stock width can consider any of the offsets we offer here, but RX8 owners looking to go with substantially wider tires should stick to our 45 to 48 mm choices. For those looking to mount maximum tire width for autocross or track events see our 45mm 18x9.5 RP-F1 alloys which are lighter than stock wheels but allow 265/35, 275/35 and even 285/30/18s to be mounted on all four corners of an RX8.
LUG TORQUE
Torque lugs to 85 ft/lbs and check that torque again every week for first month of owning new wheels or lugs.
WHEEL CARE
Most modern wheels are clear coated just like the paint on your car. Therefore, do NOT use anything on your wheels that you would not use on your Miata's paint. Only clear coat safe products should be used on wheels. We like to put a coat of fresh car wax on new wheels before we put them on our cars here, helps keep them clean.
BRAKE DUST: Brake dust can be corrosive. Some brands and compounds in particular are known for eating up the finish on wheels, especially if the dust gets sprayed on the wheels when hot at the track and then left there for 24 hours or more, particularly with some overnight dew/moisture or lots of UV gets added to the mix. Some brands' compounds are less corrosive than others, but as a rule of thumb it is always best to keep your wheels clean. Nothing more than normal soap and water is needed. Before leaving the track we'll seek out a garden hose in the pits to fully rinse the dust off before the drive home.
DO YOU NEED HUBCENTRIC RINGS?
Hubcentric rings ensure that the wheel is centered on the hub, even before the lug nuts are tightened down. It's a nice bit of low-cost piece of mind knowing that you can't end up with a wheel off-center due to incorrect lug nut tightening. However, hubcentric rings are NOT mandatory. The lug nuts seats are conical for a reason; as long as you tighten the lugs correctly (done by hand and in a criss-cross pattern) then the wheels self-center as the lugs are tightened. However, some shops don't take the time to correctly tighten lugs, they just zap them on with an impact gun and the Miata is too sensitive to imbalances for that to be good enough. So, you don't have to use them, but they won't hurt and they're cheap insurance. As a rule of thumb, the racers know they don't want hubcentric rings because they know what they're doing and the rings just become an extra thing to worry about... but if you're asking if you should get hubcentric rings, then the answer is probably "yes" for you. Note that all our hubcentric rings are sold as sets of four, so order just quantity one for a set of wheels.