Wheels or “rims”, and tires are a big investment and having the wrong sizes and offsets can look bad and result in costly damage.
Wheels and tires can make, or break, a car. We have all seen the otherwise great car with poor fitting rollers. This is not the 1980s, and tires that stick out past your fender lips just look dated. But, aside from looks, poor-fitting rims can rub your tires right into a dumpster and give you the turning radius of a bus. If you go with smaller tires, it’s pretty easy to get them happily residing in your wheelhouses, but if your goal is to maximize your tire size then you need to nail the measurements to prevent fitment issues. Plus, having your wheels made twice can get expensive.
A fresh set of rims can give your ride a sleek, upgraded look. Before you get rid of those generic wheels and slap on some custom rollers, however, take the time to figure out what size will work best for your vehicle. Once you know what size you need, you can turn your attention to the fun stuff, like deciding on a material, color, design, and finish.
First: Count the bolts on the current rim to identify your vehicle’s bolt pattern.
Look at your wheels and count the number of bolts encircling the central hub. Then, grab a ruler or tape measure and extend it from the center of one bolt to the center of the bolt directly opposite. Putting the 2 numbers together will give you your vehicle’s bolt pattern, which you will need to know to ensure that your new rims fit properly.
- Bolt pattern is typically represented as compound dimensions, as in, “5×4.5.” That is, 5 lugs with 4.5 inches (11 cm) of space between each.
- Bolt patterns come in 4-, 5-, 6-, or 8-lug configurations. Most sedans, SUVs, and small trucks, for example, have 4 or 5 lug holes, whereas large trucks and other heavy vehicles often have 6 or 8.
- If your vehicle has a 5-lug hole pattern, measure from the center of one of the upper bolts to the bottom edge of the bolt directly beneath it.
Tip: To save yourself some trouble while shopping around for a new set of rims, only compare models that match your vehicle’s specific bolt pattern.
The biggest mistake (or to be fair, misconception) people make is how wide a rim is. To a wheel manufacturer the width of a rim is measured from bead to bead, which is not how most people measure a rim, which is outer edge to outer edge. So, you measure, think you have a 10-inch rim, but, to wheel manufacturers, you have a 9-inch rim. This is a good example of how having a little knowledge can save you from making simple mistakes.
How Is Wheel Size Measured?
Of course, a wheel’s size is more than just its width. Inner measurement (A) is the hub face to the inner wheel well. Knowing this measurement will help you make sure your tire does not rub on the inside edge. The outer measurement (B) determines the clearance to the outer lip. The brake caliper (C) and brake radius (D) measurements help ensure that the calipers clear the wheel hoop as well as the spokes. This is even more critical if you are running large brakes. Hub diameter (E) and height (F) are important, as well. If the hub is too big, the wheel won’t fit on the car; too small, and the wheel won’t be properly centered, also called “hub centric,” and you’ll have to hope that the lug nuts properly center the wheel. As stated earlier, the rim width is measured from the outer tire bead to the inner tire bead. For example, a wheel with an overall width of 9 inches is really considered an 8-inch wheel (each bead takes up approximately 0.50 inch).
In this graphic you can again see that the rim width is taken from the inside of the opposing bead grooves and not from the outside edges of the rim. The offset of a wheel is the distance from its hub mounting surface to the centerline of the wheel. Given this, it can be one of three types. Zero offset would mean the hub mounting surface is even with the centerline of the wheel. Positive offset would indicate that the hub mounting surface is toward the front side of the wheel. Negative offset is where the hub mounting surface is toward the back or brake side of the wheel’s centerline. Wheels with a “deep dish” have negative offsets. Offset is typically measured in millimeters. Backspace is the distance from the hub face to the back outer edge of the rim (not the tire bead) and is expressed in inches. Modern cars, and older cars with modern suspension systems, tend to have positive offsets.
Sizing Your Wheels Correctly (Simple Math Example)
Measure across the face of your wheels to determine their diameter. Stretch your measuring device from the inner edge of one bead seat (the spot along the rim where the spokes terminate) to the inner edge of the bead seat on the opposite side. The number you get is the wheel’s diameter, or how big it is across its vertical surface. Wheel diameters can vary widely, from 10 in (25 cm) to 22 in (56 cm) or larger.
- If possible, remove one of the wheels before measuring it. This allows you to work more efficiently and decreases your chances of making a mistake.
- You can also figure out the diameter by examining the last 2 digits of the multi-part serial code printed in your vehicle’s owner’s manual, looking on your tires, or checking the sticker in the driver’s side door jamb of your vehicle.
- While the owner’s manual can tell you the diameter of your vehicle’s wheels, their overall dimensions are influenced by several different variable factors, so you will need to do the rest of the measuring yourself.
Find the width of your wheels by measuring across their outer edge. If you have not done so already, dismount the wheel and set it face down on the floor. Place the end of your ruler or tape measure against the floor next to the lower bead seat, hold it straight up, and note the number displayed beside the top of the upper bead seat. This is the total width of the wheel.
- For greater accuracy, lay a separate ruler across the upper face of the wheel and use your measuring device to measure from the floor to the ruler.
- Wheel width is expressed in inches, whereas tire width is given in millimeters. Itis a good idea to jot down your measurement in both forms, just in case.
Measure from the mounting hub to the top of the wheel to determine backspacing. Reset your measuring device against the rear face of the mounting hub (the small circular opening where the wheel connects to the axle) and line it up with the upper edge of the dismounted wheel. This number indicates the backspacing of the wheel, or how deeply inset the mounting hub is.
- Measuring and recording your wheels’ backspacing separately makes it much easier to figure out their offset, which is a crucial value when selecting rims.
Subtract the backspacing from the width and divide by 2 to calculate your wheels’ offset. If your wheel has a width of 9 inches (23 cm) and a backspacing of 6 inches (15 cm), subtracting the second measurement from the first will leave you with a difference of 3 inches (7.6 cm). Splitting that number in half (to reflect the distance to the wheel’s centerline, which is your reference point) therefore gives you an offset of 1.5 inches (3.8 cm).
- In simple terms, the offset of a wheel is the distance from its hub mounting surface to its center line. Wheel offset can be “positive,” “negative,” or “zero” (no offset).
- It is important to choose rims with an appropriate offset for your vehicle’s specs. Your wheels must have a safe amount of clearance from the braking components, fenders, and other neighboring parts.
What Measurements Do You Need to Order Custom Wheels?
This is an example of the dimensions you will need when ordering a custom three-piece wheel.
How Do You Make Sure Your Brakes Clear Your Wheels?
Bigger brakes will make nailing your wheel size even more critical. You can bust out the measuring devices to get the brake dimension info or you can contact the brake manufacturer. Aftermarket brake manufacturers usually offer schematics of all their brake kits to help make your life easier.
How Do You Measure to Determine Wheel Clearance?
With some basic tools you can get close to the perfect wheel size to fit your car. A larger ruler makes a great straightedge for this and will let you extend the hub face up near your fender lip.
You can then use a measuring tape to see how much room you have to work with on the outside of your wheel. Measuring from this plane to the inside of the wheel tub will give you an idea of how much space you have to work with on the inside of your wheel. Be mindful of things such as exhaust or suspension parts that can cause interference issues. Also keep in mind that your wheels are dynamic, especially the fronts, and need to clear even when compressed, or in the case of the fronts, when turning (or turning and compressed).
The last thing you want is for your calipers to hit your wheel spokes, so figuring out how far they extend past the hub face is critical.
This measurement is critical, as well. If the register is too small, the wheel will not go on the car. Too big, and your wheel will no longer be “hub-centric” but instead “lug-centric” and you will have to rely on your lug nuts to properly center your wheel.
If you do not get this measurement right, you will not be able to put the wheel center caps on because the bearing hub will extend out too far.
All these measurements become even more complicated on the front tires since you need to account for turning and for clearance under compression when turned.
Picking out a Set of Rims
Restrict your search to wheels of a suitable size. Once you have done all major measuring, you should have a better idea of what size rims will work best for your vehicle. Keep these measurements in mind while you are comparing different models. They will help you narrow down your options considerably, which will in turn make the selection process far less of a headache.
- If you are still confused about what size rims you need, talk it over with a qualified wheel and tire specialist.
Tip: Feel free to size your wheels up or down by a few inches as you like—just be careful not to overdo it. As their width and diameter change, so will the way they interact with the road.
Go with alloy wheels for a good balance of fashion and function. These days, most aftermarket rims are cast from alloys made with metals like aluminum, magnesium, or nickel. Alloy wheels are strong and lightweight and withstand heat exceptionally well. They also tend to have the most aesthetic appeal, since they allow for a greater variety of designs and spoke patterns.
- Other advantages of alloy wheels include improved braking, resistance to rust and corrosion, better fuel economy, and longer overall tire life.
- Alloy wheels generally cost quite a bit more than steel wheels. Even so, they will be well worth it if you are looking for the best possible compromise between style, performance, mileage, and cost.
Opt for steel wheels if you value performance over all else. Thanks to their solid, welded construction, steel wheels are more hard-wearing than alloy wheels. Their added weight and ability to hold up to impact can be a big plus if it is particularly cold where you live, or if you do a lot of driving on rough road conditions.
- The same construction that makes steel wheels so durable also makes them easier to clean, maintain, and repair.
- One downside of steel rims is that they do not come in as many different designs as alloy rims, since the way they are manufactured does not allow them to be molded as elaborately.
Choose colored rims if you want to lend your vehicle some added flair. Matching your wheels to your primary shade of paint is always a safe bet, though you could also bring together two complementary tones, like blue and yellow or green and purple, if you want to mix things up. Another popular option is to pick out rims that tie in with any other accents your vehicle may have, such as racing stripes, decals, or contrast paint.
- The color of your rims is largely a matter of preference, so do not be afraid to play around with different combinations and listen to your own sensibilities.
- The right rims can really tie your car’s many features together, but the wrong ones can come off as tacky and unattractive. Rims that are all one color, for instance, can be a bit much when paired with a vibrant paint job in the same shade.
Select a finish that works with the rest of your customizations. Rims also come in several different finishes. These include powder-coated, paint-coated, clear-coated, bare-polished, and chrome-plated for that clean, eye-catching flash. Different finishes come with different amounts of required upkeep and levels of protection from the elements. Again, this decision mostly comes down to what you like.
- In addition to the finish itself, you will have a choice between a few levels of shine. Matte wheels have a flat, understated look with almost no luster, while satin and gloss offer a couple more degrees of brightness and mirror wheels are reflective enough to see yourself in.
Make sure you are buying within your budget. Before you get too excited about a particular set of rims, think about how much you realistically must spend. On average, a single brand-new automobile wheel will run you somewhere between $100 and $300. Those numbers will only go up as you start looking at higher-end or fully custom designs and features.
- The more bells and whistles you go in for, the more money you can expect to drop on your upgrade when it is all said and done.
- If you plan on having your rims put on by a professional, be prepared to fork over $20-40 extra per rim to cover the cost of installation.
As you can see getting the right wheels for your car takes a number of steps to get right. It is worth taking your time to go thru the process carefully. It you feel over your head then it is wise to get a professional involved to help you make your selection since mistakes can very costly.
Speaking from firsthand experience in ordering the incorrect rim sizing and paid the price in ordering a new second set of rims and waiting over a month with the added cost.
As my grandfather always said; “Measure Twice Cut Once”.
