Go Big with Custom Tires for Custom Ride

Older street rods and customs...        read full caption Older street rods and customs often have large wheelwells and gaping fender openings that must be properly filled to achieve the right look. Notice how this 17-inch American Racing Hopster wheel and 245-series BFG tire perfectly fill out the fender.

The first thing that needs...        read full caption The first thing that needs to be determined when measuring wheel width is whether it’s the spring or the inner fenderwell that poses the first obstruction to the wheel/tire. Place a straightedge across the mounting pad on the rotor or drum (the flat spot the studs are sticking out of) and measure inward to both the spring (or control arm, as the case may be) and the inner fenderwell.

Keep in mind when obtaining...        read full caption Keep in mind when obtaining these two measurements that the spring moves along with the suspension and the wheel, so the tire-to-spring measurement is fixed, while the wheel/tire position can vary in reference to the inner fender as the vehicle goes down the road, particularly in turns.

We measured 7-1/2 inches from...        read full caption We measured 7-1/2 inches from the inner fenderwell to the mounting pad and 7-1/4 inches from the spring to the pad. Therefore, the smaller number will be used when determining wheel size because the new wheel/tire combo will come into contact with the spring before hitting the fender.

The second vital measurement...        read full caption The second vital measurement is the distance from the mounting pad to the fender lip. Once again using a straightedge and tape measure, we measured 5-1/4 inches from brake rotor to wheelwell opening.

Since the pickup had 71/4...        read full caption Since the pickup had 71/4 inches of clearance behind the mounting pad, we used a simple formula to determine the backspacing necessary for new wheels. Take your measurement and subtract 1/4 inch for minimum spring-to-wheel clearance, then subtract 3/4 inch to accommodate for tire bulge. That leaves 61/4 inches backspace for this application.

Backspacing is measured from...        read full caption Backspacing is measured from the back edge of the wheel to the wheel-mounting pad. If you don’t have a high-tech backspacing tool like the one shown here, place a yardstick across the rim and run a straightedge or ruler down to the pad. Notice that the backspace is exactly 61/4 inches.

Now that we’ve determined...        read full caption Now that we’ve determined the correct backspacing for our new wheels, we need to figure out overall width. Adding together the pad-to-spring measurement (71/4 inches) and the pad-to-fender-lip measurement (51/4 inches), we have 121/2 inches total width from contact point to contact point.

Since the sidewall of the...        read full caption Since the sidewall of the tire bulges out over the edge of the rim, it is important to find the overall width of a wheel/ tire combo so you can factor in these variables. The overall width of this 245/50 series tire on a 9-1/2-inch rim is 11-3/4 inches, and we have 12-1/2 inches of space. That gives us 3/4 inch of total breathing room, and since we already factored in a 1/4 inch of clearance on the backside, that leaves 1/2 inch of clearance between the outside sidewall and the fender lip. According to American Racing’s “Hoppy” Hopkins, this is the minimum, and it could still rub going over driveways.

Sidewall width must be taken...        read full caption Sidewall width must be taken into account when determining whether or not a wheel/tire combo will fit. Most tire manufacturers list the width of each tire on different rim sizes in their catalogs, so make nice with your local tire dealer to get the inside scoop.

Wheel fitment can get a little...        read full caption Wheel fitment can get a little more complicated up front, so get a friend to turn the steering wheel from lock to lock while you take measurements. It’s important to remember the turning angle of the front wheels when determining wheel width. Hoppy recommends adding an extra 1/2 inch of space on both the inside and the outside measurements.

In order to accommodate the...        read full caption In order to accommodate the turning angle of the front wheels...

...a smaller wheel/tire combo...        read full caption ...a smaller wheel/tire combo may be necessary in the front, but since most hot rodders prefer a big ’n’ little look anyway, this is usually not considered a sacrifice.

12. You should be able to...        read full caption 12. You should be able to run your fingers between the fender lip and the front tire. This will give the sidewall adequate breathing room when navigating the asphalt jungle.

Hoppy Hopkins has been with...        read full caption Hoppy Hopkins has been with American Racing for 27 years and has learned a thing or two about wheels in that time. Here he poses with what we would call the extreme end of the big roller spectrum—a 24-inch wheel. This is probably best left to the urban SUV set.

Since the birth of the automobile and the days of Henry Ford, automotive technology that was developed on the racetrack has trickled down to the street in one form or another. Fuel injection, overhead valves, multiple camshafts, and disc brakes were all developed to make race cars faster and safer before finding their way onto John Q. Public’s street brawler, and the same can be said for the current explosion in large-diameter wheel/tire technology sweeping through the rod and custom world.

Big-inch rolling stock has been prevalent in dealer showrooms for the better part of a decade, and for good reason. Larger wheels allow for the use of tires with less sidewall and a bigger footprint, which can improve handling. They also leave more clearance inside the wheel for larger disc brakes, and above all else, they can look flat-out bitchin’. For all these reasons and more, a “bigger is better” mantra has swept through the classic-car ranks, inspiring trends like the current Pro Touring craze, which preaches the gospel of big wheels, bigger brakes, and suspension designed for going through the twisties rather than simply blasting down the straights.

The street rod crowd seemed initially hesitant to embrace this trend, possibly due to the significantly increased expense and lack of traditionally styled wheels to suit their cars. However, that has been changing over the last couple years, as more and more wheel manufacturers now offer large-diameter rims modeled after past designs. Tire prices have come down as well, and there are now sizes available to fit large-diameter wheels that have more sidewall than the original rubber-band low-profile treads. When properly fitted, it’s tough to beat the look of a fender full of styled aluminum shod in high-performance rubber. Whether you’re cruising the boulevard in a slammed Merc or flying around the fairgrounds in a topless highboy, a tastefully chosen and well-fitted set of big-inch wheels can achieve a classic look with modern flair and performance.

The Experts Speak

Once you’ve made the choice to fit your ride with new rolling stock, two key decisions need to be made: what to buy and what size you’ll need. We would no sooner attempt to tell you which wheel to buy then we would pick out lingerie for another man’s wife, but we decided to ask a few experts for help in the second category.

Wheel/tire/suspension guru Phil Schmidt, owner of PS Engineering, says his company is cranking out more big-inch renditions of vintage wheel styles then ever before. According to him, the key to obtaining the perfect fit is through precise measurements and proper communication between the car owner and the wheel manufacturer. “You can’t just pull specs out of thin air,” Schmidt explains. “I listen as best as I can to what the customer is building, then ask a few questions to figure out what I need to know. With street rods, the variation of parts married together can be unbelievable, so I like to have owners use their current wheel to get a baseline measurement. We can use that to figure out if they want to go wider, taller, farther out in the wheelwell, and so on.”

Wheel Vintiques owner Mike Stahl agrees, claiming that while fitting a street rod with standard size 14- and 15-inch-diameter wheels becomes relatively simple with experience, wedging 17-inch and bigger wheels under street rod fenders that are often designed with compound curves and sweeping lines can be tricky. “We send customers measurement charts and ask them to take 15-20 measurements,” Stahl says. “You should always start with the wheel that’s on there now, because that’s what works. If you want your new wheels to be closer to the outside of the fender, then that can be adjusted with backspacing and rim width. If you want something taller, then modify the wheel diameter and tire size.”

While moving up from one wheel size to the next sounds pretty basic, we wanted some more facts on fitting maximum wheel into minimum space. To get the nitty gritty details, we turned to American Racing’s Vintage Brand Manager Hoppy Hopkins, who hauled out his trick ’55 Chevy pickup (which was chosen as one of R&C’s 100 Best last year) to give us some step-by-step instruction. As you’ve followed along, Hoppy fills the gaping fenders of his pickup with American Racing’s newest addition to its vintage line (and tribute to its veteran brand manager), the 17-inch Hopster.