I wondered if someone could explain what "backspace" is when refering to wheels? I have 10" wide wagon wheels on my CJ and I like the look, it gives it a "wider" look. I want to upgrade to an newer aluminum wheel and stick with the 10". What would be the prefered backspacing I should look for and where is it measured from? A friend has 8" wheels on his CJ and used wheel spacers to give it the wider look. I know some of you don't like the spacers, I'm not a big fan either.
How to Measure Wheel BackSpace
Items required to measure wheel backspace: Tape measure, Straight edge, Wheel w/o tire (preferred)
The easiest way to measure backspace is to lay the wheel face down onto the ground so the backside of the wheel is facing up. Take a straight edge and lay it diagonally across the
inboard flange of the wheel. Take a tape measure and measure the distance from where the straight edge contacts the inboard flange to the hub
mounting pad of the wheel. This measurement is backspace. The above photo shows three wheels with 2",3", & 4" backspace.
Measuring Wheel Offset
To calculate offset you'll need the following measurements: Wheel backspace, Wheel Width, Wheel Center line (outboard flange to inboard flange measurement / 2)
Subtract: Wheel center line from Wheel backspace to get offset. If backspace is less than the wheel centerline the offset is negative. If backspace is greater than the wheel centerline the offset is positive.
Tip: To convert from inches to mm multiply by 25.4. To convert from mm to inches divide by 25.4.
Backspace to Offset Conversion Chart
The table on the right is q quick reference for finding offset, pick the rim width and follow the row over to the backspace of your wheel.
Determining Vehicle Fitment
Fitting a wheel and tire package is different for each vehicle, but by following these guidelines your chances for success will be much greater. In most cases you'll have to use the physical dimensions of the current wheel/tire package to determine the dimensions of the new wheel/tire package. Items which are potential trouble spots: Tie Rod Ends, A-arms, Brake Calipers, Shocks and Shock Mounts, Inner & Outer Fenders (esp. front tires turned to lock).
In the drawing above, we've made two measurements. Front Side Clearance and Back Side Clearance. These measurements when used with: Tire Section Width, Tire Diameter, Rim Width and Rim Backspace; Help determine if wheel/tire clearance is adequate for the new wheel/tire package you've selected.
Suggestion: Start your search for new wheels by picking the tires first. Get the tire manufacturer's rim width recommendations and physical dimensions for the tires you want. Pay close attention to
Section Width and Measured Rims specs., these are important numbers to be used when selecting rims and determining vehicle fitment.
