Of Wheels
Let’s run through a quick exercise. Don’t take all of these numbers as gospel because your measurements can be different, especially on tires. Remember back in Step 2 when you took measurement #1, #2 & #3? Let’s say that #1 is 6" and #2 is 5" for a total of 11". The 225/60R15 we talked about had a cross section of 87/8" (we’ll call it 9"). This means that 4½" of tire is inboard and 4½" is outboard. Dimension #2 is 5". That only gives you ½" clearance between the tire and the fender using a centered wheel. If you use the 15 x 8 with a backspace of 4½" that we talked about earlier, here’s what happens: The front side of the wheel is now 3½" which is ½" shallower than it would be on a centered wheel at 4". In essence the outer wheel has been moved back ½" extra so you now have 1" clearance between the tire and the fender. Working out the numbers you also have 1" clearance on the backside - Perfect.
WHEELS Usually a wheel will be listed as 14 x 6 or 15 x 8 etc. The first number is the diameter of the wheel and needs to be the same as the last number in the tire size. The last number is the wheel width. There is also another number which is very important. This is offset or backspace. If you take the tire you just bought and put it in the fender opening you will notice that the middle of the tire probably is not centered over the mounting flange of the hub. This is where offset comes in. When a wheel listed as 15 x 8 offers a backspace of 4½" this means that 4½" of the wheel is inboard of the mounting flange and 3½" is outboard to total 8". A 15 x 10 with 4½" backspace would have 5½" to the outside.
A
B
WHEEL DIMENSIONS Wheel dimensions can be somewhat confusing so we’ll explain them for you. A. This is the overall width of the wheel. It is the total of C & D and usually " to 1" greater than B. B. This measurement is across the wheel between the mounting beads. This is the area that the tire sits in. When you see a wheel listed as 15 x 8 then dimension B is 8". C. This is measured from the mounting flange to the back edge of the wheel. Sometimes called backspace. D. This is measured from the mounting flange to the front edge of the wheel. Sometimes called front space. *The difference between B & C is called offset. If D is less than C this is negative offset. Then if C is less than D it is positive offset.
C D
VENTED vs SOLID Original style steel wheels are often called vented. This term comes from the openings or windows between the wheel center and the outer rim.
Solids are just that - solid. They do not have this opening.
VENTS
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