Sprint Cars: Wheel Offset Confusion
One question that I seem to encounter quite often on the Sprint Car tech line is the confusion among wheel manufacturers and customers on what offset the wheel is called out as, and what the offset actually measures. I would like to try to clear up the mud here and help make sense of the measurements and terminology.
When you order a front wheel for your sprint car, such as the Weld Racing Direct Mount Front Wheel, part number 8158605813, it will call that wheel out as a 15-inch diameter wheel, that is 8-inches wide and has a 3-inch offset. The confusion seems to lie within that “3 off” description.
You will notice if you take a tape measure to the backside of that wheel and go from the hub flange to the edge of the bead on the inside of the wheel, that it will actually measure 4 inches instead of the called out 3-inch offset. I grabbed a “3 off” front wheel, and a tape measure myself to show you the actual measurement visually.
I wanted to gain an understanding as to why it is that way, so I went straight to the source and spoke with a wheel company. I was told that in years past they used to measure the offset with the hub attached, which would make your measurement an inch less. Measuring from the backside of the hub to the inside edge of the wheel, you would have your 3-inch offset as described in the call out. This would be understandable if you sold the hubs attached to the wheel.
However, sprint car wheels are sold individually, and seeing the offset call out and getting an inch different measurement can get confusing. On Speedway Motor's website, we have included the offsets with the actual measurement for each front wheel to reference. Below is that same key:
Wheel sold as/Actually Measures:
3" off wheel measures 4" backspace
4" off wheel measures 5" backspace
5" off wheel measures 6" backspace
6" off wheel measures 7" backspace
Rear-wheel offsets are very straight forward. For instance, part number 81573551535, is a Weld Racing Splined Left Rear Wheel. This wheel is described as a 15-inch diameter, 15-inch-wide, 5-inch offset wheel. If you measure with a tape measure from the backside of the wheel center, to the inside edge of the wheel where the bead lock is bolted on, it will measure a true 5-inches.
Essentially with rear-wheel offset, a spade is a spade, a 5-inch offset actually measures 5-inches. Hopefully, this information can clarify any confusion in front-wheel offset and give you some confidence the next time you go to order!