Frequiently Asked Questions From Racing Industry LeadersStock Car Racing visits regularly with leaders in the racing industry to find out what questions they are most frequently asked by the average short track racer. This month we speak with Doug Demoss of Quick Performance, one of the leading manufacturers of rearends and driveline equipment for racecars.
Q: Why are most rearends for racing based on the Ford 9-inch when there are so many other styles of rearends available on different vehicles?Demoss: There are several reasons the Ford 9-inch is the preferred rearend for racing and other performance applications. First of all, you have a wide range of ring-and-pinion gear choices available. In fact, the gear selection goes all the way to a 7.33:1. The 9-inch is also easily adaptable to just about any application, with its removable center section it is easy to set up, and finally it is relatively light and can be built very strong without major modifications.
Q: What is the difference between a spool and a locker? In what conditions is running a spool better than a locker? When is a locker a better idea?Demoss: Most stock rearends are "open," meaning the setup inside the rearend allows one wheel to turn faster than another through a turn. This keeps the wheels from "chirping" as you turn, but it also means that all the power from the engine is transferred to the wheel with the least rolling resistance. That's why if your car is half-way off the road with one wheel on the asphalt and one in the mud, it is the wheel sitting in the mud that's going to spin.
A spool is a simple way of connecting everything inside the rearend. It locks both the right- and left-side axles together so that they always turn at the same rate. A locker typically will allow the outside wheel to turn faster than the inside wheel as you roll through a turn, but locks both axles together as you accelerate down the straights.
A spool is the better option any time you want the lightest possible weight or if you want both rear wheels to always turn at the same rate. Spools are most popular in dirt racing. If price is a factor, a mini-spool or a full spool will always be cheaper than a locker. A locker is better when you don't want both wheels locked together at the same time, like on asphalt when maintaining traction all the way around the track is a priority.
Q: What is a "floater" rearend?Demoss: A floater uses a hub on a spindle with two outer bearings and an axle that is splined on both ends. The wheel is held in place on the spindle and the axle's only attachment is at the splines. It can actually slide back and forth a little bit. If the axle breaks, the wheel stays in place and doesn't come flying off the car, so this is an important safety feature.
Q: How can I determine how much axle thickness I need?Demoss: The strength of the axle is usually determined by the thickness at the splines, which is the area where the axle drives the hub. We like to see one-inch diameter in the spline area on most circle track axles. Axle thickness is usually spoken of in terms of the number of splines on an axle.
Q: Is a lightened ring gear really worth the extra cost?Demoss: A lightened ring gear does cost more money than a standard ring-and-pinion gear set because of the extra machining operations involved, but there is definitely an advantage. The reduced rotating weight helps acceleration and can give you a competitive advantage on the racetrack.
Q: What type of maintenance should be performed regularly to keep my rearend operating properly?Demoss: We recommend a complete inspection after every six nights of racing, including an oil change.