Article in Chevy High Performance
Spindle Extenders for even better handling
While we had the front end apart, we decided to try out Pro Motorsports' new spindle extenders. Without going into too much theory about suspension geometry, changing spindle height changes the upper control arm's arc under suspension movement. A taller spindle generally means that under bump (when) the tire moves into negative camber, which is highly desirable for maximum cornering power. Pro Motorsports' spindle extenders do this for a very reasonable cost. We performed before-and-after testing on the Camaro with these parts, and they work. Not only that, they're remarkably easy to install.
The Extender adds 1 15/16 inches to the total spindle height. The design allows the car to be easily returned back to stock, if desired.
After separating the upper control arm and ball joint, the top half of the extender installs over the ball joint with the stock nut. A piece of bar stock is included to hold the extender and keep it from turning while the nut is tightened. Use a new cotter pin. Once that step is done, six Allen-head screws connect the two pieces of the extender together.
In place of the ball joint is a bolt that goes through the spindle and threads into the extender.
Jim Sleeper at Precision Alignment installed the extenders and aligned the car in both configurations. Sleeper also measured the camber gain at 1 and 2 inches of bump and rebound. The chart shows the results.
Specs Stock w/Extender
Camber: -3/4 -3/4
Caster +2 +3 3/4
+2" -11/16 +1
+1" -13/16 +1/4
Static -3/4 -3/4
-1" +1 15/16 -1 3/4
-2" +1 5/16 -3 1/8
As you can see, the spindle extenders have the as-advertised effect on suspension geometry. In stock form, with the front end set at a typical performance alignment of 3/4 degree of negative camber, when the car goes into a corner and the tire moves up into the fender, it rolls out to 15/16 degrees of positive camber. That usually results in a serious case of understeer. With the extenders, the tire rolls to a whopping 31/8 degrees of negative camber.
Does this theory work in the real world? You bet! With the stock suspension set at 3/4-degree negative, the Camaro ran through our sister magazine Motor Trend's 600-foot slalom at 60.60 mph and ran around the skidpad at .87g wearing p255/45Z-17 front and p275/45Z-17 rear BFGoodrich Comp T/A tires. We bolted on the spindle extenders, put in the right alignment shims (for a 3/4 negative static setting) and reran the test. The car then went through the slalom at 62.93 and pulled .90g on the skidpad. For a bolt-on, that's a significant difference.
Spindle Extender Kit . . . . . . . . . . . . . . $179.95