Posted by Mike Bales on September 29, 2009, 11:10 pm
Board Administrator
Vol. 2 The set-up Series.
The set-up of the rear end.
Part 2of 2
Next the upper link. The third link is a minor adjusting tool. Running downhill from the rear end to the frame, it will help corner entry and exit only. On the upper link, the more angle will help you get traction under acceleration, but it will also loosen it on corner entry. You will have to fine a happy medium to run. A good starting point is 5 to 7 degrees downhill to the frame. I have had a lot of luck running the upper link level to ˝ deg. downhill to the frame. It seems not to unload the chassis as much on corner entry and that will help when your passing on the outside of some one. The Pan Hard Bar. First it keeps the rear end centered. It also has an effect on the cars ability to roll from side to side. A short pan hard bar will help turn a race car as in a front mounted bar. A longer pan hard bar will promote more bite as in a rear mounted bar. When you raise the pan hard bar at both ends, you decrease the chassis roll, and take bite off the left rear tire making the race car turn better. A lower bar both ends will increase chassis roll and will increase left rear tire ability to grip the track, making the race car tighter. As seen in today’s NASCAR Sprint Cup and Nationwide Series with the big bar soft spring’s set-up, they keep lowering and lowering the pan hard bar to get chassis roll so the race car will pivot in the middle of the corner to offset the big sway bar for forward bite.
Pan hard bar split! On a right side frame mounted pan hard bar, the more split by raising the frame end will loosen up the chassis making the race car turn better. The more split the looser all the way around the track it will be. Less split the tighter the car will be all the way around the track. Starting points a front mounted bar 11” to 11-1/2” on the frame and 1” lower on the rear end. A rear mounted pan hard bar 9-1/2” to 10” and level to 1/2” lower to the rear end. Stock rear suspension Sport Stock race car’s UB Machine trailing arm Mono-Ball Pivot Kit is the way to go. As for leaf spring cars, mounding of the leaf springs 4” to 4-1/2” wider in the back then the front. Multi-leaf springs with just a shock I would run 200# R.R. and 225# or 250# L.R. If I was running a Camaro Sport Stock, I know I would run a Mono-Leaf Spring with coil-over. There is not a thing in the rules about it. Just use a steel body shock. Frame mounted height on the front and leaf spring slider on the rear with a wedge bolt mounted on the slider. Landrum makes some of the best leaf spring on the market. They also make a 2-1/2” adjustable aluminum lowering block part no. LANLSS701 that you can put lead in or take it out of the right rear. Next pinion angle. Positive pinion angle is down and negative is the pinion up. The more positive we run the more bite we will get, now the problem is the more positive we put in the rear end the more it will loosen the car on corner enter. As the engine is turning under acceleration the drive shift it is trying to force the rear tires into the track but on de-acceleration it is trying to pick the rear tires up off the track. Camber in the rear end. Without buying cambered axle tubes and crowned axles the best we can do is make sure we have “0” to 1/4 deg. negative on the right rear and “o” to 1/4 degree positive on the left rear. Now just a little note, you see the NASCAR cup cars dog tracking on TV they are not leading the right rear back. The rear end housing is in the car straight, but the rear tires are turned to the right all in an attempt to make the car turn in the middle. Next month we move to the front suspension.
Until next time
Mike
"You cannot dream yourself into a character: you must hammer and forge yourself into one." Henry D. Thoreau
