Traction Bars

[Bgbdbn]

Just curious if any one has used Competition Engineerings Slide-A-Link traction bars. If you have what is your take on them over regular traction bars? Thinking of getting them for my truck.

[desperado]

Traction bars or "Slapper Bars" are pretty much useless, unless you modify them for *** snubber (the little rubber stop at the end of the bar) to sit right against the spring.

 

Here is what you are trying to accomplish with a slide a link or slapper bars. When you launch a LEAF SPRING car, the axle twists the springs, loading them, two things are happening, one is that the springs begin to store torsional energy, which might sound good, but it's not, I will get to that in a minute. The other thing that happens is the pinion angle is changed. This is the angle of the pinion shaft in relation to the axle centerline, on a plain running from side to side through the axle. This angle is important because when it's wrong, it puts the driveshaft, and U joint in a bind, and as with ANY mechanical bind, it will absorb energy that car otherwise be used to propel the car foward.

Now the other thing about the springs storing energy, there is no way to control the release of this energy, and it's release wants to twist *** front of the axle down, in effect turning the tires in a foward motion.

To better understand this, look at these numbers.

a car with a motor that is putting 400 FT LB torque into a 4 speed with a 3.5 first gear ratio, and a 4.11 rear gear. Then the clutch locks, not figuring mechanical loss, we have 400 ft lb X 3.5 tranny gear X 4.11 rear gear = 5754 ft lbs of torque at the axle divided by two, or 2877 ft lbs of torque at each wheel. Now if the spring stores up 10% of that torque, as it peaks at 10% there is now 5754 + 575.4 extra load, that is uncontrolled as to how it hits the tire, 6329.4 ft lbs of torque hitting a street tire. So you see SMOKE, and lots of it. Second thing that will happen, as the spring unloads it's energy, and the load against the tire drops, the tire will regain traction, starting the process over again. The spring wraps up, the tire breaks traction again and the extra load goes away. This is referred to as WHEEL HOP. When you hear the top fuel guys talk about tire shake, it is similar to this except they have no springs, the tire flexes, the rim turns farther than the traction patch of the tire, and it unloads. Then regains traction over and over.

The reason that street guys call it wheel hop is that as the spring wrpas up it also lowers the ride height of the car, as it unloads, it pushes the car in the air, and the tire can actually leave the ground. The tire will of course return to the pavement, and start the process over again, now being compounded by the now lifted car falling back down on the suspension of the car, further loading it with weight ( the car doesn't really get heavier, but because it is acclerated down by gravity, it has a similar effect of being heavier.

 

So here is what a slide a link does to combat this. I assume that you are aware of what they look like and how they mount, but for others that haven't seen them, here's a brief explanation.

Slide a link goes under the front half of a leaf spring, connecting to the front spring perch and the spring mount under the axle. An adjustable link rod goes in between them. And the assembly is under both rear springs. these LOCK the pinion angle, keeping the axle from twisting at all. As it trys to twist, it generates a pulling force on the spring, as it pushes against the lower link rod. This also helps weight transfer by raising the nose, setting more of the total weight of the car on the rear tires. This plants the tires well and gets the car to leave harder and with a better consistency.

 

The two negatives about this setup is it reduces grond clearance, and it tends to eat leaf springs, because it nulifies the front half of the leaf spring, leaving only the rear half the spring to act as a suspension for the car.

[Bgbdbn]

Thanks for the info. Other than the premature failure of the springs they work pretty good then. Im not all that concerned with the ground clearance. This truck will only be bracket raced and driven on the street occasionally. I was going to go with a four link set up, but we are not going to tub this truck right away. I just need something that will plant the rear tires.

[desperado]

If you are looking to plant the tires. This is the way to go. I forgot to mention that slide a links are adjustable as well. So you can preload the suspension for more consistant launches. The othr thing to do is get a set of SOLID spring bushings for the front springs. They will lock things into place even more.

 

And like I said, only downside is that they are not as tuneable as a four link and they will eat springs. And as far as it not being as tuneable as a 4 link, it also don't cost what a 4 link does. One other thing to look at is the shocks, and the front springs and shocks. Adjustable drag shocks and drag front springs might be in order. That is unless you we are talking about the 88 Dodge truck in your sig. In which case it has a torsion bar front end. The drag shocks are still a consideration, the other thing to look at it front suspension travel limiters. If you haven't seen these before, it's pretty much a cable that one end attaches to the lower control arm, the other attaches to an eye bolt through the shock tower or some other fixed point. As the nose comes up, the cable pulls tight, stopping the suspension from going further down, basically lifting the tire from the pavement. Of course if you can get the front tire off the pavement, all the weight of the vehicle is now on the rear tires. Now these SUCK for regular driving on the street. Any time you crest a hill a bit fast, or anything else that tends to move the vehiles nose up, can yank the tires off the ground if the cables are short and may lead to sucking the foam rubber in your seat right up your ass as you fight to contol the vehicle with the 2 inches of daylight between the tires and the road.

[Bgbdbn]

Cool, thanks for the info