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i have always ran short pullbar(on a 4/4 spring behind), 21.5 in, that is just mounted just behind the axle centerline. i would like to know what advantage, if any, it would be to go to a pullbar that mounts ahead of centerline on the axle, of course this would be with a pullbar that would have to mount near the driveshaft loop. i guess the pullbar would gain angle as the rearend rotates, is this any more advantages on a dry track?
The entire car has to work together to be balanced and predictable. No one part change can be considered advantageous or not. Sometimes guys get confused and say" I used this part and I went faster." That doesn't mean it would work for everyone, it just means that part worked better on that cars/drivers total combination.
A pull bar mounted closer to the front wheels will tend to unload the front tires more that when mounted more rear. A pull bar mounted ahead of the axle will typically gain angle with Counterclockwise axle rotation(RS view) or at least it tend to not lose angle as fast depending on how much the rear axle moves away from Ride Height under acceleration.
The increase in angle increases anti-squat and rear tire loading while on the gas but will unload the tires on deceleration so a generality can be said that more angle increases the traction(tightens) at mid corner too off while also reducing traction(loosens) on corner entry. Which one you need depends on what your car is doing that you don't like and you would want to change.
Just curious about what angle most guys are running on their pull bars. It seems like I've been seeing some guys with less angle recently and am wondering how they are getting good drive with them mounted flatter.
Because angle doesn't equate to traction.
It's about overall design including mid corner speed and attitude of the car and many other things.
18-22 degrees
That's a good "Ignore List" Think I'll use it too. Speaking on pullbars, we used the long stlye Pullbar(w/Freeburg std coil unit), mounted left of center attached forward along side loop, in the same hole as the 5th arm upper bolt(forward of center) on QC bracket. We used BWRC QC plates and 5th arm as opposed to Rayburn std unit. This combined with short arms(14 3/8) dug like a D9 CAT off the corner. We couldn't use LR wheel spacer as it had too much drive and tended push on initial throttle up. Car tended to be tight on entry, but was fast in the right hands. Larry Moore ran it for us 1 night at Lavonia and ran 3rd behind Buck Simmons even after power steering failed. Rayburn cars are outta of vogue now, but I'd take one any day. Little work and brain power and I'm sure a setup could be made to run with the major players, with right equipment and driver. JMO.Quote:
Originally Posted by stock car driver
STRONGER THAN DIRT
More angle will turn a greater portion of the pull bars work into a vertical force vector so it does create more of an instant hit however it picks up closer to the back of the car than a pull bar that is more level with the same rear end mounting point. Saying that a bar that has less angle will pull more from the front of the car. It doesn't create a huge instant hit but the traction comes from forward to rearward weight transfer. The way a four link works, the upper and lower bars don't "pull weight" from anywhere. They simply move along a radius and push on the chassis. Their mechanical loading to the tires is the result of a secondary function wheel pushes on links, it walks ahead and raises car, as the car accelerates, force is then transferred onto that corner. With the pull bar, it's in tension not compression like the four links are... and because of this you create a bit of a "torque" around an axis. This is called a screw axis or instantaneous center. Now one thing to keep in mind saying all this is if the pull bar has a bunch of angle, what is it doing to the links? If it's pulling the chassis up it will be taking weight off the links (depending on where that intersection point is with the lines of action from the four links and pull bar). This can help the car get up on the bars, but does not do much in terms of front to rear traction. This is why they say more angle creates an instant hit but runs out down the straight. All the weight transfer happens very quickly and reaches maximum then drops off. Believe it has something to do with traction circles of the tires but I'm not 100% on this. As you level the bar out more it takes less work away from the links and starts to increase front to rear transfer. If we go to the extreme, and run uphill angle to the front of the car you would think it would unload the tires? Wrong. It pulls the chassis down into the links and creates a screw axis that torques the frame around the compressive force of the links. It can create violent traction and even pick both front tires off the ground. This is exaggerated even further by moving really low on the rear end housing. Going from 10 degrees downhill to 10 degrees uphill you can take a car with average drive and make it load the rear tires up so much you can't turn the car as well as literally taking all the weight off the front tires making it hard to steer. Basically like it's been mentioned already, each design of car is a bit different. Some cars like more angle, some don't. It depends on if the setup is more momentum style or if it's like a jack rabbit setup, driving style.. track size... Also rear end mount height. Same angle moved up and down equally on rear end and chassis has a huge impact on handling as well.