need more drive coming off...help please

[JustAddDirt]

we raced and the car was upside down. We swapped the shocks around on the front and shortened the rrbs a quater of an inch. The car pushed so hard is was bad it was like drivin a diffrent car than what i had.

So now you have too much drive?
did u put the 1/4" lead back in it?
Did u raise RRbottom bar 1 hole?
lower rr top bar 1 hole?
might need to even up springs in front. 2 750's
That will loosen up entry and through middle as well.

[washeduptoo]

Are you squaring the rear end in the car or are you going by bar lengths to square, that might not work depending upon how it was built.

[oldtrackchamp4x]

Sounds to me like you are doing way to many things to the car at one time and now it's really off.I would put the car BACK to where it was when it was JUST loose on exit. Then just make ONE change at a time, like BITE or LLB or LUB. JMO

[bluemod]

We took out the 1/2in trail in the rr. Did not move any bars. And swaped the shocks around.
Put it on the scales after the race and we got

this is weight at each wheel

lf625 rf 456
lr 699 rr672

same springs in same location

left%54.4
cross%46.6
rear%55.3

stagger

lf 83in rf84in
lr83in rr85in

Car would not turn going in just strait to the wall no matter where at in the turn and this is a sweepin high bank track. To me the right front weight seems alot low. please all thoughts to help

[oldtrackchamp4x]

What were your scale numbers BEFORE you made any recent changes? From what you now have I feel your bite and cross are both low. I've never been on a high banked 1/2 mile, only 1/4- 3/10, so i might be talking out my rear, but I think you should raise your bite up to 70-80 lbs, which should loosen entry and tighten exit, but i would put the trail where it was, leave the shocks as they are now then scale then try the car. I'm assuming your ride heights are all correct and you are adjusting your weight jacks correctly to keep the heights the same. There are some way smart guys on here so i'm basically telling what has worked for me now and in the past. JMO Good Luck

[bluemod]

We took out the 1/2in trail in the rr. Did not move any bars. And swaped the shocks around.
Put it on the scales after the race and we got

this is weight at each wheel

lf625 rf 456
lr 699 rr672

same springs in same location

left%54.4
cross%46.6
rear%55.3

stagger

lf 83in rf84in
lr83in rr85in

Car would not turn going in just strait to the wall no matter where at in the turn and this is a sweepin high bank track. To me the right front weight seems alot low. please all thoughts to help

before was
lf617 rf501
lf 699 rr661

left%54.1
cross 47.2
rear%55
everything else the same

[bluemod]

we swaped everything back to the way it was the last couple races when we were running good whats the easyest way to loosen the car up getting in

[charcoal01]

Raise the right lower or add steer.

[bluemod]

Will this have anyother effects on the car besides on entry? Also lowerin the j-bar on the frame puting more angle on it what does this do?

[xxxmod]

we swaped everything back to the way it was the last couple races when we were running good whats the easyest way to loosen the car up getting in

More back brake,better back brakes,softer front brake pads.

[powerslide]

Will this have anyother effects on the car besides on entry? Also lowerin the j-bar on the frame puting more angle on it what does this do?

like someone else said the two that are used mostly for entry only are the RR lower bar and then the LF spring. Soften LF spring to free entry.

[drtrkr244]

Will this have anyother effects on the car besides on entry? Also lowerin the j-bar on the frame puting more angle on it what does this do?

Lowering j-bar on frame, decreases angle, which loosens car in and off.

Changing shocks shoukd not have made that kind of difference.Have LF checked, appears the compression is way too stiff.

Soften LF spring, which will affect mostly the entry, but it will increase drive off depending on load on LF at corner exit.

[bluemod]

ok so lowerin the pull bar on the frame or raising it what effect does this have? sorry for all the questions but if i dont ask i will never know.

[bluemod]

ok so we raced to night and the car was lose. So we added bite and was still lose coming out. But it is alot closer than last week. Is the best was to fix being lose to raise the j-bar up on the frame? Another problem i have got now is im burning the tires off midcorner out what would cause this?

[rrcmotorsports]

If you raise pull bar on the housing it will take more power to "wrap up" because of the lack of leverage. Where you mount the pull bar to chassis is where you "lift the car". Visualize a line going through your pull bar to frame rail and that is the point where the weight of the car will be lifted. The higher you mount on the frame the more your drive will rely on bar angles and weight transfer, the lower you put it the more the car will "hike" both RR and LR because your pulling up on chassis. What is your pull bar angle? Also measure from your centerline of axle to pull bar hole (generally around 9"-13") Are you running a short pull bar or long pull bar?

[Dirtrunner35]

Good reading

The pull bar, or the third link as you called it, is nothing more than a mechanical traction control device that utilizes the motion (wrap) of the rear end on acceleration to enhance the traction of the rear tires. (Note: just like Gene pointed out it also affects handling on decel because of pinion dive but we'll stick with your question and its relation to forward bite.) As the pinion tries to crawl up the ring gear during acceleration the axle rotates/wraps. This motion is transmitted thru the pull bar to the chassis raising the chassis. A quick assumption would be that if the pull bar is lifting the chassis that it is taking weight off of the rear springs. That is true to a certain extent but you also have to go back to the rule of "For every action there is an equal and opposite reaction." This means that the weight that is taken off of the rear springs by the pull bar lifting the chassis is actually reapplied to the rear tires thru the pull bar into rear end housing into the wheels down thru the tires. So in actuality you don't directly gain or lose any weight on the rear tires by the lifting action of the pull bar acting on the chassis.

So at this point you're either thinking I'm full of it or you're asking yourself then why do we use pull bars at all. The answer to this question is that the pull bar keeps the center of gravity of the car higher during acceleration. If we did not use a pull bar the rear of the car would squat during acceleration effectively lowering the center of gravity. The center of gravity is important because the higher the center of gravity, the more weight will transfer from front to rear (I'm sure there is a limit to this.) So the purpose of the pull bar is not to directly add weight to rear tires during acceleration, but it is to indirectly allow more weight transfer from the front to the rear due to the higher center of gravity during acceleration.

A second function of the pull bar is to soften the application of torque to the rear tires when you jump on the throttle. This is why the pull bar is equipped with rubber biscuits, a coil spring, or both. These devices absorb some of the torque that is applied to the rear end by the engine to give the tires a chance to take a set into the track before they see full torque applied. If we didn't need to worry about softening the torque application to the tires the pull bar could just be a solid length of tubing connecting the rear end to the chassis. But since this would somewhat prevent the axle wrap motion, that means that 100% of the torque that is being produced by the engine would be passed onto the tires and give them one heck of a jolt on throttle application. That's okay if the track is tacky enough and the tires have already taken a set into the track, but if not and you're just getting back into the gas off of the corner you're just going to break the tires loose and spin down the stretch. Changing preload or spring rate on these torque absorbing devices is one way to control traction on different track surfaces. The preload determines how much torque will be delivered to the tires before the torque absorbing device begins to absorb some of the torque [i.e. if you have 250 lbs. of preload on the pull bar spring (which is about 1/4" of preload on a 1000 lb. spring), the tires will take the initial 250 pound hit of torque before the pull bar spring starts to compress and absorb some of the torque.]

Now on to the angle and height of the pull bar. The angle of the bar does have an affect on forward bite, but like Gene stated it's only up to a ceratin point. The more agressive you get with angle it's like asking the pull bar to lift the chassis higher - faster. This is okay if the tires have the traction to do this but if you're on a dry slick track the tires are just going to break loose and you wont get any lift out of the pull bar. The lift from the pull bar is a result of the tires staying adhered/stuck to the track and the pinion trying to climb the ring gear because of the tires traction. The net result is axle wrap. If you ask to pull bar to try to lift too much weight too fast it will actually direct too much torque to the tires too soon (before they take a set) and cause them to break loose. In other words and extreme pull bar angle on a dry slick track would not be a good idea. So angle becomes another tuning factor just like preload on the torque absorbing device.

Finally, the height of the rear pull bar attachment point from the centerline of the rear axle determines the amount of leverage the rear end has on the pull bar. The higher the pull bar attachment point from the center line of the axle, the less leverage the rear end has on the pull bar. The opposite of this also holds true. There are usually several holes to mount the rear of the pull bar in and again this becomes somewhat of a tuning tool. Another way to look at this would be to imagine yourself holding a two foot length of metal rod straight out from your body and hanging a five pound weight from the opposite end of the rod. You then try to lift the rod up and see how much resistance you feel. Do the same thing now with a four foot piece of metal rod with the same five pound weight hanging from the end. It will be harder for you to lift the weight with the four foot rod than it will with the two foot rod. This is the same affect that moving the rear attaching point of the pull bar (either closer or further away from the axle centerline) has on the leverage the pull bar feels. You might think that more leverage is always better, but again more leverage means more pull/lift which means the tires better have the traction to pull it off (no pun intended.)