Front traction bars

[motorwood]

I want some ideas on front traction bars. My biggest question is if I run fron the middle of the frame rails forward to the differential, will it cause my front suspension to bind since the swinging shackle is in the rear?

[Kasper Cummins]

If the traction bar swings in the same arc as the spring it will not bind. For it to swing in the same arc it need to be the same length as the leaf spring from the center of the axle to the front bolt. You could build leaf links or caltracs, they would work nice for a short length like that. You could also put a shackle on the traction bar then it will not bind but will still stop axle wrap.

[motorwood]

Thank you Mr. Kasper. I was thinking along the lines of a Caltrac style bar to prevent the bind and because my exhaust runs under my frame. I just wasnt sure if the lift action of that style would cause any trouble.

[Kasper Cummins]

I think caltracs would work the best. Try to build them so the the top of the leaf spring and the mount for the caltrac (under the axle) are 1/3 the of your tires height for them to work the best.
By the way sweet truck.

[stillsmokin]

What you want to build are a caltracs type unit like prviously stated, but the common misconception is that the bars would point toward the center of the truck. Trouble is they would antisquat, or push the nose of the truck up. You want the caltracs to squat, that means to push down on the spring the bar must go forward. Yes, it will look weird, but it's what I plan on doing. I have eliminated the chatter and some of the axle wrap in the front, but have not actually got rid of the wrap. I would benefit from these bars on the front, keeping the nose down at the end of the run.

FWIW, this isn't going to be fun to make so I haven't done it yet.

[Kasper Cummins]

Caltracs would be from the center of the axle forward when looking at the side of the truck. It would mount under the axle and to the towards the eye of the spring without the shackle.

Antisquat is not a bad thing, it applies more downward force on the tires. If your trying to make the front squat then it is lifting the front axle up and it will spin the tires easier.

With more downward force it would act like a heavier truck and allow the tires to spin less.

[stillsmokin]

With the caltracs forcing the truck to squat in the nose the downforce that is created by the bellcrank mechanism pushes down on the tire in the direction of gravity thus multiplying its effect. But really you are cancelling out the force that starts the wrap to begin with more than anything. The thought is any residual force left over must be in a direction that benefits the machine, down. Keep the center of gravity as low as you possibly can for stability and to fight the sled.

You want to keep your nose down as much as you can pulling, steering issues creep up if the nose gets too high. Its a big problem if you have serious ground speed and crappy steering. Driveline angles get hairy in the front as well as the nose rises. If you are lifted to allow for steering with 2100# on the weight rack (like pulltilbroke and myself are) all the effects are worsened. 33x12.5 tires wouldn't turn in my wheelwells with the iron on if it wasn't lifted, so I have to make it work.

Front axle wrap is bad, so getting rid of it is beneficial, however a guy gets rid of it.

Our axle wrap problem is really a front leaf spring problem. Someone needs to make us a front leaf spring for pulling to reduce wrap, more like chevy and ford trucks have, there should be 3 leaves eye to eye at the top of the pack with multiple bands. The front spring eye should have been wrapped by the second spring as well but, I am unsure if it would clear the hanger that way. With some slight change in spring rate or arch to offset the massive amount of weight we have to hang off the front to get up to say 8500# without the tires eating the wheelwells. Most of the springs I've tried are designed with soft ride characteristics only in mind. I'm on the 4th set of front springs and don't like these either. I probably need to call alcan spring at this point.

[Kasper Cummins]

With a caltrac as the axle tries to move forward the link stop it and tire tries to go under the link. With the tire trying to go under the link it is getting push downward until it is easier to push the body upwards.

If the link is above the axle going rearward it will cause the tire to want to go upwards until it is easier to for the body to go down. With the tire trying to go up it will cause less traction.

Although it may seam better to have the body going down, if its causing less traction your not going to pull as far. It may seam wrong to want the front to lift while pulling because you will be transferring weight to the rear axle but if it is pushing down on the tires causing more traction you will pull farther. Also with the front of the truck low then the rear it will make it harder to transfer weight.

[ellis93]

Look at thishttp://www.hotrodsandhemis.com/Traction.html

[Kasper Cummins]

Yup that shows the caltracs im talking about.

[motorwood]

Thanks for all the good info guys. I also thought of undoing the u-bolts, cutting the center bolt and moving all leafs as far forward as possible to stiffen the front half of the spring where I think most of the wrap occurs.

[Kasper Cummins]

No, I would not do that. That would make the back of the spring weaker and may not reduce axlewrap at all. The axle would not be able to go ahead as far but it would wrap back farther. You have the right idea, a stiffer suspension would reduce axle wrap. If you clamp the leafs together it should help but I don't know how much.

Do you have alot of axle wrap?

[motorwood]

Not too bad, I guess judging on my wheel hop is only slight to moderate and I can usually steer out of it. But it does keep me from being able to get the tires spinning allowing me to launch in a higher gear.

[Kasper Cummins]

You could try adding another leaf (and/or) clamping all the springs together.
Both would short term fix, as you get more power you will have to do more.

[stillsmokin]

With a caltrac as the axle tries to move forward the link stop it and tire tries to go under the link. With the tire trying to go under the link it is getting push downward until it is easier to push the body upwards.

If the link is above the axle going rearward it will cause the tire to want to go upwards until it is easier to for the body to go down. With the tire trying to go up it will cause less traction.

Although it may seam better to have the body going down, if its causing less traction your not going to pull as far. It may seam wrong to want the front to lift while pulling because you will be transferring weight to the rear axle but if it is pushing down on the tires causing more traction you will pull farther. Also with the front of the truck low then the rear it will make it harder to transfer weight.

I see your point, however you do realize the reason the axle is wrapping right? Look at the distance from the top leaf to the axle tube, that is a long lever perpendicular the spring. You have to control the wrap below the axle tube with our problem, if you mount a bar over top of the axle the results will be much less effective. You need to address the problem at the point of worst deflection. We tryed the over the top of the axle approach on the rear of a mod gas truck years back, it was a waste of time as the axle always had more mechanical advantage. It only dampened the chatter that way.

You could run a bar back towards the cab under the axle I suppose but, trouble is the rear eye bolt is smaller. Quite a bit of force there, plus you would need to deal with the shackle.