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Author Topic:   bent pull bar
washeduptoo
Dirt Maniac

Total posts: 155
posted February 19, 2005 07:15 PM  
The car is a 4-link lr and z-link swing arm rr, with spring behind on the 4-link. What could be causing it to bend the pull bar? Maybe chasis is binding? Last year, after a few races it would pull bracket loose from drive shaft loop and during play day today it bent the pull bar. Any ideas?

Fastride 38
Dirt Maniac

Total posts: 125
posted February 19, 2005 07:28 PM  
How much movement are you getting out of your rear? Is there something close for the pull bar to hit? Or is the hims not free enough to let it move? Which way is it bending the pull bar? Towards the driver or passenger side?

andykmod
Dirt Freak

Total posts: 351
posted February 19, 2005 08:14 PM  
Are you running a short panhard bar,if so your rear end might be moving to far laterialy and causing it to bend the pull bar, but you would think it would bend the heims first though.I think something is binding myself.

washeduptoo
Dirt Maniac

Total posts: 155
posted February 20, 2005 04:05 AM  
I believe it is bending it toward the front, I'll have to look more closely Tuesday, when I get off. It was a brand new pull bar with biscuits(sp?). We are running a j-bar. I don't know how much the rear end it moving yet.

donslink1
Dirt Freak

Total posts: 318
posted February 20, 2005 07:49 AM  
What do you have on for a dampner shock, Is your pullbar slamming back real hard when you get out of the gas. is there rubber bushings on your pullbar. just a thought

hasben
Dirt Full Roller

Total posts: 26
posted February 20, 2005 08:05 AM  
The torgue absorber is the QuickCar type, we have never used a 90/10. The swedge tube bent downward the first time and we straightened it the best we could and tried again and it bowed upward then. Never experienced this type of problem. Car also sets down real hard on LR. The car is 4link LR and z-link on swing-arm RR.

HEAVY DUTY
Dirt Full Roller

Total posts: 36
posted February 20, 2005 09:30 AM  
quote:
Originally posted by hasben:
The torgue absorber is the QuickCar type, we have never used a 90/10. The swedge tube bent downward the first time and we straightened it the best we could and tried again and it bowed upward then. Never experienced this type of problem. Car also sets down real hard on LR. The car is 4link LR and z-link on swing-arm RR.

THEY BEND AND BREAK IF THEY SLAM TOO HARD UNDER BRAKING.SWEDGED TUBES ON A PULL BAR WILL GET YOU HURT.I KNOW A GUY WHO ALMOST LOST HIS ARM BECAUSE A SWEDGED TUBE BROKE, AND TORE THROUGH HIS ARM.AFTER MANY SURGERIES AND A COUPLE YEARS REHAB, HE IS RACING AGAIN, BUT SWEARS HE WILL USE HEAVY TAPPED TUBES FROM NOW ON.A 90/10 SHOCK WILL SLOW YOUR PINION MOVEMENT DOWN AND QUIT BENDING YOUR BAR.LONG PULLBARS FLEX MORE THAN SHORT ONES UNDER BRAKING.

Dman
Dirt Freak

Total posts: 270
posted February 20, 2005 09:42 AM  
You should run a 90/10 shock for baking dampening.We tried running our mod with a softer braking shock and it started bending the pull bar from the snap it takes when you get on the brakes.Wait till you break a pull bar. It is devastating to the rear suspension not to mention if it spins so bad the brackets smack the fuel cell.The longer pull bars have a bigger tendancy to bend from the backlash.Slow it down with a good dampening shock! Dman

andykmod
Dirt Freak

Total posts: 351
posted February 20, 2005 05:22 PM  
Try the 90-10. Why don't you run one it might help the lr from slamming some.

hasben
Dirt Full Roller

Total posts: 26
posted February 20, 2005 06:16 PM  
Thanks Heavy Duty - are you talking about regular pipe that has been tapped? or a heavy duty (no Pun intended) swedge tube?
the car does not have any mount for a 90/10 i guess i will have to put one on it

hasben
Dirt Full Roller

Total posts: 26
posted February 20, 2005 06:20 PM  
Thanks Heavy Duty - are you talking about regular pipe that has been tapped? or a heavy duty (no Pun intended) swedge tube?
the car does not have any mount for a 90/10 i guess i will have to put one on it

NJantz
Dirt Forum Champ
Total posts: 755
posted February 21, 2005 08:52 AM  
I had this happen to me twice before. Broke it once, bent it the second time. I think it was all caused from cheap Taiwan swedge tubes.

After that I switched to a heavier wall tube and instead of running a real short tube from the rearend to the biscuits, then a 2nd very long tube from the biscuit to the chassis, I changed tube lengths so the swedge tubes were more equal in length.

Cured my problems. It's sure not fun when they break, things get real expensive in a hurry.

p.s. and I was running a 90/10. LR wasn't slamming much either.

[This message has been edited by NJantz (edited February 21, 2005).]

dirtywrench13
Dirt Freak

Total posts: 324
posted February 21, 2005 11:37 AM  
MY DW-8 KEPT BENDING PULL BARS BECAUSE I HAD IT SET TOO CLOSE TO THE LEFT AT THE FRONT AND ON THE HOUSING.

washeduptoo
Dirt Maniac

Total posts: 155
posted February 21, 2005 06:53 PM  
Hasben has purchased a 90-10 shock and brackets and he is going to install it. Thanks and I'll let you know if this cured the problem if we get to play this week.

washeduptoo
Dirt Maniac

Total posts: 155
posted February 26, 2005 07:03 PM  
The 90-10 shock worked wonderfully. The track was so rough, couldn't tell much more about the car or the new driver. All though it did look like it might have a pretty good throttle push. Thank yall very much.

dirtracer14
Dirt Forum Champ
Total posts: 1261
posted February 27, 2005 02:39 PM  
The tube they are talking about is seamless heavy wall so you just have to tap it. You can get it at lefthander cheap then cut and tap to length. I do not have a swedge tube anywere on my car i have broke then lots before and quit using them about 3 years ago. The pullbar breaking is scary mine took the driveshaft out also, glad it was when i was in a spot to stop the car fast.

IowaFuzzy1
Dirt Maniac

Total posts: 136
posted February 27, 2005 10:44 PM  
FYI Swedge tubes should ONLY be used in applications where the load is parallel to the tube! Swedge tubes used in applications where the load is at right angles or sideways to the tube are almost guarenteed to BREAK. All you have to do is examine one,the thickness of the metal in the threaded part of the tube in most cases;especially the"low cost"ones isn't much over 45 thousandths.Suspension components,pullbars,etc.that incur side or tortional loads should be made of threaded DOM tubeing.It might add a pound or two but it's your life and limbs you're putting at risk.

dluna
Dirt Freak

Total posts: 334
posted February 28, 2005 07:27 AM  
And where can we get this threaded DOM tubing? OR are you just buying the DOM and then tapping it?

IowaFuzzy1
Dirt Maniac

Total posts: 136
posted February 28, 2005 08:20 PM  
We buy it and thread it ourselves,you just need a pair of right and a left handed taps.
We bought a car a couple of years ago,swing arm,short left long right,J-bar with a solid pull bar.We had problems similar to washedup except that instead of bending,they would break.Pull-bar once,left side twice.The tube would break right at the inside end of the threads.We started making our own and never had another problem.
I did some research at the time and learned that it was fairly easy to break a swedge tube if you applied a torsional or a side load."You can do a lot more than just make things if you have access to a lathe and a press.
At the time we thought it was caused by too much rear brake or too soft on the rear shock,letting the car drop too hard causing a whiplash effect on the pull-bar.However,after we went to our own tubes the car worked well so we didn't look any further for the cause.Kinda the old"If it ain't broke don't fix it" thing.

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