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  #1  
Old 09-20-2009, 09:59 PM
Blake Blake is offline
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Death wobble with 42" iroks

So I've got my J10 up and running on 42" IROKS BIAS plys and a front D60 (from an '80 chevy SRW). Full high steering and a brand new OME stabilzer. I do not have hydro assist (yet). All TRE's are brand new. Leaf spring bushings are less than 6 months old. Shocks are about 6 months old. Everything is tight and looks good. Toe-in is set at 1/4" in. 1 degree of positive camber. Kingpin bearings are new. 6 month old 2" BJ's offroad leaf springs.

IROKS have 14oz of airsoft BB's in them (Discount Tire said they could not put enough weight on these tires to balance them)

I have death wobble from about 35-45 MPH, but it's not consistent. I've had it up to 75MPH and it drives pretty darn good IMHO.

I've dealt with DW on several TJ's in the past and I've done a lot of reading online on DW.

The IROKS are "out of round" slightly, but from what I've read, they all are....

So I'm looking for advice on what I can do to get rid of the DW.

One thing that I will probably do is install hydro assist, but I would like to clear up the DW beforehand.

Another possible thing I might do is add more bb's to the tires.

Discuss....
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Last edited by Blake : 09-20-2009 at 10:11 PM.
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  #2  
Old 09-20-2009, 10:03 PM
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gotmike gotmike is offline
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break the tire down and rotate it 45 degrees on the rim... then try it... eventually you'll counter the out of round on the tire with any out of round on the rim and should give you better balance...
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  #3  
Old 09-20-2009, 10:07 PM
Blake Blake is offline
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The rims are 2009 H2's taken off a brand new Hummer. I've thought about doing what you suggested, but I think these rims are pretty darn straight and perfect....
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  #4  
Old 09-20-2009, 10:19 PM
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Stuka Stuka is offline
 
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1/4" toe-in is not nearly enough for 42" tires if you are measuring from the outside of the tire. Thats proper for 31" tire or so. But as the tire gets larger, that measurement needs to increase to attain the same angle.

I suggest having it properly alligned to verify the toe-in is proper.

Also, what condition are the D60's king pins in? When they start to go bad, they can create death wobble.

Are you using high steer, or cross over steering?
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  #5  
Old 09-20-2009, 10:25 PM
Blake Blake is offline
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the guy at the offroad shop told me to run the toe-in at dead even (no toe-in), but that had worst wobble....

full high steer.

king pin stuff is all brand new.
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  #6  
Old 09-21-2009, 11:45 AM
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I have my 37" BFG's on H2 rims and they're perfectly smooth unbalanced.

My used 38" Swamper SX's are another story. I have 20oz of pellets in each one and they're finally driveable. I originally had 14oz but the death wobble ensued. I also warmed them up around town before a good run at speed. What a world of difference.


JR
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  #7  
Old 09-21-2009, 12:14 PM
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on my xj, i hafta run 7 degrees positive caster and an adjustable tracbar, and i'm towed in 1/8th in.
maybe try to get something similar to a stock grand waggy tracbar?
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  #8  
Old 09-21-2009, 12:19 PM
Blake Blake is offline
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Quote:
Originally Posted by Headhoncho
I have my 37" BFG's on H2 rims and they're perfectly smooth unbalanced.

My used 38" Swamper SX's are another story. I have 20oz of pellets in each one and they're finally driveable. I originally had 14oz but the death wobble ensued. I also warmed them up around town before a good run at speed. What a world of difference.


JR

yeah, so maybe I should add another 6oz of BB's in there and see if that helps.

I'm also going to give it more toe-in.
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  #9  
Old 09-21-2009, 12:49 PM
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Read this thread on Pirate4x4.com

http://www.pirate4x4.com/forum/showthread.php?t=806103

I had the same problem with my Dana 60F, I had a lot of things loose I taught they where tight but after checking everything that is associated with the Dana 60 and tighten everything down the death wobble has stopped. I have very little time on the road but all seems ok now.

Quote:

homemade springless caps are on. with much help from PBB'er D60 they came out sweet and with the addition of new bushings have seemingly eliminated the DW


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  #10  
Old 09-21-2009, 05:57 PM
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What kind of tire pressure are you running? I had bad death wobble with my 40in MTRs when they were at like 30psi. I ran them closer to 25psi with much better results.

Lets see a picture of your rig too! Any J10 on 42s is something i'm interested in.
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  #11  
Old 09-21-2009, 08:40 PM
Blake Blake is offline
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couple of pics taken today








I haven't had time to mess with it today, but I'm planning to searched that modified king pin cap that was posted.
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  #12  
Old 09-21-2009, 08:41 PM
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mcjeep80 mcjeep80 is offline
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Quote:
Originally Posted by onesunJ10
Lets see a picture of your rig too! Any J10 on 42s is something i'm interested in.
i have read an article about this a while ago. they said most new wheels have a mark on the inside of the wheel. this spot will be the low or light spot of the wheel. your tire should also have a mark on it . a paint mark like a triangle or spot close to the bead to indicate the same. you should put these opposite each other for best results. they even took it a step further(too far for me) and had a set shaved to true them
good luck!
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Last edited by mcjeep80 : 09-21-2009 at 08:56 PM.
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  #13  
Old 09-21-2009, 08:45 PM
Blake Blake is offline
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pic of the front end.

I'm gonna need to install a degree shimm or cut and turn the knuckles. I'm hoping that adding a 6 degree shimm may tilt my pinion up enough to run the front shaft and not set the caster too far negative.

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  #14  
Old 09-21-2009, 09:52 PM
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Austin 4x4 Austin 4x4 is offline
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well i hate to break it to ya but your problem is you are running 42" biasply tires. the biasply construction is simply not designed for those large of tires to be driven on the street. once the tires start to spin they begin flexing and deforming untill you get going fast enough, at which point centrifical force takes over and then the death wobble goes away.
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  #15  
Old 09-21-2009, 10:53 PM
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A 6 degree shim up front is going to make it drive worse than it already does. That will remove all your caster, which is important to having a vehicle that will drive straight. Your going to have to turnt he knuckles, that u-joint angle doesn't look too great.

I really think you should add a bit more toe-in.

Also, how long have you driven? The regular flat spots from sitting a day (or even less) will cause some bad vibes until the tires warm up.

The extra BB's should help.
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1981 J10 AMC 258 with TFI and Weber 32/36 DGEV Carb with a BJ's Aluminum Radiator, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 TSL's, BJ's Offroad Rear Bumper.

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  #16  
Old 09-22-2009, 04:21 AM
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Quote:
the biasply construction is simply not designed for those large of tires to be driven on the street.

My 39.5x15.5x15 TSL vibrate noticeable the first mile and then settle down, this is probably worse in colder climate it takes longer for the tires to warm up and retake their round form. I think Frank from Norway wrote that the TSL are square.tanding long with low pressure will make them feel like square.
I have 38psi on the tires on the road and this is recommended for road use.
A steering damper helps to absorb energy from any vibration and lessen the chanse to have death wobble.
Due to the size of the tires its very important that all is tight, starting from wheel bearings to steering box and springs anything loose or worn will aid to start the death wobble.
My caster is 6 degrees (follows nicely in flat tow) the toe in is there estimate more than 1/2 inch.
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Dana 60 w. ARB locker, hydraulic assist + GM 14FF w. Detroit locker.4-link rear on LC80 19mm coils
Rancho 5036 Shocks 14 inch travel. 39.5x15.5x15 TSL
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  #17  
Old 09-22-2009, 07:07 AM
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I had death wobble still after rebuilding my king pins. I added some fender washers on top of the kin pin spring to preload the springs and death wobble is gone. Many guys I know use the fender washers to preload the springs for big tires sizes over 38's.
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  #18  
Old 09-22-2009, 07:42 AM
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Mine will try to wobble with low pressure, hydro assist, new king pins with adjustable arms, etc. I think when you run bias tires that big, it just happens. Hydro assist will be a must for you anyways, I would start there.







Only way to truly fix it......put it on your trailer and hop in your comfy tow rig. No mo problem.
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Old 09-22-2009, 08:47 PM
Blake Blake is offline
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So talking about hydro steer. I'm thinking about getting this one
http://rockstomper.netfirms.com/shop...roducts_id=128

Assuming I do that, my DW will most likely go away right? I'm running a front detroit, so I'm gonna need that anyway right?

So that leads me to my real question:

If I point my front pinion towards the t-case (like my D44 was after the cut n turn), will the hydro steer allow me to drive at hwy speeds?
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Old 09-22-2009, 09:55 PM
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Quote:
Originally Posted by shepherdblake
So talking about hydro steer. I'm thinking about getting this one
http://rockstomper.netfirms.com/shop...roducts_id=128

Assuming I do that, my DW will most likely go away right? I'm running a front detroit, so I'm gonna need that anyway right?

So that leads me to my real question:

If I point my front pinion towards the t-case (like my D44 was after the cut n turn), will the hydro steer allow me to drive at hwy speeds?

Are you going to cut and turn? I look at it like this....if it wheels good, it ain't gonna work past 55 MPh. If it really wheels, it ain't gonna work past 25 MPh.
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