Death wobble!!!!!

DieselBoy · Post by **DieselBoy** » Mon Oct 31, 2011 9:25 pm

I agree with rok, look really closely at the pan hard rod bushes. Any play at all leads to wheel shimy.

Stick another set in for a laugh???

Just because they are new, doesn't mean the shop gave you the correct bush, they are fitted the right way round, have the correct washers and spacers fitted, the crush tube is the right length etc etc

Any play at all leads to wheel shimmy.

muddyhilux · Post by **muddyhilux** » Mon Oct 31, 2011 9:36 pm

definatly sort the rear panhard mate,after i lifted my truck i just had an adjustable in there and it was centred etc but under bracking shed do all sorts of weird things,cert guy got me to change brake pads and calipers and all sorts but in the end it was getting that panhard as flat as possible,ll other things i tried did nothing but the drop bracket took away all issues,again though this was all to do with lifting the back

wish i could be of more help,good luck with it,its a mint rig

SamLogan · Post by **SamLogan** » Mon Oct 31, 2011 9:54 pm

thanks guys. i will have a good look at it tomorrow and give everything a really good tighten. i will also have a look at the front wheel alignment side to side and make sure the panhard is sitting right. It should be but i will doubt check as this problem is very confusing. i will also strip all the hubs down and have a look at what i can find.

Mud_slinger we had a look around on the forums and between 2-3 seems to be the amount to aim for. i believe it was bulletproof who said he had his at 3.4 and he got a bit of wheel shimmy.

Rokhound I have heard that the 4 link fixes this but Tom has done a very good job bracing the top. Even with it braced do you think the twisting would still be a big problem?

Sam

tomsoffroad · Post by **tomsoffroad** » Tue Nov 01, 2011 5:33 am

Hey Rok, how can the panhard cause this? I haven't measured it but would say it wouldn't be more than 10deg and is inline with the draglink. Isn't bumpsteer more of an issue with too much panhard angle? As Sam said it has new bushes in the panhard which are correctly installed and tight.

I also cant imagine that the diff is twisting under braking. Its is sometimes doing it under very light braking :shock:

.

Cheers Fellas

QUADRACER · Post by **QUADRACER** » Tue Nov 01, 2011 6:13 am

Tom
i have a 130 surf at home, with a beam axle in
live in Amberley if you want to check anything.

cheers Bob

rokhound · Post by **rokhound** » Tue Nov 01, 2011 7:00 am

tomsoffroad wrote:Hey Rok, how can the panhard cause this? I haven't measured it but would say it wouldn't be more than 10deg and is inline with the draglink. Isn't bumpsteer more of an issue with too much panhard angle? As Sam said it has new bushes in the panhard which are correctly installed and tight.

I also cant imagine that the diff is twisting under braking. Its is sometimes doing it under very light braking .

Cheers Fellas

Yep, bump steer is attributable to panhard and tierod angles, but it is the mounting of the panhard that I am talking about. Any flex at all in either the mounts or the bushes will cause issues. I know that the factory axle end is what it is, but I am not a fan of the single shear mount that they have. If there is reasonable leverage at the chasiss end (ie length of the mounting bracket) this could also induce frame twist, which would also cause problems.

oldyella · Post by **oldyella** » Tue Nov 01, 2011 11:53 am

I think you could eliminate the question of it being the castor by increasing it to atleast 5deg.

I talked to the certifier about castor in my landrover. I was putting in castor correction bushes but was worried bout getting to much castor angle. He reacons if you have power steering, it will drive fine with 5degs. It would just be a bit heavy with no power steering.

The more castor you have, the more the wheels self center, essentially increasing stability.

2 degs doesn't seem much for a diff to rotate underbreaking I reacon. Both the vehicle diving and torque during breaking acting on the diff will reduce the castor.

Once your at 0deg it would be easy for any slack bushes etc to set off a wobble.

turoa · Post by **turoa** » Tue Nov 01, 2011 12:02 pm

Id be inclined to play around with wheel alignment if the panhard is fine

tomsoffroad · Post by **tomsoffroad** » Tue Nov 01, 2011 12:20 pm

If there is reasonable leverage at the chasiss end (ie length of the mounting bracket) this could also induce frame twist, which would also cause problems

Bracket at the chassis dropped about 100mm from bottom of chassis and is braced back to passenger side of the chassis. I've learnt my lessons on panhard rods :oops:

You remember the whistler mission in my old LN60 Rok? :lol:

The more castor you have, the more the wheels self center, essentially increasing stability.

This was my understanding of it too. But after searcing for info I might have to rethink my "understanding" maybe.

turoa
Post subject: Re: Death wobble!!!!!

Id be inclined to play around with wheel alignment if the panhard is fine

Yip this needs doing too Tu's ( :lol:

Fawk Im funny!!!) Anyways..... Sams picking up new ends for the tie rod and drag link then its getting a wheel alignment. :wink:

Still cant quite understand how Rob-mu's Play-doo has the same set up with 3deg caster and has no issues with wobble at all. However his tie rod/drag link ends are in much better condition.

oldyella · Post by **oldyella** » Tue Nov 01, 2011 12:50 pm

You could put some fat chicks in the back and see if it still does it :wink:

hosehustler · Post by **hosehustler** » Tue Nov 01, 2011 2:36 pm

here's just a wee bit of food for thought, those links you've made have quite a bit of length...awesome for suspension flex...I think it's possiable that due to their length when braking they could flex (banana slightly) causing problems, as stated even a little change in castor at just the right time will amplify any issue.
Not saying that is the fault, just one more idea to consider

tomsoffroad · Post by **tomsoffroad** » Tue Nov 01, 2011 7:22 pm

hosehustler
Post subject: Re: Death wobble!!!!!

here's just a wee bit of food for thought, those links you've made have quite a bit of length...awesome for suspension flex...I think it's possiable that due to their length when braking they could flex (banana slightly) causing problems, as stated even a little change in castor at just the right time will amplify any issue.
Not saying that is the fault, just one more idea to consider

So much food for thought in this thread :shock:

The links arn't all that long. Top is 570ish and bottoms are 680ish. They are 25mm id heavy pipe. Dont think they would banana in too much of a hurry :wink:

De-Ranged · Post by **De-Ranged** » Tue Nov 01, 2011 8:52 pm

Could you discribe exactly what is happening.... is this a shudder or dive from side to side... the more you can give us to go on the better our guess

Have you done an IFS hub swop ?? this increases the scrub steer, this will exagerate any other issues
Dialing the caster back (reducing it) is not a good idea.... I'd wind it up back to 3 deg, more caster will resist wheel movement but it will up the effort to steer
Pan hard is the normal cause, but I'm guessing you have eleminated this, Tyres would be the next thing I'd look at, don't just swop wheels end for end try tyres from something that drives nice (this is my guess given you have done the panhard)
Tie rod and drag link balljoints but this would effect it under acceleration and when you throw it round you would notice a delay or a bounce to the steering
Toe in / toe out, if there is too much, particually with toe out it will cause dive to one side under breaking or bump, this dosn't normally cause wooble, but with some other things it can add to them
after that I'd start looking at the caster & kingpin inclination angle on the housing (do both sides match...) not an issue normally but with an IFS hub swop I have a bar that is machined to be a nice fit into the kingpin bearing cones
I can't see a housing flexing, the only issue I could see like this is if there isn't enough sepperation height from the lower links to the top link on the housing.... not enough seperation will exagerate any movement caused by bushes flexing :wink:

a three link needs a little more seperation than a 4 link due to the increased loading on the top link

tomsoffroad · Post by **tomsoffroad** » Tue Nov 01, 2011 9:39 pm

Could you discribe exactly what is happening.... is this a shudder or dive from side to side... the more you can give us to go on the better our guess

Righto. Personally I haven't experienced what is happening. :roll:

Sam will fill you in there. but this is what was done.
Yes ifs swap is done with new rotors.
Castor is set at 2deg. Was 3deg. This alteration has improved things
Pan hard has new nolethane bushes
Tyres are 33/12.5/15's and are visually in good condition. Dont think Sams tryed others yet
Tierod and draglink ball joints are worn and are getting replaced tomorrow
Needs a wheel alignment but does not duck and dive under braking, has very little bumpsteer but has no dampner at the moment either.
The castor angle should be the same on both sides, provided it was when it left the factory :shock:

The housing shouldn't flex at all. Its braced excessively and the seperation is 240mm if I remember correctly

SamLogan · Post by **SamLogan** » Tue Nov 01, 2011 9:46 pm

I have no idea why this said it had posted but it didn't

It is a definite wobble of the steering so a shudder. It doesn't dive side to side as it is short fast movements. probably only 45 degrees of the steering wheel each way.

Yeah it was noticed after we did the wide hub swap. But in saying that the only other times i drove it before hand i didn't really brake that much. i usually engine brake.

I don't really mind how hard it is to steer at the moment. It is pretty good. Unless there is some other potential issues that could arise i don't really mind if it stays.

I was going to borrow a mates at tyres tonight but i ran out of time as i was called into work today so i will try that this weekend. Yeah the panhard has new bushes and the bolts are uft.

Yeah we came to the conclusion today that the tierods are in average to crap condition so we will give that a try first as they are probably close to failing a warrant so i need to change them anyways. As for the wheel alignment i will take it in to a place and see what they say about it. It could be that as it does drift but in saying that i noticed today driving home the amount it drifts changes all the time. sometimes at 50km/h it will drift .5m to the left over 300 odd metres and then sometime it will drift 1m over 100m. I am guessing that could be stuffed balljoints then.

As for the housing i will have to let Tom comment on that as he was the one who did welding so he should have an idea of the upper link height off the centre. I have spent too much time under there today looking and double checking stuff to be bother looking again today haha.

The kingpin angle is interesting. What does your machined device look like?

Cheers
Sam

DieselBoy · Post by **DieselBoy** » Wed Nov 02, 2011 6:54 am

Sounds like everything's mint engineering wise and the pull to the left sounds normal.

So chances are it's not wheel shimmy.

They call it the DEATH WOBBLE because it's just that!!!!!

It's so violent that you can,t hang onto the wheel, it gets worse as you go quite quickly, to the point it feels like it's going to rip the truck apart. The only way to stop it is to come to stop, and then accelerate again.

It's not a twitching of the wheel, its a violent left to right movement that you almost can't keep hold of and you pretty much have to brake hard and stop to fix it.

De-Ranged · Post by **De-Ranged** » Wed Nov 02, 2011 8:28 am

DB is spot on, sounds to me like you may have a tyre or rim thats not true and with the rod ends and hub swop are adding to this
It is rather hard to diagnose things like this without driving it :lol:

even then it can be hard... I've got a loop over Hastings that has corners with bumps, dips etc that I have driven enough that I could probably do it in my sleep :lol:

Tom as for the housing :lol:

factory they can have issues there tolerance I think is +/- 3/4 deg caster that can mean a brand new housing can have 1.5deg differance and I think kingpin inclination is even greater
When you weld up a shave it will pull about 2deg of camber and toe out a brace depending on how you weld it can add a shit load more
Oh and lets not forget any bends from the yrs of use
Before I start on a housing it is checked for true to date I've only had a couple that were straight enough that I was happy
My king pin / caster bar is just a bit of QM bar that I lathed down to just slide through the kingpin bearing cones in the housing I then use a digital angle meter off the front for caster and the side for king pin inclination

Good luck guys

SamLogan · Post by **SamLogan** » Wed Nov 02, 2011 11:05 am

i can assure you its a DEATH WOBBLE haha. It is very very violent. I will try a mates wheels tonight and see what happens. It seems strange as it was perfectly fine when it was ifs. I will let you know how it goes.

Sam

rokhound · Post by **rokhound** » Wed Nov 02, 2011 11:21 am

Death wobble is what I had. You would know it and at 60 -70 kph it would tip your truck over, mine used to start at 40 kph when you were driving it and would throw the whole truck from one side of the road to the other. My worst shake experience with it was enough to snap the tie rod.
Go thorugh all the above mentioned bits and see how you go, sounds like it will be a process of elimination.

bda4130 · Post by **bda4130** » Wed Nov 02, 2011 11:26 am

Speaking of tires, when I did my sas my old tires were worn on a hard out angle from the camber of the ifs, when they were on the pretty much zero camber beam axle it drove real wiggly till I put them on the back.

mud_slinger · Post by **mud_slinger** » Wed Nov 02, 2011 5:03 pm

chuck it on a wheel alignment machine it will give you all the angles of where camber castor toe sia kpi scrub and wheel runout is sitting. then you can work out what is not right

Post by **SV1K** » Wed Nov 09, 2011 5:18 am

So what was the verdict on this :?:

tomsoffroad · Post by **tomsoffroad** » Wed Nov 09, 2011 5:32 am

suzuki1k
Post subject: Re: Death wobble!!!!!

So what was the verdict on this

Posted: Wed Nov 09, 2011 3:18 am

Dunno yet

Sam has bought new rod ends and a heavier draglink (something to do with turning Prado one into a banana :mrgreen:

)

pruggerdore · Post by **pruggerdore** » Sat Nov 19, 2011 5:09 pm

update????????????????????????

tomsoffroad · Post by **tomsoffroad** » Sat Nov 19, 2011 7:16 pm

None sorry. Sam has ordered a heavy drag link with 80 series ball joints and I am in the process of making a heavy tierod using rod ends instead of ball joints. These items will eliminate any play in the steering, so we will see :wink:

land bruiser · Post by **land bruiser** » Sun Dec 04, 2011 6:31 pm

Im allso having problems with my landcruiser getting out of controll.
I have a 60 series with 15x10 and 33x13.5 mudzillas i have had wheels balanced + wheel alinghment. Ive noticed it seems that a bump in the road will set it off. I have to come to a complete stop and then its ok. I have recently put a new swivel hub kit in both sides. But it done this befor i cant work it out and its dodgey as

land bruiser · Post by **land bruiser** » Thu Dec 22, 2011 5:22 pm

problem solved it was the steering dampner on my truck that and the bigger tyres didnt help. new dampner and problem is 100% gone