Steering issue, very scary above 35mph

[pghfj40]

Since the guy asking seemed to genuinely want to know, I'll also share the way I understand it (as I think it diverges from Hawk's view)...

The steering damper serves to damp any relative movement between the parts it's connected to... regardless of the source of the input (not just the kind of impacts (lateral) that would serve to turn your steering wheel).

Because the steering is a system in the real world, it will display less than ideal characteristics (balance/alignment/freeplay/stiffness/etc.) leading to behavior described by harmonic motion. The damper can serve to help bring the system's response to an input back to zero (not moving) rather than growing towards "infinity" (death wobble).

Now a well-designed system with new components should be stiff enough, tight enough, and balanced enough that it will settle itself quickly enough that we find acceptable or not even notice (note that it will still have _some_ settling time). BTW, keep in mind that a new system is only new at first... so I wouldn't discount the damper's function (after no longer new) even in a well-designed system.

For example, I'll cop to having had two jeeps that I could distinctly feel this settling time, and it was not acceptable (it's ok to bring them up as the "bad" example, right?) The lifted XJ had DW (that was fixed w/ caster shims); OTOH my wife's brand new stock Rubicon has always shimmied a little for a sec or so after bumps (probably underdesigned).

So... having said all this, I'm NOT suggesting he should "throw one on there" to fix an existing serious problem that has real causes in other components or setups; just that they are not only for saving thumbs.

 

[Adventure Teq]

OK but,

A steering stabilizer will have no effect on controlling death wobble. It's all in the alignment angles. And the tightness of any of the components when they are new does not help stabilize death wobble. It simply does not exist in a new vehicle when the angles are properly set at the factory.

For example, have you ever seen a caster, on a shopping cart perhaps, that just wobbles like no tomorrow. Well that's death wobble on a small scale, and the cause of it is that it has lost it's correct caster angle maybe due to the structure it's mounted to is bent or something. It wouldn't help to add a bunch of stabilizing measures to it, you'd just have to reset it to the correct angle.


At least that's how I see it.

Theory, aint it great.

 

[pbgbottle]

steering stabilizer stopped my death wobble , but my death wobble only started when i put on my 38's .the tires where just way out of balance . but the stabilizer worked . could only go about 30 kph (20mph) after stabilizer i could take it up to 100 kph (60 mph +)

 

[pghfj40]

Hawk, I still gotta disagree about the "no effect." I know I've seen descriptions that articulate it better... but I'll give it another shot .

Everything flexes and acts like a spring to some degree at some frequency; the damper acts to create a low-pass filter.

If the filter's cutoff is enough above the system mode (that causes shimmy or DW), it will keep everything smooth.

The tighter, stiffer, and better aligned, the higher the system frequency and easier to filter (or even let it damp itself out through the non-ideal elasticity of components).

BTW--going back to my example of the lifted xj: before I knew about caster I changed the damper to another brand & my DW got much worse & at lower speeds... changed it back & the original (less bad) behavior returned. A different damper may have taken the problem out of the range I care about. OTOH: you're still right insofar as the fundamental fix was castor (if no worn components).

...at least that's how I understand things at this point. HTH someone. -Ed '70FJ40

 

[Adventure Teq]

Cool,

Point taken about dampening the overall vibrations. I can see that.

I give...

 

[pbgbottle]

isn't that the same reason we run shock absorbers .to dampen the vibrations . with stock tires you may not need a stabilizer in a perfect world , but with everybody these days running bigger than stock tires that the front end wasn't designed for can put alot of stress on components ,and just like your suspension with out a shock it would keep bouncing down the road . with the larger tire hitting ruts in the road , holes in the road ,and being out of balance .once you hit something with the tire it just keeps shaking . depending on the tire how violently . there for the reason for the stabilizer to control the tire wheel combo from shaking the truck apart . at least thats how i look at it . eventually the tire may stop shaking .but why not put a stabilizer on to get control of that big out of balance tire . my .02

 

[dustin]

couple notes-
Blue Torch Fab- my favorite wallet trash can- has steel shims. I would check there since SOR may be selling aluminum ones. Steel is mucho better.

But if you removed leaves, etc, your castor may not be too bad.

I run SOA with 37's and new TRE's without a dampenor. Runs straight and smooth with no wobble. My castor is good. So- my opinion is that a dampener just hides a prob. Fix the prob instead of plugging the holes with bubble gum. Once you fix the issue- dampener isnt necessary.

Check your trunion bearings again with weight off the front axle. I had an old Willy's 2A that had shot trunion bearings. Got serious death wobble. Replaced them and everything was cool. You need to check the wheels with weight off them since once they are loaded down, you cant shake the tire to check them. Make sure the bolts on the steering arms and underneath the steering knuckle are tight.

Theres alot of rigs runnning around with improper castor and no wobble. So, even though you need to add shims to make your steering less sketchy, I would still check the trunion bearings.

it sounds like you have the stock steering. Tighten up the drag link. There is alot of linkage in a stock 40/60. The drag link has two adjustment screws- one on each end (I think). make sure they are tight.

cheers-
Dustin

 

[roddie1154]

looks like my cruisers caster is out, i think its got that negative castor.. so lets say i fixed the castor and didnt correct the alignment, will my tire alignment toe in or toe out?

coz i made a new rod for the tie rods which were a bit too long. and i noticed the castors out..
so before i cut the rod, i want to make sure that when fixing the castor the tires wont toe out more..

 

[Adventure Teq]

CastEr (not castor like the cooking oil ) will not effect toe.

 

[Trollhole]

CastEr (not castor like the cooking oil ) will not effect toe.

I don't know about that. I would think it would.

Anyway if your doing anything on your steering it's worth the 40 bucks to get it done right.

 

[pghfj40]

I don't know about that. I would think it would.

Yes (marginally).

 

[Adventure Teq]

Yes (marginally).

Second thought, yeah it would a little.

 

[roddie1154]

so would it toe in more? coz the rod is too long and when fully adjusted the tires still toe out! if it'll toe in then i dont have to cut and shorten the rod...

right now ive just shorten the rod slightly and fully adjusted the tie rods, now it has a slight toe in(not noticeable) hope it toes in a bit more when i fix up the castEr tommorrow... then the alignment would fully be adjustable.. am i talking sense?!?

 

[pghfj40]

The short answer is I don't know, but I'll tell you how you could look at it.

Since camber is built-in (machined/welded) to the axle, it affects all three angles a little when the axle is rotated (and I don't recall the stock angles).

Here's an easy way of seeing how the angles interact, if you care...

Put your hands out in front of you. Fingers straight, thumbs up, palms facing but separated... you can even put a pencil between the two to simulate an axle if you like.

Now point your finger tips toward each other a little (toe-in)... and then a lot (to exagerate for illustration sake).

Now rotate your thumbs toward your chest (what you'll do during your caster fix). If you keep your fingers at the same original angle, and keep rotating till they're pointing at the ceiling (exaggerate for illustration sake) you'll notice that you now have zero toe-in.

Note though that we've neglected camber (if your had thumbs pointed in toward each other a little at the top, in the first step). This would have the effect of toe-out during the caster fix (leave toe out of the picture to illustrate this most easily).

If there's more camber than toe, it will toe out; or vice versa: so it depends whether the initial camber angle or the toe angle is greater. My guess is it will toe-out a little because I imagine camber overides toe (but I don't have a lot of confidence in that guess so don't hold me to it).

Sorry I don't have a real, practical answer for you; hope this gave some insight, though. Post up what actually happens for the next guy in your situation. -Ed '70FJ40

 

[Trollhole]

Toe out but even with 4 degrees of shims for bigger tires you won't have but a thread more on the rod. If you don't have that built into your adjustments then you will have bigger probems when you bend it out of whack on the trail.

 

[roddie1154]

debate between the steering stabilizer and caster shims

this is my story,
i placed an order for a rancho ss and a center arm..
so while waiting for them to arrive i decided to give the caster shims a shot..

went all around brunei's alignment shops asking if they could do caster angles for the cruizer. apparently no one has never done caster alignments for leaf sping vehicles!?!

so i went on sor n saw it was about $20.. calculated everything to ship all the way to southeast asia and it all added up to about $50! (freight, tax etc)... then i decided i should just go to a machine shop n make my own.

got the dimensions on man a fre, got how much angle was needed from sor (2 - 2.5'' longer than stock - 4 degrees) picked em up the next day and put em on..

with a busted stock steering stabilizer and a rocking center arm the wobbles disappeared!!! i can finally go into 4th gear without being scared of crashing into ditches or on-coming cars

so i'd say caster correction shims are the first to get..

but i still cant wait to put on the rancho's and new center arm.. just imagine how the ride would be

thanks alot guys....