Hey everyone I could sure use some suggestions here. We fitted all of Keith’s steering components to the big Disko and are running RTE corrected arms/link along with the 5" lift and all the rest of the goods. After getting everything fitted we eye balled the alignment in the driveway with a tape measure. We then fitted the 36x13.50 IROKS to the Allied locks with no balancing and surprisingly when we got it on the road the truck drove pretty darn good. After a few weeks you could see uneven wear on the front tires so I took it in to the local Tires Plus. Supposedly the kid who did the alignment does all the big redneck trucks and is familiar with working with oversized heaps of junk so I thought I would be in the clear.

Well, driving home from the shop I was getting some serious feedback in the steering wheel around 45 - 50mph. When I say serious I mean like in the old movies when they showed someone driving a semi-truck and the wheel was going back forth 4 - 6"...thats how much. If I speed up or slow down it goes away and there is also a vibration through the entire driving range that was NOT there before the alignment.

First thing I did was call the tire place and get all the specs. I don't know a whole lot about alignment settings other than you want the tires pointed a bit out because the natural forward motion pulls them into correct spec. [Is that correct?] so if anyone can educate me I would appreciate it. The specs are below:

Before:

Left Toe = -1.3
Right Toe = -1.48
Left Camber = .3
Left Castor = -1.4
Right Camber = -1.0
Right Castor = -1.5

After:

Left Tie = .07
Right Toe = .07
Left Camber = .3
Left Castor = -1.4
Right Camber = -.9
Left Castor = -1.5

What I am trying to understand is how before with an eye balled alignment that we KNEW was way off the truck could ride better than if it was put into supposed correct spec. Maybe I should just give up as it is a Rover...

Now, I may be way off and what they tuned the truck too may be incorrect, if so someone please chime in with some suggested settings and I can give that a shot.

I am also looking for the person who's going to say "Put it back to the before settings." And to be honest I am not opposed to that but the tire wear on BP IROKS will eat them up in no time.

Can anyone with tech on this subject please chime in?

Nadim, how about you? Your running IROKS do you experience anything like this? I am wondering if it could be the tires…I have never driven on anything this wide. As for PSI I have tried as low as 20 up to 30 and mix matched the front and rear but still the same. I was toying with the idea of throwing some CounterACT in the tires but don’t really want to break them down unless I can eliminate some more problems. Could we possibly need to look at some sort of steering assist? We've installed one of those "new" steering boxes that is remachines and uses bearings instead of seals [I think] but the pump is has around 70k on it.

PS - PT, anything thing this time? :flipoff2:

Regards,

Appearantly the search button is broken......?

The only thing you can adjust is toe. Camber is set by the swivel ball. Caster is variable depending on where in the suspension cycle you are. As for your death wobble, it is most likely a combination of swivel pin preload and you lift which changed the operational range of the castor.

-Jeff

First of all, mounting 36s without any type of balancing is just stupid. Regardless of the alignment that thing must shake like a dog shittin’ razorblades. At the very least you should be running equal in them.

The problem with it is your castor. Normal specs for a Disco I are 3 deg positive caster +/- .5. In basic terms caster is the relationship between the upper and lower ball joints in regards to the direction of travel. Zero castor occurs when the upper and lower ball joints are perpendicular to the ground when looking at the truck from the side. The further ahead the lower ball joint is from the upper, the more positive caster. Negative caster (what you’re showing) is when the lower ball joint is behind the upper.

A vehicle with a high castor reading will have the lowest rolling resistance when going straight so it will tend to correct itself from a corner quickly and track easier going down the road. (It is also harder to turn when standing still but that’s another story.) For an example, look at a big-bodied Mercedes when it’s sitting still and the wheels are turned. Some of them run as much at 12 deg positive castor but they track down the road very well at very high speeds.

A vehicle with a low caster reading will tend to wander but will be easier to steer. Not too many modern cars run negative castor anymore because everything has power steering but if you’ve ever driven a 60’s Dodge Dart you’d understand how a negative-castor car drives. There’s very little response or “feel” to the steering.

What happened in your case is the toe-out problem (almost 3 inches total!) masked the big problem, which is your castor. With toe that far negative the front wheels will fight each other enough so you won’t feel your wandering problem. Yes, the right camber is a little fawked too but that’s not going to give you too much of a problem.

You mentioned something about “RTE corrected arms” but it’s obvious they’re not nearly enough for the amount of lift you’re running. You need to re-drill the pattern on your swivel balls and pivot the lower ball joints forward. You’ve got 5 degrees too make up…A HUGE number in alignment specs. Corrected arms just aren’t going to do it.

There’s been talk about that here in the past…Do a search. :flipoff2:

Ohh my fawking gawd. Did you really take your truck to have an alignment or is this a joke. First, as stated above, you cant align anything on a rover in stock form. All you can do is set toe. Second, balance 36's? Fawk we dont even balance our 40's and up, and they drive smooth as a babys butt. Iroks run really nice from the factory with no balance. You should shoot for zero toe, but, large toe out will get rid of death wobble which is what you are getting. You likely can tighten your swivel pins as much as you want, but you will still get Wobble. This is because of the flex of the side wall on larger tires versus the tiny 33's alot of guys talk about curing death wobble on. Bottom line, you need to either live with it, get a regular tire, wear out your tires with toe out, or fix your massive castor problem.

Can anyone with tech on this subject please chime in?



PS - PT, anything thing this time? :flipoff2:

Regards,

Yes. Use the tape measure and fawk the rest. You need 16 seconds of toe out. This works out to about 1/16" on a moderate sized tire. Take your truck back to the kid that did the work and tell him to set the toe to 16 seconds toe out or your gonna stuff the old tie rods up his ass. I dearly love arguing with these guys who consistently tell my clients they need major readjustments and they can do it for X dollars.


If you have new tie rod ends, etc. I'd start looking at things like bushings and shocks to explain weird tire wear. (I didn't even think about the tire sidewall height-KC's right)

Keep it up Jason and you might be accepted, just like Adam was :flipoff2:

Thanks for the information. I have done a bit more digging and here I am confused. Should I be looking into adjusting the pre-load on the swivel pin or toe'ing the wheels back out or, both?

I don't even want to get into an argument over balancing or not balancing, I might inject some CounterACT and be done with it.

Back to my question. I came across an excerpt Slade put on D-90:

---------
I knew that swivel pin pre-load being too low can also cause DW, and had a friend in Portland with an LWB RRC that changed everything else and then checked the pre-load and had it re-set. It cured his DW, so I thought it was probably my culprit too, since I had changed everything else.

Took off the rims, tie rods and track rods and checked it. Yep, the pre-load was too low. Removed some shims, played around with various shim combinations, and got it set nearly perfectly. Did the same maneuvor (sp?) with the other side and took her for a drive. DW was cured. I didn't feel comfortable having the upper swivel pin without any shim, so the thinnest shim was left in place. I could get a better pre-load by removing it and running no shim, which I guess I could do, but I felt it needed at least one shim in there.

After the shims are all removed and the pre-load is still unable to be set properly you will need to replace the railco bushings (actually a bearing).

If you are unfamiliar with how your swivel balls should feel then you should take it to a shop that does. If you know how it's supposed to feel, then you already know this is a simple job that you can do in your driveway with basic tools.
---------

What you say PT...should I have it toe'd back out 16 seconds and then look into adjusting the pre-load? According to what Mercedes said toeing them back out is only masking the real problem of the castor. Is the only way to correct the castor truly by drilling the swivel balls? I thought that was the point of corrected radius arms. I know the RTE do not correct as truly as QT arms but from what I know they pretty much get the job done. Please fill in the gaps for me if you can. As for Slades problem above, does adjusting the preload on the swivel pin help correct castor as well or am I understanding this incorrectly?

Thanks,

Jason

Jason:
Curing Death Wobbles requires a holistic approach (in spite of all the Dead shows, I'm not one of THOSE hippies :flipoff2:).

First question, how much real-world lift do you have on this truck?

Condition of shocks, bearings, bushings?

Make sure the swivel preload is correct. When you disassemble the swivel pin, you may find significant wear on both top and bottom requiring replacement of either opne, or at the very least, the bearins on top, bottom, or both.

Then, set the toe to something more closely approximating what the designers intended-in spite of them not having intended lifts, nor tall tires.

Swivel pin preload will not affect castor angle at all. Caster angle is solely dependent upon geometry of the entire setup.

When (after) I get my engine built, next step will be QT radius arms and RTE trailing arms!

Peace,
PT (Phineas)

First question, how much real-world lift do you have on this truck?

5" RTE front springs at all four corners with 2" spacers at the rear. We wanted to keep them all retained and the fronts have more flex than the rears according to Steve but they sag in the rear hence the spacers.

Condition of shocks, bearings, bushings?

Everything is brand new.

Make sure the swivel preload is correct. When you disassemble the swivel pin, you may find significant wear on both top and bottom requiring replacement of either opne, or at the very least, the bearins on top, bottom, or both.

I will check this this weekend. Thanks...

When you need those QT's let me know... ;)

I bet the panhard rod bushes shot too...easy to check and fix(cheap to).

The 16 seconds toe out translates to 1-2mm as measured on outside of a 30-31" tire.

I'v had luck running 1-2mm toe in instead. Really not much miles on soft tires so can not say much about wear.

Rotate tires often would help with that.

There is no substitute for Castor. Look at your test report to see if your corrected arms corrected your castor...It should be 3 degrees if memory serves me.

T

I think your problem is that you did not lift it enough. Try throwing another 4" into it. And if you drop back down to a 265/75/16 you will find that the tires do not have enough gyroscopic motion to make them wobble. Oh, and I heard that someone was making a drop kit for the radius arm brackets to correct for castor. Im sure you sell those and have them in stock!!

The 16 seconds toe out translates to 1-2mm as measured on outside of a 30-31" tire.

I'v had luck running 1-2mm toe in instead. Really not much miles on soft tires so can not say much about wear.

Rotate tires often would help with that.

There is no substitute for Castor. Look at your test report to see if your corrected arms corrected your castor...It should be 3 degrees if memory serves me.

T

I'm also running toe-in, about 1mm. But I have a RHD truck with a LHD knuckle on the front right. The extra camber on that knuckle scrubs the inside edges off my tyres. Running toe in evens out the wear. I've got almost 60,000km of road work on my current BF All Terrains and they showed 8mm tread all round on my last WOF.

But the 88 RRC I just bought for parts will let me put the axle back to RHD spec, then I'll be trying toes out again.

Many (including me) have been all through this.

Steps to "cure" (yeah-right) death wobble. Any/all/some combo of:

Proper swivel preload
Tight panhard bushing
OK steering stab
reasonable toe
reasonable tire balance (not hopping off the ground)

try any combo and maybe you'll tame it to where you can at least keep a grip on the steering wheel after crossing RR tracks...

...and I'm only running 33's

Put both axles up on jack stands, and run the truck in place at the speed where the wobble is the most severe. Inspect and you might find a clue.

I searched for two months looking for the "wobbles cure" until I did this. On the stands it became obvious that it was wheel balance. One wheel was trying to jump out of the stand. The Equal I was running in my BFGs just didn't cut it. Got a true, standard, balance job done and the wobble went away for good. 8 months ago.

You should have used the QT 6 degree castor corrected arms. I have them if you need them. :p

New panhard rod bushings cured my problem. I didn't read all posts so sorry if you have already done it. I think that was the source of Slades DW also.

I think your problem is that you did not lift it enough. Try throwing another 4" into it. And if you drop back down to a 265/75/16 you will find that the tires do not have enough gyroscopic motion to make them wobble. Oh, and I heard that someone was making a drop kit for the radius arm brackets to correct for castor. Im sure you sell those and have them in stock!!

Super!

Hey Slade! Could you bring me over some of these drop kits? I think I'll fit 2.

Merv.
:shaking:

Well you guys it appears to be a combination of the wheel balance and uneven tire wear on the fronts when the allignment was all out of wack.

- I broke all the beads and inserted 8oz of CounterAct into each tire and we still had the wabble.
- I toed out the front a tad bit more [Thanks, PT] and we still had some wobble but it was better.
- We then took the fronts and swapped them to the rear and 95% of the wobble went away.

From looking at the tires the miss-alignment in the beginning really put a hurtin on the IROKS as they were all chewed up at different angles. I am going to run these until they're dead and I am willing to bet that when I install a new set the problem will be gone.

I still plan on checking SPP this weekend. Thanks everyone!

, Jason

Yeah - that was the trigger for the death wobble but not the cause.

As soon as you get another small out of balance condition or hit a hole or tracks at that just-so-right speed, it'll be right back again - out of nowhere. And, you'll be back here asking the exact same question again. Believe me - I've been there (still am there).

Did you: ??

Set your swivel preload
Examine or replace your panhard bushings
Check your steering damper

The problem is still there - it takes some input to start it up...

Disco, I agree with you 100% and I plan on checking the SPP this weekend. Just curious, what did you end up with in the way of shims on your rig to get it all straight?

Phard is good and so is damper, all BRAND NEW and intact.

Thanks,

[QUOTE=RedRhinoProducts]
Just curious, what did you end up with in the way of shims on your rig to get it all straight?

[QUOTE]

Gonna depend upon condition of bushing, pin, thrust washer, lower bearing, etc.

A bad alignment can tear up tires quickly. Toe causes a diagonal hashing to the tread. When the alignment is put back into spec, the tires cause all sorts of shaking. The tires are trying to track to the old wear pattern, but the steering geometry is trying to prevent that. Basically you have two opposing forces fighting back and forth.
If all of the suspension bushings are in good order, and the rest of the system is set up correctly, tires alone can indeed cause all of this.
Really the quickest and easiest thing to do is just swap tires front to rear and test drive. If the shaking leaves the steering wheel and either goes away entirely or moves to the seat of your pants then it’s the tires.
I have also seen this cause by warped rims, and broken belts in the tire. The warping you don’t really see until you mount it in a tire balancer.
Many times with the broken belt, you don’t get any sort of bulging of the tire, but when the tire rotates you can see a shift in the tread pattern. The tire can still balance using minimal weights, but as the tire rolls down the road, that shift in the tread will cause the tire to track differently and pull one way or the other. As speeds increase the shifting turns into a severe, dangerous shimmy.

I spent 5+ years working in a tire shop and saw this sort of stuff on a daily basis. To quote someone else “I didn’t read it on the web, but saw it with my own eyes, thereforeI must be wrong”

Pete

Just curious, what did you end up with in the way of shims on your rig to get it all straight?

Don't rightly know.

I removed one shim from one side (PS) to bring it back to a "feel right" tension when pushed by hand. Not too loose - not to tight. For a LR, I feel it's close enough.