caster is at 8*.... what's up

[slickrock]

NEw issue . . .

(73 fj40 with 60 series steering and new 60 series axle plus flipped springs and new shackle bushings steering is very tight and nothing is loose. It has all been replaced.)

I have a 4" lift and 1" over shackles and was getting some wobble after wheeling. The steering has always been quirky and I needed to keep it adjusted just right or it would get wobble.

I figured I needed caster shims and most posts said 4* shims should be perfect.

SO I installed 4* shims and my low speed vibration whet away and I was really happy until I hit 45 mphs. Death wobble. I checked my toe and it was at 1/8". Decided to check caster by putting my angle finder on the bottom of the knuckle on a flat spot before the lower knuckle bolts. My angle finder showed looking at the back of the driver side wheel, plus 8* (angle was towards the front of the rig).

Even with 35" tires, this seems way too much. Shouldn’t I be closer to 3 or 4*?

I think I need to take them out. Comments?

I took out the 1” shackles and replaced them with the stock ones late last night and I wasn’t able to check to see if that was the problem.

What about the flipped springs? Could the 4" flipped springs be the problem?

 

[dgangle]

+8 or -8?

Figure 8-48.—Caster angle

 

[rabid]

if you reversed the shims, it would put you at 4 degrees, right? SOunds like you have the shims backwards.

 

[slickrock]

+8 or -8?

Figure 8-48.—Caster angle

plus, pointer is on right side of the finder.

IF you are under the rig facing the front tire, the finder pointer is on the right side of the vertical line or towards the front of the rig.

 

[Degnol]

+8 or -8?

Figure 8-48.—Caster angle

At -8* I would think it would wobble while parked

 

[slickrock]

if you reversed the shims, it would put you at 4 degrees, right? SOunds like you have the shims backwards.

Nope. The thick part is towards the front of thr rig.

 

[voyager:01]

if you reversed the shims, it would put you at 4 degrees, right? SOunds like you have the shims backwards.

that'd be my guess..



***EDIT: i checked my shims and the thick part should be toward the rear of the vehicle to correct for + caster.

 

[slickrock]

I followed SORs picture. Thick part towards the front.

 

[FJ40-40]

My 2 cents... It seems that flipping 4" springs would create a lot of positive caster (axle tilting toward the rear). So I would think your shims should have the thick part to the rear to tilt the axle back forward. If you have 8* positive caster switching the spacer (thick part to the rear) should result in zero caster.

 

[slickrock]

OK. Imagine you are sitting under the ront of your rig facing forward with the axle at your back. You turn to the left and you are looking at the back side of the driver's tire. I put the angle finder on the bottom of my knuckle and this is what my angle finder shows. THe angle is towards the front.

With the shims positioned with the thick part facing forward, I get 8*. It seems like if I reposition the shims and put them in backwards, may caster would be at a better angle.

It really seems the me that my caster was someplae around 4 prior to putting in the shims. I think that becasue I have flipped springs, it reversed how a shim should go. If I put them in opposite the way SOR says, my csater would be almost at 1*. Think I should swap it around? I have no problem doing that, but it takes lots o time and isn't the easiest thing to do.

 

[Pin_Head]

If you flip the 4 degree shim with +8 degree caster, you would get zero caster, which is worse.

DW is due to two problems:
1) Something that locates the wheel or axle has too much play. I know you said that everything is tight. I just think you have overlooked something.
2) Alignment problems. Too much toe in or toe out. Too much or too little caster.

 

[rsc71]

is the steering arm pointing up or down?

 

[dgangle]

yes

BUT

your reported +8 degrees of caster has little or nothing to do with your death wobble. Further expanding upon the great information by Pin Head, death wobble is caused by one or more of the following:
Play in steering components
loose u-bolts
loose shackles/worn spring bushings
incorrect toe-in
loose trunion bearings
loose wheel bearings

With +8 caster and no cut and turn it's a wonder your front driveshaft will rotate at all as your pinion must be pointing at the ground.

I am not completely convinced of your measurement. As a double check, remove the DS at the pinion and measure the pinion flange angle from vertical and report back. Without a C&T, this measurement should be the same or very, very close to your caster angle.

 

[rabid]

You could pull them out and check with no shim, if you are looking for 4 degrees.

The shims are usually to help with angles created after a shackle lift. Are you running stock shackles?

edit: re read about the 1" over shackles. Never mind.

 

[FJ40-40]

From what I understand, a little positive caster (1 to 2 degrees) is good if you have power steering. If you remove your 4* shims than you should have 4* of positive caster. If you reverse the shims than you will have about zero caster. I'd try it with no shims.

 

[dgangle]

+1 is stock. When I did my C&T is set my caster at +5 which turned into +6 once the springs sagged. It steers like a DREAM...one finger on the wheel at 80MPH on the interstate. I think you got other problems. Unless the DW started after adding the 4 degree shims, leave your shims alone and go after the real causes.

 

[voyager:01]

i can say this much with absolute confidence.. my caster angle use to be +3.5.. i put in shims that are 2.5 with the thick part facing the rear of the vehicle.. my caster angle is now +1 which is where i want it.. i JUST got home from getting a professional front end allignment today.

 

[voyager:01]

...one finger on the wheel at 80MPH on the interstate.

WOW you're nutzz!!

 

[dgangle]

rubber overdrive and 3.70:1 R&P's make this easy.

 

[slickrock]

I am spring under in the front. And I am a bit over 8*. IT is difficult to guess with my gauge because 8 and 10 are so close together. The death wobble at 40 MPH happened after the shims were put in. The steering wasn't bad before them, but I wanted to do it right and put shims in to tighten up everything.

I would be safe to say that if I put the shims in backwards, I would be closer to 1* than 0* with the stock shackles. IF it sits right at zero, I could always put back the 1" above stock shackles to correct it.

Basically, before I cause my body to be in pain for two days after tearing into my suspension again, I needed a second and a third suggestion.

SO at this point, are we in agreement to put the shims in backwards to get my castor closer to 1*?