Seeking geometry lesson: Lift springs / shackle length: caster impact (1 Viewer)

[woytovich]

I want to understand how lift springs and spring shackles impact caster angles in the front of an FJ40.... (given shackles in the stock position up front.)

Adding lift springs...

Adding longer shackles...

Thanks

 

[jim land]

Longer front shackles change your caster because it rotates the front housing and knuckles

 

[woytovich]

Longer front shackles change your caster because it rotates the front housing and knuckles

And it rotates things downward, which pushes caster in the negative direction... which is bad. As I understand it.

 

[wngrog]

I explained it to you on Facebook today and now you are starting another thread.

Type in Caster and Leaf Springs in You Tube.

 

[pb4ugo]

The 40s spring pin is not in the centered in the spring. It's position is slightly towards the rear spring hanger. It's sort of going down hill already. A lift spring has more arch and quality springs are typically longer so the shackles won't invert. The increased arch rotates the axle towards negative caster and the longer shackle pushes the frt of the spring down, and effects the caster too. You need to run a longer shackles so when the spring flattens out it doesn't bind or bend the main leaf.

 

[woytovich]

I explained it to you on Facebook today and now you are starting another thread.

Type in Caster and Leaf Springs in You Tube.

I actually started this thread yesterday and no one responded so I posted over there on Facebook. Sorry if that offended you. I appreciate your answers.

 

[martymart]

Woytovich - thanks for posting this on IH8MUD. I do not have a Facebook account and never will.

 

[martymart]

Correct caster angle for front axle FJ40?

Ive been reading posted threads regarding "Death Wobble" and "Wandering Steering" linked to removing roof top and doors/ and or installing taller shackels. I am experiencing the same problems with my cruiser as well. with a side to side shaking at about 35mph and stopping at around 50mph. This...

forum.ih8mud.com

 

[White Stripe]

Lifted springs don't necessarily affect caster, it depends how the leaf pack was built. Some will affect caster some won't. Shackle length affects the resting angle of the leaf spring thus affecting caster. Basically caster is the last item addressed when installing a lift. Install the lift, flex out the suspension to make sure everything cycles well, then check and adjust caster as necessary.

 

[wngrog]

For the non FB

 

[peesalot]

Grog - cranky this morn ?
OP - We assume you are asking regarding a stock suspension ? Longer shackles will generally require shims or a cut N turn. If you are using lift springs in addition to longer shackles then a shim might not get it done and a cut n turn is nec. You can correct with shims but only so much as the pinion angle will suffer, when you get to a point you need to do the cut n turn. Wngrog would know how much lift & shackle you can put in and get away with shims vs. when you need to do the cut n turn, valuable source of data right there.