Suspension: How High On Stock Geometry? (1 Viewer)

[jaymar]

How high can I go before I need to start dropping, tilting, rotating, DC'ing and otherwise changing things up? I've been told 2.5" but would like to confirm. Some nice stuff out there, but a lot of it seems to be 50mm (1.969 inches) or 75mm (2.952 inches). Really like some of the 75mm, but concerned that may be too high for stock geometry. General info: No-winch ARB up front (~80#), double swingout with spare (~250# total) on the back and a cargo box (~75#) in rear, sliders (~150?#), cargo barrier (~30#)--so probably an extra 600# right there, empty. Plus me, makes 800# and change. Will add winch and roof rack at some point. Street and overland use, nothing crazy if I can help it.

 

[Delta VS]

2” of lift should be corrected in a couple different spots, 3” of lift will put you solidly into negative caster zone.

 

[Heckraiser]

Any lift beyond the "stock height" replacement springs will require some caster correction to handle right. Even 2". There is no concrete answer to when you need a DC shaft--it varies. Some people get away with 3" lift, some don't. Probably also depends on the age and condition of your stock u-joints and your sensitivity to vibration.

 

[Outsane]

With a 3 or 2 in lift I would do the same mods, panhard lift,, radius arms, brake lines, sway bar drops, and bump stops.

 

[Delta VS]

With a 3 or 2 in lift I would do the same mods, radius arms, brake lines, sway bar drops, and bump stops.

And panhard geometry adjustment

 

[jpoole]

As an extra data point, on my '97 which is all stock including all new bushings and original springs I added 30mm spacers on all 4 corners and now have around .7 degrees positive caster. It drives ok but I'd like to be closer to stock caster, or 3-4 degrees positive. I don't see how my lift is more than 1" over og/stock given that the spacers are 1.18" thick and my springs have surely sagged some since new. Even with the minimal lift I'm already into caster correction territory though I assume my pos caster was low to start with. I'm rolling as is for now as I don't want to risk vibration territory and I like the ride height and can live with the handling.

I'll add that when I changed out all bushings I got some height back and my stock spring sag really seems minimal. Perhaps some of what folks attribute to saggy springs is worn bushings and/or added weight over the years. My truck has very little extra weight from stock.

 

[Outsane]

And panhard geometry adjustment

Dang it, that was the best one, keeps the back end from twerking down the road. Especially over the rutted mounted passes.

 

[Broski]

Simple answer, you can't

 

[SNLC]

I have 861/862’s which is about 22” hub the flare front and rear.

I have standard OME caster bushes. I have 3.1* of caster. Cruiser is as smooth as butter up to 93mph. Zero issues, zero vibes, zero drama. I am running 315’s, low CoG, no fancy or expensive parts, does great on rocks, pavement or high speed off-road.

I guess I do have BP51’s (short ones) so that is some fancy parts. I didn’t buy them new though so didn’t pay retail.

Cheers

 

[SNLC]

Also stock pinion angle which no one seems to mention is right about 2.5*^.

You can get away with about 2* or so of variance in tcase to diff pinion angle, standard shaft and no vibes.

I got about 2.7*^ at tcase and just under 5*^ at diff. Standard and old used front shaft. Zero vibes at any speed or under any conditions.

Much more than a 2* variance tcase to diff and you will get vibes and probably need to run a DC shaft.

For bigger lifts in my shop (and bolt on solutions) we find caster correction radius arms and a DC front shaft does the trick.

However if you want to know exactly what is going on with your set up put an angle cube on your tcase output flange and on your diff pinion, if you got more than a 2-3* variance, which you will with anything over about a 2” lift you should expect vibes and or growls at some speeds.

Cheers

 

[Heckraiser]

I have 861/862’s which is about 22” hub the flare front and rear.

I have standard OME caster bushes. I have 3.1* of caster. Cruiser is as smooth as butter up to 93mph. Zero issues, zero vibes, zero drama. I am running 315’s, low CoG, no fancy or expensive parts, does great on rocks, pavement or high speed off-road.

I guess I do have BP51’s (short ones) so that is some fancy parts. I didn’t buy them new though so didn’t pay retail.

Cheers

This is a good point. As your perfect caster reading suggests, even with minimal "stock height/1 inch" lift, the truck still benefits from caster correction. This is about the only good application for the OME yellow bushings I can think of. They are inadequate for most of the lifts that they are sold with as a package.

 

[SNLC]

This is a good point. As your perfect caster reading suggests, even with minimal "stock height" lift, the truck still benefits from caster correction. This is about the only good application for the OME yellow bushings I can think of. They are inadequate for most of the lifts that they are sold with as a package.

Agree, we don’t use the bushings for much more lift than this. On a 2.5” lift they do not correct enough caster, you are in the zero to 1* range with them and that lift. As I am sure you know caster is not a set number by inches of lift. You can’t say 1” of lift removes 1* of caster, the equation simply doesn’t work this way. It’s more of a % as you go up since the axle moves in an arch vs straight up and down.

Cheers

 

[jaymar]

Was hoping that extra 800#-empty weight might push things down into no-alterations-needed territory, but looks like that's not the case. Thanks for the edumacation on this.