Rear Lift Geometry Question

[Belcher]

Can someone tell me this....hold the flamethrowers....with the rear suspension geometry does adding rear springs/shocks actually get you any more ground clearance or does it just make room for a larger tire and help with added weight?

I can easily see on the front being independent and adjustable where you can get the skid area raised up (I have Bilstein 6112's and 5160 combo uninstalled) but I'm debating the rear springs. Stock rear springs and Timbrens I get about 1-1.25" sag currently.

I'm a Overlanding/Camping type person...not a crawler...mix of highway/sand on the coast/light mud in the mountains person.

Looking to do 2nd clip with stock springs or 3rd clip with springs ??? HELP

More info: Running Cooper AT3 275/70/17 C load with no rubbing
Rear Timbren Load Leveling bump stops
Tepui Rooftop Tent and Awning
EziAwn full roof rack
Usual camping gear for the family

Thanks,
Chris

 

[codyHTX]

Can someone tell me this....hold the flamethrowers....with the rear suspension geometry does adding rear springs/shocks actually get you any more ground clearance or does it just make room for a larger tire and help with added weight?


Looking to do 2nd clip with stock springs or 3rd clip with springs ??? HELP

Thanks,
Chris

you get increase body/frame clearance lifted with shocks/springs, axle/diff is un-sprung weight and ground clearance is a function of wheel/tire diameter.

 

[kernel.panik]

rear coils, or any rear lift, will not gain you any ground clearance. Larger tires are what will give you ground clearance. Your axle in the rear is under the springs; they just raise the frame up off the axle for more articulation.

 

[Belcher]

How much do the rear springs effect articulation/suspension travel...does a 2" rear lift get you 2" more travel....or is there other factors that limit that?

My 4runner does have KDSS for extra info.

Thanks,
Chris

 

[wfo9]

How much do the rear springs effect articulation/suspension travel...does a 2" rear lift get you 2" more travel....or is there other factors that limit that?

My 4runner does have KDSS for extra info.

Thanks,
Chris

simple answer...2" lift springs will not get you 2" more travel.

However, a typical suspension lift system (shocks + springs) will give you more travel over stock. How much depends on several factors.


More info...The shocks are mostly what limit travel, but the springs will fall out if your shocks have too much travel for your springs. The Control arms also limit travel because at a certain point they will bind up. They need to be much longer to support extreme travel needs.

There are two very different types of travel when a solid axle is at play. There is vertical travel and articulated travel. Vertical travel is when the entire axle moves up or down in parallel. Articulated travel is when one side goes up and the other goes down... Solid axle rigs always have more articulated travel than vertical travel. The angles help move the tire further up/down, plus you have weight transfer helping. Swaybars will limit articulated travel, since the torsion bar is fighting to keep the axle parallel with the body/frame.

In the case of KDSS. The KDSS swaybar will also limit travel potential as it makes contact with the track bar. It still articulates well and does just fine, just not as extreme as one without that limit in place. I think it gets in the way on both vertical and articulated travel... ICON has a curved trackbar to help, but I think it still contacts with any type of long travel setup. Their standard travel setup also causes some contact, but I don't think it is a big deal at low speeds....

The main benefit of a lift is improved approach, departure and breakover. This is much more useful than ground clearance. It surprising how little ground clearance you need outside of something like a mud bog...I have a solid axle truck with only about 10.5" of ground clearance, but it can overcome near vertical obstacles that look impossible because it has such extreme approach, departure, and breakover....

 

[Belcher]

WF09...solid information...thanks alot. I assume that a lower spring rate like the SAW will help with articulation as described above rather that a heavier spring rate like the OME 895E that I have been looking at?

I'm way to anal for making these decisions :biggrin1: My brain is going to explode...I wish I was the type of person that would just slap some S**t on there and go.

Chris

 

[T5RUNNER]

Technically ground clearance is measured at the lowest point, which is the rear differential. The only way to increase that number is taller tires.

But in the real world it will increase your clearance and angles everywhere else, and make room for those taller tires.

 

[wfo9]

WF09...solid information...thanks alot. I assume that a lower spring rate like the SAW will help with articulation as described above rather that a heavier spring rate like the OME 895E that I have been looking at?

I'm way to anal for making these decisions :biggrin1: My brain is going to explode...I wish I was the type of person that would just slap some S**t on there and go.

Chris

Spring rate will impact flex, but you don't want to go to low for your weight. More weight generally requires a higher spring rate. It's really hard to setup it up so the truck is perfect both loaded and unloaded. You get somewhere in the middle and call it a day. Air bags can provide a level of adjustment for loads...

Weight is always bad, so really think about that as you build up and pack your rig for a trip. Unnecessary weight should be avoided at all cost. Keeping the weight you have to carry as low as possible also helps. Try to go as light and lean as you can (especially when out on the trails).

 

[LandCruiser]

Get an adjustable panhard rod to straighten out the ass end, or you will be moving the rear tires an inch to the side and lose clearance on one side if you try to stuff them.

 

[wfo9]

Get an adjustable panhard rod to straighten out the ass end, or you will be moving the rear tires an inch to the side and lose clearance on one side if you try to stuff them.

IMHO, you don't need to worry about it and will just cause more trouble adjusting it. It will shift things very slightly with a lift, but I haave never noticed the difference myself.

However, if you do lengthen it too much (which is required to re-center with a lift)... the drive shaft will come extremely close to the gas tank at full stuff on the driver side. I had a hell of a time modifying my gas tank skid and brackets to clear the drive shaft and diff flange at full flex. Lengthening the track bar would only make it much worse. It only became a problem once I went long travel. I thought about getting an adjustable track bar so I could shorten it.. It was that much of a problem, but I ended up fabricating new brackets and cutting the skid down more.

 

[LandCruiser]

IMHO, you don't need to worry about it and will just cause more trouble adjusting it. It will shift things very slightly with a lift, but I haave never noticed the difference myself.

However, if you do lengthen it too much (which is required to re-center with a lift)... the drive shaft will come extremely close to the gas tank at full stuff on the driver side. I had a hell of a time modifying my gas tank skid and brackets to clear the drive shaft and diff flange at full flex. Lengthening the track bar would only make it much worse. It only became a problem once I went long travel. I thought about getting an adjustable track bar so I could shorten it.. It was that much of a problem, but I ended up fabricating new brackets and cutting the skid down more.

Mine was adjusted once, it's stayed that way since.

May have rusted into the final, correct position for all I know.

 

[sandcrawler]

In the case of KDSS. The KDSS swaybar will also limit travel potential as it makes contact with the track bar. It still articulates well and does just fine, just not as extreme as one without that limit in place. I think it gets in the way on both vertical and articulated travel... ICON has a curved trackbar to help, but I think it still contacts with any type of long travel setup. Their standard travel setup also causes some contact, but I don't think it is a big deal at low speeds....

I have kdss so my sway bars are def still on. That might be another reason I have a little more flex/droop without long travel. Here's another pic

KDSS flex photos courtesy of [MENTION=123578]carlomagne[/MENTION]... i think that's a pretty satisfying amount of travel, personally. particularly for one with factory swaybars... and even more so for one with beefy swaybars that can do this off-road and then firm up to virtually flatten all corners and body roll for the duration of your ride home.

the "KDSS limits travel" bit doesn't really apply unless you're comparing to long travel, which i believe you are?

also, there's quite a bit of vagueness and ambiguity surrounding the "need" for the bent ICON track bar. many don't seem to need it; myself included. consider that it took ICON a super long time to deem it "necessary", and even after that determination was finally made it has been pretty hit or miss for cases where it actually helped anything.