4 link question???

[Jcampbell54]

I just finished up the back half on my old yota. And this may be a stupid question I'm running Fox 2.0 air shocks. Single triangulated 4 link. Triangulated uppers, the lowers are slightly triangulated. But is there any type of change to my link geometry that will help reduce body roll? I know a sway bar will do it but just curious if any adjustment will help. Not the best pictures but might show something obvious.

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[LightBnDr]

Bringing those shocks down to about 4" of up travel. Then running about 100cc over manufacture fill of oil. Bringing your final nitro pressures to about 100-125 psi.

That's really the only way you'll be able to be at very little body roll. You can also get away with no sway bar with this tune.

Other than that, nitrogen emulsions don't like a ton of up travel like a coil over or ORI strut.

The reason being it takes more nitrogen than oil to give you that 7-8" of up travel you have in the pic. So the nitro charge is constantly pushing your chassis away from the axle. This exacerbates the body roll condition.

Hope that helps

 

[TBItoy]

Re:

Looks like it's sitting at least 4-6" too high for the link geometry. Might have to remount the shocks to drop it enough.

 

[Bebop]

Bringing those shocks down to about 4" of up travel. Then running about 100cc over manufacture fill of oil. Bringing your final nitro pressures to about 100-125 psi.

That's really the only way you'll be able to be at very little body roll. You can also get away with no sway bar with this tune.

Other than that, nitrogen emulsions don't like a ton of up travel like a coil over or ORI strut.

The reason being it takes more nitrogen than oil to give you that 7-8" of up travel you have in the pic. So the nitro charge is constantly pushing your chassis away from the axle. This exacerbates the body roll condition.

Hope that helps

^
This


Lowering the vehicle always help

 

[Jcampbell54]

Bringing those shocks down to about 4" of up travel. Then running about 100cc over manufacture fill of oil. Bringing your final nitro pressures to about 100-125 psi.

That's really the only way you'll be able to be at very little body roll. You can also get away with no sway bar with this tune.

Other than that, nitrogen emulsions don't like a ton of up travel like a coil over or ORI strut.

The reason being it takes more nitrogen than oil to give you that 7-8" of up travel you have in the pic. So the nitro charge is constantly pushing your chassis away from the axle. This exacerbates the body roll condition.

Hope that helps

I'll give that a shot. In that case do I need to just add about 100cc to what is in it from the factory? I am currently charged to 200 psi


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[Zjman]

A center limiting strap helps as well


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[mac5005]

Re:

If you want to change the geometry,

Plot all the points in calculator.

You want to raise your roll center height.

Get it as high as practical and what ever fits with your chassis, without changing the antisquat values.

The lower the roll center height, the more leverage the COG has to induce body roll.

The closer the the roll center height is to the COG height (often the top bellhousing bolt for a quick guess), will minimize the body roll.

If you get the roll center height above the COG height, the chassis will try to push and slide the rear tire before the body roll begins.

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[LightBnDr]

^^^^ I love this kind of talk. It's amazing to me what geometry does for traction and how tracking the axle center lines as well as contact patch of a tire in slow motion can show how much a tire scrubs or lifts off of the ground through its range of motion. Super neat to me.

The only draw back in this particular situation is in a full body rig or even a back half link retrofit, you are extremely limited by a number of things that get in the way of these magic numbers. So companies like Ruffstuff, TMR, blue torch, ballistic have done all of the hard work for us. Building laser cut brackets and kits to make the swap easy. I think they have done a really good job of calculating what works well given the cramped area to work around.

Original poster, it looks like you're gonna have to lower your upper mounting points on the shocks to bring your shaft travel to the 4-4.5" mark. To retain your original wanted ride height.

I personally would pull the shocks and empty the fluid completely. Then fill with 10wt. They come factory with 5wt. Then collapse the shock and fill to the brim with oil.

After that you'll be adding about 10-20cc of oil IF that. I think you'll be real close w/o the extra oil. With how light that rear end is, you don't wanna be any more than 100 psi in nitro. Or you will fight body roll, no way around it, truly.

You gotta remember that at 200 psi nitro, that's basically a guy putting 200 pounds of force lifting up on each corner just to keep you at ride height. As soon as your geometry wants to put traction to the ground, anti squat numbers, that guy pushing at 200 pounds upward rolls that body over to one side like it's ain't nothin. Make sense?

So the lower your nitro pressure can be to spring the light ace end weight, the better. Because then your suspension geometry still does its work to put traction to the ground only now your chassis is not trying to push away from axles as hard.

 

[clemsonjeep]

Getting that weight down as low as possible helps too. Mounting propane tank as low as possible, coolers as low as possible, etc etc etc.

mac5005 and LightBnDr nailed it as well.

 

[Jcampbell54]

I have all my numbers in the 4 link calculator. I will try to get a screen shot of it and post it. In reference to the shock oil is one brand better than another? And the reason for such a high ride height is to keep it level. To clear my tires up front that's about the height I need to stay. I will move my mounts down and play with the shocks some more.


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[Jcampbell54]

Also the pictures do not show it but I do have limit straps on the rear of the rig. Not a center one though


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[joho75287]

FWIW - LightBnDr helped me tune my 2.5s on the rear of my YJ when I did the rear 4 link over the winter. We used almost the exact setup he describes above (changed slightly because I have 2.5s not 2.0s) and I am EXTREMELY happy with the results! I have almost no body roll at all and my rig feels extremely stable and so far works really well!!!

 

[mac5005]

Re: Re: 4 link question???

^^^^ I love this kind of talk. It's amazing to me what geometry does for traction and how tracking the axle center lines as well as contact patch of a tire in slow motion can show how much a tire scrubs or lifts off of the ground through its range of motion. Super neat to me.

The only draw back in this particular situation is in a full body rig or even a back half link retrofit, you are extremely limited by a number of things that get in the way of these magic numbers. So companies like Ruffstuff, TMR, blue torch, ballistic have done all of the hard work for us. Building laser cut brackets and kits to make the swap easy. I think they have done a really good job of calculating what works well given the cramped area to work around.

Original poster, it looks like you're gonna have to lower your upper mounting points on the shocks to bring your shaft travel to the 4-4.5" mark. To retain your original wanted ride height.

I personally would pull the shocks and empty the fluid completely. Then fill with 10wt. They come factory with 5wt. Then collapse the shock and fill to the brim with oil.

After that you'll be adding about 10-20cc of oil IF that. I think you'll be real close w/o the extra oil. With how light that rear end is, you don't wanna be any more than 100 psi in nitro. Or you will fight body roll, no way around it, truly.

You gotta remember that at 200 psi nitro, that's basically a guy putting 200 pounds of force lifting up on each corner just to keep you at ride height. As soon as your geometry wants to put traction to the ground, anti squat numbers, that guy pushing at 200 pounds upward rolls that body over to one side like it's ain't nothin. Make sense?

So the lower your nitro pressure can be to spring the light ace end weight, the better. Because then your suspension geometry still does its work to put traction to the ground only now your chassis is not trying to push away from axles as hard.

I don't know much about tuning air shocks, but I have a question:

Is it better to use a larger diameter air shock so that less nitro pressure is required to get the correct ride height, but keep "push" limited to help with body roll.

I understand the greater oil volume, so that the spring rate increases faster, and the reduction of n2o volume capacity helps keep the ride height similar with less push due to a lower n2o pressure?

Sent from my SM-G920V using Tapatalk

 

[joho75287]

Re: Re: 4 link question???

I don't know much about tuning air shocks, but I have a question:

Is it better to use a larger diameter air shock so that less nitro pressure is required to get the correct ride height, but keep "push" limited to help with body roll.

I understand the greater oil volume, so that the spring rate increases faster, and the reduction of n2o volume capacity helps keep the ride height similar with less push due to a lower n2o pressure?

Sent from my SM-G920V using Tapatalk

This is why I went with 2.5s instead of 2.0s. Obviously its dependent on the weight of the rig too. I am in a full bodied YJ, so I'm a bit heavier than a full backhalfed jeep or a truggy that is posted above.

 

[mobil1syn]

spread the uppers at the chassis out

 

[TRD]

This is pretty creative and I like it (but have never done it). Air shocks have very little low speed damping due to low oil cross section. Adding the thicker oil will combat some of that.

Handling is all about spring rates, air shocks have a non-linear spring rate which is very low for most of the travel. Low spring rates = lots of roll. Near fully collapsed the spring rates increase. This is why some people have success with little body roll at low up travel. Adding oil also helps to increase the spring rate sooner.

Here is an article about shock selection and handing: http://accutuneoffroad.com/articles/shock-spring-selection-for-handling/

^^^^ I love this kind of talk. It's amazing to me what geometry does for traction and how tracking the axle center lines as well as contact patch of a tire in slow motion can show how much a tire scrubs or lifts off of the ground through its range of motion. Super neat to me.

The only draw back in this particular situation is in a full body rig or even a back half link retrofit, you are extremely limited by a number of things that get in the way of these magic numbers. So companies like Ruffstuff, TMR, blue torch, ballistic have done all of the hard work for us. Building laser cut brackets and kits to make the swap easy. I think they have done a really good job of calculating what works well given the cramped area to work around.

Original poster, it looks like you're gonna have to lower your upper mounting points on the shocks to bring your shaft travel to the 4-4.5" mark. To retain your original wanted ride height.

I personally would pull the shocks and empty the fluid completely. Then fill with 10wt. They come factory with 5wt. Then collapse the shock and fill to the brim with oil.

After that you'll be adding about 10-20cc of oil IF that. I think you'll be real close w/o the extra oil. With how light that rear end is, you don't wanna be any more than 100 psi in nitro. Or you will fight body roll, no way around it, truly.

You gotta remember that at 200 psi nitro, that's basically a guy putting 200 pounds of force lifting up on each corner just to keep you at ride height. As soon as your geometry wants to put traction to the ground, anti squat numbers, that guy pushing at 200 pounds upward rolls that body over to one side like it's ain't nothin. Make sense?

So the lower your nitro pressure can be to spring the light ace end weight, the better. Because then your suspension geometry still does its work to put traction to the ground only now your chassis is not trying to push away from axles as hard.