4 Link Rear guys - Regarding shocks / Suspension

[NDMstang65]

I'm gathering parts and pieces to 4 link the rear of my XJ. Here's the thing that I have looked and searched and can not find a straight answer on.

I picked up a set of Fox 2.0 14" travel airshox very cheap off of pirate some months ago. Now, on the buggy that I have played with and messed with it is what is ran as a crawler and has had zero issues even finishing the king of the hammers.

I had planned on 4 linking the rear end and using these air shocks as my rear suspension. Now, I am having second thoughts for weight issues.

What is the threshold of where a 2.5" airshock/coilover combo needs to be ran?

Also, I see in the Jeep Speed forum that on particular build (Sick Dog Racing) has mounted the shocks vertical on the outside of the "frame rail" and cut the fender wells for clearance. It appears that he is just using a Fox 2.5 on a vertical mounting plane here:

Is there a straight answer for what is the cut off portion on weight, and how the shocks should be oriented? I have no problem with picking up 2.5" coil overs if it is felt that it is needed. The rig is not going to be doing any Jeep Speed events or anything of that nature, I am going for all crawl and as much droop as possible. If need be I will transfer the fox 2.0's that I have now up to the front and make new brackets with the axle swap when that time comes around.

I have searched and there doesn't seem to be any straight forward answers on this. I have talked to a few other members and they say they are unsure as well. On the buggy that I worked on the shocks were mounted on an angle, the top of the shock being closer to the middle than the bottom of the shock, and that was all that was ran. No coilover or spring combination at all. Simply air shock.

Thanks for letting me pick your brain as I am trying to wrap my head around the best plan of attack before I purchase more parts.

Thanks!
Nick

 

[Exxon Valdez Jeep]

I picked up a set of Fox 2.0 14" travel airshox...

I had planned on 4 linking the rear end and using these air shocks as my rear suspension. Now, I am having second thoughts for weight issues.

...If need be I will transfer the fox 2.0's that I have now up to the front and make new brackets with the axle swap when that time comes around.

I dont know the answer to your question, but if you are worried about the weight in the rear, why would you run them up front?

 

[NDMstang65]

I would put the 2.0's that I have now that I intended for the rear into the front, and pickup 2.5" coilovers for the rear instead to handle more weight. (if that is an issue) I am unsure of the weight of the rear of the vehicle or how loading effects things.

I guess I would really need access to a set of scales to see what curb weight is over the rear axle.

http://www.polyperformance.com/shop/Fox-2.0-Air-Shock-p-102.html

I have that in a 14" stroke setup right now with a 1.250" shaft diameter.

 

[freerider15]

I would put the 2.0's that I have now that I intended for the rear into the front, and pickup 2.5" coilovers for the rear instead to handle more weight. (if that is an issue) I am unsure of the weight of the rear of the vehicle or how loading effects things.

I guess I would really need access to a set of scales to see what curb weight is over the rear axle.

http://www.polyperformance.com/shop/Fox-2.0-Air-Shock-p-102.html

I have that in a 14" stroke setup right now with a 1.250" shaft diameter.

Well, your rear is going to be much lighter than the front (think of the nice big hunk of metal sitting in the engine bay )

So if anything, put the 2.5 C/O's in the front, and the 2.0 Airs in the rear. Though if it were me, having seen people run 2.0's in the rear on anything that isn't pretty light weight...i'de want 2.5 Airs in the rear to...

Ideally...2.0 C/O's (maybe even 2.5's) all around or 2.5 Airs all around would be your best bet.

 

[NDMstang65]

Well, your rear is going to be much lighter than the front (think of the nice big hunk of metal sitting in the engine bay )

So if anything, put the 2.5 C/O's in the front, and the 2.0 Airs in the rear. Though if it were me, having seen people run 2.0's in the rear on anything that isn't pretty light weight...i'de want 2.5 Airs in the rear to...

Ideally...2.0 C/O's (maybe even 2.5's) all around or 2.5 Airs all around would be your best bet.

Right, I had thought of leaving the coil springs that I have in the front now and putting the 2.0's that I have up there because I'm doing the long arms and everything on the front as-is and it will need the extra length. It has a REALLY soft set of springs on it so I am assuming that I could fine tune things a bit more with the 2.0 up front (although I could be very wrong here), with the soft spring that is already there once long arms and associated brackets are fabbed up properly. I got them for 300 bucks shipped as they were a blem set that has 2 small scratches on the housing, I would hate to not use them at all.

I am just unsure of what the rear needs, I really plan on leaving the front as a separate coil spring and shock assembly with long arms. Which I would be fine with putting those shocks up there.

2.5" Airs or coilovers it is..

More digging

Thanks!

 

[redrider2911]

The shocks will take the most weight and be the stiffest on an exact vertical plane. this is because if the back of the vehicle is forced down x inches (landing off a jump or obstacle, or even weight transfered to the back under acceleration) then the shock piston would travel x inches. If the shock was mounted at a 45 degree angle and the back of the vehicle was forced down x inches, the shock piston in theory would travel 1/2x. Do you follow my train of thought? The further the shock is angled the more the weight can act on it as a lever and the easier to compress.

Other things to think about... Previously I was talking about vertical movement, but take into consideration body roll. The more the shock is mounted on an angle it will be able to help absorb body roll during quick maneuvers. Ofcourse too much angle is counterproductive.

 

[Jes]

I would put the 2.0's that I have now that I intended for the rear into the front, and pickup 2.5" coilovers for the rear instead to handle more weight. (if that is an issue) I am unsure of the weight of the rear of the vehicle or how loading effects things.

I guess I would really need access to a set of scales to see what curb weight is over the rear axle.

http://www.polyperformance.com/shop/Fox-2.0-Air-Shock-p-102.html

I have that in a 14" stroke setup right now with a 1.250" shaft diameter.

You won't be able to fit a 2.5" coilover between the frame and tire in the rear. I had to notch my frame to fit my Fox coil overs and still had to limit the travel to about 14.5"s and my rear axle is 62"s WMS/WMS.

 

[RCman]

The shocks will take the most weight and be the stiffest on an exact vertical plane. this is because if the back of the vehicle is forced down x inches (landing off a jump or obstacle, or even weight transfered to the back under acceleration) then the shock piston would travel x inches. If the shock was mounted at a 45 degree angle and the back of the vehicle was forced down x inches, the shock piston in theory would travel 1/2x. Do you follow my train of thought? The further the shock is angled the more the weight can act on it as a lever and the easier to compress.

Close, but a little misleading. First if the shock was on a 45degree angle (rather steep) the shaft would enter the body by √[2(x^2)] not 1/2x. Second the shock does not become easier to compress, it's ability to do work is lessened by the angle, thus the effect of a softer shock. All of this also assumes that both sides of the axle always travels up and down equally, which is rarely the case.

You won't be able to fit a 2.5" coilover between the frame and tire in the rear. I had to notch my frame to fit my Fox coil overs and still had to limit the travel to about 14.5"s and my rear axle is 62"s WMS/WMS.

Very much truth to this. I think you'd also find it hard pressed to fit even a 2.0 coilover or even a 2.5" airshock and be able to use its 14" of travel. I think you'll find yourself mounting them inside the unirail or doing some serious notching.

 

[NDMstang65]

Close, but a little misleading. First if the shock was on a 45degree angle (rather steep) the shaft would enter the body by √[2(x^2)] not 1/2x. Second the shock does not become easier to compress, it's ability to do work is lessened by the angle, thus the effect of a softer shock. All of this also assumes that both sides of the axle always travels up and down equally, which is rarely the case.
Very much truth to this. I think you'd also find it hard pressed to fit even a 2.0 coilover or even a 2.5" airshock and be able to use its 14" of travel. I think you'll find yourself mounting them inside the unirail or doing some serious notching.

Now we're making some sense.

Is there a rule of thumb for how steep of an angle a shock can cycle efficiently? I'm not opposed to cutting/notching/doing whatever needs to be done and cross bracing everything to make it function. I definitely see what you are saying about available room between the tire and the unibody frame rail.

45 degrees is obviously very very steep (in my mind at least)

Thanks for the help!

 

[NDMstang65]

You won't be able to fit a 2.5" coilover between the frame and tire in the rear. I had to notch my frame to fit my Fox coil overs and still had to limit the travel to about 14.5"s and my rear axle is 62"s WMS/WMS.

Makes sense.

Do you have a picture of this?

Thanks!

 

[redrider2911]

Close, but a little misleading. First if the shock was on a 45degree angle (rather steep) the shaft would enter the body by √[2(x^2)] not 1/2x. Second the shock does not become easier to compress, it's ability to do work is lessened by the angle, thus the effect of a softer shock. All of this also assumes that both sides of the axle always travels up and down equally, which is rarely the case.
Very much truth to this.

I had a feeling that 1/2x wasnt the actual formula, just threw it out there for an easy example to follow. Sorry for the misleading info. Again, the wrong terminology but the same basic idea. I also mentioned the articulation of the actual in the second part of my statement. Like you said, the axle rarely moves on a perfeect vertical plane.

I hope your getting the info you need stang. :thumbup:

 

[NDMstang65]

Thanks for the input Kris!

It's looking like this is simply going to be a trial by fire situation and figure out what does and does not or will not work.

 

[Jes]

Here's some pictures of how I did mine...

Realize that if you notch the frame you will have to reinforce it somehow. I did not as all it holds on my Jeep is the back bumper and gas tank plus my junk is a POS.

 

[NDMstang65]

Definitely!

Thanks for the pics!