Suspension balancing advice

Well, I took my junk out and flexed it last night (first time since a major suspension overhaul)... the front flexes like crazy... maybe too well. The rear leaves are not performing at all... they're letting the front do all the work.

I've done damn near everything possible to make an XJ pack flex - my pack is quite broken in, I dropped the rear shackle box and my shackle angle is pretty close to perfect, I've got nonrestrictive spring clamps, each leaf is painted with graphite, and I've got Teflon spring liners!

The pack is basically a bastard pack. I don't know what most of the leaves came from, but when I got it, it was sagged down to maybe 1" of lift (pack alone, not counting the shackle). I took it apart and found a RE full length add-a-leaf. Then I added a cut down RE 3.5" lift main leaf to the pack to bring it back to about 3.5" of lift (again, not factoring in the 1.5" lift shackle). Is it possible that the main leaf I added just needs to broken in a bit now that it's part of a different pack?

OK, so... in the front, I've got some (broken in) RE 3.5" lift springs and my mounts are about 1.5" higher off the axle tube than stock. I've got about 4.5" of up travel at the shocks. Because of the limited up travel... are stiffer springs going to make much of a difference? Would an Anti-Rock type sway bar in front help motivate the rear to flex?

TIA for the help. Here's a pic if it makes a difference. I can snap a few more tonight if there is a need.



Billy

I know a lot of people hate them, but I picked up a set of used Revolver Shackles and installed them with RC 4.5" leafs and wow is all I can say for the difference they made in flex. I have a 3-link long arm setup in the front and the front and rear are quite balanced now when it comes to flex. I don't have any pics, but I flexed it out for the first time with the revolver shackles a week or 2 ago and I was amazed at how better it was than with regular shackles (I was running RC 2" lift shackles). I'm sure somebody will flame the revolvers after I post this, but I've only had good experiences in the short time that I've had them.

Billy, like was said above, you need some revolver shackles!




Are your bolts and nuts to tight?


Try flexing it out on something where the front and back are articulated and see where that leaves you. That isnt much flex from the back though. My old ass RE leaves flrx better then that. Take out one of the smaller leaves?

I'll check the nuts/bolts tonight... that's a good point. How will I know when they're tight enough again? I really didn't want to take any leaves out if I can help it... just because it's at the perfect height now.

What I want to hear is that an Anti-Rock in the front will fix the back

Billy

Introduce some bind into your front suspension, and the rear will flex...

An anti-rock would do this...

When I used to have coil springs, my suspension was pretty balanced, now with the airs, it seems like the front is taking over.

I think it also has to do with spring rates... what springs do you have in the front?

Rusty's coils are known to be softer, RE are mid grade, Skyjackers are known to be stiffer...

Might look into some stiffer front coils? I know that Avery and Goatman liked thier Skyjacker 8" springs with a coil clipped off.

XJ_ranger said:

Introduce some bind into your front suspension, and the rear will flex...

An anti-rock would do this...

When I used to have coil springs, my suspension was pretty balanced, now with the airs, it seems like the front is taking over.

I think it also has to do with spring rates... what springs do you have in the front?

Rusty's coils are known to be softer, RE are mid grade, Skyjackers are known to be stiffer...

Might look into some stiffer front coils? I know that Avery and Goatman liked thier Skyjacker 8" springs with a coil clipped off.

Click to expand...

I've got RE springs in front. Maybe I'll keep an eye out for some Skyjackers. I need 3.5" lift springs, so maybe I'll get lucky and find somebody that's moving up.
Thanks,
Billy

JeepFreak21 said:

I'll check the nuts/bolts tonight... that's a good point. How will I know when they're tight enough again? I really didn't want to take any leaves out if I can help it... just because it's at the perfect height now.

What I want to hear is that an Anti-Rock in the front will fix the back

Billy

Click to expand...

Look in the service manuals for the torque specs.



You should link the rear. That would solve your problems. party1:

Starboard M said:

You should link the rear. That would solve your problems. party1:

Click to expand...

Billy

JeepFreak21 said:

Well, I took my junk out and flexed it last night (first time since a major suspension overhaul)... the front flexes like crazy... maybe too well. The rear leaves are not performing at all... they're letting the front do all the work.

I've done damn near everything possible to make an XJ pack flex - my pack is quite broken in, I dropped the rear shackle box and my shackle angle is pretty close to perfect, I've got nonrestrictive spring clamps, each leaf is painted with graphite, and I've got Teflon spring liners!

The pack is basically a bastard pack. I don't know what most of the leaves came from, but when I got it, it was sagged down to maybe 1" of lift (pack alone, not counting the shackle). I took it apart and found a RE full length add-a-leaf. Then I added a cut down RE 3.5" lift main leaf to the pack to bring it back to about 3.5" of lift (again, not factoring in the 1.5" lift shackle). Is it possible that the main leaf I added just needs to broken in a bit now that it's part of a different pack?

OK, so... in the front, I've got some (broken in) RE 3.5" lift springs and my mounts are about 1.5" higher off the axle tube than stock. I've got about 4.5" of up travel at the shocks. Because of the limited up travel... are stiffer springs going to make much of a difference? Would an Anti-Rock type sway bar in front help motivate the rear to flex?

TIA for the help. Here's a pic if it makes a difference. I can snap a few more tonight if there is a need.



Billy

Click to expand...

Most bastard packs use 1 worn out main and u have that and a AAL.i know you need lift but the AAL is what is keeping it from flexing.It's like having 2.5 mains in back with the AAL..try removing it or the other main.. i would remove the AAL my .02

Nice front flex...especially for only 3.5" of lift!! You don't say what you're running but obviosly you're running some sort of 3 link or long arm or radius arm setup, eh?

What does the jeep look like at stock height?? What does it look like from the other side when you're flexed like that?? The rear, for what it is (bastard pack) may be doing halfway decent as is.

I don't think an anti rock swaybar will help the rear move...the spring rate in the rear is what it is. It could help may you more stable up front, but I doubt it would make the rear work that much better than it already does.

IMO, if you need the rear to work more I would either mess with that bastard pack a lot and eventually you should be able to get it to a pretty nice place where it rides at the proper height and is soft enough to flex a little better than it already does...but it looks like it is flexing....just not as much as you're good flex up front! If that doesn't work or if you don't want to put in all the time and effort that that route would take, there is one word...ALCAN. Not cheap, but it will make your rear flex, and not sag. You get what you pay for, ya know. Front suspension looks well setup!!

X3 on the AAL. I'm not familiar with your setup exactly, but most AAL lifts put one thick a**ed leaf in the pack to jack up the rest of it, dramatically increasing the overall spring rate. Check your leaf pack. I'll bet the AAL is 1.5 - 2 times thicker then the other leaves. Check out a set of Deaver leaves or any other quality pack. They all have many thin leaves. No individual leaf has a high rate.

Adding an Anti-rock bar, or any other bar to the front isn't going to balance the suspension out. It will add to the apparent spring rate in the front when flexed out, but any flex you get in the rear as a result is going to be subtracted from the front, with the added disadvantage of spreading that extra load across the chassis as a twisting load on the body shell.

Straighten out the rear springs first. When that's done, you will notice the rig doesn't feel as stable(the rear spring rates are mucking up the feel in the front right now)and you may want to add a antisway bar for stability. Don't bother with the bar until you get the back worked out.

builder said:

Most bastard packs use 1 worn out main and u have that and a AAL.i know you need lift but the AAL is what is keeping it from flexing.It's like having 2.5 mains in back with the AAL..try removing it or the other main.. i would remove the AAL my .02

Click to expand...

Yeah, but the AAL was flat before the second main.
Billy

mjma said:

Nice front flex...especially for only 3.5" of lift!!

Click to expand...

Thanks, but it's really about 5" of lift. The mounts are raised in the front.

mjma said:

You don't say what you're running but obviosly you're running some sort of 3 link or long arm or radius arm setup, eh?

Click to expand...

Yeah, sorry... custom 3 link w/ panhard.

mjma said:

What does the jeep look like at stock height??

Click to expand...

mjma said:

What does it look like from the other side when you're flexed like that??

Click to expand...

Thanks a bunch for the advice!
Billy

Very nice looking rig! the AAL + the extra main = stiff..maybe toss the AAL and add some loner softer leafs? it's all trial and error..but when you get it right..it's worth it..good luck and keep the nice build up..

Do you want to 'balance' it just because, or have you encountered situations where you think that would make it work better?

My advice is to get some seat time on it and figure out for yourself if it's really that big a deal. Balancing it is going to require a compromise on one end or the other...either increasing the roll stiffness of the front end, or decreasing the spring rate in the back...and both of these options come with their own consequences besides just flexing.

FWIW, my problem is the opposite - my rear springs are too soft, and the rear flexes before the front - even with the anti-rock and Timbren bumps. I identified this situation in late 2007, and figured I'd keep wheeling until I found a solution. Haven't changed anything yet.

Get some rocks under it and see how it actually works...I kinda have the feeling you're looking for a solution for a problem that isn't that big a deal. Just IMHO.

You have done all the right things to minimize friction in the rear pack so the problem has to be with the rear springs. To get the maximum amount of USEFUL flex out of the rear you need the low side tire pushing down on the ground either by spring force or from the high side tire pushing it down using the leafs as the fulcrum to get traction and make it useful. I have found when building bastard packs (I am always tinkering with them to balance load carrying the flex for different trails) it seems to work out best that I have a lot of arch in the pack when the springs are out of the vehicle AND the pack is nearly flat, just an inch or so arch when installed and the rig sitting at ride height.

The difference between the free arch (springs out) and the installed ride height arch is the available USEFUL down travel. On the trail the useful down travel will actually be a bit greater because the high side tire will lever the low side tire down even further with load on it.

Do you know how much free arch the spring pack has?
Can you measure the arch at ride height?

If you are getting all of your lift out of the springs then they are going to be too stiff. Try to get 1-1/2 to 2" out of the rear shackle by using a longer rear shackle and fewer leaves. I am also a fan of using a small lift block, about an inch. I machine my own lift blocks (Forged aluminum, shudder) with the axle wedge built in, about 6 inches long, full width and with a flat bottom and convex top so the leaves dont see a sharp increase in stress at a single point where the leaf crosses over the edge of the block. I run my center bolt (7/16ths) through the lift block.

If the arch at ride height is close to the free arch then you need to maintain the free arch but soften the pack so it sits closer to flat at ride height. Remove leaves but maintain fairly even spacing on the leaf spring ends. You will have to make up the lost lift through increased free arch, shackles or a block.

This is where I always end up having to adjust the pack. For pay to play parks I need just enough load carrying capacity to get me to the trail head where I unload all my spares, camping, supplies and non emergency junk. On the highway I may have no arch or just a little (1/2 inch) reverse arch but after I unload I will have 1-1/2 to 2-1/2 inches of arch. This usually ends up being just 4 leaves. If I am camping on the trail and have to carry all my stuff along I end up with 6 leaves and a nearly flat but slightly positive arch.

Post some pics of the pack at ride height, tire off, jack under axle and then the springs out of the rig (on the web site, yes?).

John

nosigma said:

Do you know how much free arch the spring pack has?

Click to expand...

Do you mean with the pack separated? This picture kinda shows them.

nosigma said:

Can you measure the arch at ride height?

Click to expand...

What's the best way to measure that? A straight edge across the top and measure the gap in the middle? This picture kinda shows how flat they are.

nosigma said:

If you are getting all of your lift out of the springs then they are going to be too stiff. Try to get 1-1/2 to 2" out of the rear shackle by using a longer rear shackle and fewer leaves. I am also a fan of using a small lift block, about an inch. I machine my own lift blocks (Forged aluminum, shudder) with the axle wedge built in, about 6 inches long, full width and with a flat bottom and convex top so the leaves dont see a sharp increase in stress at a single point where the leaf crosses over the edge of the block. I run my center bolt (7/16ths) through the lift block.

Click to expand...

I do have a ~1.5" lift shackle, and my relocated mount for a little extra height. I was really considering getting some of these "Zero Rate Add-a-Leaves"; it sounds exactly like what you're describing that you made. The price seems fair.

Thanks a bunch for the insight.
Billy

JeepFreak21 said:

Do you mean with the pack separated? This picture kinda shows them.



What's the best way to measure that? A straight edge across the top and measure the gap in the middle? This picture kinda shows how flat they are.



I do have a ~1.5" lift shackle, and my relocated mount for a little extra height. I was really considering getting some of these "Zero Rate Add-a-Leaves"; it sounds exactly like what you're describing that you made. The price seems fair.

Thanks a bunch for the insight.
Billy

Click to expand...

the 1" zero rate AAL from offroaddesigns is great product.i have one in a pack i am running now..maybe remove the AAL you have now and use it in it's place.

I was thinking more along the lines of the assembled spring pack to use as a reference to the installed arch at ride height. I was hoping to get an idea of the change in arch between the spring pack laying on the ground to installed under the static weight of the rig. The more arch "used up" by the static weight of the rig the greater the distance the tire can droop under spring pressure. Think of what would happen if you had a single thin leaf with 10" of arch standing free but when under the rid it sat flat. It would have 10" of down travel under spring pressure plus the lever action of the high side tire pushing it down even more.

There is a lot of variation in the curvature of the various leaves. It looks like the longer leaves have more curvature which is good because as the load lightens under droop they unstack and the shorter leaves dont restrict droop. The stock XJ main is a pretty flat leaf by itself which is always the limiting factor. But you should be able to get more performance out them than you are describing.

The blocks you posted the link for are along the right line. Personally I like a much larger radius but thats just me, at least these are not sharp edged which is disastrous without a stupid thick overload leaf to protect it. One nice thing about those blocks are that they are long which will help to prevent spring wrap.

Here is a pic with mine flexed out (short arms up front, 31" tires)


I will go get a couple leaf pack pics and post them up.

John

Leaf pack at ride height (axle on jack stand)

End view of the leafs

5 leaves with block, view from thick end of block, looking forward.

Front leaves unloaded and opened up

Rear leaves unloaded and opened up



Running 5 leaves right now plus the 1" block.

You can measure the arch from a line that runs eye to eye or from eye base to eye base down to the spring. I prefer eye base to eye base because it tells you how much up travel you will get before the springs go into reverse arch. I dont mind them reversing but I also rebuild my pack about once a year.

John
Hope this helps.

John