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Help me correct/tune/unfuck my front suspension. Please!

Johnny Longrifle

Johnny Longrifle

Slow learner
Joined
May 19, 2020
Member Number
147
Messages
435
Loc
Not where I want to be
I built this CJ2A a few years ago. I call it a 2A, but there is very little left of the original Willys it started as. Sheet metal is all thats left of the original 46...or 48...I dont remember. Anywho, what was once a driveable old jeep morphed into this tube juggy creation. All of the originals are gone and it now has a tree fiddy chebby, NP435 from a Ford, and Atlas3.8 married with a Jeds super short adapter, a 10.25 welded rear and a BJ60 with an ARB in the front.


Moab2.jpg




Moab1.jpg



I had a build thread going over at the old place, but abandoned it. Now that this "car" is done and Ive had it out on a few excursions I have some issues to work out. The pictures of it in Moab were of a trip I took my dad on. We had a blast, and the BlueJeep performed pretty well on the rock there. I was pleased with my first attempt at 4 linked suspension on coilovers. It rode nice and soft and didnt beat my kidneys out like I was used to in that Bronco in the background.

At trail riding pace, I have no complaints. This car is far and away better than anything I have ever (in my limited expeience) driven. My main concern in this thread will deal with the front suspension. Crawling and trail riding it does fine. I first ran into issues at JV a year ago, and then again just a few weeks ago locally out in the snow.

If I have the nose of the car facing uphill and we are climbing in the sand or snow, the front end hops violently with any kind of throttle application. To the point im scared to give er, and risk walking back camp or home..


The engine Im running is a '99? Vortec 350. Bone stock, no power adders,

So that brings me to question the geometry of the front 4 link. Real estate is very tight, and when I built this I tried to do the best I could with what I had to work with. Its not perfect, but the calculator shows that its not that bad? My suspicion is that I dont have enough vertical seperation at the axle, but Im not sure. Will lack of seperation cause a wheel hop like I am experiencing?


blue jeep front suspension.png


Shocks are Fox 2.0x14 I purchased them from Wayne with his secret recipe installed (the only thing he knew about this car was over the phone conversation).
But its Wayne, I cant imagine his valving to be too far off.

The car is sprung really soft. On a 14" coilover the current spring rate is 125/150

Please tear apart my suspension design and help me understand where I went wrong. Im a pretty good mechanic, but I aint no enginerd. My only complaint with this car that I need your help fixing is the front end bounce/hop under power.
 
My best guess is took look at what happens to as the front droops out. But given that when climbing, most of the weight is on the rear, its likely worth a look at what happens to the rear with a bit of travel, both bump and droop. I am obligated to point you towards the newer versions of the calculator, makes it easier to look at front and rear at the same time. They are available under the resources page.

On an unrelated note, could you share what the last revision number listed is in that version of the calculator? And/or would you be willing to share that file with me? I've been trying to create a database of all of them and this one does not appear to match up to any of the ones I've stumbled across.
 
so you have got 3.5" of separation on the axle side for the front links? that's not much, but if you aren't ripping your mounts off then i doubt that is a problem. consider that a radius arm rig run about the same with less on the frame side and i can't think of them as hopping on the snow commonly.
 
I would say a combo of a couole things. Soft coils, tires, link separation. Tires loosing and gaining traction at a high frequency, what PSI are you running and have you played with that? Increase the link seperation at the axle to reduce axle wrap. What kind of rod ends are you using? Increase the coil rates so the you have more resistance to the tires spinning instead of the energy compressing the coils. Center of gravity in your chart looks low to me which may be throwing off your number, what size tires are you running?
 
Provience said:
so you have got 3.5" of separation on the axle side for the front links? that's not much, but if you aren't ripping your mounts off then i doubt that is a problem. consider that a radius arm rig run about the same with less on the frame side and i can't think of them as hopping on the snow commonly.
Click to expand...

More like 6.25 separation at the axle end, and unfortunately that is all the room there is with the radiator and crank pulley being the biggest obstacles in the way. Thus far I havent broken anything, but I havent been trying hard either.
 
thedirtman said:
I would say a combo of a couole things. Soft coils, tires, link separation. Tires loosing and gaining traction at a high frequency, what PSI are you running and have you played with that? Increase the link seperation at the axle to reduce axle wrap. What kind of rod ends are you using? Increase the coil rates so the you have more resistance to the tires spinning instead of the energy compressing the coils. Center of gravity in your chart looks low to me which may be throwing off your number, what size tires are you running?
Click to expand...

Tires are TSL Swampers (because cheap) and I have been running them at single digits. I have not experimented with higher pressures. I will try that next time I can get it out of the now froze in shop door. I wish I could have more separation at the axle, but I dont have the real estate. Rod ends are 7/8" Cromo units from (if I remember correctly) Barnes4wd, and again because at the time they were ~1/2 the cost of 1 1/4"s. Center of gravity is a rough guesstimate, but that measurement is the location of the top center bellhousing bolt.

Also, HTF do you multi-quote? :homer:
 
fwiw if you need more separation at the axle side you can move the lower links down if you cant move the uppers higher, although id imagine 6.25" i enough but im not a link guru :laughing:
 
Johnny Longrifle said:
More like 6.25 separation at the axle end, and unfortunately that is all the room there is with the radiator and crank pulley being the biggest obstacles in the way. Thus far I havent broken anything, but I havent been trying hard either.
Click to expand...

I would be more concerned about the lower link angles and probably look into the rear as they seem more steep, especially if it is an uphill only thing. can't imagine that axle side vertical seperation would cause the issue.
 
Honestly while you do have a pretty low amount of vertical separation here, the actual geometry isn't the worst looking at that table. But I'd be very surprised if that thing weighs the 6k you have input. it's really hard to say what the cause is while intentionally avoiding looking at shocks because they are unknown. Shock valving will have a huge impact on axle control as well. Beyond just actual tuning, do any of them leak? Do they still have a charge? Just to try to help rule out shock health itself
 
An easy things to try is slower shock damping. Swapping to a heavier oil as an experiment would work, but really more rebound damping is what I would want to try.

It's always worth playing with tire pressure. TSLs aren't soft and your rig doesn't seem heavy given the light spring rates so I'm not sure if you'd gain much with higher pressure besides more wheelspin. Still, try the same climb with 10psi then drop 2psi and try it again, keep going until 4psi.

​​​​Hell, you could probably run those TSLs without valve cores and they wouldn't go flat. :grinpimp:

Have any video of the rig in action?
 
AgitatedPancake said:
Honestly while you do have a pretty low amount of vertical separation here, the actual geometry isn't the worst looking at that table. But I'd be very surprised if that thing weighs the 6k you have input. it's really hard to say what the cause is while intentionally avoiding looking at shocks because they are unknown. Shock valving will have a huge impact on axle control as well. Beyond just actual tuning, do any of them leak? Do they still have a charge? Just to try to help rule out shock health itself
Click to expand...

The weight is an educated guess. It has the same front and rear ends as my F350, lighter engine, similar weight trans. The Jeep has a frame that is 2x4x.250 tubing, plus all the cage and links that are .500 wall. I've never weighed the thing, but I am willing to haul it to the scale if it will help.

Shocks, (and the whole rig for that matter) has less than 100 miles on it. None of them leak oil, and I don't have the tools to check the charge. I will be looking into that tonight.

I've no experience in shock tuning or coilovers for that matter. It may be worth a pro tuning session? In all honesty, I figured my geometry was so f'd up that I would be laughed out of this thread, and torching the front suspension out and starting over. Im not trying to build a 4400 car, but the first time I stood on it up a sand hill I was quite disappointed.
 
Yotota said:
An easy things to try is slower shock damping. Swapping to a heavier oil as an experiment would work, but really more rebound damping is what I would want to try.

It's always worth playing with tire pressure. TSLs aren't soft and your rig doesn't seem heavy given the light spring rates so I'm not sure if you'd gain much with higher pressure besides more wheelspin. Still, try the same climb with 10psi then drop 2psi and try it again, keep going until 4psi.

​​​​Hell, you could probably run those TSLs without valve cores and they wouldn't go flat. :grinpimp:

Have any video of the rig in action?
Click to expand...




No joke about TSL's being stiff. I knew this going in. The LF wont register right now in the shop, yet its still holding the front end up. I plan on cutting them all up, but don't want to change too many variables all at once.

I've no experience in shock tuning. Next time I get it out I'll take a lot of notes and play with different things. Also, take someone with me to take some footage. Sadly, I don't have any vids of it.
 
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I'm gonna say you're spring rates are way to soft for one and your separations aren't enough. I ran 185/200 on the front and 200/200 on the rear of my stretched flatty if I remember correctly and I had a ferd 5.0, zf tranny and AA 4 Spd t-case and my frame was 2"x4"x.250" and the weight at each corner was like 1100 lbs or so. I'd have to go back to the forbidden site to go look at all the numbers. Anyway you can figure out the weight of each corner by taking the coilovers off and putting one spring in each and putting them back on and then let the Willys sit on the one spring coilovers, then measure how much each spring compresses and take that dimension x the spring weight. So you have 150 springs and if they compress 6" at each corner then you have 900lbs at each corner and you can calculate the proper spring rates from there. Valving will probably help too, but that's out of my league and other's will have to lead the parade there.
 
I didn't see you mention what kind of link ends you have. With the small amount of separation, any compliance in the ends could contribute. Bushings will deflect more than spherical joints, and joints with poly inserts will deflect more than a "solid" heim joint....
 
Suck down winch (or whatever it’s called) to lower the front and load it?
 
DMG said:
Suck down winch (or whatever it’s called) to lower the front and load it?
Click to expand...

I was curious about this too. He said it's happening on snow/sand so I'm not sure how much the front suspension is unloading. On steeper climbs a suckdown winch or center mounted limit strap could definitely help.
 
Yotota said:
I was curious about this too. He said it's happening on snow/sand so I'm not sure how much the front suspension is unloading. On steeper climbs a suckdown winch or center mounted limit strap could definitely help.
Click to expand...

It is easy to try it
 
I really think a couple videos would help immensely.

wide shot, show the whole car when it happens and a closer shot if you can get right to the point it happens and view the axle
 
1. Calculate your sprung weight upfront using your coil springs.

2. Did Wayne specify your spring rates and had you finalized your spring rates when he put the shocks together?

3. A simple way to check the health of your shocks is to remove them stand them upside down and compress them. If there’s any gas in the pressure tube, typically the shock will have an zone with no damping. It will be a bitch to compress so you will know if one of them has lost nitrogen if it isn’t.

Just because a shock is the new does not mean it is perfect.

6000 pounds is crazy heavy for a flatfender, even if the engine is made out of lead. Check your weight and check your spring rates. Your geometry does not look terrible. I have seen worse.

I don’t think you need a professional tune session. If you ordered them from Wayne I would be inclined to talk to him. But check your weights first.
 
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Time for a little clarification. In order to keep this post from being a wall of text, I will reference post #'s instead of quoting. I still haven't figured out how to multi-quote anyway :laughing:

#18 This is the method that I learned from Wayne (I cant for the life of me remember his username over there) and mobil1syn at the old place. And this is how I came to the spring rate currently on the rig.

#19 Thanks for bringing a pro in here!

#20 Rod ends are 7/8" chromo heims with misalignment spacers and 3/4" thru bolts

#21 I'll try that next time out

#22 The frame is 2x4x.250 The cage is 1.75x.120 DOM The links are 2x.250 sleeved with 1.5x.250 equaling 2x.500 wall

#23 The first time I experienced this was in JV on a sand hill. I needed to gather a bunch of wheel speed and lay some power down to get up this sand hill. It bounced so violently that I shut it down and found a different route. Then once I was home and took it out in the (hub deep or so, not feet) of snow all the power it would take without bouncing was just off idle, inches per minute of clawing through garbage snow. I was so disappointed that I took it home and waited a month or so before I even made this thread.

#24 :cool:cool my thoughts too

#26 Thanks for giving me an excuse to buy a go-pro :beer:
 
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Beat95yj said:
1. Calculate your sprung weight upfront using your coil springs.
This is how I originally calculated the spring rate. I bought some 100# springs to make math easy, and measured from there.
2. Did Wayne specify your spring rates and had you finalized your spring rates when he put the shocks together?
No. I bought the shocks from him after a few conversations over the phone, and at the time I did not have any coil carriers to know what corner weights a C/O would "see". I sent him a couple pics, and he did his magic. I measured spring rates after I got the shocks installed.
3. A simple way to check the health of your shocks is to remove them stand them upside down and compress them. If there’s any gas in the pressure tube, typically the shock will have an zone with no damping. It will be a bitch to compress so you will know if one of them has lost nitrogen if it isn’t.
I will do this. It's not a hard jpb at all. Kinda need to make new upper tabs anyway. Im not super happy with what is there.

Just because a shock is the new does not mean it is perfect.

6000 pounds is crazy heavy for a flatfender, even if the engine is made out of lead. Check your weight and check your spring rates. Your geometry does not look terrible. I have seen worse.
I am going to the scalehouse as soon as this weekend if I can get the shop door chipped out of the ice. I will be able to get total weight, Front and rear weight, and maybe even corners. I assumed in starting this thread that I would get laughed out of here for my shit geometry. I'm relieved to hear that maybe I did ok.
I don’t think you need a professional tune session. If you ordered them from Wayne I would be inclined to talk to him. But check your weights first.
I still have those 100# springs. I can swap them out and recheck corner weights when I pull the shocks back off to check the charge and rebuild upper tabs.
Click to expand...


Thanks to everyone who has chimed in. I hope you all have patience... I am going to do my best to work on this thing and answer this thread in a timely fashion. Just know that I have winter to deal with, while the rest of you is in wheeling season.
 
is your pinion angle going to garbage and binding the u-joint?

what does the rear suspension geometry look like?

the axle flailing under the vehicle or is it is upsetting the chassis?
 
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