Pirate 4x4 banner

1 - 20 of 35 Posts

·
Registered
Joined
·
2,788 Posts
Discussion Starter #1 (Edited)
Problem with Front Air Shocks Hopping

I have searched and found some good info on how to tune shocks in general, but most has involved how to do so by adding oil/nitrogen for initial setup. I have a very specific problem in that my front axle is moving up and down violently. I recently aquired this buggy and was told that the air shocks were setup and dialed in perfectly by the original owner/builder. It was setup for WeRock type crawling out west, and in the south we have to push the pedal a little more often. Rear end seems fine with no bounce, the front end bounces any time you get in the throttle hard and it only gets worse the more you hammer on it.

Video of the Problem (You can start to see it 1 min in and right before the 3 min mark it gets very violent)
http://www.youtube.com/watch?v=_32S3l4yP3g

Other Items of Note:
  • Rig has the 2.5" square poly bumps just above the front upper links and they are a hair above sitting on the links at ride height.
  • I had the front winch sucked down just a touch in the video
  • Rig weighs about 3200lbs, 5.7, TH400 and Atlas make for most of the weight in the front.
  • I don't have the valving specs with me, will check tonight
  • 3-4" shaft showing at ride height (Fox 2.0" x 14" Shocks)
  • No idea on amount of oil/nitrogen in the shocks
 

·
Registered
Joined
·
1,975 Posts
Is that a problem with the air-shocks or the anti-dive #'s?
 

·
Registered
Joined
·
3,857 Posts
Try a single bleed piston and 40/90 shim stack then fine tune from there. I also like more oil than stock try 330ml.

wayne
 

·
Registered
Joined
·
1,585 Posts
I would say to let the winch out some. Right now it is bouncing from the winch line to the bump stops and back again. I'm no expert on shock tuning, but if your air shocks were valved stiff enough to control what the video shows they would be miserable to drive. Aaron 871 is probably right about the geometry being off but who knows.
 

·
Premium Member
Joined
·
9,603 Posts
Have you tried changing tires? I've seen tires do the slip-grip-slip-grip thing, wouldn't be surprised if it caused your axle to bounce like that.
 

·
Registered
Joined
·
2,788 Posts
Discussion Starter #8
Nothing, they ride surprising soft down the road (considering the uptravel is minimal and the links ride on stiff poly bumps). I have heard from a couple via PM to check the valving and determine the # of piston bleed holes. Also check oil level. I would really like to get some of shock "experts" in here to help me diagnose this before I start tearing stuff down.

Other info that may be useful.

I have since added a 15" center limit strap at the center of the front axle that was broken when I got it.
The suspension is an inverse triangulated 4-link (straight uppers, triangulated lowers) with 3/4" heims at all ends.
 

·
Registered
Joined
·
937 Posts
with 3-4" of shock showing you cant have that much pressure. I would up the oil at 20cc's at a time and try it. It looks to me like its walking from tire to tire due to traction. I think that you may not have enough triangulation on the lowers. Its hard to locate with only one set of links and you have to have some good angle on them. Hell the straight uppers still need 3-5deg. If not it will flex the links and load a bunch of energy in the front end when you are "gettin" it... my .02
 

·
Registered
Joined
·
1,468 Posts
Nothing, they ride surprising soft down the road (considering the uptravel is minimal and the links ride on stiff poly bumps). I have heard from a couple via PM to check the valving and determine the # of piston bleed holes. Also check oil level. I would really like to get some of shock "experts" in here to help me diagnose this before I start tearing stuff down.

Other info that may be useful.

I have since added a 15" center limit strap at the center of the front axle that was broken when I got it.
The suspension is an inverse triangulated 4-link (straight uppers, triangulated lowers) with 3/4" heims at all ends.

shoot a PM to erick d lux

he may can help...
 

·
Registered
Joined
·
2,788 Posts
Discussion Starter #11
I have talked to mix-master Dlux about CO's and spring rates in the past and he is super helpful. Wonder if he is schooled in the air shock arts also..
 

·
Premium Member
Joined
·
19,786 Posts
Are you running a Radius arm style front suspension?
 

·
Registered
Joined
·
2,788 Posts
Discussion Starter #13
Are you running a Radius arm style front suspension?
Nope, straight uppers and triangulated lowers with heims at all ends. I know the radius arm wobble all too well, the old TJ had it. But it was more of a case of the pinion rotating from bad bushings. As you can see in the vid this is the axle moving UP and DOWN in a violent motion and the shocks moving at the same pace.
 

·
Registered
Joined
·
6,985 Posts
I know you have buddies with coilovers. Before you waste a bunch of time fucking around why don't you swap in a pair and see if that fixes the problem. If so, you know you need to mess with the air shocks. If not, time to look at suspension.
 

·
Registered
Joined
·
4,787 Posts
Whlndmn had the answer I believe. Are your link mounts all in line mounted at the chassis in the front? That is basically a radius arm (carries alot of the same characteristics) That is one of the things I fixed on the customers rig I have now.

Good luck,
Rick.
 

·
Registered
Joined
·
2,788 Posts
Discussion Starter #18
Whlndmn had the answer I believe. Are your link mounts all in line mounted at the chassis in the front? That is basically a radius arm (carries alot of the same characteristics) That is one of the things I fixed on the customers rig I have now.

Good luck,
Rick.

Not sure what you are asking, maybe I just need to take a pic so you can see what the links look like. Are you asking are all the links in a straight line (ie imaginary horizontal line from driver to passenger side of the rig?)
 

·
Vertical Limits
Joined
·
5,037 Posts
yes, that is what he is asking. are all the frame ends mounted on a horizontal plane so that they more or less converge like a rad arm.
 

·
Registered
Joined
·
4,787 Posts
Not sure what you are asking, maybe I just need to take a pic so you can see what the links look like. Are you asking are all the links in a straight line (ie imaginary horizontal line from driver to passenger side of the rig?)
Could the link mounts on the frame basically take one long bolt through them all? I f so, I would fix that. Rather than dampen the shocks to stop it. Making the shocks that stiff would bring the suck for trail rides. Also worn (loose) Heims could be part of the cause. But I bet its the links.

Rick.
 
1 - 20 of 35 Posts
Top