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Discussion Starter #1
I read through some of the older threads but am having a hard time understanding it all. We just did a little test on mine and when in 2 wheel drive while power braking, the rear end will raise about 10". The front also wants to twist to the passenger side quite abit. I planned on putting a limit strap on the rear in the center, but I am concerned that something aint quite right. Any help is appreciated.

Travis
 

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That is definitely not enough seperation. If you look at where the two angles meet and then draw a line from the contact patch through that point. Where that line crosses the center of the front tire is way above the the center of gravity, hence there is alot of anti-squat. the twisting comes from the angle and torque roll just like a TJ. Make the arms longer and seperate them more and these problems should deminish.
 

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Discussion Starter #4
jeeper111 said:
That is definitely not enough seperation. If you look at where the two angles meet and then draw a line from the contact patch through that point. Where that line crosses the center of the front tire is way above the the center of gravity, hence there is alot of anti-squat. the twisting comes from the angle and torque roll just like a TJ. Make the arms longer and seperate them more and these problems should deminish.
Are you saying that I need to raise my tri link at the frame.
 

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That would help some by moving the point where they meet futher forward but making the lower links longer so that they are at less of an angle or lowering the vehicle would help the most. I am just guessing on the center of gravity here but I figure it is close.
 

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if the two forward points were the same then you would have 100% anti-squat which from what I hear is what you want to have. I have had to deal with this same shit on project PITA and I am going to have to re-build my upper link in the rear to deal with it.
 

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Discussion Starter #7
The lower arms are already 36" long. I could lower the rear some but the front is about as low as it will go. I dont want the rear to be lower than the front so that is out. I could raise the mounting point of the lower arms at the axle. They are pretty much mounted straight forward. I could move them to the top of the tube. That would reduce the angle.
 

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yeah I think that would help too or maybe lowering the fram link mounts and just sacrificing a little clearance for better climbing performance. Everything is a compromise. This is the big reason that I have my mounts on the bottom of my frame on project PITA
 

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this isn't really an anti squat issue. The real problem is the torque being transmitted through the rear driveshaft is basicly trying to twist the rear axle relative to the chasis. Since the rear axle can't move the chasis leans. This can be a huge problem on slickrock, we have all seen video of tj's or scorpions or buggies rolling themselves over on steep but not offcamber slick rock climbs. One good way to reduce the problem is to use lower axle ratio this minimizes the torque that needs to be transmitted through the driveline and reduces the lean. different designs of rear suspensions make this problem worse or better. with your typical triangulated four link the lower links which are in compression accentuate the lean, once the chassis leans a little one link gets steeper and one link gets shallower the steeper link on the side that lifted causes that side to lift more. This can turn into an unstable system and everything can come crashing down like the TJ on the slick rock. There are a lot of different four link geometries that can minimize this problem or even eliminate it but with the uppers triangulated all you can do is make the lowers as long as you can and as horizontal as you can. All this will do is minimize the effect of the suspension geometry contributing to the lean, but you should be able to come up with a tolerable suspension lots and lots of other people have. Looking at the pics, I bet yours is fine now, just wheel it and see.

There are other ways to build a suspension to completely eliminate this effect, such as a three link & panhard with the uppper link offset to one side. That one is common in road racing.
 

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that is basically what i am doing and the upper link is on the passenger side in the rear to counteract the twist of the motor but I bet most of his suspension rise is coming from antisquat which will cause wheel hop unless he uses a limiting strap. I really want to avoid using a limiting strap though because I have about three inches of up travel and about nine of down travel and to use a limiting strap in the center would limit my down travel significantly so I am trying to get the geometry to the point where I have very close to 100%.
 

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Move the rear mount on top of the axle housing as long as you have at least 6 to 8 inches of separation it will be fine. Mounting the front under the frame is a bad idea, you will hang on them all the time. Try to make the lowers around 45" long and move the mounts together under the drive shaft out put. It will make a world of difference.
 

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you may be right about the mounts being below the frame. My angles are great though and I am going to build a ramp to angle toward the rear mounts to facilitate sliding over rocks. At least until I tube chassis the back.
 

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Discussion Starter #16
Air Ride said:
Move the rear mount on top of the axle housing as long as you have at least 6 to 8 inches of separation it will be fine. Mounting the front under the frame is a bad idea, you will hang on them all the time. Try to make the lowers around 45" long and move the mounts together under the drive shaft out put. It will make a world of difference.
Well the way I have it set up now is the upper and lower arms are nearly the same length. Correct me if Im wrong but like I have it the pinion angle will always point at the t case. The arms will travel on the same arc. I also have the arms mounted near the output shaft. This allows very little yoke travel. maybe 1" from full droop to compression. By making the lower arms longer taht will interfere with my pinion cahnging angles. I know that with a limit strap in the middle, that wont be a problem but I am going to use one anyway. That will prevent the rear from climbing. What do you mean move the mounts together under the out put. Thanks.

Travis
 

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mine are about 47" long and end up under the Tcase output. mine sit about 2-2.5" below the frame rails, but since they are in the center, i suppose i can concetrate on keeping the rocks out towards the sliders and the belly clear. i was able to keep them a lot flatter this way(sacrificing some clearance)...

i have a lot less pinion angle change then expected when the entire axle moves up and down, my uppers are ~10" shorter....
 

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there about 10" apart under the Tcase output flange....thus the imaginerry point of roll axis at this end is a lot higher then the actual end of the links, all i had to do is make the mount at the axle end of the uppers tall on the housing and my roll axis is nearly flat along the frame bottom...
 

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Wow, I hope that bow is just the pic. :eek: :eek:
 
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