illusha
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Long post warning!!! I could separate into 5 different threads. Decided to keep it all in one. Working on a 1994 SuperBurban nicknamed “Overkill”. Goal is to build an expedition vehicle that can perform great both on and off road. Running a turned-up P-pumped Cummins 12-valve intercooled diesel and ZF6 transmission with 271 tcase over Ford Dana 60’s with 37’s on 20’s. Reinforced the dinky factory frame by plating it inside and out with 1/4”-3/8” plates and strap-boxing around crossmembers. Will be a heavy rig close to 10,000 lbs with a 3-link front and a Triangulated-4-link rear.
Now I’m trying to design the best suspension. Primary consideration – being able to perform as best as possible in ALL conditions – going 80 mph on freeway as well as rallying around gravel roads with an occasional rock course or mud hole. Started learning suspension from zero a few months ago. Read a bunch by searching forums. Played with both Triaged calculators and starting to get the basic concepts. So, now, a few things that I am not yet fully understanding…
MAIN QUESTION - different sources say different things about links being parallel to the ground. On pavement-racing forums, the trend is to make lowers parallel to the ground, while angling the uppers to get desired Anti-Squat. Street cars are not going for wheel-travel or ground-clearance though. While rock-crawlers prefer to keep uppers parallel to ground and angle lowers 10 degrees up (or more) to get clearance. Although, lately, I see more pro trucks running flatter lowers with a “cage” built in the center of the rig to hold the frame-end link mounts. What are people prefer to run in the desert? Am I correct assuming that suspension built for going 80 mph over sand whoops would also perform well at higher speeds on pavement?
Another dilemma is the location of link mounts in horizontal relation to the axle center. I’ve seen designs that put link mounts right on axle centerline and some that are offset a few inches aft or forward of the axle. What factors should be considered when choosing how much to offset the link mount from axle center? How do I figure out the geometry? Is there software that could model this geometry for me or are there manual ways of getting it right?
What factors should be considered when selecting the percentage of Anti-Squat? I was thinking of shooting for about 60%, but everyone prefers it differently, so what’s best for my intended use? Additionally, is Anti-Dive selected by different logic, particularly regarding the third link location and separation?
Along the same lines go the link lengths. Some people say to make uppers longer than lowers, some say make uppers shorter, so far I figured best is to keep uppers around 75% of lowers, may affect pinion angle at large drops, but at least it will steer straight at ride-height down the road (correct caster). Also long-arms vs short-arms overall length. Advantages and disadvantages? Any opinions?
And I’ve read some discussions on mounts being above or below the axle. I see in calculators that the forces placed on links change significantly just from a 1-2” variation. So is the top of the axle still acceptable for lowers? I know not to mount them any higher than that. Or are there any significant advantages to keeping them at center of axle or even lower below? All link brackets will be custom made and angled to reduce stress as much as possible.
Now I’m trying to design the best suspension. Primary consideration – being able to perform as best as possible in ALL conditions – going 80 mph on freeway as well as rallying around gravel roads with an occasional rock course or mud hole. Started learning suspension from zero a few months ago. Read a bunch by searching forums. Played with both Triaged calculators and starting to get the basic concepts. So, now, a few things that I am not yet fully understanding…
MAIN QUESTION - different sources say different things about links being parallel to the ground. On pavement-racing forums, the trend is to make lowers parallel to the ground, while angling the uppers to get desired Anti-Squat. Street cars are not going for wheel-travel or ground-clearance though. While rock-crawlers prefer to keep uppers parallel to ground and angle lowers 10 degrees up (or more) to get clearance. Although, lately, I see more pro trucks running flatter lowers with a “cage” built in the center of the rig to hold the frame-end link mounts. What are people prefer to run in the desert? Am I correct assuming that suspension built for going 80 mph over sand whoops would also perform well at higher speeds on pavement?
Another dilemma is the location of link mounts in horizontal relation to the axle center. I’ve seen designs that put link mounts right on axle centerline and some that are offset a few inches aft or forward of the axle. What factors should be considered when choosing how much to offset the link mount from axle center? How do I figure out the geometry? Is there software that could model this geometry for me or are there manual ways of getting it right?
What factors should be considered when selecting the percentage of Anti-Squat? I was thinking of shooting for about 60%, but everyone prefers it differently, so what’s best for my intended use? Additionally, is Anti-Dive selected by different logic, particularly regarding the third link location and separation?
Along the same lines go the link lengths. Some people say to make uppers longer than lowers, some say make uppers shorter, so far I figured best is to keep uppers around 75% of lowers, may affect pinion angle at large drops, but at least it will steer straight at ride-height down the road (correct caster). Also long-arms vs short-arms overall length. Advantages and disadvantages? Any opinions?
And I’ve read some discussions on mounts being above or below the axle. I see in calculators that the forces placed on links change significantly just from a 1-2” variation. So is the top of the axle still acceptable for lowers? I know not to mount them any higher than that. Or are there any significant advantages to keeping them at center of axle or even lower below? All link brackets will be custom made and angled to reduce stress as much as possible.