Front Suspension Set up/Build Questions

[BanditBronco]

Questions for the few on here that I know can help me out. Building a set of long radius arms. I know there can be some drivers side swing due to the trackbar but does that mean I center the axle at full bump or at ride height? While I am going up and down and around on the lift during the build I can just set projected ride height based on the current frame to axle distance if I am shooting for similar numbers correct?

I am assuming I should center the axle at ride height, set caster at ride height, and bump it out for coil over tower set up. Or can I do all of it set up at full bump?

 

[79INA69]

Sounds like you are on the right train of thought. You are correct that ride height is where you want everything centered and your alignment to be as ideal as possible. Ideally you want to set all your bump clearances first, then determine the amount of up travel you want, which will usually determine your ride height. So, at bump and droop, your arc will cycle out of the ideal ride height numbers in either direction.

 

[Apogee]

X2...set all of your handling/steering related angles at ride height, since that's where they matter most. The flatter the angle of your track bar, and the longer it is, the shallower the arc it will swing and the less lateral movement you'll have throughout your range of suspension travel. The first time I put my '77 up on frame stands and let the front axle droop, it was a little shocking to see the front axle ~4 inches to the driver's side from centerline. I knew that it was there, but seeing it is still a bit of an eye opener.

Then build your suspension at the bump stops to ensure that everything clears underneath and that you bottom out on your bump stops, not your shocks.

 

[BanditBronco]

10-4 thanks guys. I have built a track bar before, one of the longest ones I have seen on a Bronco. Used a 1 ton swap jeep rear track bar mount and a custom frame side mount. I didn't do any of the axle centering or anything as it was paired with a set of duff arms. I want to say we measured arc swing on it and it came out pretty minimal.

How do most feel about measuring off of the front of the frame rail to square up the axle? Is there a better more accurate spot like the original radius arm frame mounts? I haven't checked my frame for square either which I could do. I plan on pushing the axle forward an inch so it will be floating in space where I set it until the arms are made.

 

[Apogee]

...How do most feel about measuring off of the front of the frame rail to square up the axle? Is there a better more accurate spot like the original radius arm frame mounts? I haven't checked my frame for square either which I could do. I plan on pushing the axle forward an inch so it will be floating in space where I set it until the arms are made.

You can totally use your front frame rails for reference, however I would first check the dimensions back to the front leaf spring mount, since that sets your thrust alignment. Check it for square at the same time, though even if it's not square, you still want your front and rear axles parallel to one another, regardless of what the frame is doing in between.

 

[BanditBronco]

O man, been a while since I have dealt with thrust angle. So say it is a little off hypothetically 80" on one side and 80.75" on the other to the spring hanger. How would I set the front to avoid dog tracking?

 

[79INA69]

I like that track bar set up. I wanted to lengthen the passenger side on mine like that, but I have a 79 D44 housing with the big cast on wedges and haven't come up with a good bracket idea yet.

 

[BanditBronco]

I like that track bar set up. I wanted to lengthen the passenger side on mine like that, but I have a 79 D44 housing with the big cast on wedges and haven't come up with a good bracket idea yet.

Yeah that axle has the wedges moved in to EB width so it gives you some extra room outside the wedge.

On mine I am planning on running a jeep offset 1 ton swap frame side mount from TMR customs as well. So I should be able to get away with just a little axle side bracket modification and frame side should go right on. Pretty simple combo for a full length track bar set up.

 

[Apogee]

O man, been a while since I have dealt with thrust angle. So say it is a little off hypothetically 80" on one side and 80.75" on the other to the spring hanger. How would I set the front to avoid dog tracking?

If there's a 3/4" difference, then I would find a different reference point to use as your datum for measurements. Did you check the diagonals to check for square? There are few EB frame diagrams floating around showing the critical dimensions, some of which are easier to measure directly than others. If everything checks out as square, then you could just make the front axle parallel to the rear by measuring forward from the spring hangers rather than back from the front frame horns. Just curious, but do you see the same 3/4" difference measuring to the rear frame horns, or was that truly a hypothetical measurement?

Tobin

 

[BanditBronco]

Those were completely hypothetical measurements I haven't actually measured anything yet. I was just confirming that you would "match" the rear offset if you couldn't square up the thrust alignment to be equal. Technically you have way more adjustment than needed in the joints of a non stock set of radius arms if you needed to push one side of the axle back or forward of the other anyway.

 

[Apogee]

Whew!...because 3/4" would be a lot. When I did my CAGE long arms 15 or so years ago, I found it easier to go to the rear perches since the holes referenced in the crappy installation instructions weren't there on my frame. I pushed my axle forward about 1.25" to 1.50" forward from stock and then installed it with the rod ends threaded into the arms about 75% so that I maintained good thread engagement and adjustability. Overall, worked out great and only took a matter of minutes to get things lined up reasonably close with a tape measure.