Ok so I am going with Suicide Doors Super Pivot Triangulated 4 link kit with the bags mounted on the bottom bars. I am 99.9% sure that I know where everything gets mounted, but I don't understand how you set it up before it all gets welded in permenently. I hear you guys talking about setting up your "ride height".....how do you do that? How do you make sure the pinion angle is correct? Anything else I need to take into consideration before installing the 4 link? Please explain very detailed if you can because this is my first attempt at this sort of thing. Thank you soooo much in adcance!!


Mark


PS - If any of you guys could post or send me a link to pics of how the front and rear of your bottom Tri-4 link bar is mounted I would appreciate it. How come kits like the ones Suicide Doors sell have all the brakets for the 4 link except the frame braket like this one from Air Rides website http://www.ridetech.com/productinfo/productimages/A116-1L.jpg

Well, I was just reading on Air Rides website that you try to keep the bottom and top bars of the 4 link mounted level at ride height. So let me see if I understand how to do that....put a jack under the axle and jack it up just outside the notch (guessing that I will do most of my driving at that height) then keep the axle there and mount the bottom and top bars so they are level?? Is that how you guys did yours? Sorry for all the questions!



Mark

When I set up 4 links, I usually set the 'ride height' with the top of the axle hitting the bottom of the stock frame. I generally dont do notches until afterwards, or if I do, I dont cut out the centers until after the link is setup.
Generally I measure the pinion angle as it was before bags, and level out the frame FBSS and mark the axle centerline with the leaf springs installed. Using that centerline will keep the wheels fairly centered in the wheel well at ride height and layed out.
Position your axle against the stock frame on your marked axle centerline. A good trick is to loop and old u bolt around the axle once its in place on the centerline. I set notches up at about 1/2" to 1" forward of this centerline to compensate for the arc the axle will travel on. Remember measure measure measure. Once your u bolts are tacked to the frame, then the axle cant move front to back. You can now rotate it to set pinion angle, and slide it side to side to equal out your backing plate to frame distances. Once you've established that, tack the axle to the u bolt to hold it all in place. Now you can set up your lower bars. From a side view, you want the upper and lower bars to be as close to parallel as possible, and as close to the same length as possible (basically your uppers will generally be a little longer to compensate for the triangulation...you want the pivot points equal distances from the axle...therefore the bars will appear equal length when viewed in 2D from the side)

Now not all of this is always possible, and the further from the ideal geometry you get, the worse your suspension will perform. But it is still possible to have a perfectly workable 4 link that doesnt quite meet all of these parameters. You are often limited by available space on minitrucks, but generally you have to really not have a clue what you are doing to mess it up too bad.

For example, my 4 link has much shorter upper bars then lower bars. But it is still within an acceptable range of pinion angle change throughout normal travel, so I am not worried about it. I worked around my frame as best as I could, and although its not an IDEAL setup, it wont have any adverse effects on everyday driving.

When I set up 4 links, I usually set the 'ride height' with the top of the axle hitting the bottom of the stock frame. I generally dont do notches until afterwards, or if I do, I dont cut out the centers until after the link is setup.
Generally I measure the pinion angle as it was before bags, and level out the frame FBSS and mark the axle centerline with the leaf springs installed. Using that centerline will keep the wheels fairly centered in the wheel well at ride height and layed out.
Position your axle against the stock frame on your marked axle centerline. A good trick is to loop and old u bolt around the axle once its in place on the centerline. I set notches up at about 1/2" to 1" forward of this centerline to compensate for the arc the axle will travel on. Remember measure measure measure. Once your u bolts are tacked to the frame, then the axle cant move front to back. You can now rotate it to set pinion angle, and slide it side to side to equal out your backing plate to frame distances. Once you've established that, tack the axle to the u bolt to hold it all in place. Now you can set up your lower bars. From a side view, you want the upper and lower bars to be as close to parallel as possible, and as close to the same length as possible (basically your uppers will generally be a little longer to compensate for the triangulation...you want the pivot points equal distances from the axle...therefore the bars will appear equal length when viewed in 2D from the side)

Now not all of this is always possible, and the further from the ideal geometry you get, the worse your suspension will perform. But it is still possible to have a perfectly workable 4 link that doesnt quite meet all of these parameters. You are often limited by available space on minitrucks, but generally you have to really not have a clue what you are doing to mess it up too bad.

For example, my 4 link has much shorter upper bars then lower bars. But it is still within an acceptable range of pinion angle change throughout normal travel, so I am not worried about it. I worked around my frame as best as I could, and although its not an IDEAL setup, it wont have any adverse effects on everyday driving.

Thanks so much for the info man! Probably a dumb question and I believe I know the answer, but what exactly is pinion angle and what should it be or close to? Not sure why, but I never thought about doing the notch after installing the 4 link. I guess because most people don't do that, but I think that is a good idea. Thanks again for taking the time to write all that out for me. Anyone else have any tips or tricks?? Hopefully I'll be doing this in a month (tax return $$)



Mark

pinion angle is the angle of the pumpkin (differential) just set an angle finder on the flat spot of the differential to see what yours is BEFORE you start doing the 4-link...mine is set at 3 deg positive...

pinion angle is the angle of the pumpkin (differential) just set an angle finder on the flat spot of the differential to see what yours is BEFORE you start doing the 4-link...mine is set at 3 deg positive...

Ok thanks, that's what I thought. I have a 6" rear drop (bolt in notch) in the rear so my pinion angle is already off a little too much I assume. Is 3 degrees positive a good angle to go with? What pinion angle are the rest of you bagged guys running?? Thanks again for the help guys!



Mark

Once your u bolts are tacked to the frame, then the axle cant move front to back. You can now rotate it to set pinion angle, and slide it side to side to equal out your backing plate to frame distances.


Sorry to ask another question on your reply, but what exactly do you mean when you say "backing plate to frame distances"? Just making sure I completely understand everything you wrote. Thanks!!!



Mark

The backing plate is just the plate at the end of your axle tubes that your brake assembly bolts too. You want each side to measure the same to ensure your rear end is centered in the rails.

You should be safe with a +2 or +3 pinion angle. See what your transmission is at (probably around -2 to -3) your pinion should be about opposite the trans at ride height.

To set your pinion angle, get underneath of the truck and find out your output shaft angle. then you find out the angle of the driveshaft. Say hypothetically your drive shaft angle is 5 degrees, and your output shaft is 2 degrees. So your output-driveshaft angle is 7 degrees. In this case you would set your pinion angle at 2 degrees neg/pos, which will make a 7 degree angle between your pinion and driveshaft. What you are trying to do is eliminiate the "speed up/slow down" effect that u-joints create. So all you have to do is make your angular relation between the pinion and the driveshaft the same as your output shaft and driveshaft. You don't have to worry about positive and negative angles, as long as they are the same numerically.

hopefully that helped some.

i also sell a few different 4 links if your interested. email me brian@illusivefabrications.com