Four Link Setup

Today we are starting the four link,removing the gas tank then We are going to weld in the drive shaft crossmember first ,while the stock frame is in tact then we are going to be installing the four link and removing the frame and leaf springs after but i need to know how to do a proper set up

Plans

Triangulated 4 link with bag on lower bar

Correct me if im wrong

the 2 lower bars attach to the bottom of the axle and also must be parellel to the ground at ride height
the 2 higher bars must go out in a v shape, i should try to get the top bars closest to the pumpkin as possible and mount on top, the other end should go to the outside of the frame (triangulated)

The lower bars "should" be parallel but as the suspension moves during driving that angle changes. If you don't get it exact, no real worry's. Has been a lot of discussion on here about roll center and such. Basically imagine a line from your upper mount on the axel to approximately just in front of the front bumper, then back to the lower mount on the rear axel. That would be the approximate correct angle relation between the upper bars and the lower bars.

As for the "v" or "^" arrangement of the upper bars it generally does not matter much although I have seen more setups with the open end of the "v" at the axel.

I don't know how much of this info you actually need lol. I just started typing it up to help, and realized how long it was after I finished.

Like Linn says, the bars don't have to be parallel to the ground at ride height, it's just good to do that if you know what height you'll driving at because with them parrallel it eliminates roll steer. Even if you end up driving with them angled up or down there probably won't be enough roll steer to negatively effect you at the speeds we drive.

For the triangulated bars, you want the angle of each bar, when looking from above, to angle off the frame by probably 35 degrees or so. 45 is ideal, but you need pretty short bars to do that on a mini truck, and everyone likes to run really long bars.
If there's not adequate angle on there the rear end will sway which can fatigue link tabs until they break off, among other things. I've seen it happen on my buddy's Blazer....

Either angling the bars off the center of the diff to the frame, or angling them off the sides of the axle to the center of a crossmember effects where the roll center ends up. Roll Center is an imaginary point that the rear part of the truck will roll side to side on when you go through corners. The roll center ends up where ever the bars come together. So if it's on the frame the roll center will always be at that point. But when it's on the axle it moves as the suspension moves up and down, which can give unexpected reactions from the vehicle in corners. But I don't think the difference is normally noticed in mini trucks. You can do it however way fits best into your rear set up design.

Lastly, when you look at the set up from the side, you want to measure the vertical distance between the upper and lower link mount center holes on the axle and at the frame. You want the frame mounts to be slightly closer together than the axle mounts to create an instant center somewhere forward of the rear axle. On a Mazda it's probably not going to matter much where this ends up, and there's varying opinions on where to try to get it to end up. Some ppl say the front bumper, some ppl say the transmission tailshaft, etc etc. Instant Center will determine how much of the weight of the vehicle is transfered through the link bars into the rear end instead of the through the springs. It's called anti-squat. The higher the value of anti squat, the less the rear end squats down when you accelerate. Like I said, it's not too important on our trucks to find out where it ends up, as long as it goes forward. I didn't determine where mine is, and with the 350v8 I get no wheel hop during acceleration or braking, and it doesn't squat bad at all.

Ok so we have decided to do a forward triangulated four link ,bag on bar whats the difference if the top bars go in a V or /\ shape?? the bags will oviously go on the lower bars

Like stated above, for our trucks with under 100hp, which way ( v or ^ ) it should not matter unless you plan on doing some road racing.

I don't mean to thread-jack, but BagdB that was a great explanation. I did not know all of that. Thank you.

Shorter version of what I posted, it will determine where on the chassis the rear roll center ends up. But on a mini truck you won't notice a difference either way, so which ever way the bars fit your setup best will be fine. Just be sure to get enough angle on them to keep your axle from swaying.

there is a good program you can google, and download to help you set up your 4 link... I cant remember the name of it of hand, but I think it was something like 4link calculator... and you basically plug in all your information on the truck weight, height, ect... and then you can play with your bar length and heights and triangulation to design whats best for your set up. I used it and it helped me out a lot, especially understanding how it worked....

here, this will help

Awesome info here as I have never done this or been around it before & plan on attempting this soon, thank you everyone