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A parallel 4-link requires a panhard bar to keep the axle located laterally. These do have some binding issues on turns (chassis roll), but not so on acceleration and deceleration. This looks like more of a drag truck, and a parallel 4-link would be fine. Sometimes one link bar is "pre-loaded" to alter how straight the vehicle launches.
A triangulated 4-link does not require a panhard bar, as the triangulation locates the axle laterally. There is much less binding on roll. This suspension should be the lightest.
A 3-link simplifies adjustments in that you would only need to adjust the center link to change pinion angle or instant center (or both), but you would need a panhard again for lateral location. I -think- you would still be able to pre-load one of the parallel links for tuning if you had to. Though there is an optimal location for the center link based on track width (and wheel base?) that would provide the most ideal launch - it's not centered in the middle.
Oh man, SkinnyG, one of my favorite Grassroot builders.
Correct, this is going to be a drag truck and will have a parallel 4 link. I guess my concern is, I wanted to run a wishbone style panhard bar (like I have tacked up above), and I'm curious if doing so will effect my parallel 4 link in a negative way.
I've had this idea of doing this hybrid 4 link, with a 3 link wishbone. Maybe it's a bad idea though.
Looking at the examples below, it looks like the center bar they use is telescoping.. which probably fixes the binding issue when launching.
Last edited by 9outofs10; Jan 2, 2020 at 04:31 PM.
Something looks off here
are you putting 4 link in this or stock style g body 4 bar?
Those angled links you have welded in look kind of redundant if you are putting an unequal length 4 link in
Something looks off here
are you putting 4 link in this or stock style g body 4 bar?
Those angled links you have welded in look kind of redundant if you are putting an unequal length 4 link in
4 link and you're right.. this is probably redundant essential if all I'm trying to do is limit lateral movement.
You need the wishbone (or some form of) to keep diff centered. Typically the center mount is at frame side to better support diff side to side. I would search known designs for your application. Not sure which design is best for street use.
If it were me, I would NOT do a parallel 4-link AND an a-arm. There WILL bind if the pivot points are not WELL thought out and PERFECTLY fabricated. In my opinion, that would be needlessly complex, and more weight. I don't think I realized what you were intending to do. Will it work? It can. Having it telescoping would be wise.
But.....
Either a simple panhard bar or a triangulated 4-link would be far simpler. If you simply -must- have the extra complexity, consider a watts link - but for a drag car, still needlessly complex and added weight.
Check out the final axle design on the Pink Panther on GRM. Very simple, very light, very effective.
A parallel 4ink needs a wishbone. The triangulated 4 link does a better job of keeping the rear centered but you still need a wishbone. PERIOD. Especially with small tire stuff because if your tires are spinning (they will) you want the rear to be straight so you spin in a straight line. The wishbone should slide to allow UP and DOWN movement with the rear as the tires squat and rise.
Pick of my wishbone
Last edited by MIAmotorsports; Jan 3, 2020 at 12:38 PM.
Reason: Mispell
A parallel 4ink needs a wishbone. The triangulated 4 link does a better job of keeping the rear centered but you still need a wishbone. PERIOD. Especially with small tire stuff because if your tires are spinning (they will) you want the rear to be straight so you spin in a straight line. The wishbone should slide to allow UP and DOWN movement with the rear as the tires squat and rise.
Pick of my wishbone
A ton of information, I appreciate everyone's input on this. I've done more research and I'll be building what MIA has above. I guess my last question is I see some people mount the center link on the frame, and others on the rear end housing. Any advantages/disadvantages doing it one way or the other?
It doesnt matter which way its turned. Just make sure it is centerline of the rear and center line of the frame. This needs to be as precise as possible. You cant keep the rear centered if the wishbone is off.
like stated above if it goes underneath, check clearance with the driveshaft full up and down. Alot of the wishbones that go underneath are not straight tubing like mine. The are arced on the y-part to give clearance for the drive shaft
it just dejust on how low you mount
you want the part that slide to be close to level
Last edited by MIAmotorsports; Jan 7, 2020 at 08:40 AM.
If you want to turn corners well (if this were a track car), having it on the bottom puts the roll center down low where it will benefit you. For a drag car, it won't matter.
Now that it's where I want it and moving how I want it, I'm going to take it off and add some more support to the telescoping part. It's made out of really thick walled tubing, but better to be safe.
I also may regret using poly bushings instead of heims, but I had them so I decided I'd experiment. I hope they provide a little flex on the street, but hopefully not too much where it'll impact performance at the track.
Last edited by 9outofs10; Jan 8, 2020 at 10:24 AM.
Do you have enough travel in the Heim on top of the rear end?
with all the improvising from how they are normally set up I think this thing will be dangerous at speed
Do you have enough travel in the Heim on top of the rear end?
with all the improvising from how they are normally set up I think this thing will be dangerous at speed
Just about 7 inches of total travel. Under acceleration when squatted it will have 3 inches or so. I plan on raising, and lowering the rear end in the truck to simulate when the 4 link is attached to know exactly how much travel I'll need.
If this thing bottoms out, I'll have more things to worry about. Like where did my coilovers go and why is my frame sitting on my rear end problems.
Last edited by 9outofs10; Jan 8, 2020 at 06:02 PM.
Changed a couple things around. Relocated battery, gutted and mounted bed, mounted fuel cell, etc. Excited to start putting together the 4 link this week.
Lots of tinkering but got my ride height where I want it. Now I can start welding the 4 link. Getting excited, feel like I'm so close, yet so far away at the same time.
I managed to get my 4 link in after many hours of measuring. I still have more measuring ahead too. I decided to abandon my wishbone locator idea and ordered a diagonal link instead.. will be here Friday. Next is the anti-roll bar.
Looks good
just remember when you tear it all apart to paint lower the top 4 link bars on the chassis to allow for a shorter instant center
You mean keep the angle, but move the bars down one or more notches? I should be aiming for a little above my anti squat line for radials, is that right?
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