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Coil spring front suspension for my 79 GMC

Not totally. I will try to find the info for setting it up. The lower the link, the higher the roll center. A number of factors need to be looked at. I went from radius arms to a bottom 3 link. It changed a lot. Works great in the dirt. Sucks on the street.
 
I have the 3 link calculator. I plugged my suspension into it and the roll center is 21 inches, which is lower than the CG. I want to post the calc but cant figure out how.
 
3 Link Calculator Wheelbase117.5in= Tire Diameter33.00inTire Rolling Radius15.50in Sprung Mass CG ' 37.00in Weight5,500lb Geometry Summary:Upper LinkxyzAnti-Squat107.25%Frame End41.000.0017.25inRoll Axis Angle-2.97degrees ( - roll understeer, + roll oversteer)Axle End4.000.0012.50inRoll Center Height20.68inLower LinksxyInstant Center X-Axis57.26inFrame End36.0019.0020.50inInstant Center Z-Axis19.34inAxle End4.0020.0022.25inPannhard BarxyzFrame End2.0016.0022.00inAxle End5.00-16.0019.00in-2
Sorry that came out like crap.
 
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How about some action shots! This thing is night and day compared to the leaf spring suspension. Ride and handling are awesome.
Everybody should be linked.:D

Odin in the woods.jpg

Odin in the woods 1.jpg

Odin%20test%20drive%20climbing%20.jpg

Odin%20test%20drive%20Roosting%20A.jpg

Odin%20test%20drive%20starting%20to%20climb.jpg
 
That was the shakedown run. I did get some air once, but my wife was too slow with the camera. :whistle:I gonna take it out again today or tomorrow. We got rain so Im gonna thrash it through the mud!:D
 
ktmoutfront said:
Not totally. I will try to find the info for setting it up. The lower the link, the higher the roll center. A number of factors need to be looked at. I went from radius arms to a bottom 3 link. It changed a lot. Works great in the dirt. Sucks on the street.
Click to expand...

Did you find the info?
I talked to a few guys who said the opposite. That radius arms suck and 3 link was the way to go.
 
And another guy swears buy a 4 link and another says leave the leafs. Figure out what you want and do it with the truck first. If you are desert racing in Baja, IFS 2WD, 3 link. Wheeling any terrain, leave the leafs. Want it to look cool three link or 4 link it. I have seen a stock 54 Willy's in places I would not drive mine. Build what you want and enjoy it.

I have not had time to search. Will try this weekend.
 
I agree. Ive been veery happy with it so far.
Tested it in the woods and trails quite a few times and much better than the old suspension. Ive gone over everything, trackbar mount link and coil mounts and all looks good.
Now what should I do with the rear suspension...
 
odin said:
Did you find the info?
I talked to a few guys who said the opposite. That radius arms suck and 3 link was the way to go.
Click to expand...

It looks like your CG height is 37.00" and your roll center height is 20.68"

As those get further and further apart, the body/frame will actually flop around over the top of the suspension instead of sitting level above it. It's weird to see...

Here's an example of what appears to be a high CG coupled with a low roll center value:

JoshRiver.jpg


The body and frame are practically falling off of the suspension underneath. Look at the obstacle, it's not all that severe but as the weight is transferred the body motion becomes exaggerated.

I suspect this is what people complain about most with linked suspensions. Improperly set up links can definitely create this sort of characteristic (even though the truck pictured is using a 1/4-elliptic rear setup)


Food for thought. :thinking:



:usaflag:
 
OK. I do not get what is going on there. Look at the 1/2 leaf running from the axle forward. I have never seen that setup. I agree that there is massive geometry problems on that rig. It should not roll that bad with front leafs if the rear was set up correctly.
 
ktmoutfront said:
OK. I do not get what is going on there. Look at the 1/2 leaf running from the axle forward. I have never seen that setup. I agree that there is massive geometry problems on that rig. It should not roll that bad with front leafs if the rear was set up correctly.
Click to expand...
That's a 1/4 elliptic suspension. You've never seen that before? Here's another picture of that truck:
quarterliptic.jpg
 
I am new to the crawling thing. My expertise is in high speed desert racing. It has been a challenge to slow down.
 
Greg72 said:
It looks like your CG height is 37.00" and your roll center height is 20.68"



Food for thought. :thinking:



:usaflag:
Click to expand...


So how close should the CG and roll center height be??
Mine are about 16 inches apart. Too far?? Keep in mind.
I dont use my truck for rock crawling.
 
Greg72 said:
It looks like your CG height is 37.00" and your roll center height is 20.68"

As those get further and further apart, the body/frame will actually flop around over the top of the suspension instead of sitting level above it. It's weird to see...

Here's an example of what appears to be a high CG coupled with a low roll center value:

JoshRiver.jpg


The body and frame are practically falling off of the suspension underneath. Look at the obstacle, it's not all that severe but as the weight is transferred the body motion becomes exaggerated.

I suspect this is what people complain about most with linked suspensions. Improperly set up links can definitely create this sort of characteristic (even though the truck pictured is using a 1/4-elliptic rear setup)


Food for thought. :thinking:



:usaflag:
Click to expand...

This picture shows exactly why a well designed and engineered link suspension system is so expensive. There is a lot to correct design and engineering that you never see until you see a pic like the one above that shows what a suspension does that is not well thought out.

The hard parts of a good link suspension are the cheapest part of the build. The actual trial and error and shop work is what is so expensive. I bet I have close to a hundred hours in just trying different setups in the front and rear of my buggy. Cycle, adjust one thing cycle figure out what the numbers say, adjust a mount and try agian.

Don't be fooled by the fact that the ride is better than with the leaf springs or you don't have a lot of bumpsteer. There is a lot more than that to suspension design. I have watched rigs turn corners in parking lots and take a block after that for the body to level back out. That is poor design, it might ride well but handles like sh!t, and don't be fooled by the fact that you don't do rocks.

I have seen a few vehicles that were scary at best driving 25 MPH but could rock crawl or go through a mud pit with the best of them. Handling at speed is where a suspension design will tell you if it is good or bad.
 
I agree. Its a balance of compromises. My suspension is not flexible enough ( only about 8 inches of travel) to be considered a hardcore wheeler. Thats fine for me it handles well at 65+ highway speed and corners even better than before. Its stiff enough to keep body roll out but to stiff to be considered flexable.
I tried a few sets of springs in the front and moved the outer links to come to this compromise. A/S is about 105 percent which works well in the front.
The front springs are about 550 lbs. Which is better than the 350s I started out with.
 
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