Trailing arm Airbag rear suspension.. Input needed

deerefanatic said:
Got er down to 166%.... Got some measuring to do on the truck and we'll get some more accurate numbers. Tire size is pretty much for certain. Axle end heights for the links are pretty much certain as well. Just gotta figure frame end heights.
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wait, are you trying to make a double-triangulated 4-link or a parallel 'ladder bar' suspension? I thought you were going for the ladder bar setup? (which will require you to make all 4 bars parallel from the top view) Either way, you might want to drop the frame-side mounting point to decrease antisquat even more; and to be more realistic you will also need to spread the centerline distance between the axle mounting points... or do you intend to have the mounting points be actually ahead of the axle centerline?
 
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What's the ride height of the bag? It shows 12" extended, but wondered what the "sweet spot" was in the bag's height? Do you tow heavy or put heavy weight in the bed very often?
 
Hurley said:
wait, are you trying to make a double-triangulated 4-link or a parallel 'ladder bar' suspension? I thought you were going for the ladder bar setup? (which will require you to make all 4 bars parallel from the top view) Either way, you might want to drop the frame-side mounting point to decrease antisquat even more; and to be more realistic you will also need to spread the centerline distance between the axle mounting points... or do you intend to have the mounting points be actually ahead of the axle centerline?
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here's kind of a simplified drawing of the proposed setup. Their will actually only be one "link" in the whole system. It will be a sqare tube stock about 6" tall over the axle, that will be cut at an angle coming basically to a point at the pivot.. The beam will have a drop leg in the back to anchor the bag to. Does this make a little more sense?
 

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deerefanatic said:
here's kind of a simplified drawing of the proposed setup. Their will actually only be one "link" in the whole system. It will be a sqare tube stock about 6" tall over the axle, that will be cut at an angle coming basically to a point at the pivot.. The beam will have a drop leg in the back to anchor the bag to. Does this make a little more sense?
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Yes. However your sketch still indicates the pivot point being higher than the axle tube centerline
 
Yah, it would be if the bar was level....... So what are you saying? I'm assuming the pivot and the axle centerline need to be even or lower.......
 
I'd like to not have to mess with a 4 link.... I was thinking that, but just not wanting to mess with it......

Ok Hurley, I think we are talking at different levels.. The way I sketched it was the way I was thinking of doing it... BUT, if you're saying that the pivot point should be even with the axle centerline or even below it, then I'll try modding the design and go from there. That's why I'm here. I don't know jack about suspension design. :hehe:
 
Ok, so if I put the frame pivot point at 15", then I'm down to 124% antisquat.. And if I lengthen the beam lenght from 48" to 60", my antisquat is 99%. I would assume 100% is the number we're shooting for?
 
I would assume that this is solely for load supporting?

With only having a 2 link you will have to set a drive height on you pinion angle cause its going to get wicked bad pinion changes during suspension travel. Slow speeds it might not be that horrible, but on the highway it could be deadly.
 
Well, yes, I know that there will be pinion angle changes... Now, that being said, the angle will be setup so that it's correct at the desired ride height which will be maintained via a leveling valve (with a dump valve for hooking to trailers)

But, the question is, what will the angle change be during travel? That is a good question... I'm horrible at trig/algebra, but figuring a triangle movement (I know the movement is an arc, but close enough for our situation) that means with a 60" beam, from full compression to full extension is 8.5 degrees roughly. Which means pinion angle can go off by 4 degrees from center.... Now, the question is, anything within 2 degrees of perfect is considered fine for long term setup. So is 4 degrees gonna be the end of the world? Not trying to be a smart ass, just tryin' to learn.
 
deerefanatic said:
Ok, so if I put the frame pivot point at 15", then I'm down to 124% antisquat.. And if I lengthen the beam lenght from 48" to 60", my antisquat is 99%. I would assume 100% is the number we're shooting for?
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100% AS is thrown around in the offroad circles, I'm not sure where you need to be.... but I would say 100 and down would be decent for a street vehicle. (and yes, what you changed is what i was talking about)


you could get a cv joint put into the driveshaft to combat the pinion angle issue
 
Correct 2* is fine. However if you're cruising down the road at 75mph and it changes 4* that will cause excessive bind on the u joints and will spit that shaft right out the back. Ask me how I know...

Yea a 2pc shaft would help, but to be honest I hate my 2pc shaft with my air ride. It's a pain to get dialed in and is just another wear part.
 
Hmmm. Looks like 4 link is gonna be my only choice.... Prolly bag over axle 4 link... (bag behind axle seems to be rough on the link bars....)

As for 2 piece shaft, I already have that because of being 2wd and the looooong shaft that requires. Wonder about putting a CV on the rear section, but the pinion angle at the dif will still change with suspension travel, so the problem really doesn't change.
 
I've got mine set up in a 6 link. My bags ride on 2 rearward facing bars that attach with dogbones to the axle. I've never had a single problem towing with them. However with a 5th wheel set up you'd want them on or directly behind the axle.

Firestone made a kit a few years back that worked great. It was a 2 link with a panhard and "big rig" bags behind the axle on a mount similar to the one you drew up. The front of the link bars attached to the stock front leaf spring mounts.
 
1lowdiesel said:
I've got mine set up in a 6 link. My bags ride on 2 rearward facing bars that attach with dogbones to the axle. I've never had a single problem towing with them. However with a 5th wheel set up you'd want them on or directly behind the axle.

Firestone made a kit a few years back that worked great. It was a 2 link with a panhard and "big rig" bags behind the axle on a mount similar to the one you drew up. The front of the link bars attached to the stock front leaf spring mounts.
Click to expand...

So how did firestone deal with pinion angle changes with their setup?
 
Not sure to be honest. Here is one ****ty pic of it.

0104Dmax.jpg


Also this is a kit that a company Talon put together. Very wasy to make though

Talon Air Ride

Talon1.JPG


This was another one i did similar to what i was talking about with a bag in front, over or behind the axle.

DSC_6008.jpg


And this on my dmax

DSC_3607.jpg
 
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