greencactus3
where do i want to set the roll center for the front arms? i finally got to measuring them today, and at my current 4" ride height i have the roll center underground....
also, since the upper arm is angled to provide more dive i guess?
what point on that angled axis do i use to draw the 'front view' roll center?
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greencactus3
here it is currently
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hardline_42
Wow, green, if your CAD sketch is accurate then you have like zero bump travel on those lower arms. A good rule of thumb is you want the LBJ pivot to be about 3/4" to 1" BELOW the LCA cross-shaft centerline. That means you need to RAISE the front suspension w/ more spring. Once you hit the geometric "sweet spot" you can tweak the ride height within reason (using tall LBJ's etc.). Right now, with your LCA being at such an extreme upward angle you're defeating the camber gain benefits of raising the UCA angle.
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greencactus3
yup. thats what i figured too.
when i lowered the truck this far i had no idea what i was doing geometry wise.
soooo i should be raising it up till the LBJ pivot is .75~1" below the cross shaft centerline.
im not home now so i cant pull up the CAD sketch to see how much i gotta lift it up to do that, but i will later today.
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hardline_42
Even if you go with 1/2" difference between the two points you'd be ok. The idea is that you want the lower arm to push the bottom of the spindle out (away from the car) in bump while the UCA pulls it in. That's what camber gain is. If your LCA is already angled up past horizontal, it'll actually pull the bottom of the spindle towards the car which you don't want. You should try to set your ride height for optimum front geometry first. If the amount of drop isn't aesthetically acceptible, then you can try to lower the car using tall LBJ's or drop spindles if your wheels allow it (turns out mine don't).
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greencactus3
thanks and yup, thats the plan. i had to scrap the whole idea i had on the rear anyways, so im trying to find a 'correct' ride height from the front first. then ill try to get the rear to work with that.
tall LBJ... how much more than a regular BJ will that run me?
and how much taller than a regular one is it?
and which 'side' gets taller? the side connected to the arm or the side on the spindle?
i cant afford to get tall spindles now, so if taller BJs are available, that would be nice too.
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greencactus3
hmmm... looks like i gotta lift it 2.5" to get the .5" difference i want.
which would equate to 1" drop coils compared to stock
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hardline_42
That's a good plan. The suspension geometry should dictate your ride height, not the other way around.
Tall LBJ's are expensive to do right. The only CORRECT solution is to use the Howe tall LBJ. You can try to run truck ball-joints but they don't fit the stock spindle taper correctly (that's why they're "taller") and that's not safe for street use. The Howes run $85 a piece from here:
http://scandc.com/balljoints.htmIt's a lot of money but they are rebuiladble so it's more like a long term investment. You'll get about a 3/4" drop while making the spindle taller. Think of it as a 3/4" drop spindle with better geometry and no steering arm interference. I'm not sure what you mean by which 'side' gets taller but basically you're lifting the spindle up 3/4" without changing the spring height.
As far as tall spindles, unless you're referring to the AFX aluminum ones I wouldn't recommend them (B-body spindles). You get all of the benefits with a tall upper and lower BJ without the negatives.
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greencactus3
thanks for the link
but hmm 85 each?
and to get the full tall spindle effect i would want to swap all 4 bjs to these tall ones right?
since this is also my daily it obviously has to be safe and reliable, so hacking something together is not an option
the ball joint spacers that the lifted guys use.. what is it and will that belong in the 'hacked' category?
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hardline_42
Green, I went thru this exercise not too long ago. There just isn't a way to do it cheaply. Ball-joint spacers, mono-ball joints, truck BJ's, circle track BJ's are all definitely in the "hacked" category. There are also no stock balljoints for any other application that will give you what you want without being unsafe. Marcus at SC&C (the link I gave you) has the market pretty much cornered on these balljoints since Howe makes them to his specs so you're pretty much stuck paying the price. I swore there was a cheaper way and I fell flat on my face when Marcus shot down everyone of my alternatives w/ legitimate safety and performance issues having tried them all before.
You definitely want to change all 4 BJ's to the tall version to get the full benefit of the tall spindle geometry but it's ok to change them one set at a time if you need to (you'll just need one more wheel alignment that way).
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greencactus3
damn. glad you got to it before me then, saves me a lotta time.
i guess i gotta bump the budget up yet again.
thanks for the info!
