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Originally posted by dirtrod:
<STRONG>Thats one of the great things about the 2 spring coil-over setups, U can change one or both spring rates in 15 min. my jeep weighs about 4100 equal ft/rear and I'm running 450 lb fronts and 350 lb rears, it could use a little more rear spring for baja work, maybe 350/400 would be best, but for rocks it works great, if I hammer it into a wall it will just start to bottom. It is too stiff to ramp well, but I never got too concerned about ramps anyway.</STRONG>
WOW!!! I'm running 350/130 up front and 350/110 in back, I totally goofed on the back and am switching to 350/350. But the front seems to work well with those 130's.
 

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Originally posted by steelman:
<STRONG>Ant,

i'm thinking the 14 inch travel for the front and external bypass for the rear 1/4 elliptic.
thanks
steelman</STRONG>
External bypass is only gonna help you at 100+mph, I wouldn't waste the $$
 

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Originally posted by dirtrod:
<STRONG>Thats one of the great things about the 2 spring coil-over setups, U can change one or both spring rates in 15 min. my jeep weighs about 4100 equal ft/rear and I'm running 450 lb fronts and 350 lb rears, it could use a little more rear spring for baja work, maybe 350/400 would be best, but for rocks it works great, if I hammer it into a wall it will just start to bottom. It is too stiff to ramp well, but I never got too concerned about ramps anyway.</STRONG>
when you stack two springs on top of each other the new rate is found byt the equation Rnew=1/(1/r1 + 1/r2) So your spring rate with two 450 Lb springs is 225 Lb/in and your rear is 175 Lb/in. My front coils are 225 Lb/in (BC Broncos softest EB coils) and They work great.
 

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I've got the 36"o/a x 15" travel doetsch, I don't have any experience with the others, so I can't compare. They told me the remotes are not needed unless you are racing hard and fast. They are pretty simple to work on, and the ride is fantastic. The only problems so far have been from hiem joints or rods giving away, and not the shocks fault. They are kinda noisey (spring noises) when flexing, but I can live with that.
 

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Originally posted by Ant:
<STRONG>
Originally posted by steelman:
[qb]Ant,

i'm thinking the 14 inch travel for the front and external bypass for the rear 1/4 elliptic.
thanks
steelman</STRONG>
External bypass is only gonna help you at 100+mph, I wouldn't waste the $$[/QB]
Ant,
oh they do so much more than that. granted they are better suited for faster stuff but..
if you get the 3 stage external you can set the first stage softer to take the small bumps and set the 2nd stage to control the mid secsion and rebound. the 3rd you can set so stiff they act like a internal bump stop. or you can set the 2nd stage for high rebound to stop the wheels fron comeing of the ground after a nice ramp at the local tuff truck race. i have watched the buggys that have them and with relativly light spring rates you can set the compression and rebound so high that it gives a soft on road ride but still will have the damping to give fether soft landings from 6 feet in the air. its also fun to take grandma out and hit the 8 inch parking lot cerbs at 50 MPH and not feel a thing. also going off the 4 foot high semi loading dock at about 50 is fun.

and all this adjustability with just a standard screw driver and a 5/8 wrench.

i agree they are big bucks but man would it be cool.
steelman

[ 07-11-2001: Message edited by: steelman ]
 

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Originally posted by steelman:
<STRONG>Ant,
oh they do so much more than that. granted they are better suited for faster stuff but..
if you get the 3 stage external you can set the first stage softer to take the small bumps and set the 2nd stage to control the mid secsion and rebound. the 3rd you can set so stiff they act like a internal bump stop. or you can set the 2nd stage for high rebound to stop the wheels fron comeing of the ground after a nice ramp at the local tuff truck race. i have watched the buggys that have them and with relativly light spring rates you can set the compression and rebound so high that it gives a soft on road ride but still will have the damping to give fether soft landings from 6 feet in the air. its also fun to take grandma out and hit the 8 inch parking lot cerbs at 50 MPH and not feel a thing. also going off the 4 foot high semi loading dock at about 50 is fun.

i agree they are big bucks but man would it be cool.
steelman</STRONG>
Good point, they would be neat to play with. but $600 for one... OUCH!!

<IMG SRC="smilies/eek.gif" border="0">
 

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It seems like everyone has there own different setups, doetsch said they don't like to see more that 50 lb/in difference between the top and bottom rates,so those 350/130 make me wonder what the deal is...my rear 350s try to bend sideways somewhat, and I can't see how a 130 could work at all (if they are based on the same idea/standards)...wtf
 

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Originally posted by Gordon:
<STRONG>when you stack two springs on top of each other the new rate is found byt the equation Rnew=1/(1/r1 + 1/r2) So your spring rate with two 450 Lb springs is 225 Lb/in and your rear is 175 Lb/in. My front coils are 225 Lb/in (BC Broncos softest EB coils) and They work great.</STRONG>
Excellent formula, that makes it much easier to figure out. But how do you add over-all length into the calculation?? Because isn't 12" of 225lb rate is gonna act different that 24" of 225lb rate to some extent?
 

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Originally posted by Gordon:
<STRONG>when you stack two springs on top of each other the new rate is found byt the equation Rnew=1/(1/r1 + 1/r2) So your spring rate with two 450 Lb springs is 225 Lb/in and your rear is 175 Lb/in. My front coils are 225 Lb/in (BC Broncos softest EB coils) and They work great.</STRONG>
I'm not questioning your math skills, but explain how this works effectively.

If you think about it from a strictly mechanical view, a 450lb spring is gonna need 450 lbs exerted on it to compress 1", whether it's another spring or a solid piece of metal pushing on it, it should not make a difference.
 

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Originally posted by dirtrod:
<STRONG>It seems like everyone has there own different setups, doetsch said they don't like to see more that 50 lb/in difference between the top and bottom rates,so those 350/130 make me wonder what the deal is...my rear 350s try to bend sideways somewhat, and I can't see how a 130 could work at all (if they are based on the same idea/standards)...wtf</STRONG>
I have no idea, I'm still trying to figure this stuff out myself.... dual rate, spring stops, limit straps, shock charge, spring track, spring angle... so many variables, my head is spinning!!!!
<IMG SRC="smilies/eyemouth.gif" border="0">
 

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Screw the math...All I know is that I can romp and stomp over bastetball sized rocks at 30 mph, leap over huge lumps at 50 mph, and creep along the top of slippery rocks at a crawl , I couldn't be happier.
 

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You want to be sure to throw in CG height, overall weight, roll center height, and maybe rotational moments of inertia into your list of variables to consider if you want to get really in depth.
As for the question on adding springs in series, the equation is right, not intuitive, but it's right. more on this later.
ok, I'm back. Look at the stacked springs this way: they don't really share the load, but the deflection in each spring adds up since they're stacked. Think of the 450/450 lb example above. Imagine each spring having equal amount of the load on it, so if it has 1000 lb of load on the stack (shock), they'll each move like they have the full 1000lbs on each spring. This amount is 1000/450=2.22 inches. But they're stacked, so the overall deflection for the stack is 2.22+2.22 = 4.44". The overall rate for the stack on the shock is found by dividing the load by the deflection. 1000/4.44 = 225 lb/in.

[ 07-11-2001: Message edited by: Stephen ]
 

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Ok let me explain this without Math you got two 400 lb per inch springs that means if I put my fat 200Lb ass on top of one of those springs it gets 1/2 inch shorter. If you had a 400lb guy sit on the spring (any volunteers) it would compress 1 inch. If I stacked those two springs on end and sat (my 200lbs) on them then each spring would compress 1/2 inch. So that means the total effective spring (made up of the two springs)would compress 2 inches. The same holds true if you mix the rates up. If you used a 130 and a 350 you get a combined spring rate of 95 lb/in If I was to sit on a 95 lb/in spring my 200lbs would compress it 2.1 inches
if I sat on a 130 Lb per inch spring my 200 lbs would compress it 1.54 inches, and if I sat on the 350 lb per inch spring I would compress it 0.56 inches If you add up those two deflections that is equal to the 2.1 inch deflection. OOps I guess that was math I used there.


Here is the reason you might choose to go with a 130 and a 350 instead of two 190 lb springs to get your 95 lb/in spring rate. With the two different rate coils when the 130 lb coil bottoms out your spring rate goes up to 350 lb/in This can be set up to happen a few inches before your suspension bottoms out which is good for go fast baja type stuff. (I know they dont make 190 lb/in springs but lets pretend OK)
 

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You want to be sure to throw in CG height, overall weight, roll center height, and maybe rotational moments of inertia into your list of variables to consider if you want to get really in depth.

Don't forget squat, anti-squat, unsprung rate, etc. etc. Link systems are COMPLICATED little buggers.

Randii
 

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You're right Randii, we haven't even started with the variables for the locating linkage. I don't remember all the ones you mentioned, but they should include driveshaft plunge and pinion angle control too. among others
 

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To really answer the original question here, I'd recommend a 3 link of some sort, assuming you're going to be running a crossover steering setup of some sort. A true 4 link is OK, but you have to build a good bit of compliance into the bushings in the arms for it to articulate, where a 3 link does not have that limitation. A 4 link front like jeep and dodge use is functionally equivalent to a radius arm, and radius arms have been dealt with pretty thoroughly in other posts.
You will run into some goofy stuff with a 3 leading link type suspension though. Assuming you run a 3 link similar to what the Allpro Toy ran (the one in Petersen's a while back) your caster angle will be controlled by the upper link located more to one side of the axle than the other. So you get different caster change depending on which way it articulates, or the body rolls. Other than that, I've been pretty happy with my 3 link. There are definitely issues with the coil stiffness, especially on my oinker 6600# K5, but the ride is awesome and the rest works ok and can be tuned in.
One general problem with any long travel frontend that has not been mentioned is how they lift on really steep hills. Some of that depends on rear suspension linkage goemetry, but any suspension will tend to unload on a hill, and they can get spooky when they have a lot of droop travel. The common cure seems to be a center limit strap on the front when running in that kind of terrain.
 

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Discussion Starter · #37 ·
Holy Sh_t! I think I unleashed more than I wanted to know. Mabye what I need to know is what the spring rate on my aerostar coils are so that I can somewhat match that with some front ones that will hopefully take some of the guess work out of finding a good coil. Course the front ones are going to need to be stiffer as there is more weight on the front end. Ok so I've been thinking 3 link designs and I am thinking of the kind that has two main arms about 5 feet long like you see on broncos, but when the arms get close to the axle, they branch off into two pieces, one going to the top of the axle tube and the other going to the bottom of the axle tube. That seems like it would conctrol axle rap/pinion roll more evenly on both sides of the axle housing. I wonder if I can get away with running bushings where the tube connects to the axle tubes and then running a big ass hiem joint somewhere inside the frame rails that can rotate. Any comments? I need to know about this panhard bar placement issue. Anyone got pics of a good set up? I am already running cross over steering and it is near the horizontal plane. Thanks for the discussion.
 

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Originally posted by steelman:
<STRONG>the 9000s are not 100% adjustable, you can not adjust the rebound. it never changes from the factiory only the compression.
</STRONG>
Sure does seem to make a difference in the rebound when you're trying to pull one to full extension by hand, setting one is easy and on five it's tough as hell.


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Originally posted by randii:
<STRONG>I run very soft coils on my TJ with the swaybars thrown in the trash can....used to be kinda spooky on those side hills, but I went with Rancho 9000's w/ in cab controls so I can firm up the down hill side and soften up the uphill side. And just leave 'em soft for all the other times...Ummm... so you run across sidehill sections FAST? It's not like you've charged 'em with air, they'll still just dampen dynamic movement... a long, slow lean will compress the downhill side of your rig still...

I'm with Camo. I haven't seen all that many all-coil rigs that work all that great off the ramp. Leaf springs are low tech, but generally more predictable.

Randii</STRONG>
It's not perfect, but it DOES help. Before I put the Rancho's on it would lean real bad, but now it's a lot better....not level at all, but better. And they adjust fast. Oh yea, and I never drive this beater anywhere fast <IMG SRC="smilies/csmile.gif" border="0">
 

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Originally posted by camo:
<STRONG>so tell me you guys how well do you like those soft coils up front on a off camber downhill? (with a big cliff on the side)

ya they flex like mad and handle high speed whoops like no other but i will trade those qualitys for stability.</STRONG>
my shit is more stable now than it ever was with leaves.just my truck tho not trying to say coils are the absolute end all of suspensions.but mine work really good.theyre 3.5 wildhorses in the nose 5.5s out back.the front is a 3 link with a panhard,the rear is just a 4 link.
 
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