spring question/advice

[mudddog91]

Was just wanting some seriois advice!!!!!I am building a 1991 chevy shortbed and am fabbing the entire solid axle swap.Im using a 74 1ton as the donor truck,now I was planning on using the 52" Rear springs - 2 leaves in the front of my 1991.Then i was going to move the rear springs inboard and down.Is this a good idea or bad one?ANy benefits you see to doing it like this?Any thing i need to beware of?

 

[Stephen]

I've seen a couple trucks using the 52" rears, Ned Bacon did some articles on this swap several years ago in Fourwheeler, I'd look those up to save you some brain time. You'll want to use most of the rear pack in the front to carry the weight.
I'd recommend against moving the rear springs in, I know the perches are pretty wide but that's nice for stability and control. Since you have 63"-ish long leaves now, leave it alone except for a replacement spring and call it good.

 

[mudddog91]

Thanks for the advice but can i use my early model 14 bolt on the late model rear as the spring perches are probably way too wide! Do you think if i move the springs inboard they will be too soft and not offer enough control?Maybe add a few leaves to the pack to stiffen them up after moving inboard?

 

[70~K5]

It would be easier to move the perches on the axle than move the spring mounts on the frame.

 

[Scorpion]

Moving the springs inboard will allow the wheels to get more leverage on the springs and result in better articulation. This leverage will also cause the spring to twist a little more than normal. The determining factor should be what you want to use this truck for and build it in that direction. If you like the rocks, move 'em in a little. If you intend to do some highspeed baja type jumping, leave them outward as you will need the stability when you come crashing to the ground /forums/images/icons/wink.gif

 

[Stephen]

In general the wider the spring centers the better off you are. That allows you to run a softer spring for better ride quality and still have good flex. If you move them in, you get more flex/body roll and if you go to a stiffer spring to control it you get a rougher ride. So it does depend on a lot. How much weight are you going to have and how high will it be? If it's high and heavy you want the springs wide for sure.

 

[morphed86k10]

Which makes me wonder, why did GM put the rear springs on the K30 closer together when it was planned to carry a lot of weight?

 

[Leadfoot]

Look how close the backing plate is the the spring pack on a duelly pickup and ask yourself that same question. I'm still wondering how anybody bleeds the wheel cylinders AFTER installation (it can be done but is a PITA especially if you have big hands). I bleed them before installing them in the backing plate as long as the line has enough slack in them.
It was probably easier for them to put all perches for C/K 30's at the narrow width, instead of using two different setups for SRW vs. DRW. Maybe or maybe not, but it is the only thing I can think of /forums/images/icons/crazy.gif /forums/images/icons/confused.gif

 

[mudddog91]

Ok well i guess my question is will the 1974 14 bolt axle assy fit under the 1991 springs as is except for the perches?I was under the impression that it just will not fit with the springs being spaced that wide?I called boyce about a year ago and they told me it couldnt be done without moving the springs in or finding a wide style 14 bolt........Can someone clear this up for me?I dont have any problems right now with excessive body roll or slop with the springs spaced at the 73-87 style. /forums/images/icons/confused.gif

 

[Stephen]

We're kind of splitting hairs with the perch spacing, but there are definite effects from going narrow, the 73-87 width (42.5") isn't really a problem but it's going the narrow direction.
IIRC, Ned Bacon used a early 14FF in his conversion and from the mag story it seems like there was barely room for the perches on the housing. Only way to know for sure is to try it but i think you can make it work. If so that would be much easier than relocating the perches on the frame, unless you're doing major suspension work back there anyway.
My IFS sample truck isn't in an accessible location or I could check for you. It would take me a couple days.
I think the 1-ton perches being narrow has to do with the cab and chassis trucks specifically. The problem described by someone above is exactly the case, a "c&c" dually rear can barely clear anything near the spring. We can't run tire chains our my dad's c&c plow truck due to the proximity of tire and spring. an extra inch outboard on the spring wouldn't work at all, the tire wouldn't bolt on!

 

[mudddog91]

Well i think the rear will fit but now ive got to buy lift springs to match the solid axle swap and thats gonna make the rear really stiff being that the springs are so far outboard right? Thats why i was gonna move them inboard under the frame so itll provide lift and make it flex better.Am i thinking in the right direction?The lift springs spaced out that far on any axle will make it fairly stiff right?

 

[Stephen]

Your vertical travel/ride depends only on the springs, articulation depends on the width. We do have a flip kit for the 88-98 to keep the springs flat, you have 63-64" long springs that flex nicely anyway and most aftermarket lift springs in the shorter heights aren't too bad, depending on the weight of your rig of course. I'd move the perches on the axle and call it good.