I need some engineering feedback for springs

[madmanvillain]

So i'm finally getting around to getting funds for my lift, and im not trying to build my truck into anything for rock crawling or mudding, but i want to get as much usable lift as i can andmore ground clearance.
On my uncles farm, we have gone through a company for custom springs for some of our farm equipment, all leaf springs though. Now i dont know a whole lot about them besides the fact that we keep going back to them. I want to find out if they can for coil springs and how much they will be. Long back story but heres the goods.

I did some research on the OS and found a post that the roadie posted: http://forums.trailvoy.com/showthread.php?t=52217

So the springs im basing them on are (spring rate/check load/free length)

Front 70 n/mm / 8988 n / 408.3 mm
Rear 41.9 n/mm / 4692 n / 409 mm

I plan on going with the stiffer suspension so im getting some lift there judging by the informaton in this post viewtopic.php?f=15&t=158 but i want a little more so i was planning on adding about an inch and three quarters (45mm) to the free length of both the front and read springs and make them both 455mm long.

So here it is. Im not a fancy engineer and i dont know a whole lot about this kind of stuff, so should this be about right? I think (emphasis on think) this should give me just under 3 inches of usable lift. Let me know what you think and what i did wrong.

And if they dont do custom coil springs? Ill be talking to mark soon....

[The Roadie]

We have a couple of other engineers (I"m just electrical), but what you posted sounds right to me. You can also keep the free length the same and increase the diameter of the wire to increase the spring rate.

Last time I checked custom springs at two suppliers (one local), they were over $300 a pair (or was that each?) in small numbers. Icon coilovers started to look like better performance for the money because I wanted better shocks as well.

But the community would benefit a LOT from having another source of springs other than GM. We're sagging them through use at a much higher rate than I thought we ever would.

[madmanvillain]

Id be happy spending 400-600 or maybe a little more if im getting 3 inches of useable suspension. And if they work well for me obviously ill keep you all posted on everything. Also, im sure i can snag a front and rear spring somewhere if i had t give them one for measurments, but does anyone know diameters or other measurments to make it easier?

[Trail X]

The biggest thing to keep in mind is that the front shocks have a limited range. Say +/- 4 inches from the neutral zone (where the wheel rides stock). You need to somehow modify that range along with modifying where the wheel sits when loaded with the vehicle weight. If you do not modify the shock range of motion, you'll be topping out your suspension over the slightest of bumps.

As for wire diameter, the spring company should supply that because they know the spring rate you're looking for, and the springs material properties that they will use. It might not be the same spring material as the stock springs.

Remember for the front and rear springs that you will need to supply spring mean diameters to the company (they also change top to bottom for the fronts, and the rears neck-down on both ends).

Tell the spring company that you will be loading the front end with approximately 6939 N of force, and you'd like it to sit at (280mm + [your desired lift * 1/1.45 (lever arm factor) ] ). They should be able to reverse-engineer it given your desired spring rate.

Good luck, custom springs are a difficult endeavor to get just right.

[BSalty]

Good luck, custom springs are a difficult endeavor to get just right.

Agreed. I went down that road with a '95 Trans Am. Its not as easy as doing the math I found out.

But if we could get this and about 2 more things for the front suspension I would be a very happy camper to shell out the funds to fix the limitations without doing a SAS. The A arms/ball joint issue with some taller springs/shocks would be HUGE for my application.

[fishsticks]

IMO, you should be checking out the plethora of Jeep coils out there to see if there's something close to what you want already. You'll save a ton of money.

If and (probably) when I really start to monkey with modding the IFS, that's where I'm starting.

[madmanvillain]

Does anyone have a set to measure the spring mean diameter (this is what i was looking for, not the wire diameter, sorry for the lack of info)

[NC_IslandRunner]

Rear stock coil spring I don't have the front off to measure.
The best measurments I could get from my old stock springs, they had over 100,000 miles on the so they maye not be perfect.








Hope this helps, maybe some else can measure the stock front for you.

[Rob93]

IMO, you should be checking out the plethora of Jeep coils out there to see if there's something close to what you want already. You'll save a ton of money.

If and (probably) when I really start to monkey with modding the IFS, that's where I'm starting.

XJ Cherokee springs are VERY close to ours.. they might even work on the tb... I got bored one day and decided to see if my old trailblazer springs would lift my cherokee, and they were very close to fitting. If the inside diameter of the tb spring was about 1/4" larger it would have fit onto the xjs coil bucket.. With a little hammering it probably would have fit, I just wanted to be able to get the spring back off one day so I didnt do it lol

[SteveTB03]

If anybody wants I've got a full set of 4.5" lift springs for my ZJ just waiting for me to install them. And the ZJ springs are for a V8.

I wouldn't use XJ springs though as they are lighter than our TB's by a good amount. If anything would work the best it would be ZJ front (possibly rear also) springs for a V8.

The front springs of a ZJ are the same for the TJ's, XJ's and MJ's. The rears of the XJ and MJ's are obviously leafs but TJ's have a different rear coil spring setup than my ZJ.

Front springs on the left rears on the right.