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Spring Rates

M

mgreen84

NAXJA Forum User
Location
Georgia
Man 3 posts in one night...I'm full of questions tonight...

I was looking at OE replacement springs for XJ's at work and realized the following:
(I even contacted TRW's tech line and they had no answer)

1st- The part numbers for factory 4 door 4wd springs are cc780:
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=TRW&MfrPartNumber=CC780
Note the spring rate.......

2nd-The ZJ v8 4wd springs are cc782: (higher spring rate)
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=TRW&MfrPartNumber=CC782

3rd- The XJ 4wd 2 DOOR springs are cc784 (highest spring rate????)
http://www.partsamerica.com/ProductDetail.aspx?MfrCode=TRW&MfrPartNumber=CC784

So in essence if you walk in to a parts store and bought springs for a 2 door and put them on a 4 door you would get more lift than with zj springs???

any thoughts??
 
The spring rate is different but I wonder if the lenghth is the same?
 
We know that ZJ coils give lift, using the links above you can see that both free and loaded height are the same. The load rate on the zj coils is higher, thereby when we put them on an xj its gives some lift. The 2 door springs have an even higher load rate and spring rate. Therefore should lift even more than zj coils. Correct?? I used Jeep part numbers and crossed the OEM numbers against these results and the numbers cross to their respective coils, so the figures are correct. If zj coils give 1.5 to 2 inch, 2 door coils (part number cc784) should give 2.5 to 3 inches. I asked "Donnie" at Rome Dodge and Jeep to check the spring rates and they are correct, but he could not give me a reason for the increased load and spring rate on 2 door xj's?
 
wow... you got me coonfused on spring rates...
so the 2 door XJ's have better coils? SO... my 2 soor XJ cant really use ZJ coils... Hmmm... good info man.
 
Here's something else, rusty's has coils on sale for 100 for the 4/5" coils and they have a spring rate of 150lbs/ If you cut them down some you'll end up with a higher coil rate and less lift. For $100 bones you cant go wrong, I think I'm gonna get them and cut them down about 1.2" for a 4" lift and a coil rate of about 160lbs.
http://rustysoffroad.com/mm5/merchant.mvc?

To answer your question, the 2 door coils SHOULD likft the jeep if they have the same amout of coils. no one ever touched up on the coil rates when talking about swaps from the ZJ's, but thinking about it now, the 2 doors would be a better canidate for the 4 door's for a lift. This is all IF the coils are the same amouts. Also by the looks of it, the 4 door springs have a bar thinner diameter. but the inside diameter of the 4 door and ZJ's are the same, where was the 2 door is .04" smaller.
Hmmm....
time for some aftermarket coils since I can't upgrade like you 4 door guys!
 
Guys, i ordered all the coils that I mentioned in my original post yesterday and I am looking at them now. The springs all have the same amount of coils. The 2 door coils are longer by about 3/8 of an inch when compared to the zj coils. Using a micrometer the 2 door coils have a thicker, beefier spring. Therefore, I suppose a great lift idea would be to order 2 door coils from advance auto part number cc784, because they are definately superior to the zj springs!
 
Wish I had a way to get pics.............the xj spring is slightly shorter than the zj and the 2 door xj spring is slightly (3/8 inch) taller than the zj. So in order from shortest to tallest, xj-zj-2door
 
Regarding the part number cc784, see post #23:
http://www.naxja.org/forum/showthread.php?t=43632&page=2&highlight=cc784
Sorry, but it's not new info. For the record, I had these on my old 96 and they rode well and gave it about 1.5 to 2 inches.

As far as cutting down the rusty's coils, be advised that a brand new 4.5" coil may very well sit at 6" right out of the box when installed.
 
ok hold on, this question if for everyone out there reading this since not that many people reply... please reply.

I have a '98 XJ 2 door, so I can't get any more lift from any stock springs.

Does this mean I will not get the 4.5" lift from the 4.5" coils made by any aftermarket company? Are these coils made in spring rate AND length for a 4 door since its more common then the 2 door?
If so, I should be looking at 4" of lift with the 4.5" lift coils and also 4" of lift with the 3.5" coils for a ZJ, Correct? Sorry to highjack but I'm really REALLY boggled on this whole lift thing now.
 
More importantly: why are they different? What years are we talking about? What was the difference, if any, in ride height between the two when new? I don't remember there ever being a noticeable difference. It has been a few years since I saw a "new" XJ, however.

So what was the cost, measured lift, etc?
 
anyone wanna answer my question or help me out???
 
mgreen84 said:
I must be the only mind-screwed by this?!?
Click to expand...

You are over-thinking it. Buy a brand name lift kit and install it. The lift height you get is the lift height you get. Remember, your actual mileage may vary, batteries not included, etc.

If you want infinite adjustability, get ACOS.

If you want cheap get some 2" spacers, add Xj UpCountry coils for another 1 inch.
 
He's not everthinking it, he wants to know how its gonna ride. I do too!!!
 
interesting i wasnt aware there should be anything different for 2-4 doors. I have v8 zj coils and they were the same exact height as my stock coils and gave about 1.5-.75" lift. I have heard the upcountry coils give about the same lift or a little less, I didnt know there were any other factory options.
 
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