ZJ coils vs BB - JeepForum.com
 
LinkBack Thread Tools
post #1 of 15 Old 05-01-2014, 09:05 AM Thread Starter
scox
Registered User
2003 TJ Wrangler 
 
Join Date: Sep 2011
Location: Surry
Posts: 18
ZJ coils vs BB

This is a 2 part question. I have read several threads on using the ZJ coils to lift my TJ. I have seen people claim anywhere from 1"-4" but I know that the differences can be attributed to the many variable such as engine size, extra weight, saggy springs, etc. I am hoping for 2-2.5". My questions are regarding this type of lift vs a 2" spacer lift:

1. Which would have more articulation
2. Which would have better ride quality

I know both would require new shocks and that would generate a whole new batch of questions...

scox is offline  
Sponsored Links
Advertisement
 
post #2 of 15 Old 05-01-2014, 09:36 AM
joe_jeep
Registered User
2005 LJ Wrangler 
 
Join Date: Mar 2006
Location: hazel park, mi
Posts: 6,504
Garage
i would expect about 2" of lift in the front with upcountry v8 zj springs.
what about the rear? you could put your tj front springs in the back for some lift.

shocks will determine how it rides.

glfwda #6624
2005 rubicon sahara lj #592
joe_jeep is offline  
post #3 of 15 Old 05-01-2014, 03:40 PM Thread Starter
scox
Registered User
2003 TJ Wrangler 
 
Join Date: Sep 2011
Location: Surry
Posts: 18
Quote:
Originally Posted by joe_jeep View Post
i would expect about 2" of lift in the front with upcountry v8 zj springs.
what about the rear? you could put your tj front springs in the back for some lift.

shocks will determine how it rides.

Yes, 2" is roughly what I am expecting. That is not the question. Question is regarding articulation and ride quality of the full coil lift from a ZJ vs a spacer on the stock coils. Assuming the same shocks on both which would be best?

Same height, same money, which has better articulation and which has better ride?
scox is offline  
 
post #4 of 15 Old 05-01-2014, 04:49 PM
horn5413
Registered User
2001 TJ Wrangler 
 
Join Date: Nov 2012
Location: Geneseo
Posts: 35
I bought a set of new springs online. they were zj fronts and BDS 2" in the rear. The front lifted about 2.5'. Would of been perfect but I have a 2.5l. I added 3/4" spacers in the rear and now it sits perfect.. The ride is good. I used ZONE gas shocks. I wish I nutted up for the Bilstiens, the ride would of been closer to stock.. No complaints for the cost though..

2001 TJ
horn5413 is offline  
post #5 of 15 Old 05-01-2014, 04:49 PM
joe_jeep
Registered User
2005 LJ Wrangler 
 
Join Date: Mar 2006
Location: hazel park, mi
Posts: 6,504
Garage
a longer spring is almost always better than a short spring and spacer everytime.
overcompression and coil bind are not good! that often happens with spacers.

glfwda #6624
2005 rubicon sahara lj #592
joe_jeep is offline  
post #6 of 15 Old 05-01-2014, 06:16 PM
LukeADukes
Registered User
2001 TJ Wrangler 
 
Join Date: Sep 2013
Location: Wayne
Posts: 559
The appropriate spring will be better then the pucks.

Always look both ways before crossing the stream.
LukeADukes is offline  
post #7 of 15 Old 05-01-2014, 06:52 PM
tyvanwie
Registered User
 
tyvanwie's Avatar
1993 XJ Cherokee 
 
Join Date: Sep 2012
Location: Boone
Posts: 9,932
Quote:
Originally Posted by scox

Yes, 2" is roughly what I am expecting. That is not the question. Question is regarding articulation and ride quality of the full coil lift from a ZJ vs a spacer on the stock coils. Assuming the same shocks on both which would be best?

Same height, same money, which has better articulation and which has better ride?
If you have the same shocks, why would the articulation be different between the two?
tyvanwie is offline  
post #8 of 15 Old 05-01-2014, 07:55 PM Thread Starter
scox
Registered User
2003 TJ Wrangler 
 
Join Date: Sep 2011
Location: Surry
Posts: 18
Quote:
Originally Posted by tyvanwie View Post
If you have the same shocks, why would the articulation be different between the two?
Having the same shocks sorta takes them out of the equation. That leaves the difference between the 2 as:
Lift 1---all coil spring with the ZJ coils
Lift 2---Spacer with stock spring.

My guess is that the longer coils would have more articulation but thought I would check with someone who had some experience with that.
scox is offline  
post #9 of 15 Old 05-01-2014, 07:56 PM Thread Starter
scox
Registered User
2003 TJ Wrangler 
 
Join Date: Sep 2011
Location: Surry
Posts: 18
Quote:
Originally Posted by joe_jeep View Post
a longer spring is almost always better than a short spring and spacer everytime.
overcompression and coil bind are not good! that often happens with spacers.
Thanks. That's the kinda info I was looking for.
scox is offline  
post #10 of 15 Old 05-01-2014, 08:01 PM
joe_jeep
Registered User
2005 LJ Wrangler 
 
Join Date: Mar 2006
Location: hazel park, mi
Posts: 6,504
Garage
Quote:
Originally Posted by tyvanwie View Post
If you have the same shocks, why would the articulation be different between the two?
that would depend if the shocks were the limiting factor.

overall you are probably right, the shocks probably do limit articulation.
that is not always the case though, longer springs are less likely to unseat.
longer springs are less likely to go into coil bind, than a shorter spring with a spacer.

assuming the spring rate is not completely wrong, i think longer is "usually" better.

i cant think of alot of situations that a 2" inch lift spring isnt better than a stock spring with a 2" spacer puck.

a properly set up suspension should not use shocks as bumpstops, or limit straps in a perfect world.
all to often that is not the case, they are used to limit travel.

in that case, you are correct, without a shock change, the travel will most likely be the same.

the other question is what do his springs do during flex?
do they coil bind?
do they unseat?
is their rate good?

glfwda #6624
2005 rubicon sahara lj #592
joe_jeep is offline  
post #11 of 15 Old 05-02-2014, 07:12 AM
biffgnar
Moderator
 
biffgnar's Avatar
2006 TJ Wrangler 
 
Join Date: May 2008
Location: Westchester, NY
Posts: 26,540
Quote:
Originally Posted by joe_jeep View Post

that would depend if the shocks were the limiting factor.

overall you are probably right, the shocks probably do limit articulation.
that is not always the case though, longer springs are less likely to unseat.
longer springs are less likely to go into coil bind, than a shorter spring with a spacer.

assuming the spring rate is not completely wrong, i think longer is "usually" better.

i cant think of alot of situations that a 2" inch lift spring isnt better than a stock spring with a 2" spacer puck.

a properly set up suspension should not use shocks as bumpstops, or limit straps in a perfect world.
all to often that is not the case, they are used to limit travel.

in that case, you are correct, without a shock change, the travel will most likely be the same.

the other question is what do his springs do during flex?
do they coil bind?
do they unseat?
is their rate good?
There is a difference between using a shock as a limit strap and the shock defining the limits of articulation. In almost all well done setups the amount of available travel in the shocks is the limit to articulation.
biffgnar is offline  
post #12 of 15 Old 05-02-2014, 09:43 AM
Pine_Cat
Web Wheeler
 
Pine_Cat's Avatar
2006 TJ Wrangler 
 
Join Date: Nov 2012
Location: Voorhees
Posts: 1,459
Quote:
Originally Posted by biffgnar View Post
In almost all well done setups the amount of available travel in the shocks is the limit to articulation.
Replacement springs are certainly better than a budget boost. The replacement springs will give you a higher rate so you can drive faster offroad. If you keep the factory springs, then you'll still be rocking to full compression when you're offroad.

Consider getting Moog springs for both front and back, so they'll be balanced on the freeway. I used Moog instead of OEM ZJ springs, so I can't tell you what rear springs would be balanced with OEM ZJ springs. I think some of the people who did the ZJ/ Crown Vic combo were disappointed to discover it was not balanced on the freeway.
Pine_Cat is offline  
post #13 of 15 Old 05-02-2014, 09:46 AM
biffgnar
Moderator
 
biffgnar's Avatar
2006 TJ Wrangler 
 
Join Date: May 2008
Location: Westchester, NY
Posts: 26,540
Quote:
Originally Posted by Pine_Cat View Post
Replacement springs are certainly better than a budget boost. The replacement springs will give you a higher rate so you can drive faster offroad. If you keep the factory springs, then you'll still be rocking to full compression when you're offroad.
All the hype on this site that occurs about spring rate is hilarious. Variations in springs that are made for TJ just aren't that great. When you are tuning a suspension spring rates that make a difference are multiples of each other, not 10-20%. That small a rate difference is swamped by shock setup as it relates to ride in a TJ.
biffgnar is offline  
post #14 of 15 Old 05-02-2014, 09:53 AM
tyvanwie
Registered User
 
tyvanwie's Avatar
1993 XJ Cherokee 
 
Join Date: Sep 2012
Location: Boone
Posts: 9,932
Quote:
Originally Posted by Pine_Cat

Replacement springs are certainly better than a budget boost. The replacement springs will give you a higher rate so you can drive faster offroad. If you keep the factory springs, then you'll still be rocking to full compression when you're offroad.

Consider getting Moog springs for both front and back, so they'll be balanced on the freeway. I used Moog instead of OEM ZJ springs, so I can't tell you what rear springs would be balanced with OEM ZJ springs. I think some of the people who did the ZJ/ Crown Vic combo were disappointed to discover it was not balanced on the freeway.
What do you mean not balanced?
tyvanwie is offline  
post #15 of 15 Old 05-03-2014, 01:12 PM
Pine_Cat
Web Wheeler
 
Pine_Cat's Avatar
2006 TJ Wrangler 
 
Join Date: Nov 2012
Location: Voorhees
Posts: 1,459
In a nutshell, rear springs and shocks need to be slightly firmer than fronts for the vehicle to have a stable response to bumps on the road. The front hits the bump first, so the rear needs to be a bit firmer to catch up.

It helps to have a test road where the bumps are evenly spaced, because that exaggerates the effect of unbalanced springs, such that you can feel the lack of balance even if your shocks are new. There's a test mile close to home on I-295, where the bumps are evenly spaced, so I got experience with balanced versus unbalanced springs. I can tell the difference between (1) factory-balanced springs/shocks (e.g., newer car), (2) close to factory-balanced springs/shocks (e.g., install Monroe/Tenneco shocks/struts, and you'll be close to factory-balanced, but not exactly), and (3) very unbalanced springs (e.g., worn out rear leaf packs at 90k miles).

When they design an OEM suspension, they decide on front firmness based on handling and comfort (e.g., "drop" testing, etc.), and then the rear is mathematically determined to be the right amount firmer than the front.

Instead of me just writing about it, here's what the AEV website says, since that's where I first learned about the concept:

". . . Since there are front and rear springs, the forward and rearward halves of the Jeep actually represent two spring-mass systems that must interact with each other. To understand the concept of frequency-based spring rates, think of a shock-less vehicle driving over a single speed-bump. When the front end hits the bump it starts to oscillate up and down at a certain speed. This is the front’s ride frequency. The rear encounters the same bump at a time delay determined by wheelbase and vehicle speed. The key is that the rear needs to react faster than the front so that the oscillations of the rear can catch up to the front in about one cycle (from ride height to some amount of ‘up’, then ‘down’, and back up to ride height). This is important because if the vehicle doesn’t naturally tend to level out quickly after a bump, the shocks will be overtaxed with trying to control body position/motion instead of their real purpose of simply getting rid of the oscillations.

"So to ensure the best possible combination of ride and handling, the front and rear spring rates must be derived to create the proper front and rear frequencies relative to one another. . . . To further enhance the spring’s ability to maintain proper frequencies under varying load conditions, a suspension engineer will design a progressive-rate spring (especially for the rear), which will keep the frequencies closer to constant over the expected load range."

I think people who tried the ZJ/ Crown Vic combo found the Crown Vic springs to be a bit too soft for the rear of a TJ that has OEM ZJ springs up front. There's probably a spring that's suitable for the rear of a TJ that's balanced with front OEM ZJ coils, but I haven't done the research/testing to know what it would be. To save time and money, I stopped looking at springs after I found my second replacement set to be balanced and otherwise satisfactory.

It's worth switching to dual-rate springs or progressive springs. You get to have a huge improvement to offroad performance without compromising ride quality. The spring rates published by Moog for my combo are more than 40% higher than rear OEM TJ springs, and more than 25% higher than front OEM TJ springs. With factory springs, I was always bouncing to full compression when offroad. With my current springs, I haven't touched the bumpstops yet, even though I'm now driving a lot faster when offroad. At ride height, my dual-rate springs have a very soft frequency, so I got best results with Bilstein 5100s. I like the combination of firm shocks and soft springs (at ride height).
Pine_Cat is offline  
Reply

Tags
bb , cheap , lift , zj

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.



Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome