The Polynth hybrid has begun - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 13 Old 11-01-2007, 07:30 PM Thread Starter
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The Polynth hybrid has begun

I got my new Poly Performance springs the other day and have been itching to try them out but work just kept getting in the way. So today about 5pm I finally made some time. So I opened up my boxes from Poly Performance and dug out a few tools and my 48" hi lift jack and proceeded to swap out my springs. I'm still waiting on my shocks from Poly Performance but I had to confirm a suspicion I had about the springs that came with my Nth prototype lift and how Jim had underestimated the weight of my reinforced JK.

First some notable difference in the springs. Poly Performance assured me that they made the calculations in their spring designs to accommodate all the extra steel I have on my JK. It will handle my monster winch all without making the ride like that of a really poor buck board going down the road. The way they accomplished this is by first correct load calculation plus by having progressive rate springs over linear rate springs. Now progressive rate springs are more expensive the design and fabricate so they cost more than the alternative. The benefit of course is you get a nice ride at all your work loads plus as you compress your springs they "stiffen" to reduce the compression. This gives you a good ride throughout your travel.

I was really looking forward to these springs as my Nth springs were linear rate and designed for a load about 1000 pounds less than my JK weighs in at.

So here is some driveway shots of the springs side by side for a comparison.

The springs arrived in excellent condition due to a nice packing job. Made me not wanting to get them dirty by putting them on my JK.



Here you can see the unloaded length differences. Despite the Poly Performance springs being longer than those I originally had from Nth, this only raised my back end up about an inch to make it a true 4.5" lift over stock.







Here you can see the extent of my tools I used to install the new springs. Well that and the wheel chocks, my 48" Hi-Lift and a little bottle jack.



The front springs.


The front Poly Performance springs were not a lot longer in comparison to the the Nth springs I had but I gained almost 2" of lift up front as the Nth springs really compressed under the load of the winch and winch bumper.



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post #2 of 13 Old 11-01-2007, 07:40 PM Thread Starter
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So here is the JK and how I performed the spring swap. I disconnected nothing but the front bump stop extensions. Everything else was done using jacks, gravity and the spring compressors.

It took me less than 2 hours, including two test drives to replace the springs.

The hardest part was re-attaching the passenger side bump stop extension as my hands don't fit in little tight spaces very easily.















I went for a test drive with just the rear springs and man that was nice. I could already tell I was more responsive on the steering input and the "wallow" was all but gone.

Once I did my test drive with all the springs replaced out. I was duly impressed. It seems as though Poly Performance did their homework and got the spring calculations down right.

This is making me wish I already had the new shocks from Poly Performance already so I could go test out a few whoop-de-doos!

If this is indicative of the Poly Performance lift kit and granted this is only a sampling, I will probably have no hesitation at all in recommending the Poly Performance lift kit for any one from the hard core rock hopper to the daily driver.

Good stuff guys!
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post #3 of 13 Old 11-01-2007, 10:56 PM
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Two questions...

What are your thoughts on the progresivley wound rear springs?

Also, do you use thier rear trackbar bracket?
http://www.polyperformance.com/shop/...cat=710&page=1

I was thinking of getting the one like the BDS style rear bracket but I have been wating to hear some response on this bracket.

BTW, thank you for the pictures and write up!
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post #4 of 13 Old 11-01-2007, 11:21 PM Thread Starter
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I have been running linear rear springs for about a year now and although they were under rated for the load, I am looking forward to a sense of increased stability as the spring rate increases with more compression. This should equate to a more secure and predictable feeling for varying loads as well as slowing down roll rates as one side compresses more in leans and side hills.

One thing that Poly Performance has done that is different than what I've seen and certainly different from Nth is that they may use the factory brackets to locate their parts, the parts themselves are stand alone products and don't require the factory parts to help in securing the part to, as in the case of the bracket you are looking at, the axle. This should allow anyone using a Poly Performance part or complete kit to use it with the confidence that weak factory welding isn't going to ruin your day as the Poly Performance part is holding on, on it's own.
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post #5 of 13 Old 11-02-2007, 06:25 AM
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Michael, if you get a chance can you take some measurements? I'd like to know how high your JK sits with these springs. Something like frame to ground, front and rear (and exactly where you took the measurements). As a reference could you also measure the height of your tires?

I've been considering the Poly springs and would like to know how they compare to my Superlift springs that I have right now.

Many thanks.
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post #6 of 13 Old 11-02-2007, 06:32 AM
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BTW See how straight your sway bar link is here?

Imagine it been a little further forward and then trying to come up the "wrong way" pushing the sway bar end forward instead of back and up. I'm pretty sure that is what happened to mine when it horseshoed.

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post #7 of 13 Old 11-02-2007, 08:42 AM Thread Starter
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Here you go Phil.

Btw, the sway bar was a concern for Jim and we did everything we could to try to get it to fully straighten out and we just couldn't do it. So in theory, I shouldn't ever taco my sway bar links. Well now that I've said it.....

I took some before and after measurements. Measuring from the pinch seam on the body that is to the rear, inside the well and nearest the tire, I got a 1.375 difference in height. I measured 34-3/4" before and 36-1/8" afterwards. There was a difference of 1/8" of an inch from one side to teh other but this remained constant throughout and is probably the 1/4 tank of gas that is on the passenger side.

I also measured some ground to bottom of frame measurements this morning for you. Up front and measuring from behind the sway bar and at the circle for the frame cross support up front I measure 27-1/2" from ground to bottom of the frame. In back and measuring from the location where the frame ends it's arc to clear the rear axle and returns to parallels to the ground I measure 27-3/4" from ground to the bottom of the frame.

My tires are BFG MT 37x12.5 on 17x9 wheels and this makes my tire height be 36" when measured for the ProComp speedo calibrator using a bubble level 3' straight edge and measuring tape.

HTH
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post #8 of 13 Old 11-02-2007, 11:46 AM
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Many thanks Michael.

My tires measure 34 7/8" so I lose 9/16" to you there. The figures in () are corrected for the tire difference.

Frame - Front
You: 27 1/2"
Me: 28 1/2" (29 1/16")

Frame - Rear
You: 27 3/4"
Me: 25 7/8" (26 7/16")

I have 1 3/4" spacers up front, which based on the rocker protection (measuring front and rear) makes my vehicle sit perfectly level. I do not have the spare on the back or an aftermarket bumper yet, so expect my rear to sit down a little after I do.

You've most probably got a little more weight up front than I do and my spacers obviously make a big difference.

Based on the measurements, I think I can expect my rear end to come up quite a bit with the Poly springs (but most probably sit back down to about where it is now after adding the spare and rear bumper), and the front to drop about an inch or so.

I'm either going to have to accept a drop at the front, or look for some 5.5" springs...
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post #9 of 13 Old 11-05-2007, 11:42 AM Thread Starter
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Your welcome Phil!

Wow, your frame heights are way different front and back compared to mine that sits almost level. I wonder if just by using the Poly Performance springs by them selves won't "straighten" you out? I only say that because I am baffled by the disparity you have and the need for extra bushings. Did you mix and match your "kit" or did you always have to use bushings etc to make your ride level? I know Jim at Nth did some compensation on spring calcs to make the JK ride level and I'd assume so did Poly Performance as is indicated from my install. Also noteworthy is that Poly Performance also indicates on the boxes which is front and which is rear springs which I am assuming is more than just load rating but also to accommodate different ride height.

Some comments I need to add not that I've ridden around some on my new Poly Performance springs. First off , WOW, since I have lost the "wallow" from the under rated springs, I can't believe how much more positive control I have over the direction of travel. I did a test where I filled my 37" tires to 36lbs of pressure which is a little stiff for everyday driving but eliminates a lot of sidewall flex. I took the JK out on the road and did some high speed maneuvering as well as some drastic or evasive styled driving challenges. Very impressive is how I would categorize the result. I never felt as though I was out of control nor did the JK fall out or rebound excessively after full compression side to side body roll maneuvers.

Additionally I can now open my swing out tire carrier with the 37" tire mounted and my JK does not lean with the weight extended out over the passenger side like I used to do with the old springs.

I can't wait to get my shocks on board so I can test out some wash board roads at various speeds and see if I can still maintain positive directional control while the springs and shocks are put through the test to see if they can keep positive contact on a varying surface.

Also note I have yet to experience any ESP issues. And this is with shocks that are most assuredly failing if not already toast.
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post #10 of 13 Old 11-05-2007, 12:02 PM
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Quote:
Originally Posted by MichaelW View Post
Wow, your frame heights are way different front and back compared to mine that sits almost level. I wonder if just by using the Poly Performance springs by them selves won't "straighten" you out? I only say that because I am baffled by the disparity you have and the need for extra bushings. Did you mix and match your "kit" or did you always have to use bushings etc to make your ride level?
I started with just a pure Superlift kit, but have slowly ended up removing most of it, and the spirngs will be about the last thing to go.

With no bumpers/winch etc, I had no spacers and it had a slight forward rake, by about 1". This was fine, as it meant when I loaded gear in, the vehicle didn't squat at the rear. But when I added the front bumper and winch it dropped another 3/4" or so at the front. So I added some 3/4" spacers.

I soon got bored of the forward rake and swapped the 3/4" spacers out for some 1 3/4" and it is not level. I'd actually like some of the rake back, and planned to do that when I added the rear bumper and spare to the back with some 1 3/4" spacers at the rear, which would bring the rear up about 1". But I've been waiting since January for a PJ rear bumper, and haven't done that yet.

The Superlift springs are good and provide for a great ride and they are really long when uncompressed, so they don't come lose when you are flexed. But I really want some 5.5" springs, although I may settle for the Poly 4.5" ones.
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post #11 of 13 Old 11-13-2007, 12:28 PM
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Just put the rear Poly 4.5" springs in, and as expected came up quite a bit at the rear, nearly 3" at the rear bumper. They will no doubt settle a little and I've only did a quick 20 mile test drive. Definitely an improvement over the Superlift springs (which were pretty good themselves).

may do the fronts this afternoon if I get time.

Superlift 4" compared to Poly 4.5"
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post #12 of 13 Old 11-14-2007, 10:59 AM
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Did the fronts last night. Dropped 2" at the front bumper, which is about what I expected. So gained 3" at the rear bumper, lost 2" at the front. At the rocker panels, I lost 1/2" at the front and gained nearly 1" at the rear. The vehicle definitely as a raked look now, but when I eventually get the rear bumper and spare on the back, it will sit down a little at the rear.

The springs ride great, soft enough to be comfortable, but firm enough to prevent wallowing. Now my front end is a little lower the steering feels a whole better too and the drive line angles are better.

As a side note, I was at nearly 6" at front and it was causing some issues. Without cutting and rotating the knuckles it would be hard to get any decent angles on pinion and caster with 6" of lift. The double cardan at the t-case was near it's limit. The drive shaft also made contact with the skid plate when drooped at the front. The drag link angle was too steep, a high steer kit is really needed with 6". 6" of lift is obviously possibly on the JK, but I'd say you need to deal with all these issues too, otherwise you'll have some heavy maintenance.
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post #13 of 13 Old 11-14-2007, 11:11 AM
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As a comparison, here's my measurements now, again corrected for tire size in ()

Frame - Front
You: 27 1/2"
Me: 27" (27 9/16")

Frame - Rear
You: 27 3/4"
Me: 28 3/4" (29 5/16")

Almost identical at the front, but 1 1/2" or so higher at the back, but I expect the 200+ lbs of bumper/tire to drop this down about an inch or so.
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