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Unread 06-25-2013, 10:15 PM   #31
matteo92065
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Originally Posted by J03_TJ View Post
... Not saying it couldn't be done, but not even a mediocre task for someone who does it every day like the Engineers who designed the system and obviously missed something or chose to ignore it.
Did they? Most all the DW cases are on modified Jeeps. Right?

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Unread 06-25-2013, 10:27 PM   #32
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Did they? Most all the DW cases are on modified Jeeps. Right?
No, i had my first taste of DW back in 05 after buying a brand new 04 SE in October of 04. The DW came on at about 12k miles with stock 29 inch tires on stock steel 15x7 rims.
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Unread 06-25-2013, 10:28 PM   #33
J03_TJ
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Originally Posted by matteo92065

Did they? Most all the DW cases are on modified Jeeps. Right?
I've seen the FSB(s) that address it on Dodge trucks, which I believe are the same front suspension design. Also thing the FSB they put out for XJs and TJs applies to stock vehicles? They usually don't put the FSBs out there to fix aftermarket part problems.
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Unread 06-25-2013, 10:29 PM   #34
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Originally Posted by mrblaine

I've chatted with Jim about this and they have some serious computer programs than can't even come up with a way to make sure it won't happen right out of the box. The best they can do is a close approximation and then go test it.
Is that the Jim from Nth Degree, can't recall if that was his name?
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Unread 06-25-2013, 10:33 PM   #35
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Is that the Jim from Nth Degree, can't recall if that was his name?
Yes, he was one of the suspension engineers at Jeep before he started Nth.
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Unread 06-25-2013, 10:43 PM   #36
J03_TJ
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Originally Posted by mrblaine

Yes, he was one of the suspension engineers at Jeep before he started Nth.
Yep, that's why I thought it might have been him. I would have liked to meet him. Closest I came was calling to talk to him back when nth was around to get some help on my (of all topics) DW. He was out in the hills testing one of his prototypes so I got to talk to his wife who told me to check my trackbar... Which was when I noticed how important it is to re-drill that axle end hole and not make it egg shaped. Oops.
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Unread 06-25-2013, 10:47 PM   #37
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Originally Posted by mrblaine View Post

Remember when I said "you know nothing"? This is precisely why. What I have not seen mentioned is what happens to tire inflation pressures at different temperatures and how that affects the spring rate of the tire. I have also not seen any mention of the resonant frequency change in the front suspension as the weight transfer happens going up or down hills.

When I say "you know nothing", it also means I know nothing. The more I learn about DW, the less I am convinced I know.

For every single point, there is an equally valid counterpoint which refutes the point making both null and void.
Did you say that to me, or just in general? I don't remember you saying it to me. Coming from almost anyone else, I would have been a bit miffed. However, I am familiar with your bedside manner and know you don't mean anything personal.

What I was implying by my post, but was too tired at the time to get into, was that the change in material properties with temperature changes the resonance of the system. I had DW problems a few years ago, and "fixed" it by replacing all my bushings with poly ones (I know, I know, but it was my street-only DD, and I just wanted a quick fix without really changing anything). The DW stopped, but still remained as a shimmy, only at 10-15 mph faster for the speed band where it showed up. Since shifting to poly really only changes the stiffness of the bushings without affecting the other components, this shows that this does play a role. Clearly not the only role, though, as the posts above show.
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Unread 06-25-2013, 10:49 PM   #38
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Which was when I noticed how important it is to re-drill that axle end hole and not make it egg shaped. Oops.
One of these days the correct understanding of that relationship, faying surfaces, clamping force, friction, bolt design, bolt tension, and sleeve diameter will finally take place.

Until then, the same myths will keep being repeated as truth and make about as much sense to some of us as the parable about the 4 blind guys describing an elephant.

There are 2 pieces of outstanding engineering on a stock TJ, one is the control arm and trackbar bolts, the second is the stock arms. Neither are understood very well by most.
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Unread 06-25-2013, 10:52 PM   #39
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Did you say that to me, or just in general? I don't remember you saying it to me. Coming from almost anyone else, I would have been a bit miffed. However, I am familiar with your bedside manner and know you don't mean anything personal.

What I was implying by my post, but was too tired at the time to get into, was that the change in material properties with temperature changes the resonance of the system. I had DW problems a few years ago, and "fixed" it by replacing all my bushings with poly ones (I know, I know, but it was my street-only DD, and I just wanted a quick fix without really changing anything). The DW stopped, but still remained as a shimmy, only at 10-15 mph faster for the speed band where it showed up. Since shifting to poly really only changes the stiffness of the bushings without affecting the other components, this shows that this does play a role. Clearly not the only role, though, as the posts above show.
You, I, We, as in, in general, nothing personal.

A note though, changing to poly only changes the stiffness if the poly is stiffer than what it replaced. Poly is not inherently stiffer.
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Unread 06-25-2013, 11:02 PM   #40
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Originally Posted by mrblaine

There are 2 pieces of outstanding engineering on a stock TJ, one is the control arm and trackbar bolts, the second is the stock arms. Neither are understood very well by most.
Awe, your gonna treat the curved rear springs like a step child?
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Unread 06-25-2013, 11:05 PM   #41
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Awe, your gonna treat the curved rear springs like a step child?
You should study one of those rear springs someday. It is phenomenally enlightening once you figure out what you are looking at.
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Unread 06-25-2013, 11:08 PM   #42
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You should study one of those rear springs someday. It is phenomenally enlightening once you figure out what you are looking at.
I think he felt as if you were leaving that part out when talking about good engineering on Chrysler part.
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Unread 06-25-2013, 11:13 PM   #43
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I think he felt as if you were leaving that part out when talking about good engineering on Chrysler part.
^ this. I honestly didn't know why they did it that way until I read about it on here. But he's right, probably would enjoy understanding the dynamics of it instead of just the cliff notes.
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Unread 06-25-2013, 11:14 PM   #44
mrblaine
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^ this. I honestly didn't know why they did it that way until I read about it on here. But he's right, probably would enjoy understanding the dynamics of it instead of just the cliff notes.
If the aftermarket were to employ the same spring manufacturing practices, they would be at least double what we pay now. Probably more.
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Unread 06-25-2013, 11:21 PM   #45
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J03_TJ, think about the stock spring and the way it sits, single rate spring. With the bow in it the leading edge of the spring is already more compressed than the back end and its already "harder". The back end of the spring is more relaxed and softer giving you impression of a dual rate spring. At least that's the way I understand it when I look at it.
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