Keeping the front end "down"/hill climbs/Instant Center... - Page 4 - JeepForum.com
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post #46 of 119 Old 12-20-2011, 06:17 PM
ChaseB
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Quote:
Originally Posted by Imped View Post
Fortunately for you, it appears you made straight A's in English class, which is more than I can say for a lot of people on this forum. But that's neither here nor there.

If you want to stay simple and have optimal climbing performance, stay as low as possible. Throw some good control arms on there, create clearance for your desired travel, flatten out the belly, and run it. If you start to understand this stuff over time then go get the saw zall and start over. It's amazing how much better things can get once you grasp these concepts.
Understanding that I have a lack of knowledge in the suspension department, I definitely want to keep it as simple, and as low as possible. The belly up is going to be a must for me. Ground clearance is really ridiculous with the 4 speed auto. I can't believe how low it hangs. What I want to avoid is the relentless hopping I experience in the CJ, that's spring over with reverse eye springs and a traction bar. Leaf springs and coil setups are completely different but hopping sucks either way


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post #47 of 119 Old 12-20-2011, 06:24 PM Thread Starter
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Originally Posted by jermeyg View Post
Hey Ragged, thanks for posting up the information that you have. I have been actually trying to map out what I think the stock TJ suspension would look like so this is interesting to me as well. I think there is something to learn fom all of this.

Well in the spirit of actually trying to understand the information you graciously provided, I noticed that from your information it looks like your uppers are longer than your lowers. Maybe I am wrong here but visually I think something is just a bit off. Perhaps it might change how things look?
My CA mounts are all in the stock locations. I've replaced the axle mount bushings on my front with Currie, and swapped out the factory front upper & lower arms with Currie adjustable as well. The rears are R.E., the uppers are adjustable and the lowers "fixed".

That said, Ive adjusted the uppers to set the pinion angle correct, perhaps that's where the discrepancy you've discovered lives and/or...in addition, the axle mount for the rear uppers is pretty darn close to directly in line with the center of the axle tube, and the frame mount is pretty much directly above the frame mount for the lowers. So, it's absolutely predictable that the rear uppers should be longer than the rear lowers. Am I wrong?




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post #48 of 119 Old 12-20-2011, 06:50 PM
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Originally Posted by RaggedOleMan View Post
My CA mounts are all in the stock locations. I've replaced the axle mount bushings on my front with Currie, and swapped out the factory front upper & lower arms with Currie adjustable as well. The rears are R.E., the uppers are adjustable and the lowers "fixed".

That said, Ive adjusted the uppers to set the pinion angle correct, perhaps that's where the discrepancy you've discovered lives and/or...in addition, the axle mount for the rear uppers is pretty darn close to directly in line with the center of the axle tube, and the frame mount is pretty much directly above the frame mount for the lowers. So, it's absolutely predictable that the rear uppers should be longer than the rear lowers. Am I wrong?




Hmm, interesting. Well from what I recall I believe the length of the TJ rears are around the 13.5" and the length of the lowers are 15.75". I believe what is missing here is the third axis which would help account for the length difference?
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post #49 of 119 Old 12-20-2011, 06:55 PM Thread Starter
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The lowers could be 15-3/4", it was dark when I measured mine for that drawing. However, the uppers have to be longer given the location of the mounts. When I went back to my drawing the center of bolt to center of bolt dim was 18". Maybe I bumped my empty head when I measured??? I'll double check in the daylight/tomorrow. By the way, where are you getting that 13.5" dimension for the rear uppers?
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post #50 of 119 Old 12-20-2011, 07:04 PM
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Originally Posted by RaggedOleMan View Post
The lowers could be 15-3/4", it was dark when I measured mine for that drawing. However, the uppers have to be longer given the location of the mounts. When I went back to my drawing the center of bolt to center of bolt dim was 18". Maybe I bumped my empty head when I measured??? I'll double check in the daylight/tomorrow. By the way, where are you getting that 13.5" dimension for the rear uppers?
The stock upper control rear arm is 13.5 eye to eye. Here is a link to Currie's control arm lengths which would be close to stock length. They are adjustable to about an inch.
http://www.currieenterprises.com/ins...trol_arms.html

I am betting one of your measurements might be a tad off giving the illusion of longer upper control arms.
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post #51 of 119 Old 12-20-2011, 07:11 PM
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Originally Posted by RaggedOleMan View Post
The lowers could be 15-3/4", it was dark when I measured mine for that drawing. However, the uppers have to be longer given the location of the mounts. When I went back to my drawing the center of bolt to center of bolt dim was 18". Maybe I bumped my empty head when I measured??? I'll double check in the daylight/tomorrow. By the way, where are you getting that 13.5" dimension for the rear uppers?
One more thing, I tried to graph what you have so far in the infamous 4 link calculator ( ) just to see what it says. Note: I expect there is some triangulation in the uppers and I didn't do that since it would only make the vector lengths of your upper control arms longer. I suspect there is also mild triangulation in the lowers as well.
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post #52 of 119 Old 12-20-2011, 07:27 PM Thread Starter
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Well, seems I earned another dose of humility. Turns out the frame mount of the rear arm is NOT in line with the lower. It was dark and I errored. Good job catching it! I corrected the drawing.

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post #53 of 119 Old 12-20-2011, 07:38 PM
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Originally Posted by RaggedOleMan View Post
Well, seems I earned another dose of humility. Turns out the frame mount of the rear arm is NOT in line with the lower. It was dark and I errored. Good job catching it! I corrected the drawing.

No worries! I appreciate you even taking the time to post up this information. I have small disputes with the lower control arms since it should be just a tad longer (about an 3/4").

I updated the 4link sheet with your change and also give the rear uppers some mild triangulation. I am hoping that we can see how this program lines up with what our reading says that a good suspension should do. Perhaps I will try the 4 link with the stock TJ setup to see also how that looks?


I hope you don't mind me adding to this thread. If you do then I will certainly but out.
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post #54 of 119 Old 12-20-2011, 07:45 PM Thread Starter
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(Revised)

I don't mind at all. The fact is I was having a fair amount of difficulty entering in the coordinates correctly into the Excel spreadsheet I got off Pirate. In the mean time I'm curious as t what you come up with. So, calculate a way my friend! Regarding the lowers at 15-3/4" go with it. My 15.06" dim might have fallen prey to the same gremlin that messed with the dim of the upper! That said, I think I'm the gremlin, and often my own worst enemy...when is this humility thing going to end, eh? But, I'm teachable, it just takes patience....
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post #55 of 119 Old 12-20-2011, 07:53 PM
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It would be curious to see how all this changes when dealing with an LJ. Considerings the majority of suspension kits out there are just a TJ setup slapped under a LJ... Just thinking out loud about it, the 100% AS line is going to be much flatter due to the extra wheelbase, hence wouldn't you want want less vertical seperation between the axle end control arm mounts to also flatten out those angles too... Possibly run high clearance CA axle mounts like what Clayton offers???
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post #56 of 119 Old 12-20-2011, 08:20 PM
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Originally Posted by RaggedOleMan View Post

(Revised)

I don't mind at all. The fact is I was having a fair amount of difficulty entering in the coordinates correctly into the Excel spreadsheet I got off Pirate. In the mean time I'm curious as t what you come up with. So, calculate a way my friend! Regarding the lowers at 15-3/4" go with it. My 15.06" dim might have fallen prey to the same gremlin that messed with the dim of the upper! That said, I think I'm the gremlin, and often my own worst enemy...when is this humility thing going to end, eh? But, I'm teachable, it just takes patience....
Okay, well I adjusted the 4link to have a lower length close to 16" which meant moving your frame mount horizontally (2D perpective) to the right. Trying using the data in the attached image. It should be close to your AutoCAD setup.


Quote:
Originally Posted by Idahobum View Post
It would be curious to see how all this changes when dealing with an LJ. Considerings the majority of suspension kits out there are just a TJ setup slapped under a LJ... Just thinking out loud about it, the 100% AS line is going to be much flatter due to the extra wheelbase, hence wouldn't you want want less vertical seperation between the axle end control arm mounts to also flatten out those angles too... Possibly run high clearance CA axle mounts like what Clayton offers???
Well, I am not sure what to say about the results. But here is Ragged's suspension at 104.5" Wheelbase. Someone can correct my work if its wrong.
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post #57 of 119 Old 12-20-2011, 08:24 PM
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Now look at the numbers and how terrible they are. Your lowers are way too low at the axle end, your AS and roll center are out the roof, and the roll axis is beyond excessive. Flatten out the lowers and go from there. I run my lower mount with the eye level with the center of the axle tube.

OlllllllO
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post #58 of 119 Old 12-20-2011, 08:36 PM
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Stock TJ Setup

Okay, so here is what hopefully is a close example of the TJ Suspension. I will let the experts tell us what it means.
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post #59 of 119 Old 12-20-2011, 08:41 PM
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Jermey, unless I'm going crazy the horizontal separation for the uppers is way off.

Idaho, download the calc and find out for yourself. Raising the lower mount at the axle = less separation = less angle = IC further out = less AS

For some reason, I can't open any of my old calc files, nor can I even re-download the program....otherwise, I'd post up my numbers. Excel works fine so I don't know.

OlllllllO
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post #60 of 119 Old 12-20-2011, 08:43 PM Thread Starter
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Originally Posted by Imped View Post
Now look at the numbers and how terrible they are. Your lowers are way too low at the axle end, your AS and roll center are out the roof, and the roll axis is beyond excessive. Flatten out the lowers and go from there. I run my lower mount with the eye level with the center of the axle tube.
So what your saying is that a tj, with a short arm lift, installed in the factory locations essentially ruins the geometry...I think I'll start by pulling the 1-1/4" pucks.

So, what/where should the numbers be, in your opinion, Imped?

EDIT; Here's the current image with dims;




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