Keeping the front end "down"/hill climbs/Instant Center... - Page 3 - JeepForum.com
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post #31 of 119 Old 12-20-2011, 02:40 PM Thread Starter
RaggedOleMan
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Revised the drawing to better reflect the COG. The top of the bell housing is where my estimated COG is. Also, thanks for the clarification on the AS line, I think I'm getting closer.

EDIT; So where in the revised image below, would the desirable location for the IC be, to maximize ascents/hill climbs and still maintain street friendly behavior?

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post #32 of 119 Old 12-20-2011, 03:04 PM Thread Starter
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Quote:
Originally Posted by Rescue13 View Post
I have very limited knowledge in this area. But isn't that what suck down winches are for?


Quote:
Originally Posted by mdm View Post
Three days and 40+ posts later and nobody has mentioned this:
http://www.stu-offroad.com/suspension/sdw/sdw-1.htm

Using the main winch was brought up but I've never been a fan of that method.
Post #8/page 1

I've located, saved and begun working with the Excel spreadsheet from Pirate, but so far I must be entering the data incorrectly because I can't get an answer. I'll keep working on it...until then...

What I'm hearing is that to achieve the objectives I'm after, regarding ascents/keeping the nose down, the ideal location for the IC would be somewhere along the yellow line, is this correct?
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post #33 of 119 Old 12-20-2011, 04:19 PM
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Originally Posted by RaggedOleMan View Post
Revised the drawing to better reflect the COG. The top of the bell housing is where my estimated COG is. Also, thanks for the clarification on the AS line, I think I'm getting closer.

EDIT; So where in the revised image below, would the desirable location for the IC be, to maximize ascents/hill climbs and still maintain street friendly behavior?
I have been following this thread and its way over my head, but I want to understand this. I am following the links and reading continously, over and over. There is so much to soak in.

I have a question looking at your diagram. Are you trying to keep your Rear Lower Control Arm Parallel with the 100% squat line?
Is this what helps to keep the rear tires on the ground rather than hopping? Or am I just out in left field some where?

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post #34 of 119 Old 12-20-2011, 04:22 PM
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Originally Posted by RaggedOleMan View Post

keeping the nose down, the ideal location for the IC would be somewhere along the yellow line, is this correct?
Not sure what concept that yellow line represents?

Quite simply, if the ic is above the 100% anti-squat line, it will create a down force on the front. If the ic is below the 100% anti-squat line it will help to unload the front.

Now work on the front suspension ic's. In the front you want the ic to fall below the 100% line. Just reverse the theory. You'll find it's the front suspension that's more responsible for the unloading than the rear.
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post #35 of 119 Old 12-20-2011, 04:44 PM
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Plus, keep in mind, that's not where your ic will be when on a hill. Your rear suspension will compress moving your ic lower and your front suspension will extend, moving the ic higher. Both unfavorable for maximum hill climbing traction.
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post #36 of 119 Old 12-20-2011, 05:05 PM Thread Starter
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Originally Posted by ftgiles View Post
Not sure what concept that yellow line represents?

Quite simply, if the ic is above the 100% anti-squat line, it will create a down force on the front. If the ic is below the 100% anti-squat line it will help to unload the front.

Now work on the front suspension ic's. In the front you want the ic to fall below the 100% line. Just reverse the theory. You'll find it's the front suspension that's more responsible for the unloading than the rear.


I plotted out the front in green. What surprised me is that a vertical line drawn through the frame mount centers of the rear control arms aligns almost perfectly with the intersection of the front control arm "extensions". What's this tell me/us?
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post #37 of 119 Old 12-20-2011, 05:25 PM
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Now with the concept of anti-squat in mind, imagine how much more favorable your instant centers were without any lift, regarding a hill climb.

That's but one example of how your lift messes up the geometry when the control arm lengths and/or frame attachment points stay the same.
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post #38 of 119 Old 12-20-2011, 05:35 PM Thread Starter
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Originally Posted by ftgiles View Post
Now with the concept of anti-squat in mind, imagine how much more favorable your instant centers were without any lift, regarding a hill climb.

That's but one example of how your lift messes up the geometry when the control arm lengths and/or frame attachment points stay the same.
I'm afraid I'm still working on digesting all of this. My aptitude for understanding mechanical engineering isn't as good as I want, but I'm trying...drawing my rig out helps me, but so far no cigar. Thanks a million for your patience with me you guys...
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post #39 of 119 Old 12-20-2011, 05:36 PM
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any ideas on how this relates on a stock Jeep? Just curious if Jeep engineers compensated for this in any way

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post #40 of 119 Old 12-20-2011, 05:39 PM
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Nothing against anyone.....but I feel like some of you, Ragged included, are psyching yourselves out. You're coming into this discussion thinking this is some uber-complex, difficult to understand concept when it's really not. Go take a couple shots, clear your head, go back to your high school and physics geometry classes and just visualize what's going on so that you can comprehend instead of just read.

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post #41 of 119 Old 12-20-2011, 05:40 PM
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any ideas on how this relates on a stock Jeep? Just curious if Jeep engineers compensated for this in any way
Umm . . Are you following along?

Quote:
Originally Posted by ftgiles View Post
Now with the concept of anti-squat in mind, imagine how much more favorable your instant centers were without any lift, regarding a hill climb.

That's but one example of how your lift messes up the geometry when the control arm lengths and/or frame attachment points stay the same.
Doesn't seem like it.

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post #42 of 119 Old 12-20-2011, 05:42 PM
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Originally Posted by ChaseB View Post
any ideas on how this relates on a stock Jeep? Just curious if Jeep engineers compensated for this in any way
Compensated for what? You can't just bolt on a link suspension setup without going through what this thread is discussing right now. The Jeep engineers combined convenient packaging, cost savings, and good geometry for the stock Jeep. Stock TJ suspension can climb steep hills like a billy goat. Once you go up, you raise the instant centers and completely change the behavior of the suspension. In order to get back to a great-climbing Jeep with favorable squat characteristics, you really need to chop off all the mounts and start over. While you're at it, build some ground clearance into the equation.

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post #43 of 119 Old 12-20-2011, 05:48 PM
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Originally Posted by Imped View Post
Nothing against anyone.....but I feel like some of you, Ragged included, are psyching yourselves out. You're coming into this discussion thinking this is some uber-complex, difficult to understand concept when it's really not. Go take a couple shots, clear your head, go back to your high school and physics geometry classes and just visualize what's going on so that you can comprehend instead of just read.
Problem is I failed all those classes, not all of us are engineers. Not saying this stuff is rocket science but it's not easily grasped either. That's why I'm staying on 31s for the TJ. Jeeping shouldn't be this complicated

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post #44 of 119 Old 12-20-2011, 06:06 PM
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Problem is I failed all those classes, not all of us are engineers. Not saying this stuff is rocket science but it's not easily grasped either. That's why I'm staying on 31s for the TJ. Jeeping shouldn't be this complicated
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.

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post #45 of 119 Old 12-20-2011, 06:11 PM
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Originally Posted by RaggedOleMan View Post
I'm afraid I'm still working on digesting all of this. My aptitude for understanding mechanical engineering isn't as good as I want, but I'm trying...drawing my rig out helps me, but so far no cigar. Thanks a million for your patience with me you guys...
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?
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