Suspension Geometry - Page 12 - JeepForum.com
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post #166 of 361 Old 11-24-2012, 03:39 PM
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Keep playing with the horizontal separation and you should be able to improve on that even more. Personally, I wouldn't be happy until it's within 1 deg.


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post #167 of 361 Old 11-24-2012, 10:12 PM
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Quote:
Originally Posted by Imped View Post
Keep playing with the horizontal separation and you should be able to improve on that even more. Personally, I wouldn't be happy until it's within 1 deg.
I'm the same way. I'll keep messing the numbers until I can hopefully get 0 deg.

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post #168 of 361 Old 11-26-2012, 06:46 AM
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Bama, I entered the numbers you had then fixed some stuff. You had the wrong rolling tire radius for the diameter and I'm betting the COG height and unsprung masses were a little off, but those don't effect the final outputs much. But the rolling tire radius does and you'll see I adjusted the vertical distance numbers to account for the difference. The key to getting the roll axis down was flattening out the links. The rig was sitting too high so I brought it down until things started working. If you can duplicate those numbers or get really close where it matters, that'll perform awesome.


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post #169 of 361 Old 11-26-2012, 09:24 AM
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Appreciate it. Hoping we can get the 35 pulled out soon and set the 44 back there to mock some stuff up with the parts coming in. Some of the horizontal seperation is going to be pretty fixed, like at the upper frame and axle end. I can really only play with the lowers at the axle end.

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post #170 of 361 Old 11-26-2012, 12:01 PM
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Right, and that's a big part of this stuff....recognizing where you're constrained vs. where you can make adjustments. Again, the biggest thing is getting those links close to flat. You want those lowers to have a shallow slope back to the axle and for the uppers to be flat or slightly sloping back to the axle. Generally, having a frame:axle vertical separation ratio of 75-80% produces nice results.

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post #171 of 361 Old 11-26-2012, 04:03 PM
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Just read this entire thread. Lots of good info. Finally pulled the trigger yesterday on the first bunch of parts for my 4 link. Artec truss and mounts. Ordering the JJs and sourcing the tube locally at the end of this week. Numbers are crunched and ready to go but im sure it will be tweaked a few times once its tested. Just trying to figure out why I waited till winter to do this... ahaha

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post #172 of 361 Old 11-26-2012, 04:41 PM Thread Starter
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Pulled apart the 8.8 over the weekend. I'm working with LSD and 3.73 which will have to do until I save up for a locker and gears.

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post #173 of 361 Old 11-26-2012, 06:02 PM
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Quote:
Originally Posted by Imped
Right, and that's a big part of this stuff....recognizing where you're constrained vs. where you can make adjustments. Again, the biggest thing is getting those links close to flat. You want those lowers to have a shallow slope back to the axle and for the uppers to be flat or slightly sloping back to the axle. Generally, having a frame:axle vertical separation ratio of 75-80% produces nice results.
75-80% of what? I've always seen you want at least like 7".

Daniel
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post #174 of 361 Old 11-27-2012, 05:55 AM
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Quote:
Originally Posted by hulud44 View Post
Just read this entire thread. Lots of good info. Finally pulled the trigger yesterday on the first bunch of parts for my 4 link. Artec truss and mounts. Ordering the JJs and sourcing the tube locally at the end of this week. Numbers are crunched and ready to go but im sure it will be tweaked a few times once its tested. Just trying to figure out why I waited till winter to do this... ahaha
Post up once you start so we can verify your numbers before you burn stuff in.
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Originally Posted by Bama_WJ View Post
75-80% of what? I've always seen you want at least like 7".
The frame-to-axle separation ratio. 6" at the frame, 8" at the axle = 75%. At least 7" where? The ratio matters more than the absolute value. I think I'm running 5.5" at the frame and about 6.5" at the axle so my recommendation is just a general suggestion and obviously also relies on your specific setup. And if you want to toss all numbers aside, tuck the lowers at the axle up as high as you can and keep the uppers low to the diff. The taller you are, the more important this is. The rest will take care of itself as long as you leave some adjustment at the frame.

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post #175 of 361 Old 11-27-2012, 08:13 AM
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I see now. Haven't seen the ratio before, just the seperation at the axle end for the most part. To be honest, I probably just skimmed right over it when reading some of the bigger threads about link design.

And yes, the uppers have 3 positions of adjustment at the frame end.

Daniel
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post #176 of 361 Old 12-02-2012, 06:18 PM
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http://www.4wheelunderground.com/Suspension-411.html

I found this doing some searching. Looks like it has some good details. I'm still trying to learn all this myself.

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post #177 of 361 Old 12-02-2012, 11:02 PM
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That's a GREAT link. I'm surprised I've never come across it before. That might be the best single article I've seen when it comes to explaining this stuff in plain terms and having it all on the same page.

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post #178 of 361 Old 12-03-2012, 01:37 AM
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So by looking at off the shelf suspension systems with this knowledge. Are any of them good? Obviously this will change for each rig but have any companies actually made theres as good as possible for the average rig or are the just whatever's cheapest/easiest for them while remaining acceptable. Just interested to know whether they are worth the money or just sound good.

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post #179 of 361 Old 12-03-2012, 06:50 AM
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Originally Posted by Motas View Post
So by looking at off the shelf suspension systems with this knowledge. Are any of them good? Obviously this will change for each rig but have any companies actually made theres as good as possible for the average rig or are the just whatever's cheapest/easiest for them while remaining acceptable. Just interested to know whether they are worth the money or just sound good.
In short, no. Can you change that fairly easily? Yes. The real problem is the axle side lower brackets. They are too low, which creates an excessively steep lower link. Clayton makes a solid setup and if you move the lower brackets up and get their arms with JJ's on both sides, that's about as good of an "off the shelf" kit as you can get. But at that point, you're not far from just doing a 'fully custom' setup as well--choose the brackets, build the arms, and burn it all up.

Arm length isn't as important as mount positioning.

My reasoning--similar results, different arm lengths. The constant? Nice mount positions.

Old


New


Compare that to a Rough Country/BDS-type long arm kit. What are those longer arms doing for you when your geometry is neglecting all of the basic rules?


Here's a much-improved Clayton-type setup on 4" springs. Decent frame positioning but the lower mounts still leave a lot to be desired in terms of clearance and their effect on the squat. Notice the high roll oversteer amount and borderline anti-squat amount. Flatter, slight-more triangulated lowers would fix both.

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post #180 of 361 Old 12-03-2012, 02:46 PM Thread Starter
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jwaller89, I've added that link to the first post of this thread. Thanks.

Imped, those examples really help visualize a comparison. Props, brotha.

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'12 Subaru Forester (AKA: Arctic Cat) - 2.5, non-CVT, wife's, still begging her to let me get an exhaust system


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