Suspension Geometry - Page 3 - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > General Technical Discussions > Advanced Jeep Tech > Suspension Geometry

Dan's Old as Dirt Birthday Sale!Premium LED Lighting by VISION X, Proudly sold at ROCKRIDGGEARSHADE Pocket Tops in stock and available at ROCKRIDGE

Reply
Unread 10-05-2012, 10:32 PM   #31
Bama_WJ
Web Wheeler
 
Bama_WJ's Avatar
2001 WJ 
 
Join Date: Sep 2007
Location: Owens Cross Roads, AL
Posts: 3,766
Here is a link to a WJ that is similar to what I'm going after, although I'd like to be a bit lower (depends on steering situation).

http://www.jeepforum.com/forum/f197/...ml#post8684855

I'm not all that concerned with what the COG is because I know it's going to be somewhat tall because it is a WJ.

__________________
Daniel
1 Ton WJ Build In Progress

The Daily: 2011 Chevy Cruze Eco - Trifecta tuned and 37+ MPG

Wife's Jeep: 2006 WK Overland - OME HD Lift, 265/70/17 BFG AT's, 1.25" SpiderTrax wheel spacers, 3" Gibson Cat-Back

North Alabama Jeep
42RE Vent Mod - Seal your transmission!
YouTube. - My Video Channel
Facebook - Wheeling Pictures/Videos
The Jeep Wave. Bringing it back.
Bama_WJ is offline   Reply With Quote
Unread 10-06-2012, 06:35 AM   #32
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,237
Quote:
Originally Posted by Bama_WJ View Post

1. I assume you go about measuring things with the Jeep at ride height? So I'd have to take the axles out, roll my new axles under and go from there with the Jeep somehow at my ride height (even though I have no idea what that will be)? Anyway to figure this out on stock suspension?
Ride height is ideal....but remember I said don't worry so much about the calculator? Set the rig up on jack stands at a good estimate of ride height and independently set the axles up on jack stands at their ride height (tires make this easy).
Quote:
Originally Posted by Bama_WJ View Post
2. How much is to much/not enough triangulation? Some setups I see have lower links at each end of the axle and meeting together at a new cross member behind the transfer case, in essence making a triangle. While the top links go from the frame to the center of the axle housing, making another clearly defined triangle.

On the other hand, I see others like this:

Like you can tell that it would eventually make a triangle (the top of the triangle being at the front axle), but it's not as defined as the previous setup I described earlier in my post. I'm basically talking about the two extremes.
I've never actually tested this, but it makes perfect sense....the minimum required triangulation to laterally constrain an axle is 45 degrees...so each mount is angled in at 22.5 degrees. My upper mounts are 25 degrees each coming to a total of 50 degrees.

As for single triangulated (uppers) vs. dual triangulated, good question and a good topic. I'm gonna discuss it from a TJ point of view to make it simple but the same concepts can apply to your rig. So if I were to build a dual triangulated setup instead, my lowers would have converged at a frame mounted crossmember. Almost undoubtedly, the lowers would be steeper because of this....great for clearance, but not as good for geometry. The main factor that I looked at was the roll center height. The higher that is, the harder it will be for your body to roll, which makes for better cornering....I like stability on and off the road so this is important to me. The roll center height is a function of triangulation and where that triangulation is located. If the uppers are triangulated more than the lowers, it'll be located higher. The more the lowers are triangulated, the lower the roll center height will be. So for example, look at my calc screen shot--if you change my lower frame y from where it's at now (17) to 6, my roll center height drops from 23" to 21" and my roll axis angle drops from 0 (neutral, nice) to -5 degrees, so I would experience more understeer.

When I decided on how I'd setup the suspension, I chose what gave me the best combination of clearance and geometry. My mounts don't hang down much, allow me to run a shallower lower link, and allow me to have a higher roll center height and near-perfect roll axis angle due to the slightly triangulated lowers. Minimal rear steer to speak of (due to the neutral roll axis angle) and it should even be better with the longer links. So, just relating rear steer to single triangulation is incorrect. You can make a 'single' triangulated setup do very well and in many cases, better. In fact, Bennettj13 has swapped his dual triangulated TNT kit out for a custom single triangulated setup. It should be better in every way possible. Hendrix did the same thing and much prefers the single tri setup. If you want to see a good example of a suspension that didn't follow the basic 'rules', go take a look at allgood73's build thread, especially the last few pages and my responses. The shop that built his suspension really screwed him and will need to redo it to give him good performance.
Quote:
Originally Posted by Bama_WJ View Post
3. A WJ isn't ideal for a LCOG setup (unless I cut the hell out of it). That brings me to the topic of trying to links parallel to the ground. Messing with the calculator, that variable obviously plays a big role in what numbers you get. I have to run a decent amount of lift (6"-7") to fit/stuff 37s, even with a fair amount of fender trimming. That being said, that kind of limits me as far as trying to keep links somewhat parallel to the ground. Any input on this would be appreciated.
Do what you can with the lowers and leave some adjustment in the uppers. Tuck the lowers up high on the axle and put them at a reasonable spot on the frame--not low enough that they'll be rock magnets but not so high than they're steep. How your lowers end up will determine how you set the mounts for the uppers. If the lowers are fairly steep, you'll want to angle the upper links back toward the axle a bit (instead of level) to compensate. Make sense? That's one good thing about the calc....you can make sense of some of these arbitrary concepts and they'll no longer be arbitrary.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is online now   Reply With Quote
Unread 10-06-2012, 07:31 AM   #33
55willystruck
Registered User
 
Join Date: Dec 2004
Location: East Wenatchee WA
Posts: 2,306
Imped-

I just want to say Thanks once again for taking the time to break this down in simple terms that are easy to grasp. You do that very well and much better, as well as much less words than I could ever hope to.

Seriously-Thanks, you have been a huge help for me with my build and whether I read and remember, or read and learn, I always enjoy the discussion and thoroughly appreciate the time.

With regards to what he mentioned above, I played with the calc a lot for that very reason. Due to my LJ driveshaft length being in the way, I built custom mini-crossmembers on each side sething like 4"-6" in on each side with lowers kicked out as far as I could. I forget exactly but think my uppers are roughly 27 degrees in and lowers something like 17 degrees out with this setup. This retained highest roll center with near neutral slightly negative -0.xx roll steer. I didn't like the understeer numbers if I came in any further to center, nor how much lower roll axis moved. This handles incredible for me, but it also meant notching and boxing my frame due to the greater up travel I wanted. Again, see what fits, what hits and what you're comfortable cutting or altering to make work. That will pretty much dictate what you can or can't get away with-within your comfort level anyway.

Best of luck,

Mike
55willystruck is offline   Reply With Quote
Unread 10-06-2012, 09:05 AM   #34
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,237
Now check this out....

These are somewhat rough but pretty accurate.

Stock TJ


Stock TJ +2" springs


Stock TJ +4" springs


See how quickly things go from perfectly fine and acceptable (stock) to out of hand? All you're really trying to do is account for the height difference between the frame and axle. In stock formation, they were much closer together, making the angles shallow. Once they're further apart, you've got to make changes if you want to retain the nice performance of the stock link geometry. I realize this is far and above what most noobies understand but it never fails.....the very first thing new owners want to do is "lift it", "jack it up", or whatever term they deem necessary. I always think to myself, "why do these guys want to totally screw up what already works so well?" Take care of the other junk that needs addressing first, like the horrendously low stock t-case skid, weak gas tank skid, weak steering linkage, locking diffs, etc. There are so many other ways to gain clearance and performance without screwing up the suspension.

Now that's not to say stock TJ's drive great, because they don't. They are vague, loose, and soft. But in terms of pure geometry, stock TJ's will climb walls like billy goats, much better than lifted TJ's with stock mounts. But at least with a welder and grinder one can cut the cake and eat it too.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is online now   Reply With Quote
Unread 10-06-2012, 09:53 AM   #35
Sundowner
Part-Time Swami
 
Sundowner's Avatar
2003 TJ Wrangler 
 
Join Date: May 2009
Location: The Republic of Dave
Posts: 6,162
Imped - thanks for the breakdown on the roll axis...that's a MUCH better clarification than I've found, to date. I was just looking at your setup last night and comparing it to the stock setup I drew in the link calculator...now it's all on the same screen.

Not to derail things, but: is it alright if a discussion on rear axle trusses happens at some point in this thread? Doesn't have to be now, of course, but since we seemed to be heading in that direction anyway I thought I'd bring it up. Front axle trusses would be welcome, too.
__________________
If it's worth doing, then it's worth overdoing.

The Republic of Dave: Bringing you the finest in simian testing supplies.

The build, the gear, and the mileage: The Wasteland Survival Guide
Sundowner is offline   Reply With Quote
Unread 10-06-2012, 10:02 AM   #36
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,237
I don't see why not......if it relates to suspension geometry, this seems to be a pretty good place for it.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is online now   Reply With Quote
Unread 10-06-2012, 02:16 PM   #37
Sundowner
Part-Time Swami
 
Sundowner's Avatar
2003 TJ Wrangler 
 
Join Date: May 2009
Location: The Republic of Dave
Posts: 6,162
Quote:
Originally Posted by Imped View Post
I don't see why not......if it relates to suspension geometry, this seems to be a pretty good place for it.
Well, my main concern is that a lot of the rear trusses essentially seem to be nothing more than a mounting point for the triangulated upper link ends; I can't see how they actually provide much structural reinforcement. Compared to the front trusses, they seem...well, a bit spindly. I know the front axle is seeing a lot more stress and that it's a somewhat weaker assembly to begin with, but I just can't figure out why - if you're going through the trouble of re-linking the rear and likely correcting spring/shock locations at the same time - you wouldn't want to put a Beef Supreme-strength truss in at the same time. What am I not comprehending, here? It seems that the further apart the link mounting points are on the axle housing - upper and lower, that is - the more twist and deflection the housing itself can experience.
__________________
If it's worth doing, then it's worth overdoing.

The Republic of Dave: Bringing you the finest in simian testing supplies.

The build, the gear, and the mileage: The Wasteland Survival Guide
Sundowner is offline   Reply With Quote
Unread 10-07-2012, 02:50 PM   #38
dmgiff
Registered User
1997 TJ Wrangler 
 
Join Date: May 2009
Location: las vegas
Posts: 929
I think there's a couple things I can add to this thread. First... http://www.jeepforum.com/forum/f9/wh...nking-1290791/

Secondly, one of you said something about not having a welder or not knowing if your novice welds will hold. Consider your welder part of the expense of the build. Yes, it can be expensive, but mine has paid for itself many times over. I bought a Lincoln 187 220 volt welder off craigslist for $450. I already had an oxy/acetylene setup that I inherited from my dad but had not used for 18 years. I have built my own rear tire swing out carrier, my own rock sliders, my own winch mount and my own front bumper. Not to mention my front and rear suspension now. Get a book on how to weld and practice. You can do it.

As far as an axle truss. My first truss when I 4-linked the rear was from Rock Slide Engineering. I turned it into a pretzel. I then started to realize exactly what Sundowner points out. A truss needs to be more than a place to mount your rear uppers. There are a few good ones out there, but I ended up buying a TnT. I'm very happy with it. It's pretty huge. Lots of weld surface on it.

Since making the above thread, I have finished my front. It's not perfect, but I'm happy with it. My rear setup was done not only with encouragement and advice from Imped; my front had other concerns. I recently decided I needed a v8 instead of the 4.0. I figured what better time to address the front suspension than with the engine out? And so it began. The only thing I'm not totally happy with is the angle of my front upper arms. They are not as flat as I would like due to clearance issues with the engine, exhaust and starter. I was not able to use the Poly brackets due to their size up front. My lowers all the way around are right at 23". That is because like Imped said, build what fits while knowing the prinicples. Don't get all hung up on the numbers. 23" lowers is what fit and seemed right to me.

A good example of not getting wrapped up in the numbers is my front uppers. There is a drastic difference in the numbers versus if I could have gotten them flatter. But driving it-it is way better than it was and at this point, I'm not sure how I could improve it. I'm very happy with the way it turned out.
dmgiff is offline   Reply With Quote
Unread 10-07-2012, 04:39 PM   #39
Bama_WJ
Web Wheeler
 
Bama_WJ's Avatar
2001 WJ 
 
Join Date: Sep 2007
Location: Owens Cross Roads, AL
Posts: 3,766
Thanks for laying all this out in laymans terms. I really appreciate it. I'm going to keep tabs on this thread until I actually have the time and space to work this stuff out.
__________________
Daniel
1 Ton WJ Build In Progress

The Daily: 2011 Chevy Cruze Eco - Trifecta tuned and 37+ MPG

Wife's Jeep: 2006 WK Overland - OME HD Lift, 265/70/17 BFG AT's, 1.25" SpiderTrax wheel spacers, 3" Gibson Cat-Back

North Alabama Jeep
42RE Vent Mod - Seal your transmission!
YouTube. - My Video Channel
Facebook - Wheeling Pictures/Videos
The Jeep Wave. Bringing it back.
Bama_WJ is offline   Reply With Quote
Unread 10-07-2012, 04:44 PM   #40
Imped
Web Wheeler
 
Imped's Avatar
2004 TJ Wrangler 
 
Join Date: Feb 2008
Location: Indianapolis
Posts: 19,237
Sorry for the delay, been trying to get this damn TJ out of my garage....

Old truss:


Trashed it here just minutes after this picture


You can see it pulled forward here. The picture doesn't do it justice, though.


New/current truss


Sorry for the crappy pictures. I don't foresee any issues with the truss. It's a simple/relatively lightweight 1/2" bridge welded to the tubes. The difference here is all of the extra support it receives from being tied into the diff cover. Good trusses can be done without tieing them into the center section but it takes a lot of material. This is a simple way to gain a lot of strength without using a bunch of material.
__________________
OlllllllO
Float Test Build
IndyORV
Imped is online now   Reply With Quote
Unread 10-07-2012, 08:38 PM   #41
cycleguy04
Registered User
 
Join Date: Aug 2011
Location: Federal Way, WA
Posts: 451
I like the trusses on ksilovich's thread. Very beefy and don't tie in to the diff cover. His thread is Jeffery 2.0.
__________________
[COLOR="Black"][FONT="Showcard Gothic"]'98 Wrangler Sahara - SOLD[/COLOR]

[COLOR="White"]'91 Ranger XLT 2WD - 4.0 V6, A4"hell"D, contemplating twin turbo 5.3[/COLOR]

[COLOR="Red"]'79 C10 Big Ten 2WD - 350, TH350, contemplating rebuilding to 355ci with supercharger and programmable EFI[/COLOR]

[COLOR="RoyalBlue"]'12 Subaru Forester (AKA: Arctic Cat) - 2.5, non-CVT, wife's, still begging her to let me get an exhaust system[/FONT][/COLOR]

[FONT="Showcard Gothic"][COLOR="Blue"]'01 SV650 - snorkelectomy, ebay slip-on, cam swap and re-jet in the near future [/COLOR][/FONT]
cycleguy04 is offline   Reply With Quote
Unread 10-07-2012, 09:23 PM   #42
55willystruck
Registered User
 
Join Date: Dec 2004
Location: East Wenatchee WA
Posts: 2,306
With the truss, what is "necessary", and what is "cosmetic"??? There is a pretty nice thread on Pirate with some "panty dropping rear axle truss's", or so it's titled something similar anyway... Lots of really cool stuff and some amazing work in many of them, but for the majority of us here, is all that necessary??? No it isn't.

Weight is a big deal and if it isn't needed, why add it?

My link bridge is very similar to Imped's above, with the exception being that mine runs from spring perch to spring perch in the rear. My front is shaped same as Impeds above, but clearanced for max up travel. My reason for that was I wanted to retain the entire factory rear brake hard lines in factory form and in factory position. The link bridge I made does just that. It hugs the diff pretty tight on top so as to remain low enough to run my 2.5" JJs up top and still get the up travel I wanted-though it also required tub work as well to get that. It is made from 3/8" plate that runs full 5" width across the top of the diff, then tapers down from the bends to roughly 3.5" at the axle, and is welded across a slightly greater length of weld surface to the tube from roughly axle centerline over the top at the angle of the bend itself. The factory brake lines fit underneath and run over the top of diff exactly as they did from the factory. In addition, I added a roughly 1" tall backing plate to the top which is tied through the diff cover ring, which I made from 1/4" plate and welded to the cover. Cover removes as factory with the additional work of removing 3 more bolts up top where it ties in. Greater strength for both tubes and diff, more than what is really needed, yet still relatively light weight in comparison to some of the bigger setups. Is it "panty dropping"? Not in the least, but it's more than enough to get the job done.

Best of Luck,

Mike
55willystruck is offline   Reply With Quote
Unread 10-08-2012, 01:28 PM   #43
Sundowner
Part-Time Swami
 
Sundowner's Avatar
2003 TJ Wrangler 
 
Join Date: May 2009
Location: The Republic of Dave
Posts: 6,162
I've wondered about how much the center section tie-in really added. I figured that it would be a welcome plane of strength for a bridge, but I also wasn't terribly sure how much the bridges themselves could take. I had roughly designed something in my head that vaguely resembled what Mike described, but wasn't sure how to make it all work. I got the idea from looking at the BTF unit and wondering if it might be better to spread the bridge's mounting points out a bit further on the tubes. The height looked like it would work out pretty well, though, assuming that the lower link's axle-end mounts were on a somewhat-horizontal plane with the axle's centerline; Imped's picture above seems to indicate the same thing.

I'll have to check out the Jeffrey 2.0 trusses...haven't seen those, yet. I'm checking out all my options before I start.
__________________
If it's worth doing, then it's worth overdoing.

The Republic of Dave: Bringing you the finest in simian testing supplies.

The build, the gear, and the mileage: The Wasteland Survival Guide
Sundowner is offline   Reply With Quote
Unread 10-08-2012, 03:57 PM   #44
spyder6
Got that Toyota chit
 
spyder6's Avatar
2010  
 
Join Date: Feb 2006
Location: Louisville, KY
Posts: 12,044
a little late to the game in this regard, but here is mine sporting both anti rocks. VERY stable


__________________
2010 Magnetic Toyota 4Runner Trail Teams

My builds: Bruiser and The Grey

|Forge Overland| or follow us on Facebook
spyder6 is offline   Reply With Quote
Unread 10-08-2012, 04:57 PM   #45
cycleguy04
Registered User
 
Join Date: Aug 2011
Location: Federal Way, WA
Posts: 451
I understand that this is a Dana 70, but the same principle can be applied to an 8.8. Of course I would have to leave room for spring perches. This is obviously a coilover setup. I couldn't imangine this truss having any issues...
img_1735_zpse0b95725.jpg  
__________________
[COLOR="Black"][FONT="Showcard Gothic"]'98 Wrangler Sahara - SOLD[/COLOR]

[COLOR="White"]'91 Ranger XLT 2WD - 4.0 V6, A4"hell"D, contemplating twin turbo 5.3[/COLOR]

[COLOR="Red"]'79 C10 Big Ten 2WD - 350, TH350, contemplating rebuilding to 355ci with supercharger and programmable EFI[/COLOR]

[COLOR="RoyalBlue"]'12 Subaru Forester (AKA: Arctic Cat) - 2.5, non-CVT, wife's, still begging her to let me get an exhaust system[/FONT][/COLOR]

[FONT="Showcard Gothic"][COLOR="Blue"]'01 SV650 - snorkelectomy, ebay slip-on, cam swap and re-jet in the near future [/COLOR][/FONT]
cycleguy04 is offline   Reply With Quote




Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.