Front Wishbone Help

[Beezil]

Hey, I was looking through the most recient JP Mag and noticed that they put out a book called "How to Modify you Jeep Suspension and Chassis for Off Road". Anybody read this? I'm thinking it may be helpful.
Billy

I have it.

total waste of money.

if you want, I'll post pictures of me setting that book on fire to help illustrate how useless i think this book is.

anything JP publishes sux.....

cancel your subscription today.....

 

[JeepFreak21]

I have it.

total waste of money.

if you want, I'll post pictures of me setting that book on fire to help illustrate how useless i think this book is.

anything JP publishes sux.....

cancel your subscription today.....

:laugh2: Well, you just saved me $15. Thanks!
Billy

 

[JeepFreak21]

OK, did some more research which of course equals more questions...
I drew out some very basic designs so that I could get the concept of the archs made during articulation and the only way I could get the pinion to stay pointed at the t-case during articulation was to make the upper and lower arms the same lenth and have them mount right next to each other on the frame side. I noticed this is close to what Beezil has, but not what VintageSpeed and others have done. I would think that mounting the arms (that are the same length) at the same height on the frame, would create quite a bit of antidrive. Am I incorrect or does Beez just not care cuz his rig never sees the street? Anybody have any basic drawings to help me understand?
Thanks,
Billy

 

[Beezil]

my rig is not a street rig, however, its road manners are very kind.....it does not dive too much during heavy braking.

 

[JeepFreak21]

my rig is not a street rig, however, its road manners are very kind.....it does not dive too much during heavy braking.

Then what is effected by having 6" vertical seperation at the frame compared to none? It's gotta have some effects, right?
Billy

 

[Beezil]

Then what is effected by having 6" vertical seperation at the frame compared to none? It's gotta have some effects, right?
Billy

I have about 7 1/2" of vertical sepration at the axle, and about 4-ish at the frame end.....

designing the front became more of a challenge of fitment more than anything else.....I worked harder on just getting links to work with the constraints of the cherokee front end more than trying to mess around dialing in anti-dive and roll axis and that sort of thing......I worried about all that stuff when I went to design the rear......less junk in the way.

just keep researching, clicking on links, and reading......plenty of good por discussion, but you'll have to identify who the spobi-spewing idiots are....go into it slowly and carefully, and once you start, just go with your instincts and gut feelings.....

 

[JeepFreak21]

designing the front became more of a challenge of fitment more than anything else.....I worked harder on just getting links to work with the constraints of the cherokee front end more than trying to mess around dialing in anti-dive and roll axis and that sort of thing......I worried about all that stuff when I went to design the rear......less junk in the way.

That's exactly how I planned to go into it, but I've been stranded away from the jeep and stuck in the house for about a week now, so I'm stuck reading discussions instead of laying under the jeep to see what might work.
Thanks!
Billy

 

[Beezil]

try playing with string....

tie-off some lines between various points.

this will help you SEE the relationships better......beats paper.

 

[vintagespeed]

As Beez said, mock up a model it's a good start.

As for the anti-dive. If you're not running alot of lift (like 10") it probably wont be too much of a factor, the higher you are the more sketchy it will be.

Having your frame end links at the same height will make the suspension (AD wise) much like a radius arm setup. The links will be pulling/pushing at the same vertical plane.

If you want it to work & drive closer to stock then make your link positions closer to stock separation. The factory built in alot of link separation for a reason and the closer you are to that the more drivable it will be.

My link separation at the axle is a little more than Beez's but I only did that cause I'm running 38.5s and it was recommended to get closer to 8" with 38s.

-jb

 

[JeepFreak21]

I'm wondering if we can get Goatman's opinion (I know it's hard to pry out of him :laugh: ) along with everyone else on incorporating a wishbone upper to mid arm length lowers... maybe even mounted where Goat mounted his. I think I'll page him
Billy

 

[Goatman]

I'm wondering if we can get Goatman's opinion (I know it's hard to pry out of him :laugh: ) along with everyone else on incorporating a wishbone upper to mid arm length lowers... maybe even mounted where Goat mounted his. I think I'll page him
Billy

Oh my gawd, you want to drag my sorry ass into this discussion? I'm not much on all the book learnin' stuff, and I hardly ever wheel my rig.........

Now you made me read this whole thread and I've been staying away from it. To answer your question in PM, my lowers are 19.5" long. My upper is 16.5" long, and I have 7" of seperation between the lowers and uppers on both the axle and frame. I know it's not a part of this discussion, but FWIW, my track bar frame mount is 7.5" above the axle tube centerline, and the frame mount is 6" below the frame. The track bar is mounted just slightly higher than the upper arm on the axle. If I understand this stuff correctly, this gives me a better roll axis in the front.......and the blocks and flat springs give me a better roll axis in the back.........ahhh, didn't mean to get off the subject. :spin3:

I don't see that particular link design makes any difference to link length. In other words, you get generally the same characteristics from a longer or shorter arm regardless of the specific link design. I do believe you want your upper and lower links to be close to the same length. I hate to see that pic you posted of the triangulated 3 link with the wishbone upper, that design is so far from ideal that it's a shame for anyone to see it. The length of my arms is the result of where I wanted the mounts to be, considering the space I had to work with on the upper, and ground clearance on the lowers. I would like my upper arm to be an inch or two longer (or an inch lower which can't be done), but we live and learn. Getting the pinion to point where we want it to throughout the suspension cycle is something to plan for.

Back to the track bar for just a moment. If some thought is given to the track bar positioning, there just isn't anything negative about running one. It sure makes link design easier. I know Jim had problems, but he has bigger tires and more lift, and he's willing to drive on the street with hydro steering. A wishbone upper verses a track bar is purely owner preference......I don't see any performance advantage.

 

[Willis]

Yeah, I'd love to see some drawing also. And thanks for the insight Vintage!
Billy

Sorry, I don't have any digital drawings, nor do I have a scanner. My lowers mount between the stock LCA mounts and the x-member. I have it drawn so the LCA bolt is acutally mounted right at the bottom of the framerail. The upper is mounted behind and under the stock UCA mount by probably an inch(maybe more?). The upper I have tried to keep pretty parallel with the ground(about 5*), and it's axle mount is probably about an inch in front of the vertical axle center line. I have about 7" of separation at the axle and 3" at the body, but this may change when I build it. I have my drawing drawn with the front axle pushed forward about 1".

If you end up with shorter links, don't worry about it, Goatman has had great sucess with his mid arm setup, and to tell you the truth, mine will probably change many times before I actually build it (cause who knows how accurate my drawing is).

Steve

 

[JeepFreak21]

Sorry, I don't have any digital drawings, nor do I have a scanner. My lowers mount between the stock LCA mounts and the x-member. I have it drawn so the LCA bolt is acutally mounted right at the bottom of the framerail. The upper is mounted behind and under the stock UCA mount by probably an inch(maybe more?). The upper I have tried to keep pretty parallel with the ground(about 5*), and it's axle mount is probably about an inch in front of the vertical axle center line. I have about 7" of separation at the axle and 3" at the body, but this may change when I build it. I have my drawing drawn with the front axle pushed forward about 1".

If you end up with shorter links, don't worry about it, Goatman has had great sucess with his mid arm setup, and to tell you the truth, mine will probably change many times before I actually build it (cause who knows how accurate my drawing is).

Steve

Do you have any idea what length that makes your arms? And what degree the lowers sit at? I'm assuming the lowers will be inboard of the unibody rails, but do you know about how much?
Thanks,
Billy

 

[Willis]

Do you have any idea what length that makes your arms? And what degree the lowers sit at? I'm assuming the lowers will be inboard of the unibody rails, but do you know about how much?
Thanks,
Billy

It puts my lowers at about 17*. I plan on having about 7" of lift. The lowers will be mounted just in board of the frame. I have seen a couple cool ideas where the LCAs were mounted in a pocket "in" the framerail. May be more trouble than it's worth though. I have the LCAs drawn at 27" and UCAs at about 22". I may make my lowers shorter, but that will make them steeper.

After really playing with Anti-dive number, angles, percentages, etc, it seems like it's really not as important in the front as the rear.

Steve

 

[Ed A. Stevens]

With the unibody & lots of lift you've got problems getting the link angle within an acceptable range. I had to lower my LCAs 2.5" below the frame rail to get my AD (anti dive) axis back & below my CG, this is important if you want the front braking/accelleration lift to be correct, like anything there are compromises.

The other factor about my suspension that I didn't like was body roll, with the TB you have 2 roll axises, one at the frame mount & one at the axle mount. This makes your rig roll harder to one side than the other & just generally sucks on coilovers & 12" lift. With the new wishbone mounted 7" above the axletube I have raised my roll axis to a point where it's just below my CG, body roll is much much improved and it's now balanced side to side.

-jb

I have been too busy lately to read many threads, this one included, but jb has identified two issues that are often missed: the location of the IC in relation to the CG (it must be on the opposite side of the CG from the controlled axle), and assuring a predictable height for the roll axis (the goal of a level track bar, and a three link advantage with long travel).

I don't know how much PORing it took for you to find guidance on these two small issues, but I gave up trying to get across the reasoning for considering how these impact handling (the ususal POR bs filter was not effective on these issues). Good work.