Why do the tjs lift a wheel?

[uglyota]

What is it about the suspension geometry that makes the TJs (like Creighton's and Lissa's) lift the front driver's side corner? Is it in the front suspension or the back? Creighton said it has something to do with the driveline rotation? Does anybody have a good explanation of this?

[AggieTJ2007]

I think it is the short arms, combined with driveshaft rotation. I just know that without a rear swaybar because the link is broken, I can lift the front driverside tire on the street if I make a sharp left turn from a full stop. I know cause I did it today infront of lupos and and some people looked at me real funny

[J Cooper]

how does a posi-trac in a plymouth work? they just do....

[TxCruzr]

how does a posi-trac in a plymouth work? they just do....

:gigem:


When the vehicle starts moving and torque from the motor is applied it travels down the frame towards the rear. If you notice when big muscle cars (not ricers) take off the right rear corner squats down. The same thing is happening but just not as big since jeepys have tinyer motor. So in turn it is pulling up on the left front and combined with the short arms the tire is lifted. It doesn't do this stock since the arms geometry is set right but with a lift it is thrown out of wack.

[Fredo]

---self-edited------
apparently we can't joke in tech...since our tech is so serious and involved around here.

[uglyota]

I like the short arm answer, but could it be becuase of the short arms in the back, i.e. the antisquat caused by a high roll center from steep angles on the lowers?

[BMFScout]

I think it is mostly b/c TJ suspensions suck. I'm gonna drop anti-squat and roll center in here somewhere b/c I heard flem and St.John talking about it the other day, so it must be important. Oh yeah, and Herb Adams is the shiznit, or something. All I know for sure is that I did it one day in Lissa's jeep whilst turning back onto Hwy. 6 off the shoulder, and it did it "mondo" high. It must be something with the short wheelbase, high center of gravity, and the shnitty angle the midget connecting links are at. The other thing I was thinking about is a rear locker is going to make it want to go straight, while the front right tire digs into a left handed turn. I don't know anything for sure, Butkiss do you have any lifting problems with the longer links? I think they are the problem.

[TxCruzr]

it's because Jeeps blow monkey nuts!


-Greetings from work :flipoff2:

I'm suprised your computer at work will let you type that. I bet it has a filter to block out anything with "jeep" and "sucks" in the same sentence.

By switching over to longer arms and regaining the correct geometry you can get rid of the problem though. Another gimick by DamnLar Chrysler to give money back to the after market.

[bburris]

I could lift one of the front tires, but it was more fun to cut left turns really tight and pull the left rear up. I think the driveline torque coming down such a short wheelbase combined with short control arms being used at a non-stock lift height let things get a little twisted and lifted tires are the result.

I don't have the problem anymore...not sure why - must be because it doesn't run.

[Graystroke]

I'll take a stab: when you press the gas and turn left the jeep is wanting to go forward. the rear links in the rear are what the force presses on (how the drive force is transmitted to the frame)to make the jeep go forward right? so when you turn sharp left the body sways to the right. your rear links (on the left side) are more vertical and the drive force is now traveling up the link trying to tip the vehicle. this coupled w/ the front wheels turned left and probably less suspension travel makes the front stay put (from going straight forward) and the front wheel lifts.

[savvyaggie]

yeah!!!

[uglyota]

I think I'll just make sure my lowers are as close to flat as I can get them, as much vert separation as I can get at the axle (prob only 8 or 10 inches tho) and at the frame (maybe 4 inches) and see what happens. Don't hold your breath, not gonna happen until I toast another spring pack

[TxCruzr]

Don't hold your breath, not gonna happen until I toast another spring pack

So pretty much after the next trip right? :flipoff2:

[uglyota]

nope, 2 trips...gonna build a burly spring pack this time, but I probably won't like it and will take out some leaves since I refuse to add weight to the back, so I'll have one trip with no rear spring breakage but no flex, then the one after will be another "bottle rocket" trip...whiz-pop!
I might be up for a new clutch (new to me, at least) after the next one tho! :D

[robertf03]

I think I'll just make sure my lowers are as close to flat as I can get them

why not, it worked for your shocks :flipoff2:

[AggieTJ2007]

I like grayson's explenation. I know that the lack ofa rear swaybar right now and having the front connected definetly helps in picking up the front tire. But it sure does make u turns interesting.

[stx4wheeler]

I know, i know, "cause its a jeep thing, and you wouldn't understand", but of course neither do they. :flipoff2: :laughing:

[uglyota]

back on topic, aside from longer, flatter rear links, the best solution to this would be a rear swaybar, like the currie anti-rock or whatever it's called? Longer front links shouldn't help, should they?

[TxCruzr]

back on topic, aside from longer, flatter rear links, the best solution to this would be a rear swaybar, like the currie anti-rock or whatever it's called? Longer front links shouldn't help, should they?

Longer links will return the geometry of the front suspension closer to factory. The longer links will have less of a nangle. Kind of like rigs with short rear links getting so much rear steer.

[uglyota]

okay how about swaybar tech? They mainly prevent body roll, right? Or do they also play some part in limiting how far the rear wheels can walk under you?

[robertf03]

I've spent several hours on the ****ter with just about every book Dallas public library has on the topic.... here's whats up

the longer flatter links is hillbilly talk for getting the angle set up right. You want the uppers and lowers to intersect at or above the plane parallel to the ground that the center of gravity is on or you get squat. Above the line the ass end jacks up. Lift a link suspension and the link angles go up and the 2 intersect higher above the center of gravity plane and the ass end jumps like a lifted TJ.

In none of these books was the phrase "vertical seperation" used. Thats a pirate 4x4 idiot term.

swaybar has nothing to do with locating the axle, it just increases the spring rate as the suspension compresses on one side of the vehicle while decreasing on the other side

[uglyota]

how do you know where your center of gravity is?
in hillbilly terms please :flipoff2:
and I understand vertical separation as being a convenient way to reduce stress on your links and their brackets.

[agjohn02]

[QUOTE=uglyota]how do you know where your center of gravity is?
in hillbilly terms please :flipoff2:
QUOTE]

draw a solidworks model with correct mass properties and it'll tell you. oh, hillbilly terms... jack it up in the middle where it'll balance, thats the longitudinal location. for verticle upsprung Cg id say a guess is in order.

[uglyota]

therein lies the problem. All the calculations and drawings in the world can't help unless you know where your "vertical unsprung" COG (the one Flem was talking about) is.

[robertf03]

expensive scales, weigh it, then raise one end and weigh it again. see what the weight difference is on one end, then cackulate it using a bunch of trig and vector stuff. There was an easy plug in formula I read awhile ago, don't remember it but its probably google-able.

[agjohn02]

oops, i meant verticle sprung Cg. you can assume the unsprung Cg is neglegible since the axles, tires, and wheels weigh roughly the same and that weight wont affect how the body moves.

[TxCruzr]

Look for the 4-link calculator on pirate...if you can't find it let me know and I'll hunt it up on my computer and send it to you.

[AggieTJ2007]

ive got it too

[StevenAg03]

take you shiznit to the scales at a place like a iron scrap yard...weight it on all fours. then you do several combos of lifting...i think its like lift one front tire about 2ft and weigh it...then the whole front end and do it and a couple more....then as robert said, there are some calculations involved to find your exact COG...its on pirate somewhere just not sure where. also its on a jeep site...ill see if i can find it.

[StevenAg03]

here is a site that will explain everything in good detail...i know its for jeeps but it will still work for your toyody

http://www.jeepaholics.com/tech/cog/

and here is a word writeup and a excel spreadsheet to do all the calulations...

excel spreadsheet
http://home.att.net/~email.id/COGROAss.xls

word doc
http://home.att.net/~email.id/COGROAdoc.doc

[uglyota]

thought of a good addition to this thread:
http://www.stu-offroad.com/images/vid/tracyroll.mpg

[bburris]

How is that a good addition?

[uglyota]

How is that a good addition?
maybe I should have said "appropriate"
was that roll not caused by an extreme case of what this thread is all about?
And I understand that the driver was okay...it's an Lhor guy, right?

[AggieTJ2007]

that roll was caused by not listening to the spotter, if you noticed the spotter say go right and the driver went left.

[uglyota]

well yes, that too, but the jeep still drove up under itself

[02JeepX]

And I understand that the driver was okay...it's an Lhor guy, right?

http://www.toysbytroy.com/Project_Files/Project_TracysJeep.htm

[TxCruzr]

When a jeep usually torques a wheel up due to the short arms and fubard suspension geometery, isn't it the drivers side tire that lifts?
That roll looks like it was just due to having a short wheelbase and the front suspension didn't have enough weight over it to keep it following the ground. That could happen to any one. I can lift a tire climbing stuff and I can guarantee its not from my coiled suspension :flipoff2:

[agjohn02]

thats definately from not listening to the spotter and being stupid

[bburris]

She drove up the side of a vertical wall while she was already off-camber on an uphill crevasse climb. That had nothing to do with poor suspension geometry and everything to do with female driving finesse... :D

[agjohn02]

and everything to do with female driving finesse... :D


BOOYAH!!!

[stx4wheeler]

do you think the new unlimited;s added wheel base will help this problem out? i would think it would help some, or is the same kickass suspension gonna screw it over too.

[TxCruzr]

Unlimited would probably walk it and so would a regular TJ. Just build it low and wide. Low COG will help climbing stuff like that. The whole TJ lifting a wheel thing had nothing to do with that roll.

[robertf03]

do you think the new unlimited;s added wheel base will help this problem out? i would think it would help some, or is the same kickass suspension gonna screw it over too.


they work just fine chief ;) . Did you read any of this thread? Its because they are lifted, not because the stock suspension sucks. It might not be as bad ass as radius arms :rolleyes: but it works just fine off the lot.

[uglyota]

it's much easier to make a long rig turn better than to make a short rig climb better

[uglyota]

Has anybody seen antisquat numbers for a stock tj?
how about for one with a 3.5" lift?
just wondering

[agjohn02]

yeah...

12, 16, 24, 9, 32, 27

[uglyota]

that wasn't even funny the first time

[AggieTJ2007]

they are about right. I knkow I can lift the rear end if I hold the brake and let out on the clutch, and it doesn't squat under hard acceleration.

The only real problem w/ the short arm TJ suspension when lifted is the roll-height. However because of the panhard it is only bad turning left. I can nail it in a sharp right turn and everything plants nicely, not so much going left

[uglyota]

so 100% or what? You've never calculated yours?

[AggieTJ2007]

never calculated, started to but didn't take measurements

[redcagepatrol]

so 100% or what? You've never calculated yours?
why do you care? how do you find the time to stir up some old threads this this??? R U going to get a Jeep? :)

[uglyota]

I was just thinking about link setups and about vehicles that I have personally seen perform and wanted to be able to associate what I have seen with number values.
and yes a thread on pirate got me thinking about it.

[AggieTJ2007]

it is because the roll height is in the wrong location. Scott explained it to me, I think you want a high roll center, dont' quote me on this

[Matt Conlee]

666, there now you have a number

[uglyota]

gee thanks

[bburris]

42. The answer is always 42.