why does my car rise when my weels are turned all the way?

[88jimmyoungowner]

my jimmy rises up whenever i turn m wheels all the way to the right or left. I ca nonly see it o nthe drivers side, but i imagine that it does on the left too. My tires are 31x10.50

16, 88 jimmy, kearning, but still need help

 

[JeremyK5]

Mine does too! But all I know is that it only does it once the tires stop turning from hitting the steering stops, and you keep turning the steering wheel. Maybe it is the steering joints pushing down on the axle a little when you put the extra force on the steering system. Anyone know for sure?

 

[RaisedK5]

Ya, basically, if you're turning left and the knuckles hit the stops but the box has more movement, the draglink will pull the axel forward flexing the spring, and pulling the front end up, similarly if you're turning right and hit the stops the draglink will push the axle back and the left corner of the truck will drop, this can also happen while stationary and turning the wheel, the resistance to turning the stationary tires causes the springs to deflect slightly causing that up and down motion.

Leland aka RaisedK5

"Of all the things I've lost, I think I miss my mind the most!"
"Are the voices in my head bothering you?

 

[Twiz]

RaisdK5 answerd part of the question. (a bit of a design-fluke)

The other part is an alignment deal:
This movement is a visual indication of Steering Axsis Inclination (SAI angle). If you look at the front axle, you will notice that the upper and lower ball-joints are not directly inline with each other. The upper ball-joint is set slighly inboard of the lower. This makes the steering knuckle (tire) turn in a arc that is not parallel to the ground. The high point of the arc is in the center, the low part of the arc is at both full left and full right turns against the bump stops. When the tire is turned to full left or right, it is following the down-werd slope of the arc- (this is what you are seeing) pushing up on the chasis. Gravity will try to pull the tires to the top of the arc (in the center).

The Steering Axis Inclination angle and the Positive Caster angle give the driver a "return to center" feel, and help increase cornering power.

I hope that was a good explination.


<font color=white>.</font color=white>Eric
<font color=white>.</font color=white>Twizted
<P ID="edit"><FONT class="small">Edited by Twiztid on 01/10/02 07:56 PM.</FONT></P>

 

[DieselDan]

Yep, what Twisted said, 'xcept I think he meant caster not camber. My '86 vette has got ALOT of caster. I think it specs at 7 degrees, more than twice what you would normally find in a car (later models went back to 4 degrees). If I turn the steering at a stop you can REALLY see the front end lean!

Real trucks don't have spark plugs!

 

[m j]

you dont think it has anything to do with the high scrub radius combined with that sai explaination?
basically perfect scrub radius would have the SAI intersection with the ground at the centre of the tire contact patch and would reduce that jacking

formerly 77chev
still a jerk though

 

[Triaged]

I am currious how much scrub radius trucks with large tires have...
If you use a large backspacing wheel and a tall tire it is possible to have neg. scrub radius. Maybe I'll measure it on mine sometime...
Do you know what stock is?

'71 Blazer CST w/ a 400sbc, 4" lift, 36" Supper Swampers, and alot of rust
<a target="_blank" href=http://community.webshots.com/user/triaged>See it Here </a>

 

[m j]

would love to get in on a data base like that.
I am running stock ford wheels and 39" tires so mu scrub is better then stock but i havent measured

formerly 77chev
still a jerk though

 

[Twiz]

DieselDan:

U R Right. I goofed. It is caster angle, not camber. OPPs. Good catch, thanks.. (I'll correct it, so it reads right)

By the way Dan. As far as I'm considerd. Vettes have the "perfect-feel" to them. A good-solid center. Heavy-handed, you know where you're at.

I got ahead of my-self.
With the combination of SAI and Caster, It would also, on the out-side tire, increase Camber gain (increase in negative Camber). That is why the tire looks tilted in, when the tire is at full-lock.


<font color=white>.</font color=white>Eric
<font color=white>.</font color=white>Twizted
<P ID="edit"><FONT class="small">Edited by Twiztid on 01/10/02 08:01 PM.</FONT></P>

 

[Twiz]

m.j.

scrub radius---!!!??!!?
What are you tring to do to me? (I'm seeing a pattern here)
Hay, while you're at it, can you "spell-check" my replies too?

It's cool, All-ways like to hear another point of view!

m j is kinda correct, allot of positive-off-set, would also increase the effects of the SAI/Caster deal. But since it is negative, the off-set would not have much of a infulence ~kinda~.

<font color=white>.</font color=white>Eric
<font color=white>.</font color=white>Twizted