I've recently went through some things on my 91 TA. Sportlines, Bilstein HDs, Adj tubular LCAs, LCARBs, Adj tubular PHB, Polygraphite bushings in the front a-arms, and some other misc crap. Had it all aligned (they were giving me crap for asking them to align the rear axle even though it's solid.

My question; In hard cornered the *** end likes to swing out pretty easily near the end of a turn. What causes this? How can it be corrected? And also, now I'm sure this is just sh*tty tires but it doesn't wheel hop, the tires just break loose. The LCAs are sitting in the second hole from the bottom figuring 2" drop = 2" LCA mounting? Should I put the LCAs in the lowest hole?

 

You now have too much rear swaybar. The lca angle is fine.

Either decrease the rear bar slightly in size, or lower your rear roll center (lower the axle side of panhard rod- Need to fab a bracket for this)

 

I should also note that I have the same exact problem only very slightly- I lack the raw HP so its not so much a problem for me. I get just a very slight bobble coming out of a high speed corner. My fix will be to lower my panhrd mount on the axle side. I intend to do this before I add a new motor. For now its so minor, I'm not bothering with it.


This happens only when the tires are hot and I am on the turn-out of a 45*-90* turn, after sitting neutral all the way through.

Brand new rubber and its not at all noticible.

 

do the LCAs have poly bushings?

if so it could be that bind from the poly bushings is causing too much roll resistance.

 

vsix,
Stock engine (with HSR, and t56) so is "raw hp" really that much of a concern? Should I be looking for a 22mm or something similar? What kind of bracket are you talking about?

Dewey,
Poly one side and rod end the other. What cures roll resistence?

 

with a rod end, you wont bind, so your ok there.

if your at a 24mm bar, 22 might be a good try. you might also try dropping down to the lower hole in the brackets, you will have more roll oversteer, but the extra forward traction might help. since chaning the mounting hole is free, you might give that a try, and see what you get.

 

What Dewey was refering to is if you take the same car with poly mounts vs. heim joints(rodends) the car with poly bushings will actually develop slightly higher spring rates (in a sence) because the body roll will strain more against the poly mounts than the rodends. That extra resistence can be the difference of an inside wheel lifting too much pressure off the ground or not when the car rolls outward through a corner.

I will have to find a few examples of the brackets I suggested- Let me first describe further how they help coming off the corner.
The first thing it does is lowers your rear roll center (this is the pivot point of the rear suspension that the body of the car roll on. If it is lowered, then there is more leverage to the left and right rolling axis onto the spring rates and swaybars- thus the need for higher rates (or in your case, to lower them slightly and cause a little more roll through leverage)

The added benefit you gain is the less steep angle from rear to front roll centers (this angle is called the roll axis) The lower the front than rear, the more weight transfer under braking- and vica versa. On the flip side(under acceleration) the lower the front than the rear, the less weight transfer onto the rear tires (meaning getting both planted)---------- So lower the roll center, level out more the roll axis, and thus have less weight transfer forward under braking, and more weight transfer under acceleration (two thumbs up).

I'll find a link on those brackets and some cricial info that pertains to installing them in the link (You will need to weld them very well).

 

Note: You ONLY need the bracket lowered on the axle side. Any bracket made for the body side of the panhard rod is unnessesary because of 1) the angle of panhard rod with a 2" drop, 2) dangerous because of the added length of the body side mount causes severe leverage-thus potential breakage.

https://www.thirdgen.org/techbb2/sho...hreadid=248685

 

Oh wow, thanks guys! This really helps. Welding shouldn't be an issue if it boils down to that, my best friend welded the LCARBs on and did an awesome job.

But I'll try dropping the LCAs one notch and see what that gives me. But it kind of sounds like that's more of a bandaid than a fix, is that right?

Vsix...you somehwat confused me...
Which would I be lowering to do what now? If the front roll center is lower than the rear I'd push more weight forward during hard braking? Is that good or bad? If I lowered the rear roll center more than the front I'd increase weight transfer? I'm not an all out drag racer (obviously or else I wouldn't have gotten the sportlines...) so however I can balance out my car...

Thanks again guys for explain this to a tard.

HOLY DAMN! $150 from unbalanced for PHB Relocation brackets?! That's crazy...

 

you want weight transfer to the rear under accell, it helps plant the tires coming out of a corner. you also want weight trasfer foward under braking, it helps the fronts get more grip which lets you apply more brake.

also, what does the LCA angle currently look like?

I do agree idealy dropping the rear roll height is the best move, you will solve the balance issue, and the better matched the roll heights are, the better the car is in transition. since the front roll height is determined by the a-arm angle, and the strut angle, the lowering springs in the car, make the front roll height drop significatly. whereas in the rear, it is determined by the point at which the PHB crosses the center centerline of the rear-end. so lowering the car does not have such a dramatic effect on the roll height.

 

What kind of an effect would the drop bracket axle side AND drop bracket body side have? (if the body sided one was welded sufficently?) Would that further improve? How can I tell where the rear roll center is in relation to the front? If the axle side isn't low enough then I can try getting the body side lower mount and dropping them both a bit?

 

we will see if i can explain this, it helps to have a picture.

Extend the angle from the Arm, also extend a line the is 90* from the upper stut mount. take the point where those two cross. you draw a line from that point, back to the center of the contact patch of tire, where it meets the ground. you need to do this for both sides of the car. your roll height is the point at which the lines drawn back to the tire, for each side of the car, cross.

 

Really its not neccesary to figure out where the roll centers are.

The important part is to figure how to move them form there existing points to help handling- meaning- should I raise or lower the front? should I raise or lower the rear. This is something you learn from having adjustments on your car and playing with them.
Most people don't ever drive a car with these types of adjustments to even know about them, and of course, our cars do not come with these type of adjustment from the factory- they have to be added.

Since you don't have provisions for adjusting the front or rear to begin with- the rear is the best place to start because the front get alot more timely and costly to do. This type of rear adjustment takes minutes to change once the provisions are there. The fronts can be changed, but any change will create a need for a new alignment (In otherwords- don't screw with the front roll center unless you know what you are doing)

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Now, to install adjusters on both sides of the panhard rod would be bad for a car lowered 2". The geometry of the panhard rod is at a severve angle enough when the car is lowered and you don't want to increase that angle any- You want it as close to parallel as possible. If you can install an adjuster just on the axle side with 4" of adjustment total from top mount hole to bottom hole- this will give you 2" of total adjustment on your rear roll center.

You don't need any more than 2" drop in the rear roll center, otherwise, your car will definately push way too hard into the corners and not want to turn (Now I'm not saying to drop it 2", I am saying to weld in provisions for a 2" drop max. and then gradually drop the roll center 1/2" increments at a time and the exit problem disappear without causing the turn-in to be affected)

Edit:Hot Damn, I'm off probation- see, sometimes a person can be rehabilitated.

 

For obvious reasons, Dean, you're still being watched... but you're doin' good

 

Is it because the roll center is somewhere in the middle of the PHB and if you lower the axle side 4" from it's origional position the middle of the PHB will be lowered 2"?

 

basicly yes, it all depends on exactly how the PHB is sitting currently. the rear roll center is the point that the PHB crosses the centerline of the rear axle.

As you can see in this diagram, the roll center height, is point A.