Are there any disadvantages to having adjustable rear lower control arms? Are there any strength or handling comprimises made to allow for the adjustability? I'm looking at the Spohn units (poly bushing), but not sure if I want to go with adjustable or non-adjustable.

I plan on lowering the car and install an adjustable panhard bar at the same time. I'm not sure if I really need adjustability in the LCA's, but if there is no strength compremise over the non-adjustable ones, I'd rather have it to work with future upgrades.

I did a couple of searches, but didn't find anything that really addressed this comparison.

 

I've wondered the same thing for a long time. Maybe Steve will read this and post some knowledge?

 

Okay, speaking in general, the adjustable LCA's allow you to set them at the correct length when you adjust your pinion angle. You can watch as you adjust the pinion angle the carrier rotates as do the axle tubes and that compresses the bushings in your LCA's as it either stretches out or compresses the entire LCA assembly. By using adjustable LCA's you can return the LCA to a static position which is the best way to have them as then they respond as designed to the loads you place on them while driving.

 

Right on. You do not need adjustable ones if you run the stock torque arm. You should use them if you run an adjustable torque arm to set the correct pinion angle. Non adjustable torque arms can get away with the non adjustable LCA's.

 

Why would someone want an adjustable torque Arm over the non-adjustable?

 

To adjust the pinon angle. Once you've got the angle set to where you want it, the LCAs are adjusted to center the wheels in the wells.

 

I get the adjustable LCA's but what is the pinion angle?

Sorry if thats a dumb question...

 

But are there any disadvantages or weaknesses in the adjustable ones compared to the non-adjustable?



quote:
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Originally posted by ksrammstein
Why would someone want an adjustable torque Arm over the non-adjustable?
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Traction. The angle of the pinion is controlled by the torque arm. The stock torque arm forces the pinion to be directed toward the rear of the transmission, where an adjustable allows you to alter the angle.

 

Another point is that if you lower your car you can buy the adjustables LCA's instead of buying LCA Relocation brackets, as stated above it will allow the axle housing to sit back at it's "Static" position.
I figure I'm money ahead for having the adjustable aluminium LCA's; Unspring weight for one and I will never need the brackets when I lower the IROC, My 94 Z has them now, due to the Bilstien HD kit I installed and adjusted the axle to sit under the car square (adjustable PH Rod) and Adjustable LCA's to get the housing to stop binding on the torque arm bolts.

Another note, with Adjustable LCA's you can do a 4 wheel alignment, allowing the tracking (front to rear) to be, in line.

Tony

 

No. You still need the brackets. The adjustable LCA's only change the length of the LCA which changes the pinion angle. You need to reposition them with the brackets to match the stock geometry.

 

Pinion angle refers to the angle between the rearend pinion gear and the driveshaft. The pinion angle on 3rd gens is usually 1/2 degree positive. That means the pinion is pointing down in reference to the driveshaft. A pinion angle of 2 to 4 degrees usually results in the best traction. By changing the pinion angle you change the way the torque is applied to the rearend and how it results in weight transfer and axle wrap. All work together to make for better traction.

The LCA relocation brackets allow a return to stock geometry for a lowered car and allows for better geometry on non-lowered cars. That is one reason why you have two different settings on it. By putting them on you change how the suspenion reacts and increases the mechanical leverage imparted and again, more traction.

 

Not a flame


Every thing that I've done seems to make the car ride just as it did before and I still have the stock wheel base. All you did by putting the relocation bracket in was lengthen out the distance for the mounting bolt for the LCA to compensate for the not having adjustable LCA's to start with.
I don't have the longer LCA's pushing back on the housing and pulling the drive shaft out a little from the bind in the back for stock LCA's? You add the relocation brackets for this same purpose from what I can tell.
I just don't see one being better then the other. I feel that it is a waste of money with the relocation brackets, for road course. I understand there is more leverage but isn't the stock mount adequate?
My downward travel with the adjustable LCA is less, but I better not have the body that far away from the chassis when racing.
I would like a better explination of why you need the the "stock" LCA's. Please explan what geometry I've thrown off after going back and checking all of my wheelbase lengths, adjusting for square and installing new bumpstops.

 

Gixxer92, maybe I'm just not familiar with your car, but I don't understand exactly what you want to know. The stock LCA's have a lot of flex in them in the vertical and horizontal plane. That is why boxing them helps stiffen them and gives better handling and traction. Replacing them with aftermarket units further enhances this. The relocation brackets and changing the lift point on the chasis under acceleration. If you can imagine the LCA's continuing in a straight line, then the point the intersect the straight line from the rearend is where the lift point is on the car and is where it is trying to lift the car and transfer weight. The torque arm does most of this if everything is set correctly, but the LCA's do this as well. They have to work together to get the proper lift point for the maximum weight transfer and best traction. Many factors decide what is the best point for each car and typically for 3rd gens it's too far forward and the cars don't have the power or traction to get the proper leverage from this point. By lowering the rear mount of the LCA you move that point toward the back of the car where the car is better able to apply it.

I don't know if I answered your question or further confused you.

 

This should clear it all up...

The top picture is the stock LCA angle, looking at the side of the car. The middle picture is what happens as you go over bumps (the suspension compresses causing the rear-end to move up towards the body). When you lower a car, this is the position of the LCA all the time.

The bottom picture shows what relocation brackets do: it resets the LCA angle to its stock position when the car is lowered. The top hole on the bracket is bolted to the rear-end housing where the LCA usually mounts to, and the LCA is mounted to the bottom hole of the bracket.

 

cayse,
wow, i had an idea of what they were but that drawing and your explanation were very informational. to bad my exhaust wont clear with a lowered car or i would lower it. i might still get the brackets.

 

Solid proof that a picture is worth a thousand posts... uhh, words.

 

From Steve Spohns web site"The lower mount holes are placed in the arc pattern of the OEM length LCA. Therefore allowing a non-lowered F-Body to drop the rear LCA angle and NOT require a longer than OEM LCA."

This way you do not need an adjustable LCA to compensate for anything.

 

This only holds true if you do not have an adjustable torque arm, as stated earlier (and the brackets were welded on correctly).

As for the latter, occassionally some idiot shop mechanic will weld these brackets on wrong. I wish I knew how... it's pretty straightforward, but I've read it here once or twice. An adjustable LCA would correct this problem.

But if you have an adjustable torque arm, you need adjustable LCAs to align the rear-end correctly. In the top picture below, the rear end's "pinion angle" can be adjusted with an adjustable torque arm. As you can see in the bottom picture, this moves the LCA mounting point on the rear, requiring the need of adjustable LCAs to correct the geometry with the pinion angle adjusted.

 

Here's the picture:

 

This is a diagram of why you need adj LCAs when you have an adj TA. The top picture is a stock, non-adj torque arm. on the bottom, the torque arm is adjustable, allowing pinion angle to be changed. The torque arm is near the center of the car, by the driveshaft.

Understand this isn't to scale and the angles are somewhat exaggerated.

 

If at some period in time you were going to lower the car or had the need to change the pinion angle you can do it w/o having bought the relocation brackets and done it with the adjustable LCA's instead and been money ahead, because you have the freedom pf that adjustment. I think that unless your drag racing the car, the mount point that GM started on the housing is enough to hold the housing in place with little flex.
This may be a cheap way of thinking about it, but here is another thing to wonder,
If GM had a ride height that was less then what the third and fourth gen stock position is, wouldn't it have had been cheaper for them to add a little to the LCA or make the hole in another spot, instead of changing a bracket on an axle housing?
My opinion... and I know what mine is like..., and then I'll be quiet.
I don't feel they are required unless as stated above (drag racing), GM thought the mounting point was adequate and I've not had any problems with my lowered setup and stock housing and adjustable equipment w/o the relocation brackets that I bought from Spohn and sold later after testing for a 6 month period.

Regards,
Tony

 

They make a bigger difference on cars that make a lot of power. When we lowered my roomates 02 SS he said he could hardly keep the tires from breaking loose under normal driving. After the brackets went in everything was normal and traction was regained.

 

The only other thing that I can think of is that everthing is mounted solid through-out, with aluminium bushings. I have plenty of traction witht he LT-4 hotcam kit LT-4 KM, CAI, 52mm TB and other mods with fresh rubber in the back. Yes, its a LT-1 and not a LS1, damn LS1's...
Someday I will go to the dyno w/ it, too cheap right now

Mahalo

 

Just a note,
Adjustable lower control arms do nothing to pinion angle long as the torque arm is in place .
The torque arm singley controls pinion angle..
Now LCA brackets allow you to apply twisting forces on the rear to load/push the chassis up or rear down.

 

Agreed 100%. The torque arm is what controls pinion angle. The adjustable LCAs are for realigning the rear after pinion angle adjustment.
I'm not sure I follow this statement, but I think you are stating what the stock LCA angle achieves?

 

That, and what relocated brackets achieve on a stock height car.
When the arm is trending upward toward the chassis, the forces forward and slight twisting applied to the LCA will use that energy to push up against the chassis thus planting the tires and combating squat.
Which is why they are so important on a lowered vehicle, If LCA arms are angled down toward the chassis it acts oposite trying to unload by forcing it upward on the rear and promoting squat.

 

I agree with it. (not that you need my opinion, but since I put myself into this conversation)

I would say that the adjustable LCA's work in conjunction to help keep the pinion angle, along with wheel base.

Tony

 

I am now a wiser man. Thanks, 87_TA

 

I put global west LCA relocation brackets on my rear end and their "arced bolt holes" are a joke! I went with SPOHN adj. sperical LCA's to recenter the wheels in the wheel well because my control arms definetly needed to be longer.

FYI. When your rear is completely adj. it goes something like this when I do an alignment. Set ride height/spring choice for all four corners, center rear in vehicle/adj. panhard bar, set pinion angle/torque arm adjustment, center wheels in wheel well/LCA's, then set up your alingment machine. Next, adjust thrust line of rear end through the center of the vehicle by alternating length adjustments between left and right LCA's to minimize wheel well movement. Now you can go up front and do all kinds of kick butt stuff like caster/camber and finally toe. When your done the vehicle tracks dead straight, your rear end is perfectly centered, and the road feel is awesome. Hard part is to find a guy who has a damn clue what he is doing with all those adjustable parts. I had guys drive from litteraly an hour away because I got a reputation for doing "performance alignments" and letting the customer watch and see the detail I put into their cars.

When your done with your alignment you can measure the length of all components with a tape mearsure and as long as the ride height does not change you can put everything back to where it was set if disassembly becomes necessary. :rockon:

 

You going to be in Jersey anytime in the future?