I've seen after market (eg Spohn) LCAs that are non-adjustable. What's the point of replacing a non-adjustable LCA with another more expensive one? Are they significantly stiffer? More accurately made? Lighter? I can't see the advantage except at the far outer limits of tuning. Maybe. ????

 

Well you get new poly type of bushings which will make a world of difference right there plus the cool factor

 

My best guess is that they are stronger, have poly bushings, grease fittings for easy maintanance and are powder coated so they look good too.

 

Compared to the stamped sheet-metal stock ones, there's a night-and day difference in stiffness.

 

Can the poly bushings and grease fittings not be added to the stock LCAs? Is the increase in stiffness significant enough to make it an early swap or is it something to think about after a bunch of other stuff (braces etc.) has been done? But of course you can't put a price on cool! Oh wait a moment. Yes you can!

 

You can put poly bushings in a stock LCA, but it's still a flimsy piece of stamped tin compared to a rigid, welded tube.

 

Considering the cost of new bushings and the time and expenses for someone to take the parts to a shop to have the new bushing pressed in, the cost of new aftermarket LCA's is resonable for a little stffer upgrade with already new bushings in place.

As for non-adjustable? not for me. It is a nice feature to be able to control wheelbase with ride height,roll over/understeer, etc settings as well as the basic thrust angle.

 

Great info. Thanks all.

 

Something else to be mentioned here: The adjustable LCA's can confuse the alignment techs at your local garage. For a stock-height, street-driven car I would recommend The non-adjustable poly bushing LCA. For lowered cars, A double adjustable Track (Panhard) bar, Double adjustable LCA's and LCA relocation brackets are a must! (Dosent hurt to have an adjustable torque arm, as well)

 

Imo they are a waste of money. You can buy a bushing kit for the whole car for a little more than what you'd pay for the lcas. There may be some merit in the idea that its an easy way for someone to get new bushings if they can't change them but its still a relatively expensive option.
This talk of "flimsy" ctrl arms is unsubstantiated. Id like to see some proof. I've cut 1.6 60 foot times on stock lcas with stock bushings no less. They didn't go into plastic deformation nor did it hurt my launch considering that was a dead hook.

That said, for special handling apps, an adjustable lca is needed. I'm putting together a set right now actually. Double rod end aluminum, 1" shorter than stock I'm shortening my wheelbase.

 

Usually the ones who would be confused are the ones who would assume that the rear alignment isn't adjustable anyway.

 

Let me turn your question around backwards:

Why would anybody want an adjustable LCA, AT ALL? They don't accomplish anything that can't be accomplished better some other way (like by straightening the "frame"), unless you just want to change the car's wheelbase for some unfathomable reason.

When I changed my stock stamped sheet-rubber LCAs out for some NON-adjustable Lakewoods, I was able to flex them with my bare hands, before I put them in the trash. They are IMO totally inadequate for a modified car, especially one that has traction (mine fortunately never really has...)

 

Pablo, I would be very concerned about the strength of aluminum LCAs. As for adjustability, I dont see what the point is. Unless you have basic frame alignment issues. I run Hotkis rectangular tube LCAs. Theyre brute strong and very stiff. An adjustable pan hard bar, that I can see.

 

I asked my question because I only joined TGO and started learning 3rd gen stuff a month ago and there is obviously a deep well of knowledge here. Part of my original question was about the stiffness and if it was significantly different between stock and after market. I think Vetrucks point is that at the outer limits of what can be done anything that can be adjustable should be. My '91 V6 is totally stock so starting off with adjustable anything would probably be a big wast of time and money for me. I wanted to know if the LCA swap was an early mod or could come later. I started autocross two months ago and now have 30 laps under my belt. In my case my driving needs more adjustment than my LCAs. For Vetruck and others it's probably the reverse.

 

The way to make your car faster, in any competitive activity, is to identify the ONE THING most limiting to it; and choose, WISELY, an upgrade or addition that addresses that specific limit. Once you do that, some other thing will become the next limit, and the next, and the next, and so on. Along the way, you will learn what different parts do, what the most important ones are, you'll maybe beat a few other cars: you'll learn by doing.

THe way to make your car fast is NOT to spend your hard-earned cash on every pretty thing you see hawked in magazines; or on what "everbody" gets; or on the monkey-spank you hear about in the McDonald's parking lot on Friday nights; or on what "the fast cars" "all" have. None of those things addresses what YOUR CAR needs. Just because a professional racer uses some part, doesn't mean that you need it, NOW, to the exclusion of all else you could spend your however-limited resources on.

A good way to keep your eye on the prize and not be one of those people who are easily distracted by the shiny things alongside the path and fail to keep moving forward but instead wander off into the weeds, is to always ask, "What will this part (or that adjustment or the other modification) do for me, that my car needs?" Then, "What other parts do I need worse?" Adjustable LCAs on a car with an otherwise stock suspension fail that test. Not too hard to figure that out. Things like tires, shocks, springs, bushings, frame stiffening, brakes, power, cooling system, driving technique, and just ANY NUMBER of other things, are clearly ahead of those on the "priority order". I think you'll find that they are in the class of "if you have to ask, you've already established they're not for you". Lots of things are like that. Start with the simple stuff; move toward the exotic when you learn what it's even for, let alone whether your car would actually benefit from them. When you get to "the outer limits", you'll know.

 

Ok to adress these comments, first off, there are a number of reasons why a shorter lca is beneficial 1. You improve front/rear weight distribution 2. You exaggerate roll induced understeer. 3 improves manueverability on tight sections of track - think 180 deg hairpin. 4. Can compensate for crappy gm build tolerances - are your caster/camber plates in the same place side to side? No? Do you think the tolerances are much better in the rear?

Bending an lca with your hand is pretty impressive, you must be strong. Its not relevant though because I guarantee you didn't apply force in the way its actually loaded in the car I.e, tension and compression. If car parts were designed to resist stress equally in every direction your car would be many times heavier than it is.
Also remember that if you are worried about deflection you should look at your bushings first.

As far as aluminum.... might want to avoid riding in a corvette (and quite a few other cars) if AL strength concerns you.

And I still think that for 95% or more of tgo members, a stock arm is perfectly adequate

 

The concern with aluminum isnt strength, its fatigue. Over repeated cycling, it can fail where most steels dont really care about the repetition. As long as the rod ends are large enough, and have enough thread contact area (basically you need a larger factor of safety than you would with steel), they should be fine. There were some another person posted recently that IMO are a bit on the small side and may show damage over time. One thing to note is a rod ended LCA will only see axial loading, that is compression and tension. However just because the load is axial does not mean it will not deform as if it was a bending load while in compression. One with bushings can experience some level of bending and torsion. Its pretty easy to twist the factory LCA's in torsion by hand, but I dont think you're going to bend them in any direction.

I would say if you're going to bother replacing them with something aftermarket, not much sense in fixed length. Some day you may want to adjust them... and then you're tossing yet another set of LCA's away.

 

It is true that many vehicles have aluminum suspension members. I am still concerned that a tubular aluminum LCA on a 3rd gen may not withstand the forces placed on it, especially in a racing application.

 

We run aluminum tie rods and aluminum trailing arms (3rd link setups- very simular to 3rd gen formats) on our NASCAR trucks. Our aluminum trailing arms are 37" lonmg rodend to rodend- twice that of a third gen LCA. We have alot of abuse in foreward thrust, braking forces as well as cornering loads and rubbing/bumping other vehicles contantly.

Aluminum is fine- what you have to watch out for is thread engagement of the rodends. Make sure you have long shank rodends.

 

As long as it is sized properly, the force applied is a non issue.

 

Very cool. Thank you for educating me.

 

Pablo, a lca doesn't see torsional loads with body roll? its not only tension and compression.

 

If there are rod ends, it cannot see torsion.

 

that is true. I was refering to stock arms...just didn't specify that.

 

If your ctrl arm is seeing torsional loads then something needs to flex to prevent binding. Normally that is the bushings. If the bushings are firm enough to cause the ctrl arm to flex then I would call that a good thing. I would doubt that is happening much at all anyway. You have to think then that the logical conclusion is that a stiff tubular steel LCA with poly bushings is going to cause binding as your suspension articulates. Not a good thing for a handling car.

 

I think people also need to know that aluminum LCA assemblies are heavier than 4130 tubular assemblies.
The aluminum needs to be much thicker to be anywhere close to as stong as the 4130.

The problem with alot of 4130 assemblies is fabricating costs as well as safety if not fabricated well when the threaded insert ends are TIG'ed into place. Alot of sactioned racing assocoiations will fron upon the use of 4130 since aluminum is far less expensive and does not have the issue of multiple parts being welded together. Aluminum is dimply drilled and tapped for threads and the use of long shank rod ends make the aluminum thread engagement much more strong via surface area of the long shank.

4130 is the way to go as for ultimate. It has the lightest unsprung weight as well as strength.

 

Good topic!! Forgive my suspension newbedness but what kind of benefit do Adjustable LCA's offer? I believe adjustable EVERYTHING is the way to go because I want to tune my WHOLE car to be it's best. I already have adjustable pan hard, torque arm and GC weight jack system. Anything else to help me tune the car would be excellent. If so, which one's are recommended?

 

I agree. And, in the case of stock stamped lcas, with bushings (rubber or poly) I can see the potential for this twist. ...not a good thing. with rod ends, you won't have that problem and will have a setup with more potential to handle well.

 

I have two questions:

1) 4130: Good for street abuse (potholes and such)?

2) You guys mention rod ends not twisting.. Would this be the same for del-sphere joints? I am pretty sure these are like rod ends but they are more streetable..

 

As long as the 4130 is properly welded, it will be fine. However be real cautious about that "properly" part.

Since those are designed to rotate and twist, they will do so way before anything else will rotate or twist.