While I was bolting on a pair of new bmr boxed lca's I was thinking, the control arms are now the stiffest part of the whole rear suspension. the damn mounting points would flex more than these things ever will. Why didn't I just get the tubular version? So anyway my question is did I waste my money? would I have been better off with tubular (lighter) versions? will these pay off when I reinforce the suspension more or bolt in that big block/nitrous/blower/whatever?

They are nicely made, don't get me wrong and the bushings are real nice greasable poly units. I just think I coulda went and bought some square steel tubing, fabbed my own and threw a cement block in the spare tire well for the same result and less money or is there more to it than this?

 

Square tubing or round tubing LCAs will pretty much be the same stiffness. Add that to the stiff poly bushings and you can see how they can cause bind when cornering. For straightline drag racing, they'll be ok. But for hard street driving or autox, they wont cut it.

 

I don't know what their "boxed" versions are like; but if they're stock ones that are boxed in, you could have done better with tubular ones.

All this crap about "binding" is just that, crap. I have yet to ever experience it. Now granted, I've only had these Lakewood ones on my car for 50,000 miles and 5 years or so, so I haven't experienced everything they'll ever do, I'm sure; they could begin "binding" any day now, whatever that's supposed to mean; but I haven't noticed it as yet. And yes, I've read Global West's tirade about it too, so there's no need to quote it. I just haven't figured out how a solid aluminum-alloy bushing doesn't "bind" if they're the ones that sell it to you, but a soft polyurethane one from some other source does.

What you have will be fine, even if maybe not the best possible. Don't worry about it.

 

The BMR boxed LCAs are simply square tubing instead of round.


Ok, I wont quote. But look on their website. They say right there that they use Spherical bearings in their LCAs, not solid Al bushings. Thats how they dont bind.

 

They're busy trying to sell their "Del-A-Lum" bushings in all sorts of things.... I don't recall offhand if they offer rear LCAs with them, but that seems to be what they are pushing for most of their suspension parts

Square tubing is fine. The "boxed" type I was referring to, is stck-type ones, i.e. stamped sheet metal with a U shape cross-section, and the U filled in with an additional piece of sheet metal. Like a home-made one. That would be better than nothing, for sure, and a good beginner's step up over the flimsy thing the factory supplies; but if you are paying money, pretty much a waste.

The Lakewood ones are also square tubing; maybe 1½" square, with a section of pipe welded on each end to accept a bushing. Pretty simple and effective really, and not very much $$$. I think I paid less than $80 for the pair. I have yet to experience this "binding" they talk about though.

 

From BMR website:

"Which is better, tubular or boxed control arms?"

This has to be our most commonly asked question. We personally feel that either design is equally as strong for the load that the F-body chassis places on them. Because the F-body uses a control arm/torque-arm combination, very little lateral loading is placed on the control arms themselves. The torque-arm takes the lateral loading while the control arms are subjected mainly to a "compression" loading as the rear tries to push them forward into the chassis under acceleration. While an excessive lateral load would dictate the use of stronger(laterally) rectangular tubing, compression loading is much easier to handle and round tubing(of appropriate size)is more than sufficient. Bottom line: if you are an overkill nut and are willing to spend a little more then go with the boxed design, otherwise save a little money and get the tubular arms.

 

I think you are misunderstanding what "bind" is. When cornering, the axle twists (or rotates may be a better term) to one side or the other. One wheels goes up, while the other goes down.

With a stiff poly bushing, there's little give. So, as the axle twists, it's also placing twisting force on the LCA's. It's basically fighting with the poly bushings.

With a spherical bearing (aka - rod end or heim joint), there's no resistance. As the axle twists, the sphereical bearings have a full range of movement. This eliminates any twisting force being applied to the LCA's. In turn, this frees up the axle and promotes better handling.

Now, on a drag race set up, poly bushings are fine since you want to resist any twisting or rotation of the axle. This helps both tires plant equally off the line.

As far as the "Del-A-Lum" bushings. Those are only used in the front A-arms. Whole different animal. They probably could make a Del-A-Lum for the rear LCA's, but it would only be useful for drag racing. And since Global West is all about road racing it isn't very likely.

 

I know what they're claiming this "binding" is caused by, and how a Heim joint works. I haven't observed any such thing as yet. Considering how flexible the poly bushings are, and how little the angle actually changes, I find it hard to believe that they're making such a fuss over it. Maybe it makes a detectable difference in lap times on single-purpose race cars, that is to say, one with Heim joints will turn faster laps than one with poly; but as far as street driving, it's a tempest in a teapot.

The thing BMR is talking about is square or rectangular tubing vs round tubing, not "boxed" arms. "Boxed" arms are stock stamped sheet metal ones, with an open "U" shape, that have had a piece of material welded over the "U" to close it up. A significant improvement to the stock rubbery ones, and worthwhile for a DIYer to do to his own junk arms, if he can do it for free; but pointless to spend money on, when there are so many mfrs of ones fabbed from either square or round tubing. I'm inclined to agree with them, that the tubing cross-section doesn't make a whole lot of difference; the other parts in the system (unibody) are so flexible that the difference between the 2 cross-sections is totally swamped by the body flex.

 

RB,

i have a 2 broken LCAs with poly bushings that beg to argue with you about bind.

what you really notice from bind, is an increased roll stiffness. it isn't a major 'wow, that must be bind' feeling.

 

True, but if you aren't racing, or do occassional racing I wouldn't worry about it. Poly bushings will be fine (for the street). If you do race (not dragracing), then a Heim joint is pretty much required.

 

that is unless you have adjustables, that are designed like the set that i had, in which case, the bind, looses the jam-but, and then the part fails.

 

I had the same thing occur with my Spohn adjustable LCA's. The jam nuts wouldn't (or should I say couldn't) stay tight due to bind when I had poly bushings on both ends.

I switched over to a poly/rod end combo set-up and have never had a problem since. I agree there isn't a big SOTP feeling on street car, but I still prefer the rod ends.

 

I had a binding problem with my previous insalled SLP poly/poly LCAs. Roll response was very non-linear accelerating hard through a corner, like Dewey316 mentioned. Worst case was when the rear end end break loose and hopped about 6" at the top of first gear while flooring it from a stop around a corner. I ordered a set of poly/spherical LCAs the same day. Once installed they totally solved the problem.