In order of 1st, 2nd, 3rd,4th which one is a better SFC....Sphon, MAC, G2, or BMR.

 

if all are the same 2 point connectors (per side) than they are all basically the same. you'll never notice a difference.

i like the price and choice of colors from BMR...

all my ssuspension stuff is BMR

 

They are all 2 point and tubular. Is boxed thaat much better than tubular?

 

You should look at UMIs new SFC. They look like they'll fit nice and tight and are a double diamond design. I have the Macs and I have no complaints about them.

 

I'd definately get boxed comparted to tubular. The boxed will give you more of a frame and also be a bit stronger in spots. Yes they will weigh more but i wouldn't skimp since you are basicly talking about your frame. We just started selling UMI products and they are a good quality piece.

Josh

 

A little bit of good info I found:

"Using subframe connectors for high performance street and racing applications has been done for a long time. It is no secret that tying the car together with subframes not only stiffens the chassis but improves vehicle response. Global West has been building subframe connectors for 20 years. Over this period of time we have come to certain conclusions.

Subframes that attach to unibody chassis like the Camaro/ Firebird must be welded.
Subframes on unibody chassis must extend to the strongest point fore and aft for obtaining the best results.
Round tube subframes, yield stronger torsional resistance then square, per given weight..
Subframes should have large mounting areas to distribute the loads.
If you are serious about street performance, or you drive a convertible / T top, subframes are required."


Basically, the square tubed sfc's have to be heavier to equal the torsional strength of round tubes.

As far as which of your choices are better. The thickest sidewalled one. If that is all equal, the least expensive.

 

But you are forgetting one of the most important parts...the fit. I want a item with the correct strength and build as well as a good fit. Some small tweaking is acceptable but I don't want to be cutting and grinding.

 

Is this really important? I have been looking at the SLP bolt-on subframes because I'm not much of a welder...

 

Don't do the bolt in SFC's, remember you are talkign about your cars frame. You can usally have an exhaust shop weld them in for around $100.

Josh

 

No kidding, the bolts will just stretch the holes out over time and be useless. I've had good luck with the Kenny Brown Double Diamonds on 4 of my 5 f-bodies. Awesome fit, and a noticeable improvement.

 

Has anyone tried the Spohn Chrome Moly Tubular Sub-Frame Connectors? I've been drooling over them.

http://www.spohn.net/product.cfm?productid=1394

 

my boxed BMR pieces fit perfectly. and really don't hang down very low.

i agree with the above....don't use bolt on SFC.

the point of them is to stiffen the chassis during flex. if there is a small weak point that could allow flex (the bolt connections) than over time it will increase. if you do the prep work yourself...ie grinding off undercoating, sanding off powder coat...most decent shops will do it for cheap.

about 1/3 of the way down shows several pictures from my SFC install.

 

I haven't heard of anyone having to do any cutting or grinding with the sfc's listed in the post.

My SFC's are tubular BMR clones but made with thicker walled tubing.

 

Good info but one point is a little off.

You will have more torsional stiffness from a rectangle that fits in the the same area as a round tube.

The round tube is superior if you compare weight to stiffness. But the square will win for total stiffness in a given area.

That is why your frame rails are square not round.

If space is tight the rectangle can package more strength in limited openings.

So I wouldn't turn down a SFC because it is square. Also round tubing is cheaper, so some Mfg choose it for that reason.

I agree with your other points and I like my SLP SFC. Not sure how much good they do with a Hardtop but they finished the package.

Z28

 

Stronger torsionally? What are they talking about????

You don't want "torsional strength" you want a larger "moment of inertia'. The problem with SFC would be flex not the round/square members twisting (like the action required to remove a screw-on top from a bottle). A larger MOI would prevent flex as this means the members are more resistant to deflection/bending/buckling under a load.

I'm not saying round is better/worse, it depends on thickness and dimensions really, but I just wanted to point this out.

Also, don't get caught up in the thicker the better, because if that were the cae we'd all have rail road steel under out cars, and there's a definite reason we do not- weight. With this being said there is probably a point where the extra stiffness from the thickest SFC is not justified.

If anyone had the cross sectional dimensions I could do some calculations from these in terms of resisitance to bending. I took a civil engineering course or two while studying for my ME degree.

Ben T.