tmdz28

iTrader: (2)

my buddy is buying one and wants to know which one is stiffer the tube or the box.

i personally have the bmr tube vert sfc and love it. lots of welding points, makes my car handles a lot better.

thanks.

Das Nic

The 2" square tube SFCs that BMR sells are stronger than their normal round tube SFCs. They've also got more weldable surface if he wants to get them welded all the way down the length of them, but that's a little overkill in my opinion.

tmdz28

iTrader: (2)

i always thought that the box are stronger

hmm...

Das Nic

...that's what I said...lol

sorry if you misunderstood: square tube and boxed are the same thing.

tmdz28

iTrader: (2)

reading comprehension failed me

as soon as i saw the word tube, i registered circle.

So, what about brands, UMI or granatelli?

01ssreda4

iTrader: (96)

Box or square tubing would be stiffer by the simple laws of physics.

UMI Performance

iTrader: (77)

Hello,

The boxed style will be stiffer, how ever the tubular design will work on any application with no issues. The tubular style is lighter and tucks up into the car floor better... this means they can not be seen from the side of the car. The boxed style hangs down below the pinch weld about 3/8" and can be seen slightly from the side of the car, some people don't like this. The boxed would give you a better jacking point as well.

Below is a link to all UMI subframe connectors, we offer tubular, boxed and 3-Point styles in weld in or bolt in applications. The bolt in styles reqyuire no cutting or drilling and could be welded at any time.

UMI Performance Subframe Connectors

If you have any questions please ask and I am glad to help. Thank you!
Ryan

BMR Tech2

iTrader: (5)

Our convertible subframe connectors are tubular only because the floorpan on the convertible does not permit a square tube while providing adequate ground clearance. Otherwise we would have used boxed tube in the construction because it is more "structural" by nature and the convertible needs as much help as it can get. This is the reason for the multiple weld points down the length of the connector. The connector becomes an integrated part of the floorpan, rather than just connecting point A to point B.

So to answer your question, boxed is the most rigid. You can however, do as Das Nic suggested and weld along the length of the connector to the pinch welds if additional rigidity is required. If this was done even in 2-3 points along the length of the SFC, it really wouldn't matter which connector you had, they would be much more rigid than anything that is only connected at the front and rear subframe...

To order BMR SFC's click HERE.

Shenlon

iTrader: (4)

What kind of weight difference is there between the boxed and tubular?

BMR Tech2

iTrader: (5)

The weight difference is minimal, at least with our brand. We use .120" wall thickness on both part numbers. Our boxed version weighs 13.2 lbs per side and the tubular is 8.2 lbs per side...

trik396

iTrader: (4)

If square tube is stronger, why are roll cages round? Why are entire chassis of NASCAR, NHRA fuelers, etc. all round? I seriously would like to know.

99FormulaM6r

iTrader: (2)

I think the reason for making a cage out of tubular material is because most forces are not in bending, mostly just axial (along the structure). In these cases, tubular fairs very well.

vtirocz

Brett,
On your Boxed SFCs, I don't see how you're welding along the pinch weld. There's about 1/4" clearance. Any reason why these weren't designed to butt up against the pinch weld so that it can be welded there? I believe this is how the SLP ones are designed. Should make them significanly more effective at stiffening the chassis.

Thanks.

BMR Tech2

iTrader: (5)

This is true, the gap should be roughly 3/16"-1/4". We specifically designed some gap in there just because the typical car has the pinch welds so beat up that the SFC wouldn't fit otherwise. Most people just tap the pinch weld over in 2-3 spots. You could also just bridge the gap with a small piece of steel strap sourced from Home Depot or a similar type hardware store.

vtirocz

It makes more sense (to me at least) to just design the SFC to fit properly against the pinch weld so it can be welded there along the edge. That would provide a significant increase in chassis rigidity. I've never seen damage along the pinch welds where this would get welded.... only at the very front on that thin tab.

Can you elaborate on your 'steel strap' idea? It would have to be upright and verticle to provide any structural benefit.

ninetres

iTrader: (35)

BMR makes perfect sense to me. I've seen countless camaros with lots of dents in the pinch welds. The small gap makes for an easier install for 99% of the customers that buy their subframes. I cant imagine there are sooooo many people upset that they couldnt weld the whole thing to their car.

vtirocz

I've never heard of someone having an issue with the SLP SFC's, which butt up against the pinch weld. And in all the f-bodies I've looked at, I have not seen dents in this location. Maybe you guys have seen a lot more than I have. It doesn't make sense to me to cater to a small population that might have damage.

Anyway, this is just a suggestion to BMR (or any other SFC supplier) that this small design change could have a considerable gain in effectiveness of the part (ie. better chassis rigidity), which is the reason for installing the part to begin with.

BMR Tech2

iTrader: (5)

We appreciate and always welcome feedback. A lot of part revisions and design ideas come directly from you guys. That being said, we have literally had 100's of 4th gens on our lifts throughout the last 14 years of business and have seen our share of bent pinch welds when installing subframe connectors. It seems that people or maybe shops like to jack them up by the pinch welds or something, I am not sure but it was enough for us and most manufacturers to design our SFC's as we have.

Honestly throughout the years I have seen cars come through here with SLP connectors and I do not remember them butting directly against the pinch weld, maybe a tighter gap but not a butt that I recall. Either way, the amount of people that actually weld their SFC's to the pinch welds is small. You mentioned that it doesn't make sense to cater to a small population with pinch weld damage when in reality those are actually the majority. The small population of people are those that actually weld their SFC's to the pinch weld....

Regardless, if at all possible, I would advise this extra step as it does provide much improved strength over just welding the front and rear.

ZYA_LTR

But the problem is, not all our cars are the same... They ned to design a product that will fit all our cars and the various "isms" that wil be encountered. This means leaving a slight gap to allow for fitment issues with various cars. Prime examples could be why some people have header clearance issues and some don't with the same exact header, and the same with wheel fitment and SFC's. Always have to acount for the lowest common denominator, or the worst case scenario. Prevents issues down the line.

pewter2002

iTrader: (4)

I have weld in SLP 3pt SFCs. They fit well, but hang low. The big square design seems strong, but aesthetically they don't look great. I've had people say "what's hanging off your car?". I have no desire to change them, they don't scrape (Strano springs) but the BMR under carriage brace HAS had me hung up on high/ long speed "humps" Even the SLP y pipe doesn't scrape, so the BMR piece lets me "know" before I hit something costly!