Thread: Octotat Sub-Frame Connector interest....

Sorry to burst your bubble Shawn, but if you foamed your side rails properly these really will do little to nothing for your car. The foam is bracing the same area on the same axes, is more rigid, is stronger, and has a much larger contact area where it attaches to the chassis.

You're not bursting my bubble sir. I am simply looking to make my chassis as stiff as possible sans any in-cabin bracing. If I am "already there" with my current modifications then that is a positive. I can personally spend my money on other things. Like CSK's.....or NX2K brakes...an O.E.M. 3-point FSTB to replace my Cusco 2-point.....etc...

I followed a bunch of your advice my friend, and used the U.S. Composites 8lb foam in my side rails, the cross rail under the seats, and the front rails. Those spaces/rails are fully and correctly foamed.

Additionally, your expertise and input into this thread is appreciated.

Concerning your previous post on the "three wheel/tripod" effect, my vehicle tripods up any driveway I hit at an angle. Both Sal my body-guy and I *think* I am approaching (near) zero deflection with my chassis. Although, I certainly would have bought these BIB sub-frame connectors if they would have contributed further to my chassis-stiffness.

My current chassis mods: 1) U.S. Composites 8 lb foam in my side rails, cross rail under the seats, and front rails. 2) HandiFoam 2 lb foam in my A-B-C pillars, and the entire roof channel surround. 3) Stephens Fender Braces. 4) Cusco 2-point FSTB. 5) BIB 3-point RSTB. 6) IKEA brace. 7) Progress lower control arm brace. (Well over a thousand-bucks in chassis bracing products alone).

As is and correct me if I am wrong, according to your statements, these BIB Sub-Frame Connectors should certainly help out other folks who have not done a full chassis foaming (and pretty much every other brace available).

Shawn B

Ground clearance would be my primary concern, especially since the pieces that bend down are right by where it mounts to the suspension pickup points. I'd be reluctant to put them on a street car around here, for fear of grounding out and tweaking a control arm mounting point. Similarly, I'd be reluctant to do this on a track car due to the potential to do the similar on high kerbs and during off track excursions.

As nice as it is to get that mounting point on the end, I think I'd forgo that and focus on bridging the center tunnel with an X type brace. Picture something similar to the Flyin' Miata butterfly brace. Even though the Sentra chassis doesn't have a tall center tunnel, you can still box it in and build a decently rigid 3D structure to resist torsional loads.

Unfortunately (and I do mean it, because I do like what Chuck does here), this might be one of those situations where round tubing isn't the best option in terms of materials. I think FM has the right idea using folded sheet steel to add "depth" to the floorpan. It strikes a good balance betwen rigidity, weight, and ground clearance, and if used properly can even be used to protect vulnerable parts of the undercarriage. Unless you're willing to go into or through the chassis, it'll be hard to beat that approach with steel tubing.

i have made no claims as to what these may do for your vehicle. i do predict they would have some effect, they may slow you down as a consquence of adding about 25 lbs... or not.

i'll wait 'til some testing is done before i start making statements as to the benifits/liabilities of these.


they do not hang lower than the front bushing mounts the only place ground clearance is lost is about 3/4" under the rear passenger foot wells.

i have done alot of reading re: the miata "butterfly brace". reviewers seem to be 100% that they would recomend the rails, but about 50/50 on the butterfly part. the biggest problem i see with cross bracing is how to do it without losing alot (like 1 1/2" or more) of ground clearance to accomodate the stock, let alone a 3" exhaust.


there is very little information out there about subframe connectors in front wheel drive cars. it may be that until you start getting into competition spring rates and dampers they are not needed. or that by the time you have upgraded, the car already has a cage. if anyone can point me to some specific information i would apprieciate it.

thanks
-chuck

only testing will tell