InfernalVortex

iTrader: (4)

I dont see the point of some of the "inner" style sfc's. They just stiffen the floorpan against itself. They dont properly tie into ANY real subframe in the car. When you launch a car hard, where is all the force going? Through the lower control arm mounts and the torque arm. how are those inner sfc's stiffening those lca mounts at all? I guess they do a good job strengthening the floorpan, but to each his own I guess.

I have Spohn sfc's. I use them as jacking points from time to time. They work. They're the average price. I had mw66nova weld them in and he isnt a fan of how they do the bar on the cat converter side, so he modified it a bit to be a lot closer to the driver's side since I've got long tubes.

BlackenedBird

iTrader: (5)

Actually, it is the outers that do not connect to ANY rear subframe at all (they connect to the LCA mounts which are not subframes) & only connect to the front subframe via "arms" that reach out & connect to the front subframe.

It is the outer SFCs that mainly connects to the cars floor along the pinch welds.

I will give you that you are correct as to the launching forces from the LCAs not going in to an inner SFC. But they are pushing on a bar that is not connected to the stronger part of the car, the subframe.

White'89

iTrader: (8)

Incorrect. Take a very close look at either the picture you posted or your own car, the heavier piece of steel which comprises the RLCA mounting position on the chassis is stamped on the same piece as what you are referring to as the 'rear subframe'.

Its always been my opinion that the inner connectors do nothing more than add extra weight because they really do not provide much if any lateral/twisting rigidity being positioned in a small area in the very center of the car. Plus I like my ground clearance.

However since there really isn't a foolproof method of measuring chassis rigidity, our theories won't be anything more than skepticism. All we can do is assume that the outer connectors must be dominant otherwise why would they of been re-created with the same basic design by just about every reputable company.

Gumby

The jacking test is pretty good, when you use to jack up just the left rear using the shock mount and before only that tire came off the ground.

To now the left front also comes off the ground with it, is a good sign.

Or is that way with Alstons.

Twin_Turbo

iTrader: (25)

Not true the rear control arms connect to a small boxed area offset outboard from the real rear subframe, they are not the same. The rear subframe is where the rear shocks and springs load up into and extend into the rear bumper area. Check out the pic again.

The inside SFCs positively tie the front and rear subframes together is a straight shot, the outside SFCs do the same but they do if from and offset position. Now when you want to reduce twisting/torsional the outside SFCs you can buy leave a lot to be desired. Most of them can not be welded to the pinch weld area and are nothing more than a steel tube that connects the rear of the car via the LCA mount to the front with a long bar and 1 side bar into the front subframe. This does not make for a SFC that is as effective as it could be. The lack of points where the 2 tie together is the issue. The inside SFCs weld directly to the problem areas and if the front and rear subframes want to move in respect to each other this has to twist the inside mount SFCs, which they will resist. The ground clearance is an issue but IMO they are a better design than most outboard SFCs.

hellz_wings

iTrader: (2)

The inners and outers tie in different parts of the car but in terms of connecting the front and rear subframes in the most direct way possible, the inner frame connectors do just that. The outer connectors IMO are an added bonus because they tie in the floor along the rocker (if they are stitch welded), and add that bar in the front from the front subframe, to the rocker panel, which also ties in to the RLCA mount (as mentioned above). So that is why combining both of them is beneficial, rather than thinking "one is better than the other". But if I had to choose only one, i'd go with the inners (unless I'm lowered to the ground because YES THEY HANG REALLY LOW.)

Twin_Turbo

iTrader: (25)

I agree

White'89

iTrader: (8)

I went out and looked at my car and yes you are correct. So I guess I'll just have to keep my ground clearance and cut out the back floorboard to introduce a better alternative. No backseat!?! What ever will I do?!

Thats why I chose the Spohn SFC's because they do the best job at covering all bases.

BlackenedBird

iTrader: (5)

Yes the LCA mount shares part of a sub frame plate, but it is still not as strong as the the area where the stock sub frame is. One close look at the pic I posted above shows that. So the LCA mount area is not really the strongest section to attach a SFC to.

Even he says "connect to a small boxed area offset outboard from the real rear subframe, they are not the same

hellz_wings

iTrader: (2)

Looking at your pic at the camaro tipped over.. I notice that the panhard bar mounts (rear passenger side body) more directly to the beefy front subframe rather than the rear LCA mount. The inner style SFC's attach the front subframe to that beefy part of the rear subframe, which would essentially strengthen the panhard bar mount, wouldn't it? Wouldn't this alone lead to less flex in the rear? To me this seems logical.. Except how much flex does that PHB mount actually see? I would assume probably quite a bit if one is doing serious cornering.. Recently I've been reading about the benefits of lowering the PHB mount on the body side and how critical that can be to handling, so that why I just noticed this, although what I am hypothesizing could be completely false

BlackenedBird

iTrader: (5)

I know that the stock stamped PHB has been seen to twist out of shape & get a bend/kink in it pretty easily from any kind of sideways impact.

I see that as both good & bad. Bad that it means things are flexing & might not be controlling movement like they should. But good that in the case of any kind of impact, a cheap easily replaceable parts "breaks" rather than the structural integrity of the chassis. I'm sure that is how GM sees it.

White'89

iTrader: (8)

What i meant was that they are not actually part of the same stamped piece of steel like I originally stated., they are actually two separate pieces fused togther. But I don't see why you couldn't just weld a piece of stock between the two, not that it would make any difference.

White'89

iTrader: (8)

GM sees it as a cost effective way of producing a part that will 'get the job done'.

hellz_wings

iTrader: (2)

It looks like the area in between the rear LCA mount and the actual rear subframe is flimsy thin steel. They are in no way connected in the same way that an Alston/MAC inner SFC connects the front and rear subframes. The whole rear frame of the car is connected to the rear subframe, which is then connected to the RLCA mount via thin steel. So the rear frame of the car (all the way from the part where it connects to the rear crash bar) to the beefy rear subframe beside the RLCA mount is tied in to the front subframe directly via inner SFC's. The outer SFC's tie in the front subframe, to the RLCA mount directly, as well as tieing in the center of the car via stitch welds all along the rocker. This method is still obviously re-inforcing the chassis, although it probably lacks the re-inforcement to the actual rear frame of the car that the inner SFC style actually achieves. As I mentioned before, I really do believe that they tie in different areas and having both would benefit the car in many different ways as explained above.

BlackenedBird

iTrader: (5)

I'd like to see Alston (inner) SFC modified to where the rear mount was a "double U" or some sort to capture the LCA mount as well as the rear subframe.

Wait...I have a set of Alston's I could do that to! I've thought about that before (tieing the LCA into the rear subframe SFC mount, but the idea was as far as I got.

hellz_wings

iTrader: (2)

You could probably take a small block of steel since the area in between is so small. But then you wouldn't get the advantage of tieing in the rocker to the front/rear subframes and to the RLCA mount

BlackenedBird

iTrader: (5)

Well, the idea I had was completely separate from the outer rail SFC, so the outer SFC could still be added. How about the outer rail SFC & the inner, but with a (size guessing) 6"x10" welded to the bottom of both, turning them into a "U-shaped" double rail SFC? And a tube box that fit in between the rear SFC & RLCA mount? But the tube box would have to be welded in to the body first, then the plate welded to the bottom over both SFCs & the box. Plug welds?

InfernalVortex

iTrader: (4)

Im glad I said what I did even if I was somewhat incorrect, made for an interesting debate!

I still think the rear LCA's see enough stress that outer sfc's do 90 percent of the job, especially as stiff as those things are and how they're tied into the front subframe by the transmission. But Im not automatically dismissing the effectiveness the inners anymore. I'd be either will dramatically stiffen the chassis, and adding the other set will only slightly improve it from there.

I do think strenghtening that lower control arm mount is a big deal though.

Twin_Turbo

iTrader: (25)

I welded the rear subframe and the LCA mount together with a pice of tubular steel.

hellz_wings

iTrader: (2)

That, combined with inners and outers would tie everything in together and really box everything! I'd probably just do it this way with tubular steel instead of a box just for simplicity, but either way would work i guess.

While we're on the subject of frame re-inforcement, I always liked the idea of a roll cage stiffening the roof of the car, but I never liked the fact that it becomes a nuisance and part of the interior (effectively preventing access to back seats, it looks ugly IMO, etc.)

I was thinking of having a completely hidden roll bar-like tube that hides underneath the trim panels and headliner and ties in to the roof and the b-pillars via stitch welds (like the outer SFC's do along the rocker), which then ties into the rocker and outer SFC (through the compartment behind the sail panel), and then run another bar to the rear subframe to further re-inforce it.. This would probably be more beneficial to guys with t-top cars who want to have a roof as strong as a hardtop, have the safety of a roll bar above you in case of a roll over, but still retain stock looking interior, while hiding this re-inforcement. I know it sounds a bit lol

FlippindaBird

iTrader: (10)

Twin, pics please?

Twin_Turbo

iTrader: (25)

I'll take some this weekend when I weld my SFCs in, got my stuff back from the coater

FueledSoul

iTrader: (18)

I decided against a cage (for now) i think the sub frames i built are more than adequate, but the cage would put the stiffness factor over the top with out getting to deep into hacking up the dash, fire wall and any where else you run a tube. Im just not to will to make the compromises. Just for fun you can count the points and triangulations

90firebird

In my mind, tying into the rear subframe is superior , and I will tell you why.

What are the loads the chassis is experiencing, and where are the loading points?

The front seems to be a non controversial part of this argument, with all forces directly handled by the front subframe with the exception of the dampening loads/slight lateral loads through the strut mounts.

Out back:

Weight bearing forces are handled by the springs, lateral loads by the panhard bar, and "thrust" loads through the LCA mounting points. Dampening forces are exerted slightly inboard of the rails, while swaybar loads are applied just outboard. All of these loads are directly handled by the rear subframe with the exception of the LCA mounting points.

What are we trying to achieve with SFC's?

Well, the big thing that everyone seems to seek is an increase in torsional rigidity. At what points will the chassis be loaded to create a torsional force? The spring pockets, which in the back, are part of the frame rails. Tying to the lca mounts, while part of the same stamped piece, are not tied in the strongest way to the rear frame rails, and rely on that stamping to transfer the force between the rear subframe and the SFC. In the end, it's all a great supplemental improvement to our chassis, but I believe the inner style rear mounting point to be superior.

ZZ3 Z28

A dozen or so years ago I bought SFC's for my '86 Z from Mac Products, now Mac Performance in Temecula, CA. for $99.50. Cost is now $134.50. I think they called their line Chassis Masters. Still a good deal. 82-92 part #4892, 93-96 part #4996. The driver's side bolted on with no problems but the passenger side is a different story because I have a dual cat system that takes up all of the space on that side. There was no way any SFC is going on the passenger side without a lot of customizing. If anyone around here has a workaround for this dilemma please let me know.

patricklav

iTrader: (7)

Are those the Mac-4892 sfc's? I am considering getting a set of those. They look pretty easy to install. How are those compared to the sfc's that run along along the rocker?

RicerEater78

What do you guys think about the s&w sfc listed? has anyone had it? I'm thinking of buying it for mine

patricklav

iTrader: (7)

Just got the MAC performance Sfc's.. $160, and at my doorstep 5 days later. Only weigh 19 lbs.

their website is a little bootleg as i wasnt even sure they were still in business as everything was outdated on the website.

91camarosRS

iTrader: (5)

Holy crap. I want one!

hellz_wings

iTrader: (2)

They are that light?! Wow! I had no idea when I installed them. They look so beefy! The MAC ones made the car solid as a rock, but I went a step further and installed SPOHN's alongside them (along the rocker). THAT stiffened the car completely and provides a great jacking point as well!! MAC + SPOHN work very well together.

BlackenedBird

iTrader: (5)

My Alston SFCs were only 15lbs for the pair.

hellz_wings

iTrader: (2)

Dangit LOL. 4lbs lighter, nice nice lol

ringo234

I went with Alston's they scrape on some larger spead bumps with a passenger in the though. But now they're a pound lighter.

Adrenaline1

iTrader: (1)

RicerEater78

that good eh? how was the installation? I'm going to be replacing the axle, fuel pump, and the rear brakes anyways so I figure it would be a lot easier to do that as well.

Adrenaline1

iTrader: (1)

My friend has the setup but from my experience with it, its great. He has a lot of it welded up and may have modified it a bit. Im looking to lower my firebird when i swap out my wheels and wanted something that could just be bolted in if you want it that way. He said the install was a breeze but he has a lot more resource than i do (car lift and stuff).

blakecharles

Originally Posted by FueledSoul
I vote for build your own. That is what i did...




Yea me too!! If you can make this for my vert... I have cash!!!!

peterl2111

Hello everyone,
for some time now i have planned on getting subframe connectors for my 88 iroc. based on what im hearing and seeing the inner connectors seem like the better choice. the only question i have is how low do they hang? a few people mentioned that they reduce ground clearence, but how much? would i still be able to slightly lower the car with them on? if anyone has any pictures it would be greatly apreciated. thanks for your time.

hellz_wings

iTrader: (2)

Do they reduce ground clearance? Technically, yes, but for me it didn't. And that's because my cat hangs just about as low if not a couple tenths of an inch lower (I have headers and a 3" exhaust system). So yes they hang lower than outer style SFC's (which don't hang low at all by the way, and I have those ones installed as well), and will hang lower than an otherwise stock car but for ME, it didn't lower overall ground clearance anyway. If you are lowering alot then it might be safer to get an exact measurement. I would but my car is in storage far away. I would say 1.2" - 1.5" max lowering but that's just because I think the actual car shouldn't be lower than that on the street, I'm going to probably get dropped spindles and add spring spacers or something because 2" is a bit too much for the street, and 1.5" IMO is perfect.

peterl2111

Ok, thanks for your help. I wouldnt lower much more than an inch (if at all) anyways. One more quick question. Do you know how these fit with a stock exhaust system? will any modding need to be done? And either way, would these restrict future exhaust options. (one day id like headers and exhaust upgrades)
I was looking at these http://www.top-downsolutions.com/fra...body-p-90.html

patricklav

iTrader: (7)

Mine hang down just over 2 inches. this thread has pics of mine installed.

https://www.thirdgen.org/forums/afte...rformance.html

SCCAjunkie

Anyone know why these are listed as 86-92? I have an 84 Z28, so I'm wondering if there's a fitment issue...

http://www.macperformance.com/store/...Product_ID=434

DBLTKE

iTrader: (1)

I'm planning on ordering some SFC's pretty soon but I can only run bolt in sub frame connectors due to my autocross class rules (STU). My car is also lowered about 3.5"-4" so the inner style SFC's are out of the question. Are the BMR's my only option? Maybe the OP can be edited to show weather they are bolt-in or weld-in?

BlackenedBird

iTrader: (5)

The inners are the only bolt-ion versions made & I've never heard that the ground clearance is reduced to bad that even your extreme lowering would be an issue.

My question for you is this though, and please don't take it wrong. Where did you come up with your 3.5"-4" lowering measurement?

I had a part car with zero front springs in it at all (roller parts car) with only the struts supporting the front end so it was completely as low as possible. Now while my old pics are gone that showed the measurement of it from the ground, I don't recall it being that low, or MAYBE almost that low but with zero ride so it woulda been solid & only the tire sidewalls to act as suspension/springs.

3rdgenmaro

iTrader: (9)

It only took about a year for me to do it, but I finally weighed my UMI subframes.

36 lbs. This was by using a set of bathroom scales. They are lighter then I thought so I even double checked. The driver's side weighs 19 lbs alone. Passenger side (with the unattached cross beam) weighs 17 lbs.

A lot lighter then the 60 mentioned in the first thread. Probably should update that.

BlackenedBird

iTrader: (5)

YIKES! Stupid heavy.

Alstons = 15lbs for BOTH
MAC Performance = 19lbs BOTH

BlueZee28

iTrader: (30)

I have the Alstons and Spohns welded on my car, the Alstons scrape sometimes over speed bumps because my car is lowered. They both help tremendously though.

3rdgenmaro

iTrader: (9)

36 is still a lot lighter then the 60 listed on the front page.

I am not advocating any particular brand or design. I am merely trying to contribute to the accuracy of the list in post #1.

BlackenedBird

iTrader: (5)

Yeah. I have an Excel spreadsheet that I've been keeping of every 3rd part weight I come across & corrected it based on your new weight.

Obviously I'm not "certifying" any weight on the chart since I personally didn't do 99% of them, but it is most likely very correct since the weights are taken for TGO members, not any advertised weights.

Hal87

iTrader: (1)

I thought the Alston's were either bolt-in or welded - Check TDS