vsixtoy

This question is always asked, but I never see a real answer. And I have seen manytimes poeple say that Spohns design doesn't tie the subframes together. Couldn't be further from the truth.

The Alston type mount internally paralleling the driveshaft tunnel persay. They mount from the front trans point to the rear "subframe" (the part that doesn't matter when it comes to geometry- only rear impact support) They need to tie into the front LCA mount points like Spohns design does.

Why is this important? Whether its dragracing, or cornering- the out rail style SFC's that are tack welded along the chassis help eliminate body flex (or twist). Bolt-ons won't do this, they need to be welded along the span. Even for drag launching, the alston style will stiffen front to rear but not side twist of the chassis/body.

The important part to see here is that the car is pushed by the LCA's and the torque arm. Where do the LCA's tie into? the outer rails. And where does the torquearm tie into? the front trans tunnel area. Where does the body and chassis meet in essence? the outer frame rails. Spohn's SFC's target these areas.

Whether its a drag car, or a road race car, frame stiffness is the most crucial factor in chassis setup. The more rigid the frame is from twist and flex, the more stable the suspension geometry points to both create or diminish weight transfer (based on suspension choice.

I'll explain further on the "create or diminish weight transfer" part- because both can be possible with the same SFC's:
FOR DRAG RACING (create), the front unloads at launch and weight transfer up and backwards weighting the rear tires. A weak chassis wll flex and not lift the frontend as strongly , thus needing more weighttransfer from a stiffer chassis (via-SFC's).
FOR ROAD RACING/cornering (diminish), under hard braking entering a corner, the body keeps rolling and flexing causing twist. That twist from chassis flexweight causes the rear of the car to twist from the front of the car (like wringing out a wet towel) and causes the outer rear LCA mount point to raise. This is unwanted geometry change. You want the suspension function entirely as intended, and not the chassis absorbing part of this function, and then quickly returning (the chassis is undampened by shock absorbers, the suspension is!)

Spohn's welded rail style is hard to beat in any arena.

Matthew91-Z28

Sounds like a decent explanation, but the whole point of SFC's is to create a load path for cars with a subframe. I think SFC's that weld directly onto the front and rear subframe points (alston and mac) are great. I also think that perimiter style (spohn) are great. The best is a combination of the two (e.g. KB double diamond).

What you are talking about with chassis twist and flex is what many call the "undampened spring effect" of the body. As you go into a corner, the body flexes and 'snaps' back into place as a coil spring would without a shock (dampener). To counter that, you need to provide a good path for forces to travel and dissipate. The best, of course, is a triangulated model.

So, what I am saying is NEITHER one is the best. They don't do a great job of triangulating anything. Either one will stiffen things up, but the sum of both will be much greater than with either one alone.


[FYI]
The point where the rear LCA's bolt in, is equidistant from the rear subframes to the outside of the floor pan. The load on the LCA's is easily transmitted the 2 inches to the rear subframe points. Besides, f-bodies don't even have "outer rails".

vsixtoy

You missed the whole point when you summed things up with this quote above.

Spohn SFC's = outer rails (they run the entire length of the chassis parimeter and are welded front and rear, as well as along the span

And, they do have triangular bracing that tie into the trans tunnel from midpoint of the outer rails.

pasky

I myself have always heard that welding SFC's to the skirt of the vehicle is the better thing to do, now why i don't know up until dean giving his explanation and I trust his tech knowledge as being one of the best up there with vader and all the other highly respected members, although I do agree that both would go along way, but thats a lot of added weight.

Matthew91-Z28

The FYI comment was not intended to sum up my point. It was just "FYI". Who is missing whose point here?

Your point is that Spohn SFC's are the best because by welding perimiter style bracing, you can effectively link the front and rear subframes and create a good path for force dissipation [right?]. You also say that Alstons do a good job of increasing straight-line integrity, but are poor at resisting chassis flex.

My point is that Spohn SFC's are a good design but they are not "the best SFC", as you claim.

All the stress/strain frome the front end travels down the front subframes (like wise with the rear). But, as you know, the only thing linking those 4 points (2 front, 2 rear) is a weak piece of stamped steel and the trans tunnel (which is actually a pretty good for structure as it can act as a bulkhead). So the goal is to create a path for forces to travel from the front to the rear and resist flex.

Now, if you had a few options to brace that area, then why would you ONLY pick the one that sat 20" laterally to the strongest points on the chassis? I am not saying, "Go buy MAC SFC's only because of where they connect" either. I think that either one ALONE is good but not great, certainly not "the best"

If you want the best, go buy them both and add an extra support to connect them. Or go get some KB double diamonds.

So, my point is that while Spohns are good, better designs exist.

vsixtoy

BLUE is the original subframe structure in the vehicle.

RED is the location that Spohn SFC's weld in
Note:They are welded to the unibody floorboards along the entire span of the longer red lines. I welded mine on the triangular small brace bars also (This is not my car, these are also "old style" square tubing Spohn sfc's.

YELLOW is where the Alston SFC's weld in
Note: They only are welded front and rear points, and not along the span between (can't be, they hang too low). Note how the frame can still twist like wringing out a towel front to rear with this design. They are too inboard of a design to provide lateral support, and there is no sheerwall effect when not welded along the span.

To do both is senseless because the red design is plenty adequate for sheering the frame laterally. If more is wanted, then box a cage into the car and tie them into the floorboard near the outer rails, thus 3D box supporting the chassis like done in race vehicles.

Thank you.
Dean

Dewey316

there is one fundimental problem with the alston style sub-frames. to get to this point, lets look at what we are REALLY trying get from SFCs. the whole benifit of the rigid chassis has to do with suspension mounting points, we are trying to keep them from 'moving' this is the reason for SFC's, STB's, billing strut mounts, del-a-lum bushings, ect. the alstons although they do tie into part of the sub-frames, do not tie into the suspension points. the spohn style do, the conenction dircetly to the rear LCA mount, infact the LCA bolts to it.

with this style SFC, you tie the front subframe directly to the rear LCA mount, you also attach both of those points to the trans-tunnel. it also conencts directly to the pinch area along the floor pan. (which is a big help, why do you think GM took the effect to upgrade that area from the factory on the verts?)

Matthew91-Z28

Apparantly, you disagree with this completely.

And you do miss my point if you think that I propose MAC sfc's as the single cure to chassis flex.

You are telling me that if you could weld any support to your chassis (cages not included), the only thing you'd do is weld in a set of Spohn sfc's.

If I could do any one thing to my chassis it certainly would be something like this:

I guess we can agree to disagree.



Thanks for what? :lala:

Kat

iTrader: (4)

Because I make them?

Kat

vsixtoy

Matthew,
Don't know why you're riding my *** partner- seems your trying to pick a fight.

I state some factual info- You posted pictures of SFC's for a 4th gen. They don't fit our car, so that design is not compatible and is not made for 3rd gens. Not even close th the same chassis mid and front sections.

Matthew91-Z28

I am not riding your butt.....I just happen to disagree with you.

I know that the SFC's in the pic posted are for 93-02 f-bodies. Thats why I said I do "something like it".

My chassis plans involve welding in MAC's, running lateral supports (like sphn) and then adding a support (x-brace maybe) to connect the two (each side). Too much? Maybe for a hardtop, but not for this vert.

I already have the MAC's on. Like we both agree, they don't do a lot for torsion. I need more support. Factory lateral braces are crap. I tried triangulating the front subframe to the factory braces with 1"dia 14 guage. Helped a bit but not alot.

Maybe I'm wrong. Maybe Spohns ALONE would cut it. I don't think so though. I don't want to pay $190 for a set, so I'm bending my own tubing and having them welded in. Then I'll just run a diagonal between the lateral brace and the MAC and tack it to the floor pan.


I used to drive an '00 TA. Solid from the factory. After KB double diamonds, it felt indestructable. Thats how I want my vert to feel but without having to install a cage.

nolanr0413

what about the kenny brown sfcs. I looked at those and they looked like the best kindI think they are all one piece and the spohn ones you have to weld the trusses on yourself and they come welded on to the kenny brown ones.

Matthew91-Z28

yep theres a pic of them about 2-3 posts back. They don't make them for 82-92 f-bodies. You've got to build them up yourself. Thats my plan.

Dewey316

KB does make 3rdgen SFCs, they are VERY similar to the Spohn design.

vsixtoy

KB tube is smaller diameter than Spohn. Spohn did larger for strength and reduced size at pass. side front for cat clearance. KB just use smaller size the entire structure so no reduction had to be made in Cat are (Much cheaper and easier to produce this way- Thumbs up on Spohn)

Spohn also capped the tube ends for a corrosion seal.

KB do have a nice rear cup brace for LCA mounts IF your car has a corrision problem that already exists- Good for car that have been subject to bad wheather states, otherwise not needed. Would be best though to cut out and replace any badly cancered areas before installing SFC's. Otherwise you are just temporarly masking a problem that will continue to grow. If the car is corroded here, then SFC's would only bring this area back to aprox original strength, but not make it stronger than stock. Stock subframe needs to be goood already and then you add sfc's to bump up strength.

It appears KB design already has inner braces already attached- anyone that has fitted SFC's of this style (Spohn, KB,etc) will tell you that fitment is slightly different on every vehicle. This is why Spohn opted to leave his off so you can custom trim these braces to fit you cars exact shape, and mainly custom fit around whatever exhaust routing you have( Dual cats, single cat, pipe size, distance its tucked, etc)

Here a shot what I did when I installed my passengerside brace. I bent it to:
1)tie directly into the SFC rail on the outsidepoint of the triangular crossbrace (Spohn suggest lay it on top for clearance and trim to fit if needed)
2) manipulate as much clearance as possible to route cat as high to the floorboard for ground clearance
3) top of the bend center is tack welded to floorboard to increase sheer strength of the sheetmetal floorboard(just as outer rails are). These tack welded help triangular stability (picture)

I make these comments in favor of Spohn NOT because I own a set,BUT because I investigated these qualities before I purchased any SFC's and based my decission on the facts availiable. After getting and installing the Spohn product I was very please that the end results were as expected when it come to quality and fit.

Dewey316

very much how i did mine


its hard to tell, but that upper brace is close enough that it is tacked to the floorboard.

vsixtoy

Doesn't suprise me at all John to see you did that too.

You need to get an electric cut for your exhaust dump so you don't have to climb under there each time (Especially when hot.) + you can run it partial open when db's are a problem.
http://www.dmhperformance.com/

Dewey316

I have a mccord, i just got it on my porch from UPS yesterday

i also think that picture is off the wrong side of the brace anyway, since the powercoat is still there, the side that was welded got painted black.

and a third note.
We were also very serioursly welded the contacts point front and rear of the main rails, you don't want to skimp where you weld them in there.

nolanr0413

so what kind should i go with then . I mean im gonna be doing this in my garage, i dont trust any shops to be doing this **** on my car . I knida like how the kb are all made , that means thier is less to weld and screw up . I also like how they mount by the lca mounts.

Pablo

iTrader: (1)

I wanna know how factory stock 1LEs went entire seasons without subframe connectors in the early 90s and managed to do fine.


SFCs are overrated.

Mavrick

Then dont buy one. You know what else is overrated? Fuel injection. I mean cars went decades without it and people managed to do just fine with their carbs, so clearly we dont need it

pasky

br()bert

Hell wagons had wood wheels. Who needs these fancy rubber tires!



Rubber is overrated!

BretD 88GTA

Dean,
Do you have any input on the Global West SFC's? I have long considered these but have yet to get any knowledgeable feedback on them.

I HAD a set of the original Spohn square tube SFC's but never installed them because I really prefer a tublar design, plus these weighed in at 40+ lbs. Too heavy.

I currently have a set of Alstons in the garage, but after hearing about all the recent fitment problems I am considering ditching these as well. My choices are go back to Spohn and the get the current tubular design or go with Global West.

pasky

Actually, i've heard boxed designs are superior to tubular when it comes to bracing. Something about the boxed designs have less flex. This was with LCA's anyways.

Apeiron

They were caged, were they not?

pasky

Nope. Had better suspension, but no caging.

If were talking stock that is....

vsixtoy

Everything Global West makes generally is top notch. I've seen in person some of the g-body front controlarms that Doug has developed that I wish to g()d fit our cars. Unfortunately, they have never done much R & D for our 3rd gen f-bodys. Mainly what they have are great for drag only. There SFC's are very close in design to Spohn's but without the tiangular bracing (they focused more on weight transfer lift on launch, rather than cornering and braking forces.

There TQarms are very good, but cross fit also onto the more developed 4th gen products they sell. They have more roadrace products for 4th gens. Why? well it turns out that Ron (RWB___s) recently informed me that a guy named Bill Chin who has raced AutoX here locally for years (he was part of GRA also years ago) now works for Global West and still autoX's, but now in a 4thgen z28. Thus my guess why there is greater development in 4th gen parts- Someone there has a need for it.

Doug told me a year and a half ago that he was coming out with 3rd gen tubular FRONT control arms- never happened. I talked to him recently when I bought my aluminium hubs from him and still couldn't confirm any e.t.a.

BretD 88GTA

Tom Keliher and I once talked with Scot Gilman at Hotchkis about that very same subject and the answer we got was it would be too expensive. Too much R&D required which would make the parts far too costly for the consumer.

The PA Racing tubular A-arms are close, but the spring perches need to be better designed. They don't look at all safe for street or hard cornering use.

BretD 88GTA

It depends on the application. Tubular provides better torsional resistance and that's what you want in a cornering/road race set-up.

Apeiron

No, we're talking as they were raced.

vsixtoy

I couldn't agree more with you on that statement!
I posted some picturs awhile back about a tubular control arm that broke on my truck a few years back- and it was fairly HD with gussets. Combination of everyday street punishment (potholes), metal fatigue from weight (My work truck). I'm lucky to be here alive. It snaped and bent down, but luckily didn't break off and I was able to control it. I was doing about 85 up the toll road (241fwy in Irvine) when it cut loose.

That is why I am holding off for Spohn to make tubular front Control arms- He make a damn good product and his welds(TIG) are strong. Same with the GW stuff. I like overkill on front controlarms.

BretD 88GTA

Just curious if anyone has checked this out:
http://www.swracecars.com/camaro_boltOn.asp

Pablo

iTrader: (1)

SFCs have been around since before you were born but because most vehicles had full chassis and people would generally strengthen their chassis on their own with their own welding torch they werent the hot buzzword at the track, ill bet if you told someone 30 years ago you were paying an assload of money for a painted steel tube ordered from across the country you were going to weld between your subframes on your 67 camaro they would laugh and wonder why you just didnt make it yourself. Or have your local welder buddy do for you for a 6 pack or two.

So to suggest that they are some marvelous new innovation akin to fuel injection is a weak argument.

Many a road racing car has handled worse after a chassis stiffening. The flex that occurs can influence the suspension in a positive way. Hotrod magazine learned this a few years ago with their project mont1go. Head to your local library and look up the microfiche


You simply cant reduce automotive related study to simple black and white, automotive components work in dynamic conditions and while some may perform well at some things they dont do so well where others shine. They can also place more emphasis on other parts as is the case with SFCs where your marginal struts, springs, and bushings are going to be the limiting factor far before your flexing chassis.

as for the showroom stock 1LEs and cages... Thats a good question, as far as i have read they were raced as is without any chassis stiffening allowed whatsoever. I tried looking up the rules for back then but couldnt find anyting.

I think i remember an article I read with dick guildstrand or was it hotchkiss? talking about the crap they had to go through to get these cars to run decently through a season

Pablo

iTrader: (1)

btw if Global west was so "drag" oriented youd think the guy would make a torque arm that would be compatible with a moser 9" torque arm mount, or at the very least know whether or not his torque arm would work with one. He told me he had a customer or two that had done it and all they needed to do was a little grinding on it but he didnt know what exactly except to tell me it didnt sound major.

ill save you the hassle should you ever upgrade to a nine inch, it wont work no matter what you do and I have access to alot of tools. It basically needs to be refabricated completely.

vsixtoy

I love guys like this-

He's going to go buy a $400 tube bender and a few different $200 bend dies to make his own SFC's for his car when you can buy an excellent perfabbed unit for $200.

Before I was born? bet I'm older than you.

Dick Guldstrand? What do you want to know from him? I'll ask him for you, I've literally known him since I was in diapers.

Think you've got the handling down like an expert, Lets run a sloalom, I'm in So.Cal also. I enjoy a friendly challange.

I've heard rummors from the locals here about you- Hear you talk more crap than I do

pasky

Haha, little off topic, but this reminds me of that time you got pist at someone and just uploaded a pic of you walking over a beam with a big smile haha, hard to see the threat like that, lol, good laugh. Your quite a character dean .

Anyways, its a nice chang eof pace around here to at least see a intelligent response with info to back it up.

vsixtoy

Thank you Pasky. I try to post some of this info to help others gain some factual info to base there purchases on. Some people I guess don't like that and want to always challange me.

Note to all-
"I've got a car that can back what I say"

Just remember, 1.07g's on street rubber is hard to beat with a full interior weight car. And yes I can caress a vehicle smooth and fast- in otherwords, I can drive.

pasky

Yea, seen your cousin post a few pics of you at some circle track in Cali, nice! I wish one of those were somewhere near me. I'd love to hit an auto cross track.

vsixtoy

That circle track is Calif Speedway. The picture is part of the infield section of the 2.8mile roadrace course. This is not a race, only an internission lunch tour. But I was 3rd car out after these two, what a blast that was.

vsixtoy

Here's the track layout, I marked the position we were on the track in the picture above.

Mavrick

Im curious, how did you get out there on the track? Are there local clubs that rent the track and you just join them? ow much does it cost? That looks a lot more fun than drivnig through the Q's parking lot

pvt num 11

Yeah, really. The local SCCA club rents the track for a day, but usually on Sunday - I want a Saturday SCCA thing. I'd really like to take the car down to test it when I start throwing parts at it. Heck, maybe a Drift Session would work, I could always NOT drift on purpose. I WANT TRACK TIME!

vsixtoy

I have always hung out at Vintage racing events. This is lifes little secret (No crowds at all) because it is the best type of racing there is to watch(just nobody knows about it). So many different groups of car types to see(most of these I grew up watching in there hayday's at Riverside raceway, Ontario raceway, and Pomona Fairgrounds back in the late 60's and early 70's. Pomona fairgrounds is still in existence, but they haven't had major racing venues there other than the AAA shootouts & the Winter Nationals (NHRA) for years and years. I have ridden on all three when I was a kid.

Nowadays, Vintage racing is growing more popular (Its a rich mans sport bigtime with MANY $1,000,000 + historical and unreplacable well known cars out there running by wealthy collectors-and they do bang them up quite often.

At these events, since the crowd draw is very small (More drivers there it seems than spectators) they always have lunch session tours of the track, You take you own vehicle out there and toule around for 45min (for $20 per car)with the minivan crowd at informal speeds of 85mph max (just don't pass on the corners- If anybody's looking). There are slow periods, but also many chances to aggresively hit a few turns. The picture above with the LaMans LolaT-70 ($600,000 car) and the full race A/C Cobra (aprox $200,000 car the way it was built) were let out first for some alittle more aggressive laps before they let the public go- to my surprize they flaged me through with them and we turned 3 decent laps before they let traffic out and we were slowed up- Then sidelined and leactured that we were to keep it cooler than we were.

What you don't see in the picture is the two of them walking away from me on the 3rd lap coming onto the front straight and bank1/2- they left me down that straight like I was stuck in glue, but what a bitchin site to see- the view driving right behind them. I did give it all I had and ran the bank at 123mph- but then got lectured- it was worth it.

The two tight corners after the high speed bak were a challange for me on the greasy hot street tires coming down from speed- especially the rears from my currently imbalanced larger rear binders. But it slipped through nicely.

Edit:Spelling errors

Rembrandt

BretD 88GTA,

I will be running the S&W SFC/crossmember soon, having them welded on immediately after next week (will be out of town for Indy GP).

I'll get a digital camera and do a review once they're on.

They're already at my house, nice quality of the welds and powdercoat.