Frame connectors

[wrenchturner75]

Hello everyone, got a question concerning subframe connectors, im currently installing new floor pans and the car has a 4 point roll bar installed however theres no frame ties. now im not keen on the bolt in style (if there are any even) nor the weld ins. has anyone built there own frame connectors? ones that connect both front and rear frames but also tie into the rocker for added rigidity. ive thought about using 2x3 steel stock to make my own but figured id ask to see if anyone has already done it. ive seen it done on foxbody mustangs. any pics would be great! i dont mind cutting on the new floors to get this done i think the benefits outweigh the cost. thanks all!

 

[Qcode351mach]

Hello everyone, got a question concerning subframe connectors, im currently installing new floor pans and the car has a 4 point roll bar installed however theres no frame ties. now im not keen on the bolt in style (if there are any even) nor the weld ins. has anyone built there own frame connectors? ones that connect both front and rear frames but also tie into the rocker for added rigidity. ive thought about using 2x3 steel stock to make my own but figured id ask to see if anyone has already done it. ive seen it done on foxbody mustangs. any pics would be great! i dont mind cutting on the new floors to get this done i think the benefits outweigh the cost. thanks all!

Subrame connectors are one the best upgrades you can do to stiffen up the chassis for better handling. But in order to really see significant gains & get the most out of it you need the upgraded suspension components , you need to stiffen up tie in the hinge pillar to shock tower like so (I'm going to custom fabricate a set of these for my car)

& You need the monto carlo bar to tie it all together..It's the whole package ! Stiffening up one thing just moves the stress somewhere else in the chassis..Personally I'm going to use the global west connectors..I don't think there's a huge difference in weld in vs bolt in for a street car UNLESS your building a drag track car then I would weld..But I've only seen weld in for our cars..So weld in it is ..You could fabricate your own..& the rocker reinforcements.. But they are so cheap that to buy the metal..then powder coat then your time ...it's not saving much money..A better approach to stiffening the rockers chassis structure is to install convertible inner rockers but again unless it's pure track car I don't see the need.

http://www.globalwest.net/67-73-mustang-body-and-frame-stifners.html

They also have the rocker rail support kit on the same page as the connectors.

 

[72Mike]

That looks smart, and pretty easy to fab, Scott. Look forward to seeing those come together in the Saturday Morning Garage.

 

[Qcode351mach]

That looks smart, and pretty easy to fab, Scott. Look forward to seeing those come together in the Saturday Morning Garage.

Like I said it's the whole package when it comes to chassis stiffening..I have a feeling I may do a half dozen pair..Once I have the template I'm going to look into having the sheet part laser cut.

 

[Widowmaker00]

That looks smart, and pretty easy to fab, Scott. Look forward to seeing those come together in the Saturday Morning Garage.

Like I said it's the whole package when it comes to chassis stiffening..I have a feeling I may do a half dozen pair..Once I have the template I'm going to look into having the sheet part laser cut.

I'd buy some!

 

[PAPPY HAROLD]

I"m not trying to say that I am an expert in this area, but I have some experience in the job. About a year ago I posted some pics in the other vehicle forum called the last project. It is a 67 Camaro that we back halfed with a narrowed 12 bolt and 4 link. Now to relate this to your question. Yes the floor structures are similar and if you want to tie the frt and rear you will need to cut the rear floor to access the rear frame opening, I don"t think you would want it underneath the rear rail. Also in order to attach the back half we installed a cross member from rocker to rocker, with the center configured to the drive shaft hump and put the drive shaft loop under the bottom of that. Now as far as Scotts suggestion I cannot say I disagree but IMHO I dont think it would be as benificial as thought unless you go to a 10 point cage so that the top of the A pillar can be supported to help the windshield post from flexing. That being the reason for 12 point cages. Might not help you but I tried.

 

[coilwire]

I put bolt in sub frame connectors in my Mach. Easy to install. When I get back home I will get the product name and part # posted. It took about 3 hours or so to install.

Jim

 

[OMS]

I agree with sub frame connectors if they are welded in.

Every bolt in one I have seen always enlarges the bolt holes.

Shock tower cross braces help too.

The 71-3's have a nice rocker tie in to the t- boxes. Tying them into the sub frame might be overkill as it is only a 4 ft span. Depends on what you are going to do with the car.

Get a hold of VAMACH1 see what he did, he races his car.

For the Mazda Miata brace...

I see no gain from a door jamb brace. It is probably a huge help on a miata. The mustangs have a good frame rail, torque box set up there tied into the rockers.

 

[Mister 4x4]

Interesting. I would think that anything would help in strengthening the unibody, especially the "Miata" brackets Scott's thinking about. I know from after swapping the front clips on mine, there really isn't much in the way of solid support other than some sandwiched and spot-welded sheet metal where the cowl meets the tops of the aprons.

Conversely, it seemed to be a good enough design for Ford's liking, so it can't be all THAT bad.

All I know right now is that the only things really holding my front clip on are the where the torque boxes match up to the rockers, where the aprons meet the firewall, and floor pans meet the frame rails and tranny cross-member (I haven't re-installed the cowl tie-in plates yet, since I'm still repairing the cowl damage...). Of course, I have no engine and tranny in mine, either - so of course it should feel very solid. But I'm pretty sure there would be issues (i.e., sagging and caving in the firewall) if I were to try to run the car without the cowl plates.

Good discussion.

 

[OMS]

Eric, I've seen these car not sag with very rotted door jambs, rotted shock towers and aprons.

Again I think it depends what you want to do with the car.

Look at the jacking points on the 71-3's.

You can jack it up at the pinch weld on the rocker.

I just think that Miata door / bolt in brace won't do much on the 71-3's

The cowl to tower braces would do more and then tie them accross too.

 

[Qcode351mach]

For the Mazda Miata brace...

I see no gain from a door jamb brace. It is probably a huge help on a miata. The mustangs have a good frame rail, torque box set up there tied into the rockers.

I totally disagree with you D..They may be fine for stock I take my car out on sundays type driving but thats about it. When you start doing the stuff I'm doing with the suspension it becomes a new ball game..In order to maximize see the most gains for the suspension mods I did (frt coilover conversion..tubular arms ...lowered..18" super sticky tires...modified geometry) You need to brace the chassis accordingly. Do a little test on a stock car..Jack at the rocker pinch weld hinge post area..Watch the fender to door gap get wider at the top.

If you really want to understand chassis torsional stiffness & how it relates to suspension handling..Here's some reading for you.

http://www.scribd.com/doc/71130602/Design-of-a-Winston-Cup-Chassis-for-Torsional-Stiffness

 

[PAPPY HAROLD]

Oh boy! Well from my chair and what I"m reading the bottom pic of Scotts would relate back to what Don previously said which was that you would gain more from the cowl to shock tower bracing than from the mazda brace on the side. and with a monte carlo bar even alittle more. My other concern would be that as eric said about the sheet metal, unless the mazda bracket was severly redisgned it would only fasten to thin sheet metal and not a major structural piece. It could soon become a costly redesign in order to acquire structural integraty. And it still wouldnt have much diagonal support which greatly affects twisting.

 

[c9zx]

Since you car appears to be completely disassembled you make consider stitch welding all of the the panels at about 1 inch apart and continuous welding at critical suspension pick up points. You may also consider boxing the upper and lower control arms. It adds marginal weight, low cost but, considerable effort. I've never seen bolt on sub-frame that did not pull loose and damage the sheet metal when used in a racing environment. I'd suggest weld on Global West or other similar part. Good Luck, Chuck

 

[Mister 4x4]

Eric, I've seen these car not sag with very rotted door jambs, rotted shock towers and aprons.

Again I think it depends what you want to do with the car.

Look at the jacking points on the 71-3's.

You can jack it up at the pinch weld on the rocker.

I just think that Miata door / bolt in brace won't do much on the 71-3's

The cowl to tower braces would do more and then tie them accross too.

I believe you - I know you've worked with WAY more of these cars than I'll ever see in my lifetime.

And by cowl plates, I was talking about the fitted pieces that weld onto the cowl and tie across the gap to the apron. I had actually forgotten about the 'export braces.'

I can see where Scott's ideas would go a long way as well. Having rigid bolsters between points that could offer any kind of flex only helps the suspension systems do their jobs better. I'm thinking as flimsy as the export braces appear, they wouldn't be much help in the way eliminating of cowl-to-tower flex, but they do work. I would think somehing tubular would do a better job, though. And yeah - definitely install a 'Monte Carlo' bar between the towers to complete the 'no-flex ring.'

My comment was just to add to the discussion - I have no informed opinion either way, to be honest. I'm just interested in this because I guess I just hope that mine doesn't fold up with the first railroad track crossing once it's all back together.

 

[PAPPY HAROLD]

Since I"m taking a late lunch break I had a chance to read some of scotts reference article and noticed that in many of the diagrams you can see the diagonal bracing that Don refered too. and I agreed with. also c9zx pointed out a very important point in that stitch welding is superior to spot welds. My shock towers have been stitch welded and have considered doing the rear aprons also, because I too am running a big block thats modified.

 

[will e]

I put subframe connectors on my convertible about 25 years ago. Best investment ever.

 

[Mister 4x4]

Not wanting to take any chances, I plug welded the holes from the spot welds around the permiter of the torque boxes to the rockers, as well as laid a bead all the way around on both sides.

Not liking the 'pinch weld jacking point' idea so much, I took some pieces of sheet metal, folded them over the pinch welds at the torque boxes (kinda like a 1-piece-of-bread "fold-over" sandwich), and welded the crap out of them. Not only for extra strength, but then I also didn't like the idea of putting the jack straight under the unreinforced pinch welds (which were bent to crap for whatever reason).

 

[Qcode351mach]

Everybody is making good points & what a thread this has turned into

What it really comes down to is what you desire to get out of the car handling wise & your intended use. For me I want to be able to blast through a winding canyon road at 90 -100 mph & have the car stick like glue..I want to pull g's & carve ..Hence the suspicion mods I made..On the other hand everything I did is bolt on BECAUSE I want the option to put the car back to it's stock configuration being that the car is relatively rare..& for the most part #'s matching..I'm not going to start welding cutting modifying the chassis everything has to be bolt on IF I have a choice, hence making the BOLT ON hinge pillar to shock tower bracket, The hinge pillar is tied into the cowl JFYI.. It's what the cowl is welded to at each end. Is it the best way ..maybe..maybe not.. BUT it sure is better than nothing & I can remove if I want.There are benefits to be gained doing the Miata hinge pillar mod but it has go hand in hand with the other chassis stiffing mods..The whole package. Now if I ever get to build my 67-68 Shelby clone from a new dynacorn body shell I have no problem doing the mods as a full weld in like so



Besides being I-Car certified in unibody repair I have spent countless hours researching suspension & chassis mods for handing.. There's tons of books & good information out there. You just have to weed through the B.S. to get to the meat & potato's. This is just one of the certifications I have

https://my.i-car.com/EWEB//DynamicPage.aspx?WebCode=CourseDescriptionLive&site=publicus&course=DAM12 I would highly recommend taking a course or 2 for anyone who's doing a major ground up resto. They now have a bunch you can take online really good stuff !

http://www.i-car.com/html_pages/training/courses.shtml

There's many well known builders who have done the mods required & proven them out in real world driving ..Here's a cut & paste from 1 of them

CUT & PASTE

"You have to address the forces applied to the chassis by the front suspension. In the case of the Mustang, all front suspension loads are carried by the shock towers (and to a lesser extent the front frame rails). These loads are carried to the roof structure through the sheet metal of the engine compartment aprons and the cowl. To reinforce these areas we must box the cowl area with structural tube and then triangulate that structure to the “A” pillars /hinge pillars and the top of the shock tower.

These modifications will reinforce two key areas of your chassis. First, tying the shock tower to the cowl will greatly stabilize the front suspension. This area is rated as number two on the list of most sensitive structural member in regard to torsional deflection. Second, reinforcing the cowl will carry the forces applied by the front suspension directly to the roof structure (as well as the rockers), again, netting big results. The cowl structure is rated as the ninth most sensitive structural member in regard to torsional deflection. Now, when you add that expensive aftermarket front suspension, it will perform exactly the way it should greatly improving road feel, grip and responsiveness. "

 

[machman_73]

Great thread guys.