S4Gunn's Front Subframe Braces DIY - TCCoA Forums
 
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post #1 of 4 (permalink) Old 11-16-2016, 01:39 PM Thread Starter
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S4Gunn's Front Subframe Braces DIY

I'm rapidly running out of random projects to do on my tbird 24 Hours of Lemons track car so I decided to make my own front braces. I find it laughable that some places will sell you these braces -- which you still need to weld on, for $165x2 = $330 for what is <$20 in materials.
You can study their pics here:
https://www.supercoupeperformance.co...to-install-602
https://www.supercoupeperformance.co...-every-car-236

Pros:
* I'm very skeptical about the added stiffness for the front end. The subframe is bolted to the frame rails with EIGHT bolts. MadMikey says that the rear ones will help resist twisting of the front end but I'm very, very skeptical about what value they add to the car. The front braces especially, while super easy to make, don't seem to add much value since is merely connects two parts of a pretty heft K-Member.
* It's something to build.

Cons:
* Slightly added weight (<3 LBs) on the front end.
* My exhaust is already tucked up in the transmission tunnel so these new braces will be the lowest point on my car. I have seen scuffs on the front of the subframe K-member so at least once (probably on an off-track excursion), I've hit that front bit before. With these subframe bolts, the low point is another 1" lower.


Easy Way: just weld on the square tubing to the car!
* Instead of making the braces removable with bolts, just weld them on.
* You'll save yourself money and installation will literally take 20 min.
* The downside is that if you ever need to remove the bars, you'll need to cut the braces.
* For materials, just buy 64" of square tubing cut into (4) 16" lengths.

Tools Required
* Welder - even the SCP bought braces will require some tabs to be welded to the frame rails
* Drill w/ bits to drill out the 3/8" and 1/2" holes. I found a few small bits plus these Step bits worked the best.
Steel Step Drill Set - 3 Piece, Titanium Nitride Step Drill Bits
* Assorted sockets/wrenches


Materials List
12" x 8" of 3/16" thick sheet steel cut into the following pieces:
(2) 2" x 4" piece w/ 3/8" hole at one end - hereafter referred to as TAB A & B
(6) 2" x 4" piece w/ 1/2" hole at one end - hereafter referred to as TAB C,D,E,F,G,H
(2) 2" x 8" piece w/ 1/2" hole at one end - herafter referred to as TAB I & J

44" of 1" diameter Square Tubing cut into the following pieces:
(2) 14" lengths - hereafter referred to as TUBING 1 & 2
(2) 8" lengths - hereafter referred to as TUBING 3 & 4

(2) 3/8"-16 x 1" long Grade 8 bolts
(2) 3/8"-16 Grade 8 nuts
(4) 1/2"-13 x 1" long Grade 8 bolts
(4) 1/2"-13 Grade 8 nuts
OPTIONAL: some lock washers.

Instructions
* Look underneath your car and locate the forward attachment point of the strut support rod at the Subframe (also referred to as the K-Member). The Strut support rod connects the front of the K-Member to the front lower control arm (LCA). There should be a small hole on the "lip" underneath the attachment point. Drill that out to 3/8". I will refer to this as POINT-A. I suppose you could do everything in 1/2" to make things simple but I thought that would weaken that attachment point too much.



* Cut all the TABS above. I found it easiest to get the big cuts done when I bought the metal. You don't need to be religious about the sizing but having them all approx the same size helps.

* Drill holes in approx the same spot on all the TABs. I did this by stacking them in a press vice and drilling into them all together. While this was easier with the small bits, I found going from the 3/8" hole to the 1/2" hole to be particularly challenging until I tried my step bits for kicks. Those worked FANTASTICALLY as the initial cutting surface is much larger vs a drill bit (which you are relying on just the tip).

* The second attachment point is underneath where the LCA bolts to the subframe. You'll use a 1/2" bolt through that hole.

* Weld TUBING-1 to TAB-A and TUBING-2 to TAB-B. This will be the forward support brace ("FSB"). Bolt the FSB to POINT-A


* Bolt TABS C & D to POINT-B with the ends pointed forward towards POINT-A. This will be the back half of the FSB.


* I found that the FSB didn't line up perfectly with the TABs C & D (angle was slightly off). In order to correct things, with the FSB firmly bolted to the POINTA I would push up on the bar to bend TABS A & B. Once TABS C&D sat flush underneath the FSB bars, I tack welded them on, removed the FSBs, firmly welded the TABs C&D onto the FSB, and re-bolted them on.



* Weld TAB E to TUBING 3 and TAB F to TUBING 4. This will be the front part of the Rearward Support Brace ("RSB").

* Bolt the RSB to POINT B. Stack it like a sandwich with the FSBs.

* Bolt TAB I to TAB G & TAB J to TAB H using the last two 1/2"-13 bolts. The longer Tabs (I&J) will attach to the side of the most forward point on the frame rails.

* You will notice that the frame rails don't line up with the square tubing so you will have to put a slight bend in the tabs. I did this by clamping the I/G and J/H tab pairs, grabing one tab, and bending it.

* The key here is to make is so that when you weld Tabs I & J to the front of the frame rails, they sit flush with the frame rails. You also have some slip as the RSBs can rotate around POINT-B to make this happen. Mine stuck out a bit at the end (which I bridged with weld) but that's clearly the weak point in my braces (that and how the forward support brace is lower than the subframe which is an inherent drawback of this design).

* Next, be careful to position TABS I & J so that they do NOT come down lower than the frame rails. I ignored this on my passenger side and then decided I needed to trim the bottom off the Tabs I & J so they don't protrude too far down.


* When you have Tabs I & J in position, tack it to the frame rails. Dont forget to tack the TABS G & H to the RSB.

* Remove the RSB and firmly weld Tabs G&H.


* Firmly weld Tabs I&J to the frame rails.

* Clean, paint the FSB and RSB pairs and reinstall. I found it helpful to draw arrows indicating which direction the FSB & RSBs should point and add markings so you know which side the braces were "designed" for.




This project took me ~6 hours over three nights but 2 hours of this was just prepping the tabs with the necessary holes with just hand tools (hand drill & angle grinder).
Regards,
-g

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post #2 of 4 (permalink) Old 11-20-2016, 05:37 AM
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Nice write-up Gunn!

This should be pretty helpful to any of the members that can weld..






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post #3 of 4 (permalink) Old 11-20-2016, 11:08 AM Thread Starter
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Quote:
Originally Posted by Rayo View Post
Nice write-up Gunn!

This should be pretty helpful to any of the members that can weld..

Rayo..
While the subframe mounting points are already there (one has to be drilled out), even the kit you buy from SCP requires welding....
-g

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post #4 of 4 (permalink) Old 11-20-2016, 11:29 AM
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I've long said the businesses selling these things for the ridiculous prices they do try to amortize the cost of their welding equipment on the first sale. It would be easier to justify if they came up with something original where they're actually bolt-ons, but anyone who has the capability to weld a 1/4" plate to the frame rail can fab up these things blindfolded.

They are pretty effective - although I don't find the section linking the K member to the K member necessary at all - but linking the K member to frame rails are something OEMs have been doing on newer cars as well, they aren't there to keep the K member from moving(as you said, the 8 large bolts do a fine job at that) but to triangulate the frame rail itself

-Matt
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