When a STB is a SFC

Suspension, brake, and hydraulic/electric steering discussion.
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Scot
Posts: 25
Joined: Thu Mar 10, 2022 11:04 am

When a STB is a SFC

Post by Scot »

Long ago Holden did an engineering review of its Monaro, Commodore and Statesman cars and identified a chassis source of some steering imprecision. A subtle flexing of the chassis in both front shock towers mid points.
The spring rate was miniscule but enough to measure and notice, especially later when electric power steering became employed.
When creating the 2004 GTO and then the 2008 G8 and 2011 PPV and 2014 SS, Holden was in a corporate death spiral, and they did not incorporate the fix they already had engineered.
By 2008 BMR SUSPENSIONS co-opted the fix and labeled it, as had Holden, a SUBFRAME CONNECTOR. Below is the early link to what BMR now calls a strut tower brace. The page did once say Subframe Connector. I remember and still have the link.
Holden's rational was that while it might look like a shock tower brace, it wasn't attached to the top of the strut tower because the chassis flex it was mitigating was 10 inches below that point. They called it a subframe connector because by 2008 the front subframe was bolted to the chassis without an isolator or bushing, it's a metal-to-metal connection, so they claimed it was employing the subframe in the fix. In this early picture its mounted slightly under and slightly in front of a Whiteline STB.

HEAVY DUTY BOXED SUBFRAME CONNECTORS (bmrsuspension.com)

Instructions:

First weld in the top mounted SFC from BMR (It mounts parallel to a traditional STB, slightly in front of it), then mount a traditional STB.
So went the first half of Holden's fix.
There are 2 of the bolts that attach the front sub frame to the chassis which are used to add an adjustable brace. The two most rearward attachment bolts.
Spohn Performance makes Adjustable Front Subframe Chassis K-Member Brace | 2010-2015 Chevrolet Camaro | eBay. No need to buy that, just fabricate one like it cut to fit the Caprice, Commodore, G8, SS or Statesman, adjustment center section is a really good idea. Pre-load some tension and for <$12 you've got the part two Holden Sub Frame Connector to mitigate the weak spot on the front shock towers. The part one brace that looks like a Shock Tower Brace but is actually a Sub Frame Brace when they are welded to the sub frame on both sides with two pieces of 3/16" steel, 2" wide X 6 1/2" long.
BMR also makes a traditional SFC,
SFC007 - Subframe Connectors, Weld-on, Boxed

again, Holden inspired. It's a heavy square steel tubing with 1/4" and 3/16-inch steel plate. Welded in (bolted in is much weaker, does move around more) and adding a 6-8" extension of 3/16" steel 2' wide at the front allows for welding the lower connector to the upper BMR SFC's that look like STB's. Cynics will insist there is <0 structural benefit (Holden emphatically disagreed but others can decide) but Holden did attest to a positive perceptual change in steering response and camber changes under load. To mount the part one to a SS, it must be welded onto the shock towers ~6-8" below where a STB mounts.

Secret documents reveal the VE Commodore models Holden never built (whichcar.com.au)

While not the Holden original evaluation, this "news" piece refers to it. I can't imagine that any of their tech papers survived the collapse. I know I didn't save them.
The millennium evaluations by Holden were many, done while saving the company was still viable.

My 2014 Caprice (only one in Zurich) has the Whiteline STB and the part one BMR STB012 and the part two front + rear frame braces and the SFC013 described above. This is typical of my nontraditional chassis mods. The other two 2014 Caprices I have here also have all of this. Ride quality un diminished. Hi Bill
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