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Discussion Starter · #1 ·
Hello folks,
I proudly own an og 9-3 and I have been upgrading it in terms of suspension (b6 + eibachs), the rear arb, the steering rack (which hasn't been fitted yet tho) and already some PU bushes on the stabilizer links
But I steel feel this car is an overweight boat around corners, and I really hate that
Therefore I'll keep going and given the simplicity of the 2 point subframe brace I'll be making one on my own
Problem is I have no idea on the bar to use, in terms of thickness and diameter, afaik what's most important is the thickness so it could be something like half an inch OD but 3mm of thickness? If that makes any sense

Thanks and have a great day
 

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If you are going to make one, make a six point. They help, especially on a 'vert if that's what you have. I don't see how the two point can really be effective.
 

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Discussion Starter · #5 ·
Maybe not much help to someone in Spain. :)
Hahahaha exactly, if it was 200$ for me I'd be quite happy. But it's about another 200$ to get it posted
If you are going to make one, make a six point. They help, especially on a 'vert if that's what you have. I don't see how the two point can really be effective.
I cannot really be sure we will be able to make a six point tbh, maybe at some day when we have enought welding experience and I need the six point...
Besides I am installing a custom 3" downpipe and I don't have the time and courage to start having issues because of making it as it's not that straightforward, you can already see I don't even know which pipe size and thickness to use haha

I believe the 2 point already gives some improvement, and if theparts are not so expensive it would even serve as a "training" for a future 6 pt...


the taliaferro six-point brace can be difficult to install but is worth every penny. 6-Point Subframe Brace, GenuineSaab.com
Shipping + customs are another 200$ unfortunately


I think I will be getting the size for a regular strut bar anyways
 

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The commercial subframe bars are more like 20mm outside diameter. I can measure mine I don't know the wall thickness but thicker is better. The strength of a hollow tube grows at an exponential rate as diameter and wall thickness increase. I can measure mine today.

You should also make a rear bar upgrade. That makes the biggest difference of all in these cars. 19mm or 22mm solid.
 

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sure, well that is your decision! skilled labor here in just about any discipline is $100/hour.

i have this six-point brace, so, i went to the garage and measured it for you. the front and rear bars are 16mm OD, the crossbar is 20mm OD. the skid plate that ties them all together is anywhere from 3mm to 5mm thick -- it is hard to tell with my calipers at that angle since i didn't have time to get it up on ramps -- but i think it is only 3mm. each of the "cups" where the bolts are is 25mm OD and 3mm thick. i assume all of the tubing is 3mm thick.
 

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^ I don't think that listing is valid anywhere. It shows "relisted" and when I follow the links it leads to another, and another, then a dead end.
 

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Is this what the Taliaferro brace looks like?...for some reason I can't get a pic of it to load. These ebay pieces have no triangulation & offer little to no real structural rigidity, just a bit of added weight.

If you're making a piece be sure to add triangulation in the load bearing design to give actual rigidity against torsional forces. If you can make a 2 pt brace you can make a 6 pt brace, its just doing a bit more of the same & will give actual benefit so far worth it in the long run. FWIW these eBay pieces aren't true 6pt braces...they are multiple 2 pt braces connected at a flimsy center.
 

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Is this what the Taliaferro brace looks like?
that is exactly it, yes. in fact that appears to be someone who ordered a bunch of them for resale in europe, or, who simply copied the design.

These ebay pieces have no triangulation & offer little to no real structural rigidity, just a bit of added weight.
not sure what you know about engineering that i don't, probably plenty, but i have already slammed my car into a curb cracking the subframe at the rear control arm mount, replaced said subframe, and then bounced off the asphalt in a hidden dip in the road at 35mph, and the GS brace is still completely fine, plus it saved my oil pan on that one. it's not flimsy.
 

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Of course the brace is fine after that, slamming into things aren't torsional forces. Bracing is meant to resist torsional forces....aka adding chassis rigidity/resistance to flex. That style of construction is not effective for torsional rigidity.

What you are describing would be the job of a simple skid plate. Bracing & skid plates are for different things, hence different designs.

Random example below showing triangulation of the bracing. The strut tower braces do not have this...typically they are made of thicker pieces depending on the level of bracing they are designed to provide since it affects under/oversteer significantly (also they aren't usually as large as underbracing). Underbody bracing should [almost] always have triangulation in the design, otherwise it falls into the realm of dress-up bolts, vinyl decals, spray painted engine bays, & huge trunk mounted wings.
 

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Bracing may be interned to resist torsional forces. Strut bars are an example of bracing not designed to resist torsional force. I don't think the intent of the 6 point subframe brace has anything to do with torsional force either. That is not the shortcoming of the NG900 subframe.
 

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ahh i follow you now! so if i borrow this illustration of the idea for context, to get that additional strength you're talking about, i would need all six additional pieces here? or like just lines 2 and 5? i think 5 is forward and 2 is rear because the square hole is at the back.
Slope Triangle Rectangle Font Parallel
 

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Bracing may be interned to resist torsional forces. Strut bars are an example of bracing not designed to resist torsional force. I don't think the intent of the 6 point subframe brace has anything to do with torsional force either. That is not the shortcoming of the NG900 subframe.
this makes perfect sense to me but in this particular case i'm just interested to know if maybe it could be even better than it already has been. might be a cool project to teach myself how to weld.
 

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I'm thinking that if Abbott didn't include it and Nick didn't add it, it's not necessary or whatever improvement is to be had isn't worth the cost (time, money, hassle) of including the feature. The historical issue of the front ends of cars is that it's a big open box, and on many cars it's not even a box - just bulkheads stretching out into space maybe tied together by some sheet metal or a couple bolts.

The NG900 is one of those cars - there is very little forward structure, so the bulkheads tend to deform when loaded. The NG900 includes a strut bar to tie the left side to the right side to reduce that deformation, but the strut towers are quite close to the firewall leaving the two bulkheads essentially free to deform. Making matters worse is that the steering rack has a dumb location and dumb relationship with the knuckles, so any change in geometry from loading has a pretty dramatic effect.


The subframe brace is designed to close off that big open area by tying the left to the right which in turn lets the steering and suspension work as its supposed to rather that "fight" the deformations in the bulkhead. I don't think there is a concern of torsion (twisting) of the bulkhead independently or sympathetically.

I think the issue is side-loading, and a 2 point brace (positioned properly) could ameliorate and a 6 point brace would address. We're talking about a single plane here. I think. i bet a big crossmember like the c900 has would also work, but forming an 8" wide piece of aluminum and then fastening it to the car is lot more difficult than some tube thoughtfully assembled and installed using existing locations.
 

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ahh i follow you now! so if i borrow this illustration of the idea for context, to get that additional strength you're talking about, i would need all six additional pieces here? or like just lines 2 and 5? i think 5 is forward and 2 is rear because the square hole is at the back.
View attachment 283872
In simple terms, yes you would need those numbered pieces (red lines) to triangulate the load on the brace to give it significantly higher rigidity. Triangulating allows for lighter/less material to have superior strength. Essentially everything involving handling is a torsional force...such as how sway bars function. Side loading usually results in one wheel wanting to lift off the ground, hence the torsional aspect of the force. Sway bars can’t be a triangulated design so the same thing is accomplished by shortening the lever arm (using the shortest holes to make an adjustable sway bar shorter) or by installing a thicker bar.

Contrary to popular/idolized belief there is definitely a such thing as too much rigidity for a street car....not just from the perspective of ride comfort but traction on roads with bumps, potholes, etc. That said if I were making an underbody brace I’d definitely go through the extra step of triangulating the piece....in for a penny in for a pound at that point.
 

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That seems like a "not enough back pressure" type of hot rodder's myth. Modern cars have superb chassis rigidity in an absolute sense but especially compared to cars of even 10 years ago. The chassis should be rock solid and the suspension should do it's work without being affected by structure not being where it was a second ago.

The reason you typically don't see that sort of rigidity in street cars is because the amount of structure necessary to get there is either very expensive, very heavy, or intrudes on the car's function. I've driven multiple fully caged cars on the street (including an ace 99 Turbo) and with proper suspension there is no problem with ride comfort or traction. It's the part where you have to navigate a brace to get out of the seat or lose the trunk to steel tube that it starts to be a problem. If you need chassis flex to make the car comfortable, you're not a very good engineer.
 
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