Will a strut brace help with the overall flex of the body?
After nearly 280k miles, the unibody on my 87 flexes like a wet noodle. No rust or accident damage, just years of driving. I would think the front of the vehicle would be more susceptible to flex since the rear has a subframe mounted underneath, but wasn't sure what people's experience has been with a cross brace back there.
Everything I've read here over the years basically states that a strut brace in a Fiero is totally unnecessary, due to the very near proximity of the front of the trunk to the strut towers. The sheet-metalwork structure of this trunk area supports the strut towers.
Yes, the trunk firewall has a hefty box section incorporated into it. I never understand why many engine swappers cut all this structure away? They are the ones who need a strut brace in order to get back some rigidity.
As for our cars flexing, they do a little bit. You can hear the panels, and especially the doors, moving and creaking. However, this seems normal. And the mouvement is very small and doesn't affect overall safety. When you jack up the car on one corner at a time, you can still open and close the doors.
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
Some view the strut brace as a nice looking addition. As for practicality, just look at the inside front trunk wall and there is already reinforcement there. The strut towers do not move or shift. If they did the car would regularly go out of alignment. On swaps where some owners have wrongly cut out the trunk, a strut brace may help but I have little faith in cutting out the trunk.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Has anyone actually proven that the trunk bracing is tied into the strut towers? They look like it but if you strip all the thin metal and sealant away, they look separate from each other? There are only spot welds on the inside of the strut towers where the bracing would be?
Few years back I had read a study done on various strut tower braces, no measurable improvement with flex or handling. But i was thinking under my circumstances maybe, just maybe it might help reduce the flex, slightly. Thankfully my trunk has not been cut out, but turning into a driveway, theres a ton of flex...more than in previous years. Even the sunroof moves slightly. Maybe it sounds worse than it is. I guess as long as the windshield and rear window stay intact, flex cant be THAT bad. Lots of miles on this old girl, guess it just is what it is.
Has anyone actually proven that the trunk bracing is tied into the strut towers? They look like it but if you strip all the thin metal and sealant away, they look separate from each other? There are only spot welds on the inside of the strut towers where the bracing would be?
The torque strut (dog bone) is attached to the box section that runs across from one shock tower to the other. I'm sure the engineers made this part strong enough. You can actually lift the car up from the torque strut mount, albeit slightly offset. The shock towers don't go out of line with this procedure, so yes it's well attached. (It's not just thin metal; the incorporated cross brace is quite a chunk.)
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
Few years back I had read a study done on various strut tower braces, no measurable improvement with flex or handling. But i was thinking under my circumstances maybe, just maybe it might help reduce the flex, slightly. Thankfully my trunk has not been cut out, but turning into a driveway, theres a ton of flex...more than in previous years. Even the sunroof moves slightly. Maybe it sounds worse than it is. I guess as long as the windshield and rear window stay intact, flex cant be THAT bad. Lots of miles on this old girl, guess it just is what it is.
Yeah, if you crack a windscreen, than the whole car has lost too much rigidity! (Rust etc...) No, strut tower braces don't do a whole lot apart from looking cool, to some people? Race applications often use diagonal cross bracing to really add stiffness. But acces to the engine bay then becomes more difficult.
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
[This message has been edited by Frenchrafe (edited 11-13-2024).]
The torque strut (dog bone) is attached to the box section that runs across from one shock tower to the other. I'm sure the engineers made this part strong enough. You can actually lift the car up from the torque strut mount, albeit slightly offset. The shock towers don't go out of line with this procedure, so yes it's well attached. (It's not just thin metal; the incorporated cross brace is quite a chunk.)
Trust me I know that part is strong as I have used it in the past to lift the vehicle up as well. My question is if that brace is actually structurally tied to the shock towers like everyone always says or assumes? If you peel all the thin metal and glue away it doesn't seem to be attached to the towers other than spot welds. I am positive the brace does tie into the frame for sure because GM did use this as a point for a motor mount. Just begs the question about being attached to the tower.
Now, would a strut brace make a difference, probably not other than looks for the very reason you already pointed out.
[This message has been edited by Spadesluck (edited 11-14-2024).]
Trust me I know that part is strong as I have used it in the past to lift the vehicle up as well. My question is if that brace is actually structurally tied to the shock towers like everyone always says or assumes? If you peel all the thin metal and glue away it doesn't seem to be attached to the towers other than spot welds. I am positive the brace does tie into the frame for sure because GM did use this as a point for a motor mount. Just begs the question about being attached to the tower.
Now, would a strut brace make a difference, probably not other than looks for the very reason you already pointed out.
A good spot weld can hold up to 2000 lbs so I would assume that they are strong. The way I view it is that the trunk is an integral part of the Fiero frame structure. On the half dozen or so swaps that we have completed, the entire trunk was always kept in place.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
The load is spread over many spot welds. Each spot weld can hold at least a tonne (1000N). Yes the thinner sheet metal assists with this load spreading; that's why it's not great to remove all of it. In my application, I had to reposition the trunk firewall to make room for the turbo. However, the thinner sheet on either side was left original to act as a lower gusset betweem the cross brace and the rest. The cross brace is "spotted" (tied into) to the upper part of the shock towers.
You could always add a small upper foward facing gusset on the left hand side? The right hand side has the bracket for the torque strut which acts as a gusset already.
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
