240Dave
09-24-2003, 07:28 PM
Two part question: Frame damage and frame strengthening.
Obviously when looking for a daily driver one wouldn’t want to put in the work to repair much more than a dented fender or cracked bumper. But if you’re shopping for a project car, should one with "frame damage" be immediately dismissed?
The answer I always get is a big YES. But why? And what part do you call the frame when considering what is frame and what is body damage.
What does a frame really do for you?
Your rear suspension connects to the rear sub-frame, so if this is damaged, it is understandable that your car won’t handle right. But since the rear sub-frame is bolted, (not welded) on, it can be replaced without much trouble. I can’t picture what the rear sub-frame is bolted to, but it doesn’t appear to connect to the frame rails in any way.
The front sub-frame/cross-member holds the engine and front suspension and seems to be extremely strong, just like the rear sub-frame; Replaceable if damaged.
Then you have the lowest and outermost part of the car under the doors. Now to me, (looking at the rear of a front clip) this seems to be what really holds the shape of the car.
Finally, the frame rails. Now, these pieces, generally regarded with the highest importance, just seem worthless to me. Extremely thin metal just attached to the underside floor of the car. It eventually turns upward towards the front and becomes a solid place for the front sub-frame and shock towers to mount to. I've seen new/stronger framerails for sale for other cars.
Other bits would be the upper framing from the firewall to the front of the car at about the height of the top of the shock tower. The horizontal pieces above and below the radiator. And, of course, the rest of the cars framimg that the sheet metal is attached to.
The goal for any car would be to have a frame that doesn’t twist and flex under cornering and engine torque; causing suspension geometry changes. So what parts are responsible for this and which ones aren’t so much? Why are some considered irreplaceable (frame rails) while others (like the outermost part beneath the door) are just cut out and replaced with undamaged pieces.
I saw, in another post, the mention of a cage that goes through the firewall and mount to the shock towers. Say you install an 8 or 10 point cage that goes from the front shock towers to the rear.
Main hoop behind the driver with rear supports going down to the rear shock towers
A bar horizontal welded in between the rear shock towers
A horizontal bar at the base and in the middle of the main hoop.
Diagonal bar from the top of the main hoop to the bottom
Forward bar from the top of the main hoop, lining the roof, going down the a-pillar and down to the floor
Horizontal bar at the top of the forward bars at the top of the windshield
Door bars in an X shape from the main hoop to the vertical part of the forward bars
And finally bars going from the forward bars, through the firewall, and welded onto the front shock towers
Adding gussets where necessary
Then some form of bolt-on front strut tower brace from one to the other and triangulated into the firewall and/or the front frame-like piece above the radiator
I think it is safe to say, you would have no chassis flex in a car equipped with such a cage. Now after that, how important would the stock frame be? If someone put their bottle jack through the frame rail, who cares right?
Ok, so say you can’t or don’t want to go that wild. Other than strut tower braces, what are some ways to stiffen a cars chassis and let your expensive suspension do it's work? I’ve heard about foam injection…
NOTE: This is just a general post, I’m not implying that I will be doing anything mentioned...So don’t ask why the heck I’d want to put a 37 ½ point roll cage in my street car(dare me to? hehe). Just trying to get an understanding of everything in order to help me build a solid toy, and possibly make this thread (after you all add what you know) a good resource on this stuff.
Obviously when looking for a daily driver one wouldn’t want to put in the work to repair much more than a dented fender or cracked bumper. But if you’re shopping for a project car, should one with "frame damage" be immediately dismissed?
The answer I always get is a big YES. But why? And what part do you call the frame when considering what is frame and what is body damage.
What does a frame really do for you?
Your rear suspension connects to the rear sub-frame, so if this is damaged, it is understandable that your car won’t handle right. But since the rear sub-frame is bolted, (not welded) on, it can be replaced without much trouble. I can’t picture what the rear sub-frame is bolted to, but it doesn’t appear to connect to the frame rails in any way.
The front sub-frame/cross-member holds the engine and front suspension and seems to be extremely strong, just like the rear sub-frame; Replaceable if damaged.
Then you have the lowest and outermost part of the car under the doors. Now to me, (looking at the rear of a front clip) this seems to be what really holds the shape of the car.
Finally, the frame rails. Now, these pieces, generally regarded with the highest importance, just seem worthless to me. Extremely thin metal just attached to the underside floor of the car. It eventually turns upward towards the front and becomes a solid place for the front sub-frame and shock towers to mount to. I've seen new/stronger framerails for sale for other cars.
Other bits would be the upper framing from the firewall to the front of the car at about the height of the top of the shock tower. The horizontal pieces above and below the radiator. And, of course, the rest of the cars framimg that the sheet metal is attached to.
The goal for any car would be to have a frame that doesn’t twist and flex under cornering and engine torque; causing suspension geometry changes. So what parts are responsible for this and which ones aren’t so much? Why are some considered irreplaceable (frame rails) while others (like the outermost part beneath the door) are just cut out and replaced with undamaged pieces.
I saw, in another post, the mention of a cage that goes through the firewall and mount to the shock towers. Say you install an 8 or 10 point cage that goes from the front shock towers to the rear.
Main hoop behind the driver with rear supports going down to the rear shock towers
A bar horizontal welded in between the rear shock towers
A horizontal bar at the base and in the middle of the main hoop.
Diagonal bar from the top of the main hoop to the bottom
Forward bar from the top of the main hoop, lining the roof, going down the a-pillar and down to the floor
Horizontal bar at the top of the forward bars at the top of the windshield
Door bars in an X shape from the main hoop to the vertical part of the forward bars
And finally bars going from the forward bars, through the firewall, and welded onto the front shock towers
Adding gussets where necessary
Then some form of bolt-on front strut tower brace from one to the other and triangulated into the firewall and/or the front frame-like piece above the radiator
I think it is safe to say, you would have no chassis flex in a car equipped with such a cage. Now after that, how important would the stock frame be? If someone put their bottle jack through the frame rail, who cares right?
Ok, so say you can’t or don’t want to go that wild. Other than strut tower braces, what are some ways to stiffen a cars chassis and let your expensive suspension do it's work? I’ve heard about foam injection…
NOTE: This is just a general post, I’m not implying that I will be doing anything mentioned...So don’t ask why the heck I’d want to put a 37 ½ point roll cage in my street car(dare me to? hehe). Just trying to get an understanding of everything in order to help me build a solid toy, and possibly make this thread (after you all add what you know) a good resource on this stuff.