C4 FRAME TECH. Talk about frame specs and flex solutions...
Burning Brakes
Joined: Dec 2007
Posts: 1,125
Likes: 8
From: Taft TN
To do it without upright's(cage) is the hard part. and without mods to the car makes it impossible. but any how......A rear crossmember needs to be installed behind the rear seats...atleast 3/16" thick and hold the pinion of the rearend. since we are holding the rearend we tose the POS dana 44 case and install a race case dana 44. It has the best sandcast for the 44 and has more beef in the week areas. next box the c-beam from front to rear which will extend up to mid plate between the BH and motor. going from the midplate foward to just behind the front suspension and out to the footwhells of the car will help the front. here comes the kicker...the c-beam cage needs to be lower than the outer frame rails to act like a "upright" where you will get the strength from cross members running from the cage to the pinchweld on the car. now look at all the parts that are in the way....where do they go?? Whats in the way that cannot be moved?? What type of engineered structure will it take to get around thse parts?? Math & Materials!!!!
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
You wouldn't happen to have pictures of how you did this, would you? I am interested in stiffening my '91 coupe, and this sounds like a great approach. I also like the rods that vette2vette sells, but they are out of my price range ($700). I figure I could get the stock x from a salvage yard, and con a buddy into doing the welding.
Melting Slicks
Joined: Dec 2009
Posts: 2,749
Likes: 50
From: Westmont Il.
Midnight 85 and Trog, your work sounds like good old Yankee ingenuity.
I have installed the R-D cross-frame and camber brace.
The intersection of the cross-frame X is "floating" as delivered.
I bolted it together for added stiffness.
Anchoring it through the floor under the seats like you did might be a winter project for me.
I have installed the R-D cross-frame and camber brace.
The intersection of the cross-frame X is "floating" as delivered.
I bolted it together for added stiffness.
Anchoring it through the floor under the seats like you did might be a winter project for me.
Drifting
Joined: Oct 2008
Posts: 1,278
Likes: 35
Great thread! Lots of people that know what they are talking about here. From my background of messing with civics and rabbits/golfs, this pic gives me all kinds of ideas.
Econo boxes are flexie by design. To stiffen them up, most people just bolt up braces that tie together the strut towers and the lower control arm mounting points. Kinda works with a unibody but the c4 has a frame with a pan. I can see how the camber brace would help, the x brace would also help some but I think something like the Miata floor plate would be a help making the trans tunnel into a tube. The JDM guys have a couple other tricks that might help. The first is what they call a door bar. It is a set of tubes that mount at at the upper and lower seat belt mounts on the B pillar, then one leg of the triangle goes forward hugging the floor and mounts in the forward seat mounting point and the other come down from the upper mount and meets at the seat mount.....like this.....
http://www.imageinmotion.com/cuscopillarsidebars.php
The next brace that might help is the fender or door brace. It mounts at the door mounting points and goes forward helping to tie the door pillars into the forward part of the frame....something like this....
http://949racing.com/bossfrogfenderb...0-05miata.aspx
sorry about posting the non vendor links but I do not think this stuff would work on a vette...
Econo boxes are flexie by design. To stiffen them up, most people just bolt up braces that tie together the strut towers and the lower control arm mounting points. Kinda works with a unibody but the c4 has a frame with a pan. I can see how the camber brace would help, the x brace would also help some but I think something like the Miata floor plate would be a help making the trans tunnel into a tube. The JDM guys have a couple other tricks that might help. The first is what they call a door bar. It is a set of tubes that mount at at the upper and lower seat belt mounts on the B pillar, then one leg of the triangle goes forward hugging the floor and mounts in the forward seat mounting point and the other come down from the upper mount and meets at the seat mount.....like this.....
http://www.imageinmotion.com/cuscopillarsidebars.php
The next brace that might help is the fender or door brace. It mounts at the door mounting points and goes forward helping to tie the door pillars into the forward part of the frame....something like this....
http://949racing.com/bossfrogfenderb...0-05miata.aspx
sorry about posting the non vendor links but I do not think this stuff would work on a vette...
Le Mans Master
Joined: May 2004
Posts: 5,866
Likes: 60
From: Hellinois
Finalist 2020 C4 of the Year - Modified
Midnight 85 and Trog, your work sounds like good old Yankee ingenuity.
I have installed the R-D cross-frame and camber brace.
The intersection of the cross-frame X is "floating" as delivered.
I bolted it together for added stiffness.
Anchoring it through the floor under the seats like you did might be a winter project for me.
I have installed the R-D cross-frame and camber brace.
The intersection of the cross-frame X is "floating" as delivered.
I bolted it together for added stiffness.
Anchoring it through the floor under the seats like you did might be a winter project for me.
Just kidding you, thanks for the compliment.
Le Mans Master
Joined: Oct 1999
Posts: 6,366
Likes: 34
I got into this chassis stuff back when the C5 came with it clams of being so much better. I picked up a book on this topic and it was holding the kit car chassis for the cobra as one of the better ones out there based on it having a cage around the trans like the C5 but perhaps a little better with a larger backbone for the area behind the seats. This book is a bit old and maybe out of date. Anyhow these greenwood pics surfaced a while back. Just wanted to share.
This was built up for the g572 which I think was planned to have a bb572 in it.
This was built up for the g572 which I think was planned to have a bb572 in it.
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Thread Starter
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
I got into this chassis stuff back when the C5 came with it clams of being so much better. I picked up a book on this topic and it was holding the kit car chassis for the cobra as one of the better ones out there based on it having a cage around the trans like the C5 but perhaps a little better with a larger backbone for the area behind the seats. This book is a bit old and maybe out of date. Anyhow these greenwood pics surfaced a while back. Just wanted to share.
This was built up for the g572 which I think was planned to have a bb572 in it.
This was built up for the g572 which I think was planned to have a bb572 in it.
I also agree with mustclime that boxing the tunnel is low hanging fruit.
Drifting
Joined: May 2003
Posts: 1,979
Likes: 48
From: Lakeport CA
I love the birdcage work behind the seats on the greenwood... must really tighten up that area, plus the twin roll hoops is a nice feature leaving room to reach & SEE through the middle. I hate how my DRM chassis bar (can't call it a roll bar due to legal issues, thank you lawyers of the world, may you all burn in hell), blocks my rear view mirror.
Last edited by Trog; Jul 7, 2010 at 06:04 PM. Reason: spelling/syntax
Team Owner
Joined: Mar 2001
Posts: 30,858
Likes: 293
From: Boston, Dallas, Detroit, SoCal, back to Boston MA
I've uploaded what I have so far of my suspension file if anybody want's it.
https://www.yousendit.com/dl?phi_act...eFVIcWRjR0E9PQ
https://www.yousendit.com/dl?phi_act...eFVIcWRjR0E9PQ
Burning Brakes
Joined: Dec 2007
Posts: 1,125
Likes: 8
From: Taft TN
I got into this chassis stuff back when the C5 came with it clams of being so much better. I picked up a book on this topic and it was holding the kit car chassis for the cobra as one of the better ones out there based on it having a cage around the trans like the C5 but perhaps a little better with a larger backbone for the area behind the seats. This book is a bit old and maybe out of date. Anyhow these greenwood pics surfaced a while back. Just wanted to share.
This was built up for the g572 which I think was planned to have a bb572 in it.
This was built up for the g572 which I think was planned to have a bb572 in it.
Melting Slicks
Joined: Sep 2008
Posts: 2,376
Likes: 111
From: Cherokee National Forest TN
JMO, I do not think the C beam adds much of anything in the way of structural support. The motor mounts are rubber as well as the bat wing mount bushings. Installation of solid motor mounts & solid bat wing bushings would help.
While looking at this pic:
http://i176.photobucket.com/albums/w.../RearClip2.jpg
It seems to me that reinforcement of the rocker boxes would be beneficial for lateral support. Opening the rockers to install tubing would be labor intensive even for a dedicated track car.
My thought: Level the vehicle front to rear. Bore a hole something on the order of 1 & 1/4 diameter with a hole saw through the top of the door sill & the metal reinforcement "shelf" directly below the top sill & fill the entire rocker box with tiger hair. Tiger hair is reinforced resin. Here is a link that I have no affilation with & is posted for information regarding the product.
http://www.repaintsupply.com/pd-fe-1190-tiger-hair.cfm
The weight of the product may be a consideration since the quantity of tiger hair required to fill both rocker boxes may exceed 10 gallons (SWAG). If the volume of the cavity could be calculated a rough idea of product quantity & weight could be established. If the weight of the product is acceptable an upside to the added weight is that it would be located below the CG height.
Torsional stability can be addrssed to a point by using an x brace under the car + tying the floor pans to it and adding the dreaded brace between the windshield & halo.
IMHO the above are all band-aids that will help and will have to suffice for a dual purpose vehicle.
If you need a stiff chassis consider installing a full cage with supports to the front & rear suspension attachment points.
While looking at this pic:
http://i176.photobucket.com/albums/w.../RearClip2.jpg
It seems to me that reinforcement of the rocker boxes would be beneficial for lateral support. Opening the rockers to install tubing would be labor intensive even for a dedicated track car.
My thought: Level the vehicle front to rear. Bore a hole something on the order of 1 & 1/4 diameter with a hole saw through the top of the door sill & the metal reinforcement "shelf" directly below the top sill & fill the entire rocker box with tiger hair. Tiger hair is reinforced resin. Here is a link that I have no affilation with & is posted for information regarding the product.
http://www.repaintsupply.com/pd-fe-1190-tiger-hair.cfm
The weight of the product may be a consideration since the quantity of tiger hair required to fill both rocker boxes may exceed 10 gallons (SWAG). If the volume of the cavity could be calculated a rough idea of product quantity & weight could be established. If the weight of the product is acceptable an upside to the added weight is that it would be located below the CG height.
Torsional stability can be addrssed to a point by using an x brace under the car + tying the floor pans to it and adding the dreaded brace between the windshield & halo.
IMHO the above are all band-aids that will help and will have to suffice for a dual purpose vehicle.
If you need a stiff chassis consider installing a full cage with supports to the front & rear suspension attachment points.
Last edited by Churchkey; Jul 8, 2010 at 12:28 AM.
Melting Slicks
Joined: Mar 2008
Posts: 3,022
Likes: 3
From: Chandler Arizona
This is an interesting idea. There "are" expansion foams that can be utilized for this idea as well. I've heard of this type material being using in an article once... the magazine tried to determine if the stuff actually aided in the structurally integrity of the frame.
JMO, I do not think the C beam adds much of anything in the way of structural support. The motor mounts are rubber as well as the bat wing mount bushings. Installation of solid motor mounts & solid bat wing bushings would help.
While looking at this pic:
http://i176.photobucket.com/albums/w.../RearClip2.jpg
It seems to me that reinforcement of the rocker boxes would be beneficial for lateral support. Opening the rockers to install tubing would be labor intensive even for a dedicated track car.
My thought: Level the vehicle front to rear. Bore a hole something on the order of 1 & 1/4 diameter with a hole saw through the top of the door sill & the metal reinforcement "shelf" directly below the top sill & fill the entire rocker box with tiger hair. Tiger hair is reinforced resin. Here is a link that I have no affilation with & is posted for information regarding the product.
http://www.repaintsupply.com/pd-fe-1190-tiger-hair.cfm
The weight of the product may be a consideration since the quantity of tiger hair required to fill both rocker boxes may exceed 10 gallons (SWAG). If the volume of the cavity could be calculated a rough idea of product quantity & weight could be established. If the weight of the product is acceptable an upside to the added weight is that it would be located below the CG height.
Torsional stability can be addrssed to a point by using an x brace under the car + tying the floor pans to it and adding the dreaded brace between the windshield & halo.
IMHO the above are all band-aids that will help and will have to suffice for a dual purpose vehicle.
If you need a stiff chassis consider installing a full cage with supports to the front & rear suspension attachment points.
While looking at this pic:
http://i176.photobucket.com/albums/w.../RearClip2.jpg
It seems to me that reinforcement of the rocker boxes would be beneficial for lateral support. Opening the rockers to install tubing would be labor intensive even for a dedicated track car.
My thought: Level the vehicle front to rear. Bore a hole something on the order of 1 & 1/4 diameter with a hole saw through the top of the door sill & the metal reinforcement "shelf" directly below the top sill & fill the entire rocker box with tiger hair. Tiger hair is reinforced resin. Here is a link that I have no affilation with & is posted for information regarding the product.
http://www.repaintsupply.com/pd-fe-1190-tiger-hair.cfm
The weight of the product may be a consideration since the quantity of tiger hair required to fill both rocker boxes may exceed 10 gallons (SWAG). If the volume of the cavity could be calculated a rough idea of product quantity & weight could be established. If the weight of the product is acceptable an upside to the added weight is that it would be located below the CG height.
Torsional stability can be addrssed to a point by using an x brace under the car + tying the floor pans to it and adding the dreaded brace between the windshield & halo.
IMHO the above are all band-aids that will help and will have to suffice for a dual purpose vehicle.
If you need a stiff chassis consider installing a full cage with supports to the front & rear suspension attachment points.
Race Director
Joined: Sep 2001
Posts: 14,682
Likes: 753
From: NEwhere Ohio
get this one:
I added a 6 point welded roll cage with permanent diagonal sidebars (you have to climb over) and I did not notice a difference in stiffness.
Its welded in 6 points to the frame. This is on my 93 vert.
I was like wth.
heres pictures of it.
I feel like I need to connect the windshield with the rollbar hoop in order to improve torsional stiffness to where I want it.
RD Camber brace appeared to help with top-down cornering (ie. felt like I could turn a sharper corner at speed vs. without it).
However, with my supercharger I cant use it and my RD camber brace is for sale.
I added a 6 point welded roll cage with permanent diagonal sidebars (you have to climb over) and I did not notice a difference in stiffness.
Its welded in 6 points to the frame. This is on my 93 vert.
I was like wth.
heres pictures of it.
I feel like I need to connect the windshield with the rollbar hoop in order to improve torsional stiffness to where I want it.
RD Camber brace appeared to help with top-down cornering (ie. felt like I could turn a sharper corner at speed vs. without it).
However, with my supercharger I cant use it and my RD camber brace is for sale.
Last edited by dizwiz24; Jul 8, 2010 at 09:22 AM.
Race Director
Joined: Mar 1999
Posts: 12,597
Likes: 237
From: Bartlett Illinois
This is not the technical answer you are looking for. Only my seat of the pants experience. I installed the Vette2Vette torsion bars a few days ago and tourqued them down good and tight. I did a test run on a local twisty 2-lane blacktop road that has about 8 of the "30mph" curves (per the peed limit signs)> I have run this road several times with my previously owned 60,000 mile stock suspension 87 vert that has the standard X brace along with a GM hardtop that I modified to fit.
I also ran this with a 40,000 mi LT4 vert with no hardtop and F45 selective handling turned to the max setting.
I ran this road 2 days ago with my 110,000 91 coupe with the targa top off. It has the FX3 selective ride option and I had the switch turned to the max setting.
My impression was that the 91 took the curves faster than the 94 which took them faster than the 87. With the torque of the L98 engines at the speed I was running the LT4 did not really make a difference. Handling did. The tires were new on the 91 and 87 but were not high performance skins. The tires on the LT4 nice, meaty GS D3s with only about 5,000 miles on them.
I drove the 91 over a set of double railroad tracks that I must negotiate on my way to and from work daily. I was suprised that the 91 did not rattle over these tracks like it used to do. It feels tight and drives like a much newer car. I love these rods!
It took me under an hour to install these. There are brackets that use 4 bolts to attach to the front X brace threaded holes that are drilled on all 86-96 coupes and convertibles. The rear brackets use the bolt that attaches the lower dog bone.
Here are some pics. The car was only about 18" off the floor so I had a hard time getting good shots.
Disclaimer: I do not receive any commission on any of these that or sold and I am not an employee of the manufacturer. Jeff over at the Corvette Guru forum is putting together a group purchase. He is the owner of the ZR1 in the picture.
I just want to say that this 110,000 mile coupe drives tight and like a new car even with the hatch roof off.
I also ran this with a 40,000 mi LT4 vert with no hardtop and F45 selective handling turned to the max setting.
I ran this road 2 days ago with my 110,000 91 coupe with the targa top off. It has the FX3 selective ride option and I had the switch turned to the max setting.
My impression was that the 91 took the curves faster than the 94 which took them faster than the 87. With the torque of the L98 engines at the speed I was running the LT4 did not really make a difference. Handling did. The tires were new on the 91 and 87 but were not high performance skins. The tires on the LT4 nice, meaty GS D3s with only about 5,000 miles on them.
I drove the 91 over a set of double railroad tracks that I must negotiate on my way to and from work daily. I was suprised that the 91 did not rattle over these tracks like it used to do. It feels tight and drives like a much newer car. I love these rods!
It took me under an hour to install these. There are brackets that use 4 bolts to attach to the front X brace threaded holes that are drilled on all 86-96 coupes and convertibles. The rear brackets use the bolt that attaches the lower dog bone.
Here are some pics. The car was only about 18" off the floor so I had a hard time getting good shots.
Disclaimer: I do not receive any commission on any of these that or sold and I am not an employee of the manufacturer. Jeff over at the Corvette Guru forum is putting together a group purchase. He is the owner of the ZR1 in the picture.
I just want to say that this 110,000 mile coupe drives tight and like a new car even with the hatch roof off.
I don't have mine as tight as yours I don't think, but need to adjust them again. I have noticed a difference with them.
Race Director
Joined: Sep 2001
Posts: 14,682
Likes: 753
From: NEwhere Ohio
unless you will also have bars that parallel the front windshield pillar, windshield and connect on both sides to the rear hoop, dont expect a big improvement.
I really didnt notice anything with my welded 6 point and permanent diagonal sidebars.
(see pictures in my prev post. )
I really didnt notice anything with my welded 6 point and permanent diagonal sidebars.
(see pictures in my prev post. )