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David McCauley noticed his C8 Side Skirts were moving away from his C8 body when going up his driveway. He made some measurements and found one rear coilover chassis tower was moving significantly (by chassis stiffness standards) from the other. He developed a cross brace that attached to the chassis coilover towers and the chassis near the passenger cabin. McCauley had the rear cross brace he developed tested by a company that measures chassis stiffness for race cars. They found his device, that attaches to the rear coilover aluminum chassis castings, provided over 8% higher stiffness. Thought: "Although the C8 is stiffer than the C7 by 13.8 %, according to GM could be better!" Some car chassis are 2 and 3 times more ridged.
The GM carbon fiber engine compartment brace is quoted as ONLY providing UP TO 3.4% more stiffness. It does not connect to the aluminum rear coilover chassis towers. McCauley's Cross Brace is made from Carbon Fiber tubes and stainless steel brackets. It's an easy install, although as usual,found some install tricks. It sells for about a quarter of the price of the GM brace. Looks great.
This is a 13 page How To Install PDF with many pics and a detailed discussion of the importance of chassis stiffmess. http://netwelding.com/E-Ray_Mod_1.pdf
Below are some pics. The finished install on my Cacti E-Ray including some engine compartment carbon fiber pieces added so it was not the only CF part.
Decided Black engine cover complements Cacti best so will keep the black cover. Added this CF look center part. This real Carbon Fiber fits on the raised sheet metal in the engine compartment. This is the driver's side. Passenger side the same.
Thanks for the PDF too. I did find one typo if you care. Page 4, row 4 text box, "have" rather than half.
Thanks, always finding things to change or add every time I read again! Your find is fixed on the Word Doc, will make new PDF and post on website when I find a few more things to change or update,
Yep those aFe improved side chassis braces would help as well. Can't be too stiff! C8 has a way to go to come close to race cars.
Jerry, great mods and awesome PDF description and instuctions! I saved it in my E-Ray file for when the day comes my E-Ray arrives. Where did you purchase the carbon fiber engine cover insert?
Jerry, great mods and awesome PDF description and instuctions! I saved it in my E-Ray file for when the day comes my E-Ray arrives. Where did you purchase the carbon fiber engine cover insert?
Both it an the real CF sheet metal covers on Amazon. Cannot tell the engine cover piece is faux CF.
The AFE brace will twist much easier than the Speedway one based upon what we can see. Since the EOS unit appears to have a "flat" configuration, like the Chevrolet unit, and if it is open on one side ,when viewing a cutaway, it will offer only a miniscule benefit. Neither one shows rigorous engineering test data unlike the Speedway unit which shows quite a bit of test data.
The AFE brace will twist much easier than the Speedway one based upon what we can see. Since the EOS unit appears to have a "flat" configuration, like the Chevrolet unit, and if it is open on one side ,when viewing a cutaway, it will offer only a miniscule benefit. Neither one shows rigorous engineering test data unlike the Speedway unit which shows quite a bit of test data.
Yep as I note in my PDF Dave did quite a bit of testing of his cross brace. I cover info I found in the 15 page doc. http://netwelding.com/E-Ray_Mod_1.pdf
They showed a pic of a C8 with their brace at a shop that measured chassis stiffens for race cars. That firm said it was at least 8% and could reach 10% higher stiffens than stock. GM quotes their carbon fiber brace that does not connect to the rear coilovers as a up to 3.4% added stiffness. They also did a stress analysis to optimize the design.
I added some carbon fiber in the engine compartment to make the cross brace "feel at home!" When I found my Artemis interior was named after the Greek Goddess of the Hunt and Nature (GM states it has Hues of Dark Olive Green) I bought an Artemis statue. Put it on a carbon fiber part at Car's & Coffee!
So based on this assessment it appears there is significant flex occurring between the shock mount and the factory mount??
Would that much stress and flex in such a short distance yield deflection that would crack the mount?
Does this add up??
I doubt the issue with the stock C8 would cause cracking. Here are some pics from my PDF:
This is a Pic of the E-Ray chassis. Note there is no cross member directly between the top of the rear coilover towers. Dave, the inventor, said Tommy Milner (Team Corvette Driver) saw his Cross Brace and said “connecting to the shock towers makes total sense.”
What's funny there is a large cross member in the front of the E-Ray coilover towers.
I doubt the issue with the stock C8 would cause cracking. Here are some pics from my PDF:
This is a Pic of the E-Ray chassis. Note there is no cross member directly between the top of the rear coilover towers. Dave, the inventor, said Tommy Milner (Team Corvette Driver) saw his Cross Brace and said “connecting to the shock towers makes total sense.”
What's funny there is a large cross member in the front of the E-Ray coilover towers.
connecting to the shock tower or connecting 2 inches away is unlikely to make that large of a chassis stiffness difference.
If it truly is that much of a difference than the shock towers are going to crack because all the stress is concentrated in 2 inches.
Drivers and chassis engineers are two different kinds of people, and only one is an engineer
I do agree that attaching the shock towers is better. I just don’t believe the differences that significant..
connecting to the shock tower or connecting 2 inches away is unlikely to make that large of a chassis stiffness difference.
If it truly is that much of a difference than the shock towers are going to crack because all the stress is concentrated in 2 inches.
Drivers and chassis engineers are two different kinds of people, and only one is an engineer
I do agree that attaching the shock towers is better. I just don’t believe the differences that significant..
This one appeals to me as it is simple and attaches to the shock tower. I didn't hunt for it, but I do recall a good thread in the Z06 forum comparing the GM X to this one. I recall the the thread actually having a good discussion of loads and why the GM X may be more effective than it would appear. Maybe @RedLS6 was the one who dissected the issue and remembers the threads.
connecting to the shock tower or connecting 2 inches away is unlikely to make that large of a chassis stiffness difference.
If it truly is that much of a difference than the shock towers are going to crack because all the stress is concentrated in 2 inches.
Drivers and chassis engineers are two different kinds of people, and only one is an engineer
I do agree that attaching the shock towers is better. I just don’t believe the differences that significant..
I also have this data in my PDF:
As noted, the C8 13.8% stiffer than the C7 (GM's numbers.) They were proud of that increase. Dave is an engineer as I'm sure the fellows who test race car stiffness at their facility are as well. IMO 8 to 10% better IS SIGNIFICANT.
As noted, the C8 13.8% stiffer than the C7 (GM's numbers.) They were proud of that increase. Dave is an engineer as I'm sure the fellows who test race car stiffness at their facility are as well. IMO 8 to 10% better IS SIGNIFICANT.
Note the Porsche Carrara Type 997 is 33,000.
my point is only the 2” or so inch difference in mounting has minimal effect on overall chassis stiffness between stock and new tubular shock mounted design.
i’ll send attaching to shock towers is not a bad thing!
my point is only the 2” or so inch difference in mounting has minimal effect on overall chassis stiffness between stock and new tubular shock mounted design.
i’ll send attaching to shock towers is not a bad thing!
bottom line: you have an apples and oranges test.
It states that GM tested their cross price to 3.4% improvement in stiffness over stock, you had another test performed elsewhere that says tubular is 8 to 10% stiffer than stock. In essence, attaching to the shock towers instead of a few inches away improves stiffness by up to 6- 7%. The structural implications of this are pretty severe.
Please have the same shop do the same test with the GM product on the same vehicle and publish the results for an accurate comparison .
It states that GM tested their cross price to 3.4% improvement in stiffness over stock, you had another test performed elsewhere that says tubular is 8 to 10% stiffer than stock. In essence, attaching to the shock towers instead of a few inches away improves stiffness by up to 6- 7%. The structural implications of this are pretty severe.
Please have the same shop do the same test with the GM product on the same vehicle and publish the results for an accurate comparison.
Even with Dave's cross Brace it's ~18,000 Nm/degree are not as good as a 911 of any type. The one I noted has 33,000 Nm/degree Note the Bugatti at 60,000 Nm/degree. One reason is the Porsche body panels contribute to the chassis stiffness. The C8 zero!
I recall Tadge's concern when building the C8, he said he was "paranoid and deathly afraid" (his words) about the oversteer issue of his Dad's early Porsche. One clue he mentioned in that >1 hour Autoline After Hours interview is he said you can't have the chassis acting like an undamped spring. Particularly an issue with the suspension locations. He said it took Porsche several generations to correct the issue and they had to get it right the 1st time-AND DID.
If you did not read my PDF the issue started with Dave when he saw the side skirts on his C8 have a gap as he went up his driveway. He attempted to instrument the movement of one rear coilover tower to the other. He realized he need more definitive measure and had it done by a shop specializing in that activity. I'm sure GM measured as well to quote "Up To 3.4% improvement.".
The GM brace looks pretty! But so does Dave's at 25% of the price!
03-30-2024, 07:35 PM
1st E-Ray Mod- Cross Brace
Both it an the real CF sheet metal covers on Amazon. Cannot tell the engine cover piece is faux CF.
