John,

Just bumping this thread back into the daylight, in case you log back onto the site and see this post. I'd like to see what the factory did for the SC/RS torsion tube, to see if they made any changes from what they did for the RS and RSR cars of the 70's.

Thanks,
Jeff

X2. I'd love to hear feedback on how those bars tightened up the feel of the car.

For those people with long hoods, the torsion bars were not supported in the middle, at least up to 73.

Here is what I did in my build thread to address that when I added wide tires.
http://forums.pelicanparts.com/porsche-911-technical-forum/626050-saving-73-crusher-24.html#post7376528

http://forums.pelicanparts.com/uploa...1365516516.jpg

Sorry, missed this.

Yes, I have been driving all season.
Unfortunately I'm a crap as a test driver, for example I could barely notice the change from 27 to 29 mm tbars...
Also, It's hard to quantify improvement when you haven't driven the car in 6 months.
But I think the change is significant. Not like a coupe, but closer.

How important is rear shock tower reinforcement? I believe that this area is subject to movement with heavier (coilover springs) but will larger 245-275 tires do the same in forcing the shock tower out of alignment in cornering?

If your car maintains the torsion bars, you don't need to reinforce the shock tower on account of larger wheels & tires. If the car has coilovers? You definitely need to reinforce the shock tower. Even if the coil springs are rather soft. The coilovers can easily tear the shock tower from the side longitudinal frame area and also punch thru the top/cap of the shock tower.

To update the data from the original 2006 post on chassis reinforcement (#16), here's a most recent chart of chassis stiffness on various Porsche vehicles:

http://forums.pelicanparts.com/uploa...1524779815.jpg

It looks like the early 911s estimates by Donohue were a little off, but still open to various methods to improve the structure.

Assuming the above figures are accurate, use this as a reference when comparing various vehicles/platforms.

Sherwood

Aaron, What I see there is an equivalent of a lightweight Celette frame jig affixed to a 911 chassis. Excellent. Can we see more?

Sherwood

Hi Sherwood, I cannot find some of the preliminary photographs of the design and construction of the reinforcement. However I did post them to Instagram at that time.

The idea is to tie these into the front longitudinals by making box section from to base of the A pillar(@the floor) to those front sections.

Currently, the net weight increase is 3 lbs per side and the longs are spectacularly rigid without the rest of the panels welded in.

Will try to gather the photos for your thread

Edit, anyone have the data for the G body ? Would love to quantify this

Stiffness

torsional stiffness of 1957 Lotus Elite was 3,000 lb/ft per degree – first fiberglass structural body

Porsche has achieved significant gains in body stiffness over the previous-generation 911 Turbo, increasing torsional stiffness in the 2001 model by 49 percent and bending stiffness by 82 percent.

The aluminum bodied Lotus Elise has a torsional stiffness of 11,000 Nm/degree

Porsche Boxster is 10,000 Nm/degree


Fraise ST ReCreation – reinforcements of unit body add about 50 lbs. and make it about as stiff as a 996 GT3, or 997
- but involve about 55 hrs. labor on a fully stripped shell ($5,500)

http://forums.pelicanparts.com/porsche-911-technical-forum/400571-journey-begins-911st-recreation.html

Hello, jumping in here. Burn-Bros, nice project..

I have a 69" that needs complete floors and much else, LOTS of rust.. this car will be seeing primarily track use so I'll be designing/redesigning the body.. its getting a 300hp ej257 and the new(awaiting) 6spd reverse sti box from subaru gears..

Anyhow, has anyone looked at/studied modern car body design? I have a great txt book that lays out the SSS(simple structural surface) method for chassis design, attached pic. I'll be working at this project in the coming months and will to use LOTS of software, FEA, RBD(rigid body dynamics) to set things up, so this looks like a good place to add comments and what I encounter..http://forums.pelicanparts.com/uploa...1644447546.png