Stangar

I want to increase chassis rigidity. You know how a shoebox is easily twisted without the top on? Put the top on and it's super rigid. I want to make the regular C6 super rigid.

Has anyone ever turned their C6 into a REAL hardtop (not a targa). Can the magnesium frame bolted into the top of a Z06 be used to turn a regular C6 into a hardtop?

I greatly appreciate constructive comments. Thank you.

jdurhan

add an elite tunnel plate 1/4" or 3/8", it will make a noticable difference. I have one on my car, I also got it with thermal abs, really helps with heat transfer to cabin.

justpassedu

or buy a z06 not only will you get the rigidity but the power also

Wayne O

I agree....the Elite Engineering tunnel plate will help increase chassis rigidity.

The Z06 (a great car) has rigidity in its permanent hardtop configuration but it doesn't have the structural integrity to handle a targa top.

gitgone

Sounds great! Can anybody tell me how chassis rigidity is measured and what the measurement units are?
Thanks!

cfi_luz

I'm with you on this one, I never take the top off and would gladly make it permanent (and get rid of the squeeks too).

ranchero

I agree. I only want a hardtop. Not a targa. Not a sun roof. Not a convertible. I only want a two door hardtop. I want the lightest car possible and the most structurally sound and that is a two door hardtop (or sedan if we are talking '61 Bel Air or such). I would prefer a fixed roof hardtop without the glass hatch - a car like the C5 generation Z06. That would be a coupe with a B/C pillar and a trunk. I will take and live with the C6 coupe as it is currently sold but I would prefer a lighter, more rigid, fixed top coupe. - ranchero -

FloydSummerOf68

I wish it had been an option

opus1111

A great question. It's a little funky, but chassis stiffness is measured by the lowest frequency (or 'fundamental frequency') it resonates at when vibrated by a vibrating machine or 'shaker'. Typical units are cycles per second, a.k.a. hertz (hz). This test setup is like driving down the road, but under controlled conditions. Can't really measure this value at home though by any means I'm aware of.

The higher the number the better, like a great sports car's fundamental frequency (or fundamental 'mode') is 20hz or 30 hz. The C5 Coupe w/ top in place is supposed to be 27hz reported by GM. C5 vert is supposed to be 23hz (source: "Corvette C5", Peternie 2004) Poorer response is like 5hz. Don't have any C6 numbers. I'm not an automotive engineer, but I've studied modal analysis in my mechanical engineering Bachelor's and aeronautical engineering Master's, which is the study of things like chassis stiffness.

gitgone

OPUS111:

Thanks for the detailed response, sounds like you are very knowledgable in the field. I hope our highway department hires more like you to help with the nation's bridges!

Sounds like the OP would like to know relative rigidity of various body styles (specifically - coupe vx targa) ie. How much more rigid is a coupe vs a targa vs a convertible? Is there much difference?

For any of you out there that might know - Is this info available from GM or Bowling Green? or are the numbers we hear just subjective?

Likewise with the tunnel plates that are being marketed. When you go to the websites, you see terms such as "improved rigidity". Maybe I missed it, but so far I haven't seen reference to actual numbers or what equipment was used to get those numbers.

The equipment necessary to measure the parameters OPUS1111 mentioned is probably very expensive. Not sure any of these companies have the budget for such testing. Although, I for one, would like to believe we can improve ours cars performance for such a nominal cost!

And last, a little food for thought:

Is more rigidity always better?
- or do you need some flexibility?

How does the Vette compare to faster or more responsive sports cars in this area?

I seem to remember that Carol Shelby's Cobra derived some of its phenomenal success due to the chassis "flex" enabling it to put its emense power to the ground.

Comments/Corrections Welcome!

shopdog

All chassis flex. It can't be helped. But the suspension designer's ideal is a chassis with no flex at all. That lets him do idealized suspension calculations to get the perfect suspension tuning. When he has to include chassis flex in his calculations, the equations get messy, with too many independent variables that won't allow a single solution.

opus1111

No problem. Couple more comments. Suspension engineers (subtle distinction from suspension tuners, who might like some chassis flex to help w/ certain issues like the previous Cobra example) always prefer a stiffer chassis over more flex because as the previous poster put it, suspension tuning just gets more complicated when the chassis is doing its own thing while you're trying to dial in the suspension components. A very stiff chassis means your suspension adjustments are the 1st order effect (ie primary effect) on whatever response you're trying to acheive/correct; a flexible chassis complicates the tuning problem a lot.

The C5/C6 Vette in the high 20hz region compares very favorably w/ Italy and Germany's best, I suspect. Anyone have numbers to support???

rexracerx9

I do not recall where I read this but I think the Mercedes SL55 and 996 series 911 Porsche Cab has a stiffer chassis then a C6? Not 100% sure though? One of the car magizines wrote about this several years ago.

Adding a top makes a huge diffrence. The Cayman is 2.5 times stiffer than the open top Boxster. It is noticable when you jack up the car from the front wheel. The Cayman will lift the rear wheel much sooner than the Boxster. The Cayman is more responsive and has quicker response. Leave it to Porsche to charge more for the hardtop on this one? Everyone else charges more for the vert.

I don't know what the numbers are for a C6? I would think the coupe with the top on would be stiffer than with it off? You can feel the C6 chassis flexing over bumps if you place your finger between the targa top and side window. That movement it the source of the noise in the targa tops.

Race cars want the most rigid chassis possible. Installing a roll cage saves your life but it also stiffens up the chassis a lot.

I wonder also if the after-market center plates actually make the C6 chassis stiffer? You would think the factory center plates would be distorted or the screw pattern in older cars would not align up when removed if there was a signifigant amount of chassis flex with the factory plate? The after market plates probably are worth it for the heat deflection alone though?

This is a great topic. Hopefully someone has information on how stiff the C6 is compaired to the competition? I wonder how much stiffer the C6 Z06 is over the C6? Was the Z06 hard top required for the larger tires and stiffer suspension and/or for the huge torque from the motor? Is the aluminum Z06 chassis as stiff or stiffer as the steel C6 frame? It would make for interesting reading if someone knew and felt like posting?

rz2mbc

The tunnel plate WORKS....less flex in body, center console is much cooler

LTC Z06

and untill I see the frame tested with one of these new tunnel plates I'll believe what one of the GM Corvette chassis engineers told me when I asked him what these after market tunnel plates would do he said, "Add mass."

talon90

This is the last data I have seen. I don't have any specifics on the C6 but it is reported to be the most rigid frame yet.

LTC Z06

From my observations I'd bet good money that the vette chassis is just as good as any of the top sports car out and better than some costing twice as much.

With modern cars the stiffer the chassis the better the suspension engineers can create a suspension to do what they want it to do.

I wouldn't be surprised is Shelby's good chassis flex was a fortuitous accident.

opus1111

Yup yup. This is a cool post. Thanks talon90 for posting the graph.

gitgone

I agree, thanks talon90. It was great to see some actual data backing up what a lot of us suspected.

rollin18

id like to ask you...
how is your car behaving that makes you think its not stiff enough??

also what is hot abs?