jp951

Hi all,

Just a quick question that has given me some concern recently. The older our cars get, does the chassis start to flex more?

Thanks.
Manuel Scettri

Damian in NJ

Manuel, I guess this is a question you could ask about all cars, not just a 968 coupe or cab. One thing may make it worse if you have a cab; some owners, in a attempt to save weight, have removed the vibration dampener from the trunk cubby. I'd be very wary of doing this, the long term effects over time/mileage are unknown, but logically it would cause harm.

sasilverbullet

As long as the car hasn't been in a wreck, I don't think so. I'm pretty sure that what you're really dealing with is how rigid was the car first constructed. Most all cars have some chassis flux, some more than others. Porsche's are tighter and have less flex than most, but they still have some and can be beefed up by adding braces and plates.

Are you planning on tracking the car?

flash968

here we go again - less mass equals less kinetic energy - less kinetic energy equals less chassis effect from oscillation - removal of the weight results in an increase in high frequency low amplitude oscillation , but a decrease in low frequency high amplitude oscillation - metal fatigue and therefore chassis damage (sheeetmetal) would occur from the latter - fastener damage (latches and hinges) would occur from the former - this mod may not be for everybody, as there is definitely a change in the feel fo the ride - by the way, the scuttle shake all dissapeared almost completely when i put in the roll bar

to the original question - porsches, especially this one, feel like they have a lot less flex than other cars, but really don't - they do build in a certain amount of additional rigity with the extra materials, which is what makes them so heavy, but the real difference is because of all the rubber damping going on everywhere in the car - remove that stuff and replace it with rigid materials, and you will quickly see what is going on - the rubber isolates you from a lot of the flex - it makes the car more responsive to replace the rubber stuff with solid materials, but it does make the ride quality change

it's all about choices

Damian in NJ

Manuel, as you can see there are people who disagree with the chassis engineers at Porsche-take your pick as to whose opinion to trust, especially when it comes to your safety and the well being of your car.

jp951

...my car isn't a cab, so I wasn't talking about the dampner. What I was looking for was more along the lines of flexing in a coupe due to age. I guess installing a roll cage solves the problem. I did notice a huge difference when I installed the strut brace. I didn't think the car was that flexy for a strut bar to make that much difference, thats why I'm wondering if theres a lot more flex going on than what I think....

Manuel Scettri

flash968

there is - while the sheet metal itself does flex, there is a lot you can do prior to installing a complete cage that will make the car a lot more responsive, and get rid of the slushy stock feel

like i said, if you were to replace the rubber bushings with solid ones, things would immediately show up - right now a lot is being absorbed by the rubber - the rear suspension to body bushings alone make a huge difference in tightening things up - you will feel a lot more in the chassis though - if this is a race car, you probably won't mind - in a street car, this might drive you nuts - once you've done this though, then you can start making better decisions on where to stiffen things in the chassis