Urethane Foam chassis stiffening

[gnegroni]

Not sure if Aftermarket is the correct place, but since its not necessarily stock talk...

I was reading the Feb 2009 issue of Sport Compact Car focusing on the 240SX modification article Project S13: Part 2. One of the modifications they were using was employing urethane foam to stiffen the chassis. I don't know about people in most states, but my Solara creaks, bitches and moans like hell with only ~70k miles. Speaker, sunroof rattles and recently developed creaks on driveway ramps or particular curves got me thinking if we could stiffen the chassis some noticeable improvements. However, don't have the slightest idea of what to do (if I had the money) or if somebody attempted this on a vehicle.

I saw SMAN's thread on stripping down for adding insulation but still clueless.

Anybody?

[ThatVietGuy]

Don't do it.

It's not worth it on a daily driver type car. A normal car chassis NEEDS to have flex or the thing will just shake itself apart and wear out even faster.

You only use the expanding foam idea when you're building racecars or heavy-use track cars.

[gnegroni]

Don't do it.

It's not worth it on a daily driver type car. A normal car chassis NEEDS to have flex or the thing will just shake itself apart and wear out even faster.

You only use the expanding foam idea when you're building racecars or heavy-use track cars.

Understood. Thanks for the input!

[ArtinNC]

Don't do it.

It's not worth it on a daily driver type car. A normal car chassis NEEDS to have flex or the thing will just shake itself apart and wear out even faster.

You only use the expanding foam idea when you're building racecars or heavy-use track cars.

But my wifes new Solara Convertible with 226 miles on the clock don't need to flex as much as it does.

[JamesT]

But my wifes new Solara Convertible with 226 miles on the clock don't need to flex as much as it does.

Try the RSB and other stuff before you decide to do this.

[ArtinNC]

But my wifes new Solara Convertible with 226 miles on the clock don't need to flex as much as it does.

Try the RSB and other stuff before you decide to do this.

The Solara isn't that bad but would like to take out a little of the frame flex. Don't think I'll try the foam idea.
Art

[1gSE]

Don't do it.

It's not worth it on a daily driver type car. A normal car chassis NEEDS to have flex or the thing will just shake itself apart and wear out even faster.

You only use the expanding foam idea when you're building racecars or heavy-use track cars.

agreed. They also did it a long time ago with their project 300zx, but that was making 500+ hp and was mostly ran on the track...but happened to be streetable

[panic]

A normal car chassis NEEDS to have flex

Errr.... no.
Can you find one engineer, any brand, who made such a statement?

The flex in a chassis is called "suspension".

[ThatVietGuy]

I had this discussion awhile back with an ME friend and that's what he told me.

I'll stick with the part about not doing it on a street car though, making the car ridiculously harsher than it has to be.

[ArtinNC]

(((The flex in a chassis is called "suspension".)))
I'll agree with that.

[Ilovemylara]

My friend builds racing go carts out of alumium and their chasis flex like crazy.It acts as a suspension. Very smooth and fun to drive...

[panic]

I'll expand on that.

Many karts don't have any suspension - not legal.

A certain amount of "give" is built in to all late model stuff - even trucks, but it's not to permit the chassis to flex (it doesn't), it's for NVH (noise, vibration, harshness) control and it doesn't modify the chassis at all (which should be as rigid as a bridge truss in any and all cases) but instead isolates the driver's compartment, power subframe, cooling, unsprung weight, and some other bits from the chassis.
Chassis flex is welcome if the existing suspension doesn't have enough travel to accommodate the road surface and the alternative is either immediate breakage (not squeaks after 50,000 miles), or a wheel coming off the ground, but the vehicle would work far better if new suspension were permitted.
Urethane foam works if it makes a sandwich of 2 or more closely fitting sheet metal panels that are already structural but still move, and in some vehicles there aren't many. An example: formed sheet metal control arms, which would otherwise have to be re-welded (lot of work) to improve stiffness.
If used, it sometimes expands too much and buckles the panels outward, or pops the spot welds. In all cases it retains moisture (splash and condensation), and speeds up rust by a factor of 10.

The first place to start is what was said: better strut braces, tie all suspension points into the existing chassis, box all "open" members.
If ride harshness is not important, substitute polyurethane for rubber in 1 of the 2 bushings (not both - too stiff!) supporting the shocks and sway bars - quickens and intensifies the effect especially in small movements.

Yes, harsh ride would result from extreme chassis stiffening and "compliance" (unintentional, comfort-derived non-suspension movement) removal, because when a wheel moves it's 1st effect is to squash the rubber etc. in the control arm, shock eye, sway bar etc.
Only when all the compliance is exhausted will the actual suspension (springs, shocks, sway bars) begin to move and gain control of wheel motion and chassis reaction. If all compliance is gone, the wheel goes straight to suspension resistance, which is much stronger. Every little bump goes straight to your teeth!

BTW: lighter wheel/tire combo always helps (regardless of diameter), and increases wheel tracking accuracy without changing the spring rate. In theory you could even reduce the spring rate and have good control, but you'd have clearance issues, etc.

[Sparky5e]

Panic...you made my head hurt

time to go watch the Flinstones

[youngblood]

I'll expand on that.

Many karts don't have any suspension - not legal.

A certain amount of "give" is built in to all late model stuff - even trucks, but it's not to permit the chassis to flex (it doesn't), it's for NVH (noise, vibration, harshness) control and it doesn't modify the chassis at all (which should be as rigid as a bridge truss in any and all cases) but instead isolates the driver's compartment, power subframe, cooling, unsprung weight, and some other bits from the chassis.
Chassis flex is welcome if the existing suspension doesn't have enough travel to accommodate the road surface and the alternative is either immediate breakage (not squeaks after 50,000 miles), or a wheel coming off the ground, but the vehicle would work far better if new suspension were permitted.
Urethane foam works if it makes a sandwich of 2 or more closely fitting sheet metal panels that are already structural but still move, and in some vehicles there aren't many. An example: formed sheet metal control arms, which would otherwise have to be re-welded (lot of work) to improve stiffness.
If used, it sometimes expands too much and buckles the panels outward, or pops the spot welds. In all cases it retains moisture (splash and condensation), and speeds up rust by a factor of 10.

The first place to start is what was said: better strut braces, tie all suspension points into the existing chassis, box all "open" members.
If ride harshness is not important, substitute polyurethane for rubber in 1 of the 2 bushings (not both - too stiff!) supporting the shocks and sway bars - quickens and intensifies the effect especially in small movements.

Yes, harsh ride would result from extreme chassis stiffening and "compliance" (unintentional, comfort-derived non-suspension movement) removal, because when a wheel moves it's 1st effect is to squash the rubber etc. in the control arm, shock eye, sway bar etc.
Only when all the compliance is exhausted will the actual suspension (springs, shocks, sway bars) begin to move and gain control of wheel motion and chassis reaction. If all compliance is gone, the wheel goes straight to suspension resistance, which is much stronger. Every little bump goes straight to your teeth!

BTW: lighter wheel/tire combo always helps (regardless of diameter), and increases wheel tracking accuracy without changing the spring rate. In theory you could even reduce the spring rate and have good control, but you'd have clearance issues, etc.

Love this stuff, man! Keep it coming.