Stiffening the chassis

[Danio]

All right I got a question. Where should I begin to stiffen the chassis?

I got Tein HE coilovers recently and I drive on bumpy mountain roads frequently. Also practice drifting in parking lots once in a while. The car has always made creaking sounds but it has gotten worse. Even when driving on a relatively smooth road that becomes uneven just a little bit, I'd hear creaking and popping sounds. They're not coming from any particular area. Just all over. I'm sure the huge sunroof that the previous owner had put on doesn't help.

I'm wondering which part of the car I should stiffen first. I really don't know much about physics and stuff but I'm guessing that if one part becomes more rigid, another part is gonna become more likely to flex? Like when you're snapping a twig or whatever, it's the weakest part that snaps.

Well I'm a bit worried that stiffening one area is going to cause other parts of the car to flex more quickly so I'd like to know what thought you guys might have on this. Should I get front and rear strut bars first, or roll bar first, etc...

Same with the suspension parts. Any particular parts that are weak that I should replace with stronger aftermarket ones before they break? Like the toe links?

Thanks.

[ca18guy]

The most common thing to stiffen the chassis is strut tower bars. There cheap so start of with those. After that nothing really comes to mind. You could stiffen the chassis with "catalyzed rigid structural polyurethane foam" called FoamSeal, Structual foam can drastically stiffen chassis parts, some higher end cars use it. I'm sure others have chassis stiffening ideas, thats all i can think of right now.

EDIT: also a roll cage would improve stiffness, but might be a little to much for a daily driver.

[SilviaDriver]

you can also start welding your chassis together, in certain spots haha

[Dousan_PG]

roll cage

sell your car get no sunroof one haha..

go w/ a 4 point cage, do luck parts nams bar and stbs. should help dramatically.

[BadMoJo]

There was a great thread on this over on FA not to long ago.

the search there is messed up so i spent like 15 minutes looking for it with no luck :(

But i would guess the do luck RXB and the under chassis brace things would be a good place to start.

[Dousan_PG]

i have a rxb and LOVE it. thing rocks.
going to dump it wheni get a roll cage next year (no, not for sale, going to my friend)
i am getting a do luck flb soon and then a rlb as well
i love suspension mods. hehe.

[Danio]

All right, here's how I think I should do this:

1. Nismo power bar
I think maybe this should go on first just because people have said it's a bitch to put on when the holes don't line up due to chassis flex.

2. Do Luck RXB
To lessen the twisting in the middle of the car.

3. Front and rear strut tower bars
To stiffen the upper parts of the front and rear. I feel like I shouldn't do this first, even though it's cheapest, because it might cause the middle to twist more.

4. Front and rear sway bars
Since people tell me that these make a big difference in handling, I'm guessing they'd also make the middle of the car twist more.

Any other suggestions on what I should get or in what order I should put them on?

I'm not sure about that FoamSeal stuff and welding certain points of the car. If I do any of that, I should probably get a roll cage so that if I end up in a big accident, the cockpit doesn't collapse since the areas that are designed to collapse might not. And I'm not really sure about getting a roll cage. =P Hmm... Maybe later, cuz that'd take me many months to save up for.

Damnit. And I thought I was saving up for wheels. Looks like I've got other priorities now. Maybe I should even take off the Tein HE and put the stock suspension back on for now, cuz the car really creaks a lot. ... Nah.

[Dousan_PG]

i say do those you listed and see how it is

i have the same (except the nismo power bar) and mine never creaks. well i have no rear interior and no sunroof too and my tiends are usually close ot or near full stiffest for the street and full on the track (still too soft)

try those and see how you like it!

[Danio]

After doing some more reading, I think the foam stuff and welding might not be a good idea, since if the car doesn't flex, it cracks. And if I wanna keep this car for many years, I'd rather it flex than crack. Wow what a headache. So I want chassis flex but I don't want chassis flex. -_-; ... Aaah whatever...

[West]

A list of what I have installed so far is shown below.

If I were you I would start with Strut bars and then get a Do Luck FLB. Just a FYI, Jspec.com has them for about 150$ right now. The rear honestly isnt needed because our rear subframe is damn stiff stock.

The Cusco Tension Rod bar is the same thing as the Nismo Power Brace, just alot cheaper. There is a GB for them right now in the GB Section.

There might be a GB for some NAMS Front Fender Bars which cost about 150$ and you have to install them by taking of your front fenders.

SUSPENSION:
-Monkey Magic Front Tension Rods
-Do-Luck Front Ladder Bar (FLB)
-Do-Luck Rear Ladder Bar (RLB)
-Stillen Rear Upper Contol Arms
-Greg Dupree's Subframe Spacers
-Whiteline Adj Front Sway Bar
-Whiteline Non Adj Rear Sway Bar
-Cusco AS Rear Strut Bar
-Ebay Front Strut Bar
-Cusco Tension Rod Bar

[Danio]

All right I'm an idiot. I paid more attention today and it seems that all the creaking is coming from the ceiling. Every part of the ceiling. Front, back, sides... Everywhere. But all from the ceiling, not all over the car. (Damn sunroof.) Ah well at least I learned some stuff cuz of this.

If I just let it creak until there's nothing left to snap-crackle-pop, will it eventually stop? I mean like is it gonna becomes so flexible that it no longer creaks?

[mrdirty]

Originally posted by Danio
After doing some more reading, I think the foam stuff and welding might not be a good idea, since if the car doesn't flex, it cracks. And if I wanna keep this car for many years, I'd rather it flex than crack. Wow what a headache. So I want chassis flex but I don't want chassis flex. -_-; ... Aaah whatever...

You're right that if u strengthen certian parts and not others the weaker ones will have more focused loading but at the same time strenthening the car as a whole will not lead to fractures.

The body of a car can be looked at as a closed thin walled vessel, and the point of highest stress would therefore be at the thinest section. The load carrying capacity is det' by the thinnest section. I think all sheet metal is the same thickness. INOTW welding the seams of this mofo will only strengthen and increase torque capacity.

With my own 240 I think that after looking at it, I would benifit a lot more by just stripping the tar off and repairing any rusted sections first, then welding the seams, THEN bolstering w/ more members. I got busy and lost my welder so I added a strut bar first...makes a difference though.


I tried to make this post simple, 'cause people don't seem to like it when I use formulas and stuff.

[mrdirty]

Originally posted by Danio
All right I'm an idiot. I paid more attention today and it seems that all the creaking is coming from the ceiling. Every part of the ceiling. Front, back, sides... Everywhere. But all from the ceiling, not all over the car. (Damn sunroof.) Ah well at least I learned some stuff cuz of this.

If I just let it creak until there's nothing left to snap-crackle-pop, will it eventually stop? I mean like is it gonna becomes so flexible that it no longer creaks?


Sunroof? They all do that, stiffening the car will help a lot; my front strut bar alone took away a fair bit.

And no, it will just creak more over time because you're fatigueing (sp?) the body and loosining connections.

[s14slide]

There is a GB for them right now in the GB Section.

I found them for cheaper here, www.japanparts.com, and this place has some good prices on quite a few things. Just found the site not too long ago. Also check www.takakaira.com

[Dark]

Found this at 240sx.org

My sunroof made that same irritating sound at highway speeds. I solved it by unscrewing the plastic latch and inserting a couple of lock washers on the screw between the metal of the roof and the latch body. This lowered the height of the latch body and now my roof shuts with a very satisfying thunk, though it does admittedly take more effort to open and shut it. The seal is much improved, and the noise has been eliminated.

I did the handle tightening adjustment, but still had this problem so, I called a sunroof place and explained my problem them. They recommended simply rubbing vasoline around the top seal of the sunroof. As the rubber ages, the rubber becomes more pourous and the vasoline fills and restores the rubber. Fixed it for me. Also restores other aged rubber.

Hope this helps

[SmackedSilly]

This Is What Sports Compact Car Feels About THe Foam, THey Love It.

"Foam-Filling the Chassis
In any high-performance car, it is impossible to make the chassis too stiff. The stiffer the chassis, the higher its natural frequency, making the energy imparted to it by bumps less likely to excite the body's structure. A stiffer chassis enables the use of stiffer springs and shocks without hurting the ride. This is because a stiff, non-flexing chassis transfers more force into the suspension where it can be dissipated by the springs and shocks instead of transferring the force to the occupants. A stiff chassis is also more responsive to roll rate tuning for balancing understeer and oversteer. This is one of the reasons why automotive engineers are continually investigating ways to stiffen chassis without adding weight.

In a final bit of reengineering to stiffen the body, we injected the chassis with catalyzed rigid structural polyurethane foam. Structural foam, in the 2 lb per cubic foot density that we used, can stiffen chassis members up to 40 percent.

Higher densities of foam can increase stiffness by up to 300 percent. Since we cannot retool custom parts to redo the Z's body, we figured that this would be an excellent, low-cost way of greatly increasing chassis stiffness. Injecting foam is not a new technique for chassis stiffening. The Infiniti Q45 uses this sort of foam in some of its chassis members to increase stiffness, as do a few other premium cars. In fact, the foam we chose is the foam recommended to repair damaged Q45s.

To get the correct foam for our project, we contacted Art Goldman, Foamseal's automotive product manager and author of an SAE (Society of Automotive Engineers) paper on the use of structural foam for the stiffening of automotive unibody structures. We used Foamseal's two-component foam kit, p/n 11-22 to fill the main members of the chassis. Like we mentioned earlier, Foamseal is the supplier that I-CAR, a national certification group for quality auto repair, recommends for the repair of damaged, foam-filled chassis. The Foamseal kit uses a two-part catalyzed polyurethane foam, which quickly cures into rigid, waterproof, closed-cell foam. To prep the car, we carefully masked off all painted areas anywhere where the foam could drip. As this sort of foam is a thermosetting catalyzed plastic, we realized it could be icky if it spilled on paint or any part of the car's interior. This foam is nasty stuff. It is impervious to all known solvents and cleaners.

Rubber gloves must be worn. Get some of it on your hands and it will stay there for more than 3 weeks--don't ask how we know. Do not get this stuff on your paint. Wear old clothes; we ruined ours while learning how to handle the product. We injected the foam into the rocker panels and frame rails of Project Z through existing bolt and drain holes. When injected, the foam reacts like shaving cream and quickly expands to fill the empty space. You can judge how much foam to add by watching its expansion progress through some of the holes. Once injected, the foam expands and begins to cure in about a minute so you need to work fast and plan how you inject the foam before you start.

The life of the foam kit is limited to a few hours once the seal is broken. We filled all of the Z's unibody frame members using five foam kits. When foaming a chassis, you must remember the wires and other lines that pass through the chassis must be relocated or they will be entombed forever.

We were amazed at how this simple procedure improved the performance of the car. The chassis now almost feels like it has a roll cage. A sloped driveway can be driven up sideways with nary a creak. Even though the Z already has a pretty tight chassis, it feels more solid. The ride has improved and road noise has been reduced noticeably. We bet that the car will be even more responsive to chassis tuning measures in the future. If you are a slalom racer, a road racer, have a lowered car or even just want a smoother ride; foaming is a worthy, easy-to-do modification. Foamseal has foams in densities as high as 10 lbs per square foot if you desire to make things even stiffer.

Do not--I repeat--do not attempt to use cheap, hardware-store canned foam. This is not the same thing, and if injected into your chassis, will form a gummy mass that won't dry. Foamseal foam is a professional grade foam, which although it is a little unforgiving to cleanup mistakes, has superior mechanical properties and catalytic curing so it will dry even in an enclosed space."

http://www.sportcompactcarweb.com/projectcars/0006scc_proj300zx/

[Danio]

Originally posted by Dark
Found this at 240sx.org

... blah ...

Hope this helps

That's a completely different problem. It's talking about that annoying whistling sound from S13 moonroofs. I had that problem too when I drove an S13. I'm talking about the entire roof creaking and making popping/cracking sounds. Well thanks anyway.

[mrdirty]

Originally posted by Danio
That's a completely different problem. It's talking about that annoying whistling sound from S13 moonroofs. I had that problem too when I drove an S13. I'm talking about the entire roof creaking and making popping/cracking sounds. Well thanks anyway.

no, it's the same problem; the roof creaks because the chassis twists...

[Danio]

Originally posted by mrdirty
no, it's the same problem; the roof creaks because the chassis twists...

The stuff he posted wasn't talking about the roof creaking. They're talking about the whistling sound common on S13s with moonroofs.

[mrdirty]

Originally posted by Danio
The stuff he posted wasn't talking about the roof creaking. They're talking about the whistling sound common on S13s with moonroofs.

right, I thought u were refering to the post from smacked; sorry.

BTW: nice post smack.

[daisosasen01]

Sup dan..

Long time no see. Your cell number does not work, so how about shooting me your new one. Also I lost the e-mail with Ralph form spriso address on it. Can you send it to me again.
[email protected]

Also before you go and buy anything yet for your chassis. I found a shop that does really good jobs on roll cages. They weld cage so that you will not even need strut bars or what ever else.
Since you are going to keep your car for ever and ever hehehe
I think this is a better investment for you. Also I still owe you $20. Let's meet some time so I can give it to you. I am going over to Justin's house to pick up a radiator in fremont on tuesday. tell me when you are available. And also come with me to 510 motorsports. It is in fremont also, they will show you what cages are all about and give you good prices. Better then buying a freaking cusco cage, just for the sake of being JDM.. **** that...
But altimately... to each his own.

Koji