240Z Chassis Flex. Do strut tower bars make a difference? (Any Suggestions?)

[Jayru]

Hi Guys,

I have been injoying my 240Z for a while now, but one thing is really bothering me about it. The chassis rattles/squeaks and is just generally loose while driving. Drive into a driveway and feel the car twist, hit a bump and feel the chassis flex, rattle, etc...

It's not a structural rust problem because the car is solid metal wise in all the key areas. I know the metal is a little thin from the factory to begin with, so is this just a common problem with these cars?

What can i do to stiffen it up (Besides welding a cage in)? Are strut tower bars worth the money? Do they do a good job of stiffening up the car? Any better to go with the more elaborate ones that attach at multiple locations (front & rear)?

Let me know.

Thanks,

Jay

[alternativez]

Haven't tried it myself, but have an article saved somewhere. I definitely will do this on my Z during this rebuild. You say the metal is good, and I'm not doubting your assessment, but it can oxidize inside the frame as well, especially in the air chamber above the front wheels. This area is notorious for internal rust, and in a place which is difficult to see. Front frame rails also rust from the inside and can fold without much warning. Tapping with a drift punch may point out thin metal. There is also metal fatigue in otherwise sound-looking metal, which has flexed so much over the years to either become too soft or too brittle.

Are you sure you are not hearing movement between body panels or springs in their perches? Also the doors always were "tinny", and can be improved with panel sound deadening mats like Fatmax. I think that's a product name among others, and one that I have not used but will also definitely look into.

To respond to your question about strut tower bars, yes they will help, and yes a multipoint brace, say adding bracing from towers to upper firewall will help even more.

The foam won't help if the metal is bad, but will add strength, rigidity, and sound deadening at a slight addition of weight. Worth it I'd say,for a street car.

I owned a 70 Z when it was practically new, and they were not well insulated, much like most cars of the day, so they came with the problem. Today we expect our sports cars to have that solid "thnk" when we shut the door, etc, but look at all the sound deadening material they have, and the weight they have gained. Just make sure the car is solid and you may just have to learn to live with some of this idiosyncracy.

[jmortensen]

I always thought strut tower bars were really ricey and didn't do much. Then someone convinced me to try them on my Z. Big difference. Really big difference. Triangulating to the firewall in the front is a very good idea.

Foam in the frame is good, but it has to be the correct structural foam and once its in there you're pretty much not fixing that part of the car again from what I understand. So inject this stuff into a frame rail and then it starts to rust off the car, you're pretty well stuck.

[Ed]

What's the condition of your suspension? Could all your flex and rattle be coming from suspension components that are old and worn out? My Zed when I first got her felt loose and rattled. But once I changed all my bushings, u-joints, shocks, springs, ball joints, and tie rod ends she feels as stiff as a board.

Look at the upper rear portion of your door. Right below the windows. Is the paint chipped? If there was flex in your body then the doors would hit in this area causing paint to chip.

The upper strut bars will help stiffen your body. But I think it's for lateral support. You racers out there please correct me if I'm wrong.

Also do a search on upper strut bars. They have been discussed before and If I remember correctly there was a really good write-up about them.

[71ZZZZZ]

I spun my 240Z out years back and bent the body slightly in the back, after straightening it would track OK but I felt some of the flexing you spoke about...I installed this three-point brace from Top-end Performance and it really helps firming up that area now...I'm thinking about their front brace to complete the effect:

[benny240]

My Z has a home made role cage that conects to all four strut towers. (is that what is called a four point cage)???

Any way I also have the strut tower bars. The guy I bought it from did all this so I do know the original way of handing.

Point is, if I manuver a steep driveway sidewalk aprotch at an angle A tire or two will come of the ground.

The cage is not track worthy (YET) but it is rigid and lets the suspention do the work.

In my opinoin the tower bars would help your handling but the car will still twist.

[Jayru]

What's the condition of your suspension? Could all your flex and rattle be coming from suspension components that are old and worn out? My Zed when I first got her felt loose and rattled. But once I changed all my bushings, u-joints, shocks, springs, ball joints, and tie rod ends she feels as stiff as a board.

Look at the upper rear portion of your door. Right below the windows. Is the paint chipped? If there was flex in your body then the doors would hit in this area causing paint to chip.

The upper strut bars will help stiffen your body. But I think it's for lateral support. You racers out there please correct me if I'm wrong.

Also do a search on upper strut bars. They have been discussed before and If I remember correctly there was a really good write-up about them.

Ed,

I've recently replaced the strut's/springs, that fixed other problems (bottoming out/thumping) the bump stops had deteriorated completely. I had bought Poly bushings but the original owner had replaced many of the bushings a few years ago, so they were not needed.

On a side note, the PO kept books of records on the car including dates and times of all things replaced/done. Kinda neat, although a little anal if you ask me

So it's not an issue of suspension looseness, the car handles great. It's just a flimsyness feeling of the body itself. Think of a peice of plywood flexing up and down or side to side, that's kind of what i'm talking about.

I'm going to start saving for some strut bars and maybe some new longer/stronger frame connectors underneath.

71zzzz, thanks for that pic and name of the company who makes it. I couldn't remember where i had seen a bar like that, but that's the one i want.

Thanks,

Jay

[madkaw]

I hope the bars help since I just bought some carbon fiber ones from ebay. From what i read they help stiffen the chassis but don't harshen the ride which sounds great to me

[240ZX]

I'll agree that the stut tower braces certainly help, which I have installed as well but, I added a SCCA approved rollbar (Autopower) and it also decreased the flex in the rear of the chassis beyond what the stut tower braces added.

[zguitar71]

I have the MSA bar on the front and rear of my car. I do not think they do nearly as much as the bars that are triangulated.

http://www.pdkfabrication.bravepages.com/240%20front.htm

This looks like a good bar or system. I have not heard any comments or testimonials about this bar though. Just having a bar that runs across like mine realy does not do anything as far as stopping the towers from twisting or moving for and aft. To stop that you need to have a bar that ties to the firewall too, like the one on the website above. I like the fact it ties to the frame rail in the front too. I have concerns about the way the hole thing ties together on either side (near the tower tops). It looks as though that could be a week spot eventually from stress over time, the metal could get miss shapen where the hole thing bolts together (ovalized). Does any one have experience with this bar?

[Ron Carter]

There have been several write ups on strut braces and how they work. I was involved with the design of the PDK solution and can answer any questions you might have.