Front strut tower brace

[KrackaC8]

This broke my brain. My understanding is that a strut tower bar is there to keep the chassis from flexing. Why would we want a preload on the bar creating an inward flex. Wouldn’t we want the support be keeping the strut towers from flexing inward toward each other ? . Thoughts?

I spent WAY too many hours working through all this a few weekends ago... Probably need to do a deep dive in chassis engineering and suspension geometry, but it does come pre-set from the factory that way. End of the day, goal is to tighten/stiffen the chassis and allow for less flex. There are some who prefer to set it neutral with no preload or tension.

 

[FSUZ33]

Mounting hardware is self-explanatory, two screws and one nut on each side.
The adjuster and hardware are circled below.

In the image you see three nuts, however the outer two are actually separate/loose nuts ("jam nuts") where the center one is part of the adjustment screw.

Illustration below shows the individual pieces (quick and dirty, but it gets the point across).
The blue adjustment screw is all one piece.


- When tightening or loosening the jam nuts always hold the center adjuster with another wrench to keep it from rotating.
- The adjustment screw is threaded left-hand on one side and right-hand on the other, so the lefty-loosey/righty-tighty rule only works on one side. Fortunately you can see the threads to determine which is which.
- Preload is adjusting the bar out (to be longer) not in (shorter).

To unload or remove the bar:
- Hold the center adjustment screw nut in place while loosening the jam nuts on either side. Spin them so there's a little space between the jam nut and bar, and jam nut and mount.
- Turn the center adjuster until it feels loose and you can spin it by hand. It's not going to turn very much with both mounts attached/tight, but if you can move it a little by hand, it's unloaded.

Install and preload:
*This is assuming the jam nuts on the bar itself are loose*
- Place the bar so that the mounts line up with the holes and fit over the studs on both ends. If the bar doesn't fit over both sides don't spin the bar or mount, turn the adjustment screw to shorten or widen the assembly so both sides fit.
- Center the mount on one side of the bar over the holes/stud, install and tighten the hardware.
- Twist the adjustment screw so the holes in the other mount are relatively centered on the stud and holes.
- Tighten the hardware.
- Twist the adjustment screw by hand (LOAD direction) until it gets tight. At this point the loading is neutral. EDIT: Stop here and tighten everything back up if you want a neutral setup.
- Turn the adjuster screw with a wrench the same direction to add preload. I do not know degrees of rotation, so up to what others feel is suitable. Maybe 1/2 turn, maybe more, maybe less. It doesn't take much. You may be able to see the center of the bar over the engine cover raise slightly when preloading.
- Once you're happy with the preload, hold the center adjuster screw nut stationary with a wrench and tighten both jam nuts, one against the bar and the other against the mount.

 

[FSUZ33]

This broke my brain. My understanding is that a strut tower bar is there to keep the chassis from flexing. Why would we want a preload on the bar creating an inward flex. Wouldn’t we want the support be keeping the strut towers from flexing inward toward each other ? . Thoughts?

I don't know if preloading is good, bad or has no effect. And not sure if it was actually the case, but the bar on my 1st 350Z moved when I removed it, and would barely fit back over the studs. The fix was to undo the jam nuts and shorten it. My brain said it did that because it was slightly preloaded, but I have no clue if that's true or not. The amount or preload I've put on all 3 of my Z's has been so minmal I don't think it would make a difference even if preloading was bad. Maybe we should start a thread on the uselessness of preloading strut tower breaces vs tthe uselessness of catch cans,?...idk.

Seriously though, I've never once spoken with anyone or searched online about strut bar/brace preload.

 

[VR30Infection]

Well. For the record, I just slightly preloaded my bar in the outward direction. Put the bar on, put all of the fasteners on just slightly loose, snugged the tensioner down by hand, and then tightened down the fasteners the rest of the way. Of course I also tightened the jam nut as well. As far as the catch can is concerned, I pull enough contaminated oil out of it to justify the purchase. lol.

 

[trackratZ]

One key thing is, similar to my Cusco bar on the 240Z, when removing ensure the jam nuts are loose and adjuster turns easily. Don't force the bar off!. Since over time the strut towers may have shifted even just a micro millimeter. You don't want to strip the softer tower nuts or bolt threads.

 

[KrackaC8]

I got my bar adjusted a bit more today, along with adding some thin adhesive foam underneath to prevent rubbing on the plastic engine cover (snug fit with the Mishimoto intercoolers).

 

[AshwinSan]

Highly highly recommend utilizing the preload adjustment on a bar like this. It is a fantastic design that Nissan implemented for situations like this. The preload ensures that the load transfer occurring on the shock towers have no deflection to mitigate dynamic alignment change (core fundamental to a proper strut tower brace). I honestly think the factory design is top notch. When I did Cusco type 40 and carbon brace on my Lexus GS it really reduced the chassis lag and improved transient response which is lightning fast on the Z from the factory from what I’ve noticed. The bars definitely help a lot more than what people think especially when running coil overs with pillow ball upper mounts. Every panel is a spring but when preloaded it reduces transient lag and ensures proper mitigation of loads traveling through the front members if the car. Please don’t overlook this adjustment lol!

 

[Midz10]

Tip: 370Z front strut tower brace tower fits the new Z. And the OEM one has 3 points contact and looks nicer IMO. (center cowl removal/modification required)