Strut bars

[MarusGTR]

Hey guys,

Just wanted to know if any of you guys felt any difference between having a front strut bar and not, from a purely objective standpoint. I've always run mine on track so I have nothing to base myself to.

Reason why I'm asking is because most aluminium and mild steel bars have length adjustability. While honestly without thinking I thought it was for fitment, I've been pondering about the implication of actually preloading the bars by expanding their lengths while they're secured on the shock towers. This tensile load would create a tensile buffer zone which would make an opposing stress to the inward flex from the shock towers, way above what could be achieved by the soft metals' tensile strengths.

And I'm asking if you guys feel any difference is because if you do, preload could be beneficial and increase some of the structural integrity of my cheap alum bars. If not, its not worth my time to keep thinking about it lol.

...

Yes I have too much free time. And google? Holy hell what a mess. Apparently Some people in 240sx forums think preload is for warping towers for camber adjustment? LOL.

[hozer]

I have no evidence that I can provide you but a preload will do nothing for you but put stress on your car. I don't imagine you'd be able to get it "evenly" preloaded on the chassis either unless you have a frame tester or similar machine. Also you would experience both tension and compression whilst driving, so at any given time it could be "loaded" in the wrong direction. The load you could even achieve would be negligible anyways.

Wheel, suspension and alignment guys swear by it preloading. Restoration guys (resto-mod mainly) and some very reputable auto-x competitors would say not to do it under any circumstance.

Neither side has concrete evidence but I think having stress on strut mounts and bars 24/7 is stupid so I don't do it; but as I said I can provide 0 evidence for my thoughts.

Your essentially making a spring based upon the tensile strength of the material, when all it serves a purpose for is bridging the 2 sides of the frame. So your putting pre-flex on a piece designed to stop flex... If you were to use the brace to pre-load the strut tops, regardless whether moving them closer together or further apart, over time and as loads were released and reloaded, that would work away at the welds around the strut sheet metal. Inevitably you'd get a relaxation of the stresses in the body structure over time and thus movement back towards the nominal and static position that you've just tried to alter.

Truth be told its debatable wether or not they even help at all. Saw a gentleman once replace his strut bar with a wooden dowel and proceed to lap, back in the pits, the dowel looked the same. Any flex at all would have made some impression.

Just to be clear again I have 0 evidence besides what I have gathered from qualitative first hand experiences

[MarusGTR]

^ Interesting point. I agree that loading the suspension may be bad but from a materials standpoint it would have minimal effect; the preload is made on aluminium or mild steel bar which (I assume) has a considerably lower tensile strength than the steel/welds used for the chassis. Preloading the bar under the response limit of the chassis would just make the load be diffused in the chassis.

Also I agree that the towers may have instances of outward flex, but the deflection would mostly be in compression and thus be less likely to actually present some movement. However the preload could exacerbate the issue by making additional stress in the same direction.

Anyway I might preload my rear bar a bit, I feel like I can flex it just by arm strength. Feels stupid weak.

PS: As for the rear bar I can confirm it helps, I originally didn't have one and could hear the rear flex on big dirt lumps when I had my GTR stored in a field next to my parents house. The addition of the bar stopped the audible flex.

[r33_gtst]

Upgraded sway bars/bushings? A lot of people rely on adjustable suspension or strut bars to do a sway bars job. Imo strut bars are to provide additional stability between the two towers and prevent flex. I neglected to do sway bars on my r33, have almost every other suspnsion component and can feel the missing link.

[NismoS-tune]

Go buy an $4-800 bar and like some of us, you'll notice they are fixed.

The End

[hozer]

Go buy an $4-800 bar and like some of us, you'll notice they are fixed.

The End

Precisely

Also important to note, strut bars are not a suspension component and 90% of folks on here I will wager do not drive aggressively enough to have chassis flex.

If you want one for looks (they look wicked no denying that) then get $100 one. But it's not going to provide you much benefit. If you can flex it by hand what chance does it stand against a flexing frame?

Most would notice a far better driving experience with some new sway bars instead

[MarusGTR]

I'm on a budget of lint and pebbles, I'm trying to do the best with what I have and try to use it at its full capacity.

[hozer]

I'm on a budget of lint and pebbles, I'm trying to do the best with what I have and try to use it at its full capacity.

I in no way was trying to infer more expensive is better just meant to illustrate If the bar can be preloaded by hand or simple tools its not going to resist the forces of a torqued chassis.

Also maybe worth noting if your pinching pennies, putting preload on will affect your alignment so keep that in mind if you are unable to test it yourself. Would be no more than a degree but if we're talking about nitpicked advantages of preloaded strut bars, I'm assuming perfect alignment is of importance as well.

However all being said I also believe 100% that driving is also a mental game. If you feel it will make a difference, do it. And you'll probably 'notice' one That's the name of the game

It won't hurt anything if you do it so why the heck not if you want to I'd say !

[MarusGTR]

My comment was more towards S-tune, so no biggie. Right now I'm just trying to run the tightest ship I can so that I can maximize the fuzzy feelings of enjoying the open road before I get funds and maybe finally build a race-only car.

But again, I doubt it would affect the alignment, the preload would be residual stress contained in the bar, not the chassis. And you're absolutely right, the only thing stopping me right now of making flying laps at the track is mental; I don't trust the condition of the old chassis. Doesn't help when that my AMS control arms failed on the track too. I think I'll just have to change them, to have piece of mind.

[Skym]

From what I understand, the strut braces are designed to help hold top of strut towers in close to same position (not push inwards which changes alignment and affect's grip, etc) when strut tower is loaded, thus alignment stays close to what it should be.

I was told the adjustability in middle of strut brace is due to chassis bends over time and strut towers are not in same position as when new. Also I have tried over tight, tight in the middle of strut brace on rear of car and doesn't make much of a difference.

But adjusting the height of the end plates makes a difference (front of car), as if higher on one side than other, can get more bump steer in one direction (interesting experiment).

Also strut towers don't move towards the middle in a straight line from left side to right side and vice versa, but more towards the firewall and on a roughly 45 degree angle. To understand what I mean, have a look at the mounting point for top of upper arm (engine bay side) on both strut towers and it should make more sense.

That's why when they make a rollcage for R32 GTR, they put bars that are on a 45 degree or so angle towards the firewall, from those mount points on both sides of front of car (both 45 degree angled bars go through firewall and are connected to middle of bar on front of rollcage and have 2x bars from middle of front of rollcage to top of driveshaft tunnel)

For example (without the 2x bars to top of driveshaft tunnel)-

[hozer]

In the end, the difference really is negligible. Preloading does for sure affect your alignment though.

To test this, install one while your car is on the ground, then install it while the car is in the air. Installing in the air will "preload" the bar and will change alignment.

My argument is if one claims they can notice preloaded strut bars they would also then be leet enough to notice the otherwise negligible alignment change.

But just like Marus says, if it allows you to cross a mental bridge about how far you can push your ride then I'd say worth it! Often times we neglect or even disregard entirely how much silly changes affect us mentally. If a strut bar allows you to shelf worries and drive harder, well that's a better lap and you can't argue that.