What do you think of your strut bar?

[Mikepage]

You have some info about Cusco into this video : [ame]http://youtu.be/m4KgS8ertHU[/ame]

I know it's a old video but...

[wu_dot_com]

Originally Posted by boredom.is.me

Where do you see any testing? I see nothing.
http://www.whiteline.com.au/product_..._number=KSB652

The biggest argument with these bars isn't what they are made of or of how many bends there are. Yes those do play a part, but so far, the biggest argument has been regarding the means of attachment. The WL, Cusco, GTSpec, and a few others all have hinged joints. Grimm, Hotch..., AEM, and a few others have solid joints. My logic tells me that the ones that are hinged are just for show and do not actually do anything. I don't have any personal data to prove this, but like I said, my logic.

actually, some hinged joints are for cosmetic, while others are for performance. it all depends on the tightness in tolerance of the hinge.

by definition, hinges have force transferring capability in one axis. while a wielded joints have force transferring capability in all three axis plus transferring of both torsional and bending load.

as shown in cusco's strut bar page, the design intent of the strut bar is to prevent strut sidewalls from flexing inward into the engine bay. the load path is uniaxial and it puts the strut bar in compression loading condition. thus a hinge design is perfectly sufficient for the load transfer that is needed for this application. the 3 piece hinge design also makes manufacturing easier and in most cases cheaper when compare to a wielded design.

now according to Grimmspeed's data, the total deflections between the strut towers are .017". a typical bolt hole tolerance in aerospace manufacturing setting is .010". thus if the two hinge were manufacture under those condition, the tolerance stack up between the two hinge hole will be at .020", which is greater than the total allowable deflection. Therefore, the strut bar will not work in this condition because load transfer cannot occur unless the strut bar is properly loaded under compression. on the other hand, if they drill the hinge hole to .005" tolerance, the total stack up will be at .010" and the maximum rigidity improvement will be less than .007" assuming zero deflection. On the other hand, a wielded design will not have such tolerance stack up issue.

Another problem with the hinge design is that over time, the loading and unloading cycle due to vehicle operation will elongate the hinge hole. Thus eventually a hinge design will be less and less effective as the unit age.

PS. keep in mind that .017" Grimmspeed data is only applicable under their specific test condition. it does not mean that if the hinge hole were manufacture to .010" tolerance wont have a positive improvement during real life operation of your car. this number is only being use for reference only. in addition, the .010" tolerance refference above is a statistical tolerancing average of both positional and diametral tolerance.

[Mikepage]

Very good post thank you! Then we need to know the tolerances from Whiteline, to know if the bar do the job.

I will try to calculate the tolerances when I will install the strut bar. At least I will measure the holes.

[wu_dot_com]

Originally Posted by Mikepage

Very good post thank you! Then we need to know the tolerances from Whiteline, to know if the bar do the job.

I will try to calculate the tolerances when I will install the strut bar. At least I will measure the holes.

okay. when you do that, you need to measure the bolt OD, the hinge flange ID (both sides), and the bolt tube ID. the compound tolerance will add up to the total slop you have in this system. when you do take the Dia measurements, be sure to take 3x per hole 120 deg apart. with that we can get an average runout of each holt

[Mikepage]

Am curious to know how much the Hinge hole will enlarge.

[dem00n]

I had the Grimmspeed one, too much understeer for my taste. It was obvious, sold it.

Stock everything.

Honestly, the car doesn't need one. You won't be missing out if you don't buy one. Just stick with bushings if you wanna do small changes.

[wu_dot_com]

GS (GrimmSpeed)
Attach pt:2
Type: Bar
Weight : L
MATL / Fabrication: STL/ Wield
Price: 160
Good: reasonable price, solid wield attachment, light weight.
Bad: 2 pt attachments introduce additional bending load on stock strut bolts. Did not know if such load were properly analyzed.
Comm: overall this is a solid design in all area function, weight and price point. This design is well thought out with 2 color options.

Hotch
Attach pt: 3
Type: semi Box
Weight : M
MATL / Fabrication: ALUM/ Wield
Price: 250
Good: solid wield attachment, reasonable weight. Semi box design improve rigidity from for/aft axis engine bay bending.
Bad: 3 pt attachments introduce additional bending load on stock strut bolts. Did not know if such load were properly analyzed. Semi Box design of the firewall attachment allows for additional flex. Expensive.
Comm: this is a solid design balancing both function and weight. What it suffers is in the price. You get what you paid for. If performance is what you look for, then this is the right bar for you.

AEM
Attach pt: 4
Type: full Box
Weight : H
MATL / Fabrication: Steel/ Wield
Price: 189
Good: solid wield attachment, Full box design improve rigidity from for/aft axis engine bay bending. Inexpensive, integrated MC brace. The 4 point attachment distributes the additional bending load from strut towers more evenly.
Bad: this things weights a wooping 18.3 lbs. it’s a beast. In addition, it is also bulky which may limit your engine bay real-estate for other mods.
Comm: this is a solid / over design targeting both function and cost. You get the most functionality out of this bar than most market offerings at a reasonable price. However, this unit suffers in weight. If you can live with the additional 10-14 lbs, then this bar is the right choice for you.

GTSpec
Attach pt:2
Type: full
Weight : M
MATL / Fabrication: ALUM/ Wield
Price: 315
Good: solid wield attachment, reasonable weight. Full box design improves rigidity.
Bad: : 2 pt attachments introduce additional bending load on stock strut bolts. Expensive.
Comm: This is a solid design targeting both rigidity and weight. However at 315, it is expensive when compare to current market offering. Hotch offers similar capability for much less.

WL
Attach pt: 4
Type: Bar
Weight : L
MATL / Fabrication: ALUM/ Hinge
Price: 179
Good: light weight. Inexpensive, The 4 point attachments distribute the additional bending load from strut towers more evenly.
Bad: : Hinge are less desirable than a wielded construction. The long term effective of hinge design is yet to be determine (hinge hole elongation over time).
Comm: this is a decent alternative for appearance, price, and weight. Though being a hinge design I would expect them to be around 140-160 price range rather than 180. This is a direct competition against Cusco.

Cusco
Attach pt: 4
Type: Bar
Weight : L
MATL / Fabrication: ALUM/ Hinge
Price: 179
Good: light weight. Inexpensive, The 4 point attachments distribute the additional bending load from strut towers more evenly.
Bad: : Hinge are less desirable than a wielded construction. The long term effective of hinge design is yet to be determine (hinge hole elongation over time).
Comm: this is a decent alternative for appearance, price, and weight. Though being a hinge design I would expect them to be around 140-160 price range rather than 180. This is a direct competition against WL.

Racseng
Attach pt: 2
Type: Bar
Weight : L
MATL / Fabrication: ALUM/ weild
Price: 299
Good: light weight. Colorful.
Bad: : Very Expensive for engine dress up while offering no additional benefit from OEM setup.
Comm: this is a complete decorative option. It offers no performance benefit while being pricy. a waste of money IMO

[Mikepage]

From My experience with cusco, I don't think the holes will enlarge and even after many years....

The movement between the 2 shocks tower is too small to enlarge the hole from my opinion... And If this happen, it can happens also to every part of the suspension like the hole in the body where the top plate is attached.

Do you think I have a good point?

Wu_dot_com, thank you for this great list.

[Mikepage]

Originally Posted by dem00n

I had the Grimmspeed one, too much understeer for my taste. It was obvious, sold it.

Stock everything.

Honestly, the car doesn't need one. You won't be missing out if you don't buy one. Just stick with bushings if you wanna do small changes.

Less chassis you have more the suspension can do their job and more the driving feeling you have, you can always fixe your understeer/oversteer with a good set of seats bar.

[Mikepage]

Good article to read : http://www.e30m3project.com/e30m3per...bar_theory.htm

[wu_dot_com]

Originally Posted by Mikepage

From My experience with cusco, I don't think the holes will enlarge and even after many years....

The movement between the 2 shocks tower is too small to enlarge the hole from my opinion... And If this happen, it can happens also to every part of the suspension like the hole in the body where the top plate is attached.

Do you think I have a good point?

Wu_dot_com, thank you for this great list.

you have a very valid point. Since I have no historical data, I can only say that there is a possibility of hole distortion based on similar experience.



though the movements of 2 shock towers are small, the forces those hinge hole experience can be vastly different depends on the loading condition. for example, lets say the strut bar is loaded in perfect compression, that means the hole would need to provide equal and opposite force to remain in static condition. if resisting force is lower than the material yield limit, then the hole would not become elongated. if the resistance force is greater, than the hole would elongate over time. if there are slack in the strut bar system, then when an input force is apply, you may have an impact loading situation at the hinge hole which can rapidly approach the material yield limit. Cusco may have shock dyno their test car to get the necessary info for their design, but that is something I would never know for sure.



in either case, the elongation for each hole would probably in the magnitude of .002-.004" (the thickness of 1 to 2 sheets of paper) depends on the operational environment. That couple with the many other factors throughout the life of the unit makes a generic prediction for of an art than exact science.

[wu_dot_com]

Originally Posted by Mikepage

Good article to read : http://www.e30m3project.com/e30m3per...bar_theory.htm

this article you've posted does give some very basic static force analysis. however, the static analysis is not explain properly.

under all driving condition, point 4 and 5 actually experience a moment along with reaction forces in both X and Y axis. this is why the strut bar can experience tension rather than pure compression.

with the hinge design, the hinge itself does not transfer the bending load (the hinge will rotate), the bending load is being carry by the bolts (bolts needs to handle both clamping and bending).

with a wielded design, the wields carries the bending load while the bolt only handles the clamping load.

[Mikepage]

What is your job? You seem to have a good knowledge.

[dem00n]

Originally Posted by Mikepage

Less chassis you have more the suspension can do their job and more the driving feeling you have, you can always fixe your understeer/oversteer with a good set of seats bar.

Of course you could dial in understeer and oversteer, theres more than one way to do so.

But i wanna keep stock feel while updating a few weak spots, i didn't find the grimmspeed bar necessary.