Eibach 25mm RSB

[Yonder]

Hi All,

After searching far and wide on the Forums i cant seem to find any threads/posts of Si's running Eibach's 25mm RSB. Granted it is listed for the CTR, so maybe that keeps people from purchasing it? Although, CTR RSB (20.5mm) swaps are very common here, which theoretically means we can run the CTR aftermarket sway bars. I know handling is purely subjective to your driving style, but looking for less understeer and hear great things about Whiteline (22mm solid) and Eibach (22mm tubular) being able to really plant down the Si's suspension. I was just curious if anyone other than the CTR guys have ran 25mm. If not, looks like il have to be the first to try it out lol

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[REBELXSi]

I have the Eibach 22mm set to the stiffest setting and I felt it helped a lot. Can't imagine the 25mm being able to do much more.

 

[jakabony]

@Kon3_Kilr has one.

 

[fenix-silver]

I have the Eibach 22mm set to the stiffest setting and I felt it helped a lot. Can't imagine the 25mm being able to do much more.

25mm seems a bit extreme w/o also upgrading the front one. And even then, that seems like a lot of bar for the street.

 

[Yonder]

I have the Eibach 22mm set to the stiffest setting and I felt it helped a lot. Can't imagine the 25mm being able to do much more.

Thats what i hear! The RSB Type R swap is only 2.5mm difference and people report its a helped quite a bit. Then again its all subjective lol

@fenix-silver 100% agree. I just enjoyed the FR layout for years (350z) and want to have a pretty stiff rear to mitigate understeer, but have the benefit of FF's ability to correct oversteer with the accelerator. I know Type R's FSB is 29mm and im planning to mimic that set up but with a stiffer rear. Depending on how this pans out.

@jakabony Oh word, Thanks for reference! @Kon3_Kilr How is the handling and drivablity with the 25mm?

 

[jakabony]

Thats what i hear! The RSB Type R swap is only 2.5mm difference and people report its a helped quite a bit. Then again its all subjective lol

@fenix-silver 100% agree. I just enjoyed the FR layout for years (350z) and want to have a pretty stiff rear to mitigate understeer, but have the benefit of FF's ability to correct oversteer with the accelerator. I know Type R's FSB is 29mm and im planning to mimic that set up but with a stiffer rear. Depending on how this pans out.

@jakabony Oh word, Thanks for reference! @Kon3_Kilr How is the handling and drivablity with the 25mm?

No problem. I did the 22mm Whiteline with Accord end links and it is a world of difference. The car is super flat in the corners with virtually no body roll, even with the stock all seasons.

 

[Yonder]

No problem. I did the 22mm Whiteline with Accord end links and it is a world of difference. The car is super flat in the corners with virtually no body roll, even with the stock all seasons.

Damn even with All seasons?? That's impressive. I've been debating CTR's or Accord end links but for the price and now your testimonial, Accord it is. Still cant see why the Si's got the shit end of the stick with the plastic OEM links. Is your Whiteline set to the stiffest setting?

 

[jakabony]

Yeah the OEM end links are pretty flimsy. The Accord ones are cheap too and aluminum. Yeah I am on the stiff setting. The RSB didn't sit right with the lighter setting. The end links flared in too much.

 

[JO3L]

@Yonder I just posted in comparing the 18mm solid Si bar vs the 22mm tubular Eibach bar, feel free to read that thread. Since I am in the mood of educating, here is some more math. To calculate the stiffness factor of a tubular bar you take the fourth power of the bars Outside diameter and subtract it from the fourth power of the bars Inner diameter. Not knowing the exact wall thickness of the Eibach bars, these statements are not 100% fact but they will give you a good idea when comparing tubular to solid bars.

Base= 16.5mm solid = 74,120 Stiffness factor or SF from now on
Si= 18.0mm solid = 104,976 SF
CTR= 20.5mm solid = 176,610 SF

25mm^4 = 390,625 SF
(1.0mm) x 2 = 2.0 mm wall thickness
25mm - 2mm = 23mm


23mm is our inner diameter so...
23^4 = 279,841 SF

Putting it all together
390,625 SF – 279,841 SF = a stiffness factor of 110,784 for a hollow bar of a 25mm outer diameter and 1mm wall thickness. This represents a 5% increase for the Si and a 33% increase in stiffness for the base models.



Now lets look at this again with a different wall thickness.


Eibach 25mm tubular bar - using 1.5mm wall thickness

25mm^4 = 234,256 SF
(1.5mm) x 2 = 3.0 mm wall thickness
25mm - 3mm = 22mm


22mm is our inner diameter so...

22^4 = 234,256 SF


Putting it all together
390,625 SF – 234,256 SF = a stiffness factor of 156,369 for a hollow bar of a 25mm outer diameter and 1.5mm wall thickness. This represents a 32% increase in stiffness over the Si bar and a 52% increase for the base models.

Simply going from a 18mm Si solid bar to a 20.5mm FK8 solid bar represents an increase in stiffness of 40%. For the Base model Civics with a 16.5mm bar it represents a 58% increase.

That being said I went with the Whiteline 22mm solid bar for my Si because it offered the best value of price vs stiffness. I bought it right after Honda caught on to everyone buying brand new FK8 20mm bars for next to nothing so they raised their price. Personally I think the car could use more rear bar to help with rotation, but I am not willing to shell out nearly $500 for the Karcepts sway bar kit even though it is a really nice looking piece.

 

[jakabony]

@Yonder I just posted in comparing the 18mm solid Si bar vs the 22mm tubular Eibach bar, feel free to read that thread. Since I am in the mood of educating, here is some more math. To calculate the stiffness factor of a tubular bar you take the fourth power of the bars Outside diameter and subtract it from the fourth power of the bars Inner diameter. Not knowing the exact wall thickness of the Eibach bars, these statements are not 100% fact but they will give you a good idea when comparing tubular to solid bars.

Base= 16.5mm solid = 74,120 Stiffness factor or SF from now on
Si= 18.0mm solid = 104,976 SF
CTR= 20.5mm solid = 176,610 SF

25mm^4 = 390,625 SF
(1.0mm) x 2 = 2.0 mm wall thickness
25mm - 2mm = 23mm


23mm is our inner diameter so...
23^4 = 279,841 SF

Putting it all together
390,625 SF – 279,841 SF = a stiffness factor of 110,784 for a hollow bar of a 25mm outer diameter and 1mm wall thickness. This represents a 5% increase for the Si and a 33% increase in stiffness for the base models.



Now lets look at this again with a different wall thickness.


Eibach 25mm tubular bar - using 1.5mm wall thickness

25mm^4 = 234,256 SF
(1.5mm) x 2 = 3.0 mm wall thickness
25mm - 3mm = 22mm


22mm is our inner diameter so...

22^4 = 234,256 SF


Putting it all together
390,625 SF – 234,256 SF = a stiffness factor of 156,369 for a hollow bar of a 25mm outer diameter and 1.5mm wall thickness. This represents a 32% increase in stiffness over the Si bar and a 52% increase for the base models.

Simply going from a 18mm Si solid bar to a 20.5mm FK8 solid bar represents an increase in stiffness of 40%. For the Base model Civics with a 16.5mm bar it represents a 58% increase.

That being said I went with the Whiteline 22mm solid bar for my Si because it offered the best value of price vs stiffness. I bought it right after Honda caught on to everyone buying brand new FK8 20mm bars for next to nothing so they raised their price. Personally I think the car could use more rear bar to help with rotation, but I am not willing to shell out nearly $500 for the Karcepts sway bar kit even though it is a really nice looking piece.

This is potentially more thought and calculation than Eibach, Whiteline, and Honda combined put into their rear sway bar R&D lol.

 

[Yonder]

@jakabony

Duuuuuuuuuude, yessss! @JO3L haha thanks for that post! For sure going to take a look at that thread. Its the Eibach 22mm Vs OEM 18mm one right?

EDIT: So if i'm understanding correctly... 25mm Eibach RSB is providing the same stiffness (or at least close to it) to the OEM FK8 RSB?

Re-Edit: My last question makes no sense now that i think about it. Why would a company make a RSB exactly the same stiffness as the OEM lol Definitely not be understanding correctly

 

[JO3L]

@jakabony

Duuuuuuuuuude, yessss! @JO3L haha thanks for that post! For sure going to take a look at that thread. Its the Eibach 22mm Vs OEM 18mm one right?

EDIT: So if i'm understanding correctly... 25mm Eibach RSB is providing the same stiffness (or at least close to it) to the OEM FK8 RSB?

Re-Edit: My last question makes no sense now that i think about it. Why would a company make a RSB exactly the same stiffness as the OEM lol Definitely not be understanding correctly

It all depend on the wall thickness of the Eibach bar and unless someone has a bar they want to cut up and share the specs with us then we won't really know for sure. Based on my calculations the wall thickness will need to be at greater than 1.75mm to offer any sort of increase in stiffness at 25mm OD. This is why I went with the Whiteline 22mm solid rear bar because it is a like for like comparison with our factory solid rear bars and I have no questions that I am getting a performance increase in stiffness.

The only real advantage hollow bars have over solid bar is the weight, but how much weight you think you really save going with a tubular 22mm bar vs a solid 22mm bar? I am sure there is enough junk in your car that you can take out to offset this difference. Or just skip that drive thru line on the way to the track if you really cared about saving weight.

 

[JO3L]

My track car is a 91 NA Mazda Miata. There is a popular company called Racing Beat in Anaheim, CA that makes tubular sway bars and also solid bars for these cars. I just checked and their normal sway bar has as 0.125" or 3.175mm wall thickness and their race bar has 0.188" or 4.77mm wall thickness. That being said I am sure Eibach's bar wall thickness is probably greater than 2mm or else why would they offer this bar in the first place. Still I am not going to be the one to buy one to cut up and know with certainty.

The examples I gave at 1mm and 1.5mm wall thickness are worst case scenarios at best. I guess the point I am trying to make is it is a bit of an unknown when it comes to tubular bars, unless the manufacturer posts this info. Bet you Racing Beat got tired of explaining to people about their tubular bars so they just posted the OD/ID for people to see and be able to draw their own conclusions.

 

[Yonder]

@JO3L Yeah the eibach one has to be greater than 2mm thick or else (like you said) why even put it on the market. To con everyone? I doubt it lol but dude you have been a real big help. Thanks for all this info regarding sway bars. My pops just got the type R so if he ends up upgrading that RSB before i do il probs just shark his OEM haha il try and see if i can email eibach regarding the tubular thickness. I do want the stiffest possible RSB so fingers crossed for the wall thickness haha I used to have a 350z so kicking out the tail is something I'm very much comfortable with lol i’ll let you know once if i find anything out!

 

[JO3L]

@JO3L Yeah the eibach one has to be greater than 2mm thick or else (like you said) why even put it on the market. To con everyone? I doubt it lol but dude you have been a real big help. Thanks for all this info regarding sway bars. My pops just got the type R so if he ends up upgrading that RSB before i do il probs just shark his OEM haha il try and see if i can email eibach regarding the tubular thickness. I do want the stiffest possible RSB so fingers crossed for the wall thickness haha I used to have a 350z so kicking out the tail is something I'm very much comfortable with lol i’ll let you know once if i find anything out!

Glad I could help. I wanted to get a FK8 too but got a steal of a deal on my Si from the dealer. Been more than impressed with it so far. Last weekend at autocross I took out a new Porsche 718 Spyder and Mustang GT350 just to name a few higher $ cars with like double my HP. Of course these are much more expensive cars so maybe the drivers were holding back in fear of crashing. Cant get much safer than an autocross course though.

The biggest bar out right now is the Karcepts one, but it is pricey and because of the spherical end links it is noisy from what I have heard. Maybe they would sell you the bar without links and then you can just get the adjustable ball joint to bushing style ones from Whiteline? Just a thought...

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