Sway Bar stiffness For BSF36XZ and BSF37XZ

[STi4Q]

I am interested in the BSF36XZ and BSR37XZ sway bars for an 05 STi. The outer diameter of both bars are 24mm. What are their equivalent stiffnesses in each of the three positions in both mm and % relative to the stock 20mm bars.

Thanks for any information you can provide.

[STi4Q]

I just wanted to add some more information.

I have seen a lot of different specs for the bsf36xz and bsr37xz bars and was hoping to get a clarification of how stiff the different settings are. For example, I have seen people say that the bsr37xz can be adjusted between 23-24-25mm and some say 24-26mm and others say 22-24-26mm.

Knowing the different mm settings is a great start, but it still does not allow me to compare the whiteline bars to the stock bars because the materials may be different. This is where the stiffness given as a % comes into play. In order to know how the bar will perform, I need to know how stiff it is relative to stock. I don't know if Whiteline has this info but it would be very beneficial. I hate reading posts that say "the 24mm bar is great, my car stays flat". This is great but it does not help me decide if the bar is right for me.

Once again, thanks in advance for any info that can be provided.

[Peter]

G'day,

I think this may be a situation of not really knowing the answer that you need. There is a lot more to a swaybar than just size - eg: to equate the effect of the added rate provided by a given bar you need to know the spring rates, motion ratio of the springs and bar and very importantly the type of tyres and intended use ie: street, track, high performance street tyres, semi slicks or full slicks etc etc, power output levels etc ? all of which will affect grip and chassis balance.

It may be preferable if you were to describe the intended use of your vehicle, including, tyres, and power output, current chassis mods etc and what it is that you want to achieve. We can then advise you accordingly.

To start with, a link to the Fact Sheet on your chassis and a couple of articles are here:

http://www.whiteline.com.au/docs/fact_sheets/CK_STi_P25.pdf

http://www.whiteline.com.au/articles/0507_P25_1.htm

http://www.whiteline.com.au/articles/AS_0509_P25_1.htm

http://www.whiteline.com.au/articles/F4_Power_V_Handling_1.htm

http://www.whiteline.com.au/articles/0604_Shocktherapy_01.htm

http://www.whiteline.com.au/articles/PT_05_AE_WRS03R_1.htm

cheers
Peter
peter@whiteline.com.au

[STi4Q]

Thanks for the reply.

Here is the situation I am in:

Right now I have a stock 05 STi. I intend on leaving the power the same (300hp, 300ftlb) and continue to use the RE070 stock tire (I like the stiffer side wall).

Eventually I will move to a setup that has stiffer springs, in the range of 7-8K front and 5-6k rear. The car will not be lowered more than 25mm. The car will still be a daily driver but will see 5-10 track days a year. I can tolerate a stiffer ride so I think the spring rates I mentioned should still be "comfortable" for me, but I still need to prove this out.

In terms of other chassis modifications, I will look at strut bars and lower bracing but I don't know if they are necessary.

The one complication comes in the winter where we get snow for a good 4 months and from my research it looks like I should reduce the roll bar rate to reduce the amount of weight transfer to the outside tires (this will increase compliance and allow a longer transition time for the tire to settle).

So I was thinking of running the bsf36xz and bsf37xz so that I can use the middle setting for the street, the siffest setting for the track and the softest setting for the winter. I was also considering the bsf37z for the rear but I felt I could not make a proper decision without seeing the relative stiffness of these bars to my stock 20mm bars.

Let me know if you would like any more information.

I appreciate any help you can provide, this suspension stuff is not very easy to design. Each component is connected with another and you can never isolate one part and try to analyse it on its own without affecting something else. I have a feeling that I may spend the rest of my life trying to fine tune my suspension setup.