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Tracking / Autocross / HPDE / Drifting What these cars were built for!

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Old 05-30-2013, 07:39 AM   #1
mla163
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RTR/CS people - Front Sway bar FRS vs. BRZ

With respect to a modifying the front sway bar, is there any significant difference in front swaybar selection for a BRZ compared to a FRS.

The FRS has 135/211 #/in springs and is more tail happy than the BRZ. A big front bar works well here. For a 22mm Strano bar, I get a 72.5% TLLTD from my magical spreadsheet.

The BRZ has 153/195 #/in springs and is a little more pushy than the FRS. In concept, putting on the same size bar (as you would on the FRS) would make the BRZ understeer more. For a Strano bar, I get a 73.1% TLLTD (a tad more push). To get the same handling characteristics, a smaller bar than the FRS would make more sense - say a 21mm. The tradeoff would be more body roll with the smaller bar.

Has anyone taken this into account?

Is there any appreciable difference between an FRS and a BRZ with the same sway bar?

Or am I trying to apply too much logic to stock class? Put on a big ass bar and race it.
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Old 05-30-2013, 07:59 AM   #2
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Have you done much autocrossing with the car yet in stock trim?

I would not consider the car pushy enough to change direction... I'm pretty sure the only bar readily available that is a smaller rate than the Strano bar is the OE bar anyway.
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Old 05-30-2013, 08:54 AM   #3
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Originally Posted by mla163 View Post
With respect to a modifying the front sway bar, is there any significant difference in front swaybar selection for a BRZ compared to a FRS.

The FRS has 135/211 #/in springs and is more tail happy than the BRZ. A big front bar works well here. For a 22mm Strano bar, I get a 72.5% TLLTD from my magical spreadsheet.

The BRZ has 153/195 #/in springs and is a little more pushy than the FRS. In concept, putting on the same size bar (as you would on the FRS) would make the BRZ understeer more. For a Strano bar, I get a 73.1% TLLTD (a tad more push). To get the same handling characteristics, a smaller bar than the FRS would make more sense - say a 21mm. The tradeoff would be more body roll with the smaller bar.

Has anyone taken this into account?

Is there any appreciable difference between an FRS and a BRZ with the same sway bar?

Or am I trying to apply too much logic to stock class? Put on a big ass bar and race it.
I don't think the difference between the two cars is great enough to warrant using a different bar on one versus the other. I debated this myself early on when installing the Strano bar. I also have a Whiteline 20mm adjustable bar and felt the Strano was right in the middle of its two settings in my non-autocross testing earlier this year.

I was going to try each at different events but got lazy and have just left the Strano bar installed so far, but will be using the WL next event. The WL has more adjustability obviously with two holes (can use different holes on each side) as well as adjustable endlinks.

Perrin also now makes a 19/20mm adjustable solid bar.
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Old 05-30-2013, 08:58 AM   #4
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Originally Posted by mla163 View Post
Is there any appreciable difference between an FRS and a BRZ with the same sway bar?

Or am I trying to apply too much logic to stock class? Put on a big ass bar and race it.
Not sure how much it will help, but we had a BRZ and an FRS on identical 20 mm Cusco bars and 235 Dunlops at Nats last year, turning roughly the same times.

The BRZ had much more oversteer. You might ask TRev, or John Ryan, the car owner.

My FRS wasn't pushy, but there wasn't much in the way of rotation. And still isn't.
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Old 05-30-2013, 05:26 PM   #5
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Originally Posted by des View Post
Not sure how much it will help, but we had a BRZ and an FRS on identical 20 mm Cusco bars and 235 Dunlops at Nats last year, turning roughly the same times.

The BRZ had much more oversteer. You might ask TRev, or John Ryan, the car owner.

My FRS wasn't pushy, but there wasn't much in the way of rotation. And still isn't.
All true, but I don't think our alignment was exactly the same at the time. (I had a fair amount of rear toe in, but I'm now running less. Not that you would expect loose from more toe in, but I might have been excessive.)

I felt all last year that the 20mm Cusco was not quite enough, even on the 'pushier' BRZ. I kept it in the garage for fear the Strano bar would be too stiff, but I have no plans on changing back as the Strano bar feels pretty good to me and Sam was able to turn some pretty good times with the setup that is on the car now. (link)

The final answer is probably a bit driver dependent, ymmv, etc.
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mla163 (05-31-2013)
Old 05-31-2013, 08:24 AM   #6
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Originally Posted by mla163 View Post
With respect to a modifying the front sway bar, is there any significant difference in front swaybar selection for a BRZ compared to a FRS.

The FRS has 135/211 #/in springs and is more tail happy than the BRZ. A big front bar works well here. For a 22mm Strano bar, I get a 72.5% TLLTD from my magical spreadsheet.

The BRZ has 153/195 #/in springs and is a little more pushy than the FRS. In concept, putting on the same size bar (as you would on the FRS) would make the BRZ understeer more. For a Strano bar, I get a 73.1% TLLTD (a tad more push). To get the same handling characteristics, a smaller bar than the FRS would make more sense - say a 21mm. The tradeoff would be more body roll with the smaller bar.

Has anyone taken this into account?

Is there any appreciable difference between an FRS and a BRZ with the same sway bar?

Or am I trying to apply too much logic to stock class? Put on a big ass bar and race it.
Let me guess, you are an engineer?
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Old 05-31-2013, 08:36 AM   #7
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Let me guess, you are an engineer?
Affirmative.
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Old 05-31-2013, 09:20 AM   #8
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For anyone reading this please also remember that bar diameter is in no way a direct correlation to the bar rate. Unless you know the wall thickness of a hollow bar, it's material, how it was treated, and the bar-to-wheel motion ratio, you really cant guess at the true influence on wheel rate too accurately.

I was trying to gather all this info before, but essentially gave up because claims and numbers didn't match... need real data, too much coming from the internetz.
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Old 05-31-2013, 12:43 PM   #9
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Let me guess, you are an engineer?
Hahahahaha!
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Old 06-01-2013, 01:14 PM   #10
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Put the magical spreadsheet down, pick up the phone, call Stranoparts, order their 22mm bar, install it, drive the car, have fun. Made a significant difference on my BRZ for autocrossing, subtle improvement for driving on the street. Love it.
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