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Discussion Starter #1
Would a 26mm rear sway bar be overkill with the stock (21mm?) Front bar and sportline kit on a 07 sedan? I have a mazdaspeed3 rear bar laying around, I've heard it bolts on and I'm wondering if it's worth buying bushings/endlinks for it and throwing it on...
 

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Nah it'll work good.
It's a lot better than the other way around.
 

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2006 ZX3 2.0, 2006 ZX5 2.0, 2004 ZX3 SVT
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Would a 26mm rear sway bar be overkill with the stock (21mm?) Front bar and sportline kit on a 07 sedan? I have a mazdaspeed3 rear bar laying around, I've heard it bolts on and I'm wondering if it's worth buying bushings/endlinks for it and throwing it on...
My only concern would be the rear control arms. Known to fail at the sway bar location. New control arms are reinforced.
 

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Thats What She Said
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There are people that will run no front bar and a massize rear bar for Auto-X and even some track use. The car will turn in differently so take it slow the first few times you take the car for a drive.
 

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Would a 26mm rear sway bar be overkill with the stock (21mm?) Front bar and sportline kit on a 07 sedan? I have a mazdaspeed3 rear bar laying around, I've heard it bolts on and I'm wondering if it's worth buying bushings/endlinks for it and throwing it on...
If you have it throw it on......
 

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26mm is overkill. It works on the MS3 because it weighs 32xxlb. There's nearly a 500lb difference between that and your sedan.

You're going to get better/more stable handling from a 'mild' sway bar and a sportier rear alignment.

chucking a huge stiff bar onto the rear of a light FWD car is going to produce really unpredictable lift-off oversteer.
 

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Discussion Starter #7
I think I'm going to give it a shot and see how I like it. I have heard that it could give the car some unwanted oversteer, but I'll see how I like it and if I don't then I'll throw on a SVT bar with poly bushings instead
 

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Thats What She Said
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26mm is overkill. It works on the MS3 because it weighs 32xxlb. There's nearly a 500lb difference between that and your sedan.

You're going to get better/more stable handling from a 'mild' sway bar and a sportier rear alignment.

chucking a huge stiff bar onto the rear of a light FWD car is going to produce really unpredictable lift-off oversteer.
Do you relize the Eibach swaybar combo is:
•Bar Diameters: Front 22mm, Rear 25mm

So he is only going up 1mm and down 1mm with respects to the Eibach set up. Its not that big of a change.
 

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You're assuming the arm length is the same which it likely isn't.

It's something like ~120% stiffer than the stock bar... (if my math is right)

It's not smart to just slap on a part from a completely different car just because it 'fits' But try it, I don't care. Just telling you what I know about suspension balance.

And FWIW, yes I DO know the Eibach bar specs because I have that kit installed with the Ford Racing springs which are a little stiffer than the Sportline springs.

It's also worth pointing out that the MS3 spring rates are even higher... The torsional strength of that 26mm bar is way way way too high for our cars. It just is. I'm done arguing about it.
 

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Discussion Starter #10
Well once I put the speed3 bar in and drive it for little bit I can give my thoughts on how it handles for people in the future and whether I think it's a worthwhile mod or not. It very well may be too much for my setup but I figured I'd give it a try
 

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Thats What She Said
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You're assuming the arm length is the same which it likely isn't.

It's something like ~120% stiffer than the stock bar... (if my math is right)

It's not smart to just slap on a part from a completely different car just because it 'fits' But try it, I don't care. Just telling you what I know about suspension balance.

And FWIW, yes I DO know the Eibach bar specs because I have that kit installed with the Ford Racing springs which are a little stiffer than the Sportline springs.

It's also worth pointing out that the MS3 spring rates are even higher... The torsional strength of that 26mm bar is way way way too high for our cars. It just is. I'm done arguing about it.
Well that escalated quickly... did not think anyone was arguing, just discussing information. [wiggle]

He has the sport line suspension kit, on a 07 sedan. (if he running a stock OEM front bar also? OP does not say) Also the sedan is on the heaver side of the focus spectrum (Focus is 2600ish lbs vs 2800 lbs of MS3) (compared to the Mk1 Hatch backs). 200 lbs ... at least per google searching curb weight of xxxx and seeing the results.

you are comparing 120% stiffer than OEM of 21mm. whats the % of difference from the Eibach ones? How different is the geometry and effective spring rates due to the arm lengths, positions, etc on the MS3? depending on those things the stiffer springs may have a similar effective spring rate.

I don't know either the arm, but if its a direct fit, the arms cant be that much longer due to how the links connect to the control arms.

There was a Steeda race/competition rear swaybar that was even larger at 28.5 mm (this yes was intended for track use). its about balance and what you want in the car and then re learning how it may behave.

I would call anything in the 24mm to 26 mm to be a mild bar being that OEM is 21 and the Steed racing one was 28.5mm. (Steeda recommended using a 22mm or larger front bar with the 28.5mm rear bar, which is now discontinued so this may be a good option if it works out to be stiffer that Eibach)

There are many Auto-X set ups that will remove the front swaybar all together and run a rear swaybar because of the rules for SCCA. If you know how it changes the balance of the car then you adjust the driving style as needed.

I hope further discussion can be had.
 

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Discussion Starter #12
So I've had the speed3 rear sway bar in with the stock front bar for about a week now and so far the car handles great. Not really any of this oversteer problem I've heard about, seems very balanced. Maybe the ball joint style mazda endlinks are more forgiving or something. All I can say is this is definitely a worthwhile mod for how cheap everything was.
 
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