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Old 11-07-2020, 12:20 AM   #1
GrahamOD
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Default 22mm front swaybar, which size rear?

Hi guys,

I read through a lot of the swaybar "theory" threads before posting this. General consensus seems to be to add a bigger rear bar to dial out understeer or for track use consider bigger on both front and rear. (I know that's an oversimplification)

I bought my 2016 WRX when 1 year old. It seems the previous owner switched to a 22mm adjustable 2-point front bar and left the rear stock. Can anyone help me understand the theory in this? I'm told the stock front bar is 24mm.

I've tracked the car twice and intend to do more. I've recently installed coilovers and rear LCAs. I'm considering an adjustable rear sway bar but a little confused now what size to go for, since the front is now essentially softer than stock?

Would I want a matching 22mm rear, or would that make a weird balance with a smaller front bar? Or should I go to replace both?

Since people seem to change bars to dial out understeer, but I'm not exactly starting from stock, I'm not really sure what would be the direction to go.

Any thoughts welcome.
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Old 11-07-2020, 07:36 AM   #2
Norm Peterson
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Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

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Let's first try to solve the situation instead of the mathematical equations. Regardless of which bar or bars you were to stiffen - and by how much - still has to be accomplished with respect to where your car now sits (handling-wise).

Does it feel like it's understeering too much, or is the rear feeling a little too "loose"? If neither one is obviously apparent, leave things alone until something is. Kind of like "don't fix what isn't broken", don't tinker until you can identify the need to on your own car for your driving. How your car's current spring rates compare to OE will have some influence here, as their front:rear balance is likely different from stock (this would show up in the math if I had enough other information about things like suspension pivot point coordinates).

In general, while a "less understeerish" car is likely to work better at autocross and feel a bit more 'lively' and willing in street cornering, it's possible for it to be too loose for comfort/too demanding at the higher speeds encountered out on a road course. With all of two track days under your belt, you want a car that you can trust rather than one that might throw a surprise at you from time to time.


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Old 11-09-2020, 01:47 PM   #3
GrahamOD
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Default

Thanks, that's fair enough. I have some track experience but you're right in saying I've probably not pushed this car to it's full limits in just 2 track days.

Maybe I can rephrase my question then:

Help me understand what the original owner of my car was had in mind by installing a smaller front sway bar as opposed to the conventional logic I see on these forums, which is to replace the rear swaybar with a larger one? (Or replace both with larger which some people have done).

In theory, installing a smaller front bar should have a similar effect as increasing the rear size in terms of overall balance of the car but overall the car would be a little "softer" installing larger after market sway bars.

I didn't find the balance of the car to be bad. I would say it leaned towards understeer in higher speed corners but not terribly so. I did find the car overall have a lot of roll through corners.
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Old 11-09-2020, 03:06 PM   #4
Norm Peterson
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

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Softening the front bar setting while leaving the rear bar and everything else alone does make the car softer, and aside from shifting the load transfer balance rearward also improves mechanical grip up front slightly. That does imply different settings for things like the damping and alignment, and the driver would have to be OK with somewhat more roll (some people seem to have a lot more trouble with this than others).


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Old 11-11-2020, 02:25 PM   #5
Maester
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Default

Biggest one you can fit in there
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Old 11-11-2020, 04:08 PM   #6
Norm Peterson
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'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

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^^^ that approach may work for choosing a rear bar for a stick-axle muscle car that mainly sees drag racing and not much else . . .


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Old 11-28-2020, 01:34 PM   #7
gasgaskid
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Default 22 mm swaybar

Quote:
Originally Posted by GrahamOD View Post
Hi guys,

I read through a lot of the swaybar "theory" threads before posting this. General consensus seems to be to add a bigger rear bar to dial out understeer or for track use consider bigger on both front and rear. (I know that's an oversimplification)

I bought my 2016 WRX when 1 year old. It seems the previous owner switched to a 22mm adjustable 2-point front bar and left the rear stock. Can anyone help me understand the theory in this? I'm told the stock front bar is 24mm.

I've tracked the car twice and intend to do more. I've recently installed coilovers and rear LCAs. I'm considering an adjustable rear sway bar but a little confused now what size to go for, since the front is now essentially softer than stock?

Would I want a matching 22mm rear, or would that make a weird balance with a smaller front bar? Or should I go to replace both?

Since people seem to change bars to dial out understeer, but I'm not exactly starting from stock, I'm not really sure what would be the direction to go.

Any thoughts welcome.
GrahamOD, You have a 22mm front swaybar? i have been looking for a smaller swaybar for my 2016 WRX, can not find one, any idea who made it?

Thanks anyone for any info.
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Old 11-29-2020, 03:45 AM   #8
speedyHAM
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XP class Impreza L

Default

Quote:
Originally Posted by Norm Peterson View Post
Softening the front bar setting while leaving the rear bar and everything else alone does make the car softer, and aside from shifting the load transfer balance rearward also improves mechanical grip up front slightly. That does imply different settings for things like the damping and alignment, and the driver would have to be OK with somewhat more roll (some people seem to have a lot more trouble with this than others).

Norm
This is exactly what I was thinking. So, if you are going to up the size of the rear bar you probably want to up the front bar size as well. If your front bar is currently 22mm and rear is 20mm, I would upsize them linearly- 26mm front and 24mm rear for instance.
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Old 11-29-2020, 08:24 AM   #9
Norm Peterson
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Member#: 498642
Join Date: Mar 2019
Chapter/Region: Tri-State
Location: our wrx IS the family sedan
Vehicle:
'19 WRX Ltd 6M dgm
'08 Mustang GT (the toy)

Default

Quote:
Originally Posted by speedyHAM View Post
This is exactly what I was thinking. So, if you are going to up the size of the rear bar you probably want to up the front bar size as well. If your front bar is currently 22mm and rear is 20mm, I would upsize them linearly- 26mm front and 24mm rear for instance.
That should be good enough as long as the front and rear bars are not of hugely different diameters (like the 34/20 OE bar combination on my other car). And that the bars at each end are either both solid or both tubular with comparable wall thickness to diameter. The 22/20 case is only about 6% more front-biased than a 26/24 would be, all other bar dimensions held constant. Less than half a mm's worth on the diameter.

For results much better than that, you'd have to throw a whole lot more numbers at it, including the contributions of the springs to roll resistance.


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