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View Full Version : Recommendations for Swaybar Sizing


downeyer
19-07-2007, 01:02 PM
Dear Whiteline,

I'm interested in reducing the body roll of my 2002 USDM Subaru WRX. To do so, I plan to increase the swaybar sizes on my car. My current modifications include the following:

1) Prodrive Linear Springs
2) Koni Inserts
3) 21mm Cusco Front Swaybar
4) 22/23/24mm Cusco Rear Swaybar
5) Cusco rear strut tower brace

The current at the limit balance of my WRX is very controllable. The car has a tendancy to understeer slightly with the ability to rotate the car with lift throttle. I enjoy this level of control and would like to maintain it if possible.

My current direction is to increase the front and rear swaybar by the same stiffness % by using your Diameter Conversion Chart.

Front: Having read several reviews on big swaybars, it is my understanding that a larger front swaybar will reduce dynamic camber changes, therefore resulting in more grip. Is this true? If so, I'd like to go as big as possible with the front bar, which leads me to a 27mm bar. On the other hand, my WRX is primarily a street driven car. Should I avoid the big 27mm bar?

Assuming that the 27mm bar is not recommended for street use, I would go to the next level, which is 24mm. Increasing the size from my current 21mm to a 24mm increases the stiffness by 71%.

Rear: With the stiffness increased by 71% for the front, I'd be looking for a similar 71% increase for the rear. That puts me at either a 26mm (63%) or 27mm (90%). Which bar would you suggest using?

Is my methodology correct here? By that, I mean is increasing the front and rear by the same percentage stiffness going to keep the same handling balance?

The reason I ask is because I've heard that bigger front swaybars result in less dynamic camber loss, resulting in additional front grip, therefore, oversteer. Also, a larger rear swaybar will also result in oversteer. Am I setting myself up for an oversteering car by increasing the sizes of both the front and rear swaybars?

Regards,
Eric

Whiteline
20-07-2007, 09:43 AM
Hi Eric,

You are correct in saying a large front bar will reduce dynamic camber change due to not transfering as much load on to the ouside wheel which will cause less wheel movement , some camber change will be required to keep the contact patch of the tyre on the road at all times. so going to stiff on front bar rates can in effect have a negative effect on handling as we want to transfer some load onto the tyre as well. When setting up vehicles what works for one person may not work for another due to so many different variables ie tyres and turn in feel etc. Generally speaking i wouldnt go larger than a 24mm front bar for street use.
If you have a good balance already increasing the bar rate front to rear evenly will keep a similar balance. Always make sure you use blade adjustable bars so you can fine tune/manipulate the understeer/oversteer in or out of the vehicle.This can also be achieved through wheel alignment settings as well.

Regards,
Dave

downeyer
25-07-2007, 11:29 AM
Thanks for the input Dave.

As for the adjustable swaybars, can you tell me the relative sizes for the 24mm adjustable front swaybar and the 27mm adjustable rear swaybar? If I understand correctly, the rear is adjustable to 26/27/28? How about the 24mm front?

Regards,
Eric

Whiteline
25-07-2007, 04:00 PM
Hi Eric,

The adjustable sway bars are generally in theroy like increasing the bar size in diameter 1mm either way their are a lot more factors that come into it by decreasing the pivot length it point it will alter the bar stiffness rate but may not be the equivelant of 1mm. i dont have the exact specs but pressume it is closer to about half a millimeter in bar diameter increase

Cheers,
Dave

downeyer
27-07-2007, 10:07 AM
Thanks for the explaination...I understand that the adjustment doesn't duplicate an exact 1mm adjustment. I'm just trying to understand where you have positioned the nominal size.

So, for the rear 27mm bar, are the setting as follows (where the 27mm setting is in the middle)?

26.5 / 27 / 27.5

For the 24mm front bar, is it

24 / 24.5?
or
23.5 / 24?

Again, I'm just trying to understand if I will be able to adjust up or down from the nominal.

downeyer
02-08-2007, 01:08 PM
Can someone help me? I just want to make sure I understand the sizing before spending a few hundred dollars...

-Eric

Whiteline
02-08-2007, 02:37 PM
Hi Eric,

The bar adjustments are taken at the stiffest hole ie Rear 27mm then it works back from there 26.5/26.00 etc same on the front so you will be able to soften the bar off from the maximum rate.

Cheers, Dave