I just measured mine. I also see a lot of questions about stock sizes on other models. If you know what your stock bar size is please add to this thread. I am sure this info is somewhere on nasioc, but it would be really cool to find it here so that people might know how much of an improvement any new sway bar might be. MY06 2.5i Wagon F: 20mm (new guess until I can get a better look) R: 13mm (confirmed with 13mm open wrench) If I am off, and I might be as I don't have highly accurate calipers, please correct me. And I do apologize if this is already covered somewhere, but I have been searching for a while.
03' WRX is 20mm Front and 17mm Rear I believe. I think that is the case for all the WRX's, unless the 06's changed.
The rear is definitely smaller than the front, and the front is definitely 20mm. This is why most WRX's replace rear bar first. The STi is 20mm all the way around, and that is why most STi people replace their fronts first as this controls camber through corners.
OK, now I'm curious. Here, we have a couple of "I'm sure"s and "I think"s. I just went over to NASIOC, and I've gotten tired looking for posts that have stock sway bar sizes stated with conviction. Anyone have something solid? I did find this at NASIOC, where the author states that the '02 WRX has a 20mm front and rear stock: http://forums.nasioc.com/forums/showpost.php?p=15678450&postcount=5 This matches what I believed to be true.
http://www.clubwrx.net/forums/showthread.php?t=10040 Read post 6, its 17mm in the rear 20mm in the front for the wagon.
If I remember correctly... 2002 WRX was 20/20 2003 WRX downgraded to 20/17 2004-05 WRX 20/17 2006+ WRX...no idea 2004 STi was 20/19 2005-2006 STi was 20/20 2007 STi (according to monk) returned to 20/19 I have no idea on the wagons, but from what I can remember, its basically a fairly similar setup to the sedans. The only major difference is that in the front, the wagons have a wagon specific swaybar.
Is there a standard device (caliper?) and a standard place to measure the thickness of the bar? I would assume (assumptions are always dangerous though) that I could measure at any straight point on the bar. They are not conical (narrower toward the end or middle) in any way right? I was hoping we could all just measure them whenever we happend to be under the car and get actual physical numbers and not just spec numbers. I guess you could even use an open-ended wrench set and just start with the smallest and try each till you found the wrench that fit over the bar, that way we would all be using a very standardized measuring. For example, use the 17mm wrench that you use to tighten the oil plug and see if it fits over the rear bar. Just tried my "wrench method." It confirmed the rear at 13mm, but the front is closer to 20mm.
I suspect that a raw measurement isn't sufficient. Note that adjustable sway bars have different "effective" thicknesses depending on the attachment hole used. Note also that there are hollow sway bars. I would guess that the quoted measurement represents a stiffness equivalent to that of some standardized bar.
Very true. However, just for the sake of argument, lets keep this limited to stock factory subaru bars. If we only compare stock to stock, wouldn't that be a way to "standardize" the measurement, especially if we list the make and model year and compare within those parameters?
Yeah, but if you change the bar, you have to go with the manufacturers. Clemsonscooby has pointed out that your model has a 17mm rear bar stock (sorry again for the confusion). If you buy a stiffer bar, work off of that number rather than the physical measurement. Otherwise, you might not really get a stiffer bar.