mhamilton Posted August 21, 2006 Share Posted August 21, 2006 Which anti-sway bars are known -good for stock height OB XT ('06 or '07) ? Perrin? Cusco? I asked Cobb and they said no, their bar is not recommended. Maybe they just have not tried and don't want to find out the hard way. Link to comment Share on other sites More sharing options...
leftride Posted August 21, 2006 Share Posted August 21, 2006 i'm running the JDM 20mm in the rear. its not as aggressive as the cobb, but its noticeable. *vb gallery* Link to comment Share on other sites More sharing options...
LittleBlueGT Posted August 21, 2006 Share Posted August 21, 2006 Somebody tested the COBB bars, and the RSB worked just fine. The front had to a have a colar put around it to prevent lateral bar movement, other then that it was fine. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
Guest *Jedimaster* Posted August 21, 2006 Share Posted August 21, 2006 JDM 20mm over here as well-nice improvement. Link to comment Share on other sites More sharing options...
flatsphere Posted August 21, 2006 Share Posted August 21, 2006 Which anti-sway bars are known -good for stock height OB XT ('06 or '07) ? Perrin? Cusco? I asked Cobb and they said no, their bar is not recommended. Maybe they just have not tried and don't want to find out the hard way. Cobb may not be supporting their use on OBs due to potential subframe damage caused by larger SBs. I've heard of from several Subaru techs of damaged subframes from larger than stock sways (it appears to be a weakpoint in the Legacy structure's design). That said, I'm considering replacing mine but I'll also be installing the support brackets to help prevent potential damage. I have installed cusco's rear strut tower brace, which reduced body roll considerably. Cheers! Link to comment Share on other sites More sharing options...
vel0mac Posted August 21, 2006 Share Posted August 21, 2006 I asked Cobb and they said no, their bar is not recommended. Maybe they just have not tried and don't want to find out the hard way. They do work, and they work very well. They are not a drop-in replacement though, you will need to do a little bit of extra work. I have installed the COBB bars, both front and rear, on my OBXT and I have had zero problems -- after I did the quick retrofit that I explain in this post: http://legacygt.com/forums/showthread.php?t=38084 BTW, I sent my original *.pdf (that I used to create the above thread) to Trey Cobb, so they are aware of the fitment issues that I had. So far so good. No problems after ~2 months of use. Both the collars and spacers are readily available from McMaster-Carr (www.mcmaster.com) fairly inexpensively. The above forum thread gives the collar p/n. For the spacers, look up "Fixturing Washers" on the McMaster-Carr website or use this p/n: 94768A106, it is almost identical to the ones that I machined. Good luck. - C. Link to comment Share on other sites More sharing options...
mhamilton Posted August 22, 2006 Author Share Posted August 22, 2006 Some how I missed your write up in my search. I see that AVO has a new RSB for the OB. It is solid and 20mm. So I expect it is a little more rigid than the JDM. Maybe a nice compromise for on-road/offroad? If anyone has stiffness comparison for this, please post. Link to comment Share on other sites More sharing options...
Boulderguy Posted August 26, 2006 Share Posted August 26, 2006 I think that's what he means. I've been using the Perrin rear reinforcements. They were a pain to install, but no issues with subframe after 1 yr. Still trying to figure out why Vel0Mac's Cobb bars kept his car flatter in turns than my Perrin bars tho... Link to comment Share on other sites More sharing options...
vel0mac Posted August 29, 2006 Share Posted August 29, 2006 Still trying to figure out why Vel0Mac's Cobb bars kept his car flatter in turns than my Perrin bars tho... Didn't you say that you only had the Perrin rear, or did I misunderstand? From what they advertise, the COBB front is somewhere near 50% stiffer than the OEM and the COBB rear is ~200% stiffer than OEM. I don't know how this compares to the Perrin bars. I know the COBB set is a lot stiffer than the OEM front/JDM rear. And when I broke my front end link (when I first installed the COBB bars before I added the captivating collars) the car had a ton of body roll. So it seems to me that the front COBB really helps a lot. I have never set the rear bar to any setting other than its softest, so I don't know what effect that would have. It would be fun to do some 'lab tests' to see the different ultimate stiffnesses of all the available bars (and it would be fun to have the money to do such a test), but now I suppose I'm just being an enginedy geek... Link to comment Share on other sites More sharing options...
vel0mac Posted August 29, 2006 Share Posted August 29, 2006 Now are we talking subframe damage that is avoidable by using the reinforcement brackets or something else? With regard to concerns over sub-frame damage, I'd be surprised if there is any concern about damage to the front of the car. The mounts in the front are on some pretty stout frame members. The rear is the weak link. The rear stiffening brackets (COBB and Perrin) seem to fix that issue and they transfer the stress to some very stiff parts of the sub-frame. Furthermore, I figured that if I kept the OEM end links that they would be the weakest link (no pun intended). If there was any concerns about progressive damage to the system that the OEM links would break first, acting as an indicator to other potential damage (they will act like a mechanical fuse, if you will). If that happens, I will go back to stock. Other than the initial problem that I had with the misaligned bar, I have had no problems with the end links or sub-frame and I drive the car harder than before, although I do NOT take it on real off-road stuff, only forest service roads at most. Link to comment Share on other sites More sharing options...
Boulderguy Posted August 29, 2006 Share Posted August 29, 2006 Yup, Perrin F & R, front's set to soft, rear to medium. I did some research as to theoretical stiffness to torque of hollow vs solid. The math says that all other factors being equal, the torsional resistance is an expression of the wall thickness of the hollow bar vs. the total thickness of the solid bar, hence solid usually being the stiffer of the two. Given your engineer-ness, what are your thoughts? Link to comment Share on other sites More sharing options...
vel0mac Posted August 29, 2006 Share Posted August 29, 2006 Given your engineer-ness... That is enginerd to you, sir Without going through my old materials books to give the full lowdown, basically what you are saying is correct. The operative thing here is that all other factors are equal. It is difficult to know what materials are being used in both applications, and every bend along the way has an effect since the total length, tip to tip, is also a big factor. I am not an expert in spring construction or design and the sway bars are, in concept and function, simple torsion springs. So with what I yammer about below I am merely borrowing my knowledge from other manufacturing that I have been involved in over the years. My guess is that the hollow bars are not made from the same type of steel as the solid bars. I have never worked with spring winding or forming, but my understanding and intuitive guess is that bending hollow tubes versus solid bars will require different materials so that the tubular material does not collapse when bent. Again, through intuition and similar experience with sheet forming, I would think that the tubular bar design would not tolerate over-bending to arrive at a desired bend angle as easily as the solid material would. Some materials will have a stiffness curve that rises more rapidly before the material permanently bends (yields). And, some materials are naturally more 'springy' than others. For example, a titanium bike frame as compared to an aluminum frame as compared to a steel frame will exhibit different stiffness characteristics -- especially if all dimensions (wall thickness, diameters, etc…) are equivalent. There are many different kinds of steels and they will exhibit different stiffness and yield characteristics. I believe that the stresses in the material used in the tubular bars will have a tendency to more quickly rise to the yield point, and ultimately be less forgiving, than the material in the solid bars. If a tubular bar fails it will fail due to breakage, or crossectional collapse (buckling) and it will not 'slightly' and permanently bend as a solid bar would. So while the solid bar may be ultimately stronger than a tubular bar, the solid bar may deflect further to get to an equivalent resisting force. In this case, more deflection to a particular resistant force equates to more body roll. Just my $0.02 and it won’t even buy you a gumball at Walmart… Link to comment Share on other sites More sharing options...
Boulderguy Posted August 29, 2006 Share Posted August 29, 2006 Wow. Nerd. Great explaination. So if I'm following correctly, the hollow bar may be practically stiffer while the solid bar is absolutely stiffer? The way it's shaping up in my head is the solid bar may flex more readily under load w/o failing while the hollow will flex less but fail with a smaller maximum load. Link to comment Share on other sites More sharing options...
vel0mac Posted August 29, 2006 Share Posted August 29, 2006 Wow. Nerd. Great explaination. . Ha, I resemble that remark. I just don't have the adhesive taped glasses and ink stained pocket protector to back it up. So if I'm following correctly, the hollow bar may be practically stiffer while the solid bar is absolutely stiffer? Kind of, yes. What I was referring to was more about ultimate strength and the amount of deflection to yield point. I think in this case, when we compare your setup to mine, the hollow bars may have a steeper stiffness curve (unit force to unit deflection) before they will ultimately fail and that failure point is (hopefully?) high enough so that they won't fail under use. But, in the end, the solid bars are probably stronger in that they will probably fail at a higher force. I think the materials selection is a huge factor here when comparing two bars, for example the solid Perrin to the hollow Cobb, and that is why simply measuring the bar's diameter is not enough to make a reasonable comparative determination of stiffness. Other factors like lever-arm length, wall thickness, bends, etc... come into play as well. The problem with the sway bars is that they don't give pragmatic stiffness values like with coil spring rates (force per unit deflection). They will say that one is x% stiffer than the other, but there is no real surefire way to say under what conditions (measured in use, measured as the raw material is deflected, etc...), and it is a harder to accurately measure and verify the published value since you need more fixturing. I was going to try and do this when I installed the Cobb and compared it to the USDM, but it would have taken me a long time (and a lot of tool dollars) to get the stuff together, and in the end I tried to simulate the comparative measurement by jacking one wheel and comparing it's lift to the others (diagonal loading of the car). Measuring a standard extension spring's rate is, effectively, as simple as putting a mass on top of it and measuring its deflection. To really compare two sway bars with only specification values, they would need to give values similar to coil spring rates, say force per unit length of deflection at the link hole when the bar is affixed as designed, etc... and every manufacturer would have to measure it the same way. I doubt they would standardize like that, it may remove some competitive advantages... The way it's shaping up in my head is the solid bar may flex more readily under load w/o failing while the hollow will flex less but fail with a smaller maximum load. Yes, that is the way I see it too. And in fact, there was someone on this forum that had a tubular bar fail. It looked like it twisted and kinked near the end link. That failure mode would never happen with a solid bar. Link to comment Share on other sites More sharing options...
HansGT Posted August 29, 2006 Share Posted August 29, 2006 cusco's fit. guy at work has them on his Outback, no problems. Link to comment Share on other sites More sharing options...
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