BRZ Rear Sway Bar Advice PLEASE HELP
 

So I'm looking to get a rear sway bar (yes JUST a rear sway bar) for my BRZ as I've been having understeer issues for a while now when auto crossing. I have michelin pilot super sports up front in 215/45/17 and I have the original primacy's in the rear (I've run super sports back there as well but they wear so fast that I don't like burning money away back there: and the handling is much better than stock with the odd staggered setup anyway). I'm going to be changing to a cheaper max performance summer tire in the back, probably a pair of kumho's at the same time as I add the sway bar. If I only get the rear Perrin 16mm sway bar and only use the softest setting (only 130% the stiffness of the original sway bar) would I be fine using stock endlinks? I feel like the OEM end links wouldn't really have a huge problem with ony 30% more stiffness… And I also don't think that the slight added stiffness will induce tons of oversteer, just dial out the understeer (if you think I am wrong please educate me on why) I'm only interested in changing the rear sway bar right now, and I only want a tiny bit more stiffness in the rear to dial out some of the understeer that the car exhibits during short and tight autocrosses/ spirited mountain driving. Am I on the right track? (no pun intended) :iono:

You might be able to fix the understeer without getting a rear sway bar.. adding sway bars are like putting patches on problems and should be done last, not first.

What suspension are you using and what is your alignment setup?

what's your alignment like? Before you spend some $$$ on a sway it's probably a better idea to optimize your alignment for your desired applications

+1 Car suffers from a lack of camber up front and toe can make or break rotation and responsiveness. My understanding is you're taking grip away from the rear to balance the car with the sway, most would prefer to add grip to the front as more grip usually means more speed.

Of course classing rules may prohibit you from doing this which is why you're chasing a rear bar, the C Street guys struggle with similar problems, most take their lumps on the understeer and actually add a front bar to get stability through the slaloms and do some footwork to balance the car through the sweepers that you struggle with.

If you're feeling like you have too much time on your hands, this 179 page thread might prove very valuable to you:

http://www.ft86club.com/forums/showthread.php?t=35855

There's some weirdness going on in your car too, you say staggered setup but that shouldn't be true, the car is supposed to come with 215/45/17's on all four corners of the same compound, I'm honestly impressed you're getting understeer with a noticeably less grippy compound in the rear. I'd guess that 99% of 86's run all four tires the same and rotate frequently if concerned about uneven wear. The fact that you're wearing the rear faster does not point to understeer which makes me think that you could get more rotation out of working on your technique, lots of understeer can be driver induced, keeping the front end loaded during turn in via the brakes (maybe brake dance would help, I haven't tried it myself yet) and aggressive steering inputs can overwork the front end before you can get back on the power.

I think you are on a correct path to get the results you desire, however it may not be the most optimal path towards speed.

Good luck, and certainly don't let anyone on the internet discourage you, first hand experience is worth a thousand internet posts, you can always change the sways back, sell the new one, keep it around as you tune other suspension parts and use it to balance say a coilover setup, beat the neighborhood kids etc.

Stock alignment. I just wrote a paragraph of stuff but my power went out so I'm going to summarize it really fast.
Stock alignment, also considering adding camber bolts up from and doing 3* of camber as so many have suggested… I'd probably do that at the same time as the sway bar. I am in no way experienced at this but I've done my best to do my homework on the subject and at least try to inform myself.
I'm also considering hotchkis front and rear sway bars as well as hotchkis springs.
I'm also considering RCE Yellow Springs
(But changing springs is expensive as I don't have the ability to do it myself, while I could change the sway bar myself)

By staggered I meant compound not width! I understand how that could have sounded really weird, I just have really good tires up front and crap in the back to try and fix the understeer, its worked somewhat but now I'm also going for better rear tires again. The rear tire wear comes from everyday driving and I am always about 2%-4% over the rear limits of grip (I even end up late apexing with a slight amount of opposite lock on S-bends) when I'm auto crossing on every turn but the hairpins, you could call the style "toe-ing the line". Unfortunately the hairpins are where I'm losing the vast majority of my time. I've gotten the understeer down a lot with driving style buy unfortunately I've still got a bit left that I can't compensate for anymore. I'm much more of a driver than a car-setter-upper but at this point I just need a little of the factory understeer taken out for those bigger sweepers. And yeah the whole go-back-to-stock-thing-if-necessary is something I recently explained to my girlfriend as a way of rationalizing the situation for her a little haha.

You should start with alignment. The factory alignment is crap and inconsistent anyway. If you're wearing your tires that drastically then you have an issue. Sort that out first.

I wouldn't recommend the staggered tire compound set-up since you're leaving a lot on the table by removing rear grip...in this case a significant amount. That is not the right way to set up a car.

Full stop. Don't think about parts. Get your tires and alignment sorted.

- Andrew

Agreed with Racecomp, ideally you should do one change at a time to observe the difference it makes.

Alignment plus sways in one weekend means two+ changes, if you go too far which one would you undo to dial it back? Maybe you undo the one that that could make the problem worse, wasted time, frustration.

Can't reccommend going up to more than -2.5 degrees of camber enough, ran ~3 degrees last outing and it was great, stock everything else, Z2SS tires in oem size, and some decent brake pads. All the understeer was me asking too much of the front end imo.

It seems to me like you're describing oversteer, not under.

Thanks everyone! I'll start with a new alignment then. I'm actually winning my class right now at all the events I'm attending even with the weird setup...take that with a grain of salt: they are smaller events and I am by no means a pro, but in all modesty I'm not bad. I'm just looking for better and better... I have friends with spec miatas that really aren't doing that much better than me time wise... And I know the difference between oversteer and understeer -___- I DO have oversteer on some corners but it's very slight: and I don't mind it at all, the understeer comes into play in the sweepers, especially ones where even my weight offsets the car's balance a little to the outside of the corner (i.e. Right sweepers) and its that understeer that I want to edit out... It's the standard understeer that Subaru puts in for safety and I want it gone. It's always a battle but I'm putting better tires on the back in a week or two... The primacy's in the back with super sports in the front were just a test, a learning experience, and it went very well for the most part... But I'm always looking for little improvements. Thank you RCE too!, I never expected one of your guys to comment but it does allow me to ask a brief question since RCE yellows are at the top of my wish list right now: do your alignment specs that come with the yellows shoot for neutral handling or a slight understeer bias like stock? Also would you suggest OEM Subaru crash bolts as part of that alignment? (I'm guessing that's what everyone would suggest i install before I start changing the alignment) I'm really curious. @Racecomp Engineering And thank you to @strat61caster for the forum link, I've started reading it and I will certainly read it in its entirety, it has so far been very informative.

Crash bolts or lobed camber bolts aren't going to get you more than 1.5*, and are more likely to max out around 1.2-1.3*. If you want a good amount of camber you're going to need bolts + slotted struts, or camber plates.

I'm at -2.2* front with whiteline bolts and slotted struts, I could go further with a different offset front wheel but as it stands I have VERY little clearance from spring perch to tire (with 17x8 +45 wheels and 225/45 tires).

I guess I'd be fine with 1.3-1.5 degrees to start. Little changes... Plus I like the idea of staying in C Street class now that I've been reading up on it for a while.

Sounds more like driver error to me. Your braking way too late.
Next time try breaking a bit early. 2 cones before should do the trick.

Check out the STX thread too, more options for modifications, but that of course means more money to be competitive:

http://www.ft86club.com/forums/showthread.php?t=25779

Glad to help. The standard alignment specs we give are for a broad audience...good for most people for street and light auto-x/track work. So it's a neutral-ish with some understeer at the limit compromise with tire wear. We do recommend custom alignments for those that are more serious about auto-x or the track.

Definitely think about what class you want to play in...CS will keep your set-up simple but STX can be a lot of fun.

Bolts and plates are good...at the very least you'll want camber bolts.

- Andrew