sjfehr

My 2004 Boxster S is severely camber-limited in the front, but I can't fix it without bumping myself out of BS. I get a lot of understeer and am eating front tires at an abysmal rate; between my wife and I, we're going through 2 sets of star specs an autocross season. One of the faster drivers from out of town (s2k guy) recommended I try a stiffer front sway bar which at first seemed counter-intuitive, but makes perfect sense as it may help balance out my utter lack of camber and help even out tire wear. I haven't started running r-comps yet, in part because I'm afraid of cording the outside corners the first event...

What front swaybar should I run? Is the GT3 swaybar too stiff, even at full soft?

MechanicalEng

The GT3 bar is not that stiff, I would give it a try, or maybe look at the GMG bars, they are supposed to be very good and dont cost and arm an a leg...

utkinpol

stiffer sway bar in front will increase understeer and if you do already have it - not sure it gt3 bar is a great idea to fight this problem, but increase in overall stiffness may have some positive reaction despite increase in understeer, so, you can try that and definitely look at your rubber, try may be 710 kumhos with round shoulders, not square ones and you can try to play with front/rear tire sizes after you get GT3 bar to work around understeer.

GMG bars are stiffer than GT3 stock bars, so, not sure if you would want them. primary reason to get GMG is that you get both matched bars in a set and rear bar has 5 adjustment holes and not only 3 as stock GT3 bar. stock GT3 front bar has 5 holes. also note that on different years front GT3 bar had different diameter - current one is stiff and larger, so you can research and find on what years it was thinner so you would be able to adjust it more conviniently for your purposes as you have to keep rear sway stock.

Jim Michaels

My AS Cayman S is front camber-challenged as well, but I also question the stiffer front sway bar "solution" to excessive understeer and tire wear. Maybe you've already tried these cheaper "solutions" and found them wanting, but it might help to increase front tire pressures, and adopt more of a "slower in, but faster out" driving style to reduce plowing through turns. Most stock cars plow through tight turns when trying to go too fast.

Tires: From what I've read, the Star Specs are good street tires for AX, but stiffer side walls might help some. I don't know how the Star Specs side walls compare to those of the RE-11s that I sometimes run, but R-comps might have stiffer side walls than either of those. Sometimes I run R888s instead of the RE11s, but I can't actually feel much difference in terms of side wall stiffness. The R888s seem to provide a bit more grip, but my run times relative to those of others don't seem to be any quicker.

utkinpol

i assume stock boxster/cayman has same suspension limits as my 997 c2 had with -1 degree of front camber and -1.5 degrees in rear?

front sways here can work in one area only - to improve overall stiffness so you could use tires like kumho v710 (as hoosiers a6 will not work good with such camber) and then playing with front/rear tires sizes and pressure you can try to dial out some understeer that stiff front sways will create.

quite a questionably strategy considering that same v710 tires with round shoulders will work acceptably with stock camber anyway. but less amount of sway will result in a faster slalom, so...

i went totally out and beyond with my car mods and do not regret it but running stock SCCA class is definitely a very respectful challenge.

00r101

I use the GT3 bar on my '08 BS Boxster. I highly recommend it and the Tarret endlinks. Especially if you have a non-M030 suspension on your 986 the big bar will reduce body roll and therefore reduce the need for negative camber. You do have to drive around the understeer but for autocross its worth it. As an added benefit a big front bar settles the rear under power which reduces inside rear wheel spin on corner exit.

In an ideal world you would be able to add more front neg camber through camber plates and you could reduce roll with heavier springs or matched heavy front and rear bars. But SCCA stock class rules preclude that. You have to do whatever works and ignore the theoretical ideal.

While I respect Jim Michaels and utkinpol's input on this matter, I disagree with both of them. I run Hoosier A6 on my stock class 987 Boxster. I get 70+ runs out of the fronts and 90+ out of the rear (I do flip them on the rim when they get to about 35). I also have a set of Dunlop Star Specs for the street but have run them in about 15 events and about 9500 street miles in the last 1.5 years. I have not flipped them and I cannot see any extra wear on the outsides.

sjfehr - I suggest you get the GT3 bar and start with it on the second hole from the end (that's the next to softest position). I have run mine on the 3 softest settings and like 1 or 2 depending on grip and temperature. You will find the car wonderful in fast slaloms at the expense of a little entry and mid-corner push on the slow stuff.

sjfehr

I don't have M030, just base 986S suspension. I can only get about -.75 camber in the front and wear is heavily uneven. I've got about 130 autocross runs and 3000 miles on these tires since March; the front tire inside corners are fine, but the outside corners are simply gone. I have -1.4 camber in the rear, and wear has been fairly even and will last the rest of the season. (I'd have to increase rear camber if I put on r-comps, I'm pretty sure.) Between wider front tires and better pressures, the car is handling much more neutrally, but the uneven wear really bothers me because I know I'm not putting the tires square on the ground. I've so far made no mods to the car besides tires, and was hoping the front sway bar alone would make a difference. [For those not familiar with SCCA stock-class rules, I'm limited as to what I can do and still stay SCCA BS legal- I can't install ROW M030, for example, I'd have to use the US M030 version which is not as good and costs twice as much because few want it, nobody stocks it, and it's all special order. Unless someone upgraded to ROW and wants to sell me their old US set??? I can do whatever I want to the front swaybar, though.]

Now, I'm curious why you say the front sway bar will increase turning but also cause understeer. My thoughts were that a slight increase in sway bar stiffness will plant my front-outside tire flat on the ground which would increase grip (and decrease understeer), while a large increase would cause excessive dynamic weight transfer, even lifting the inner wheel off the ground in some cases, and increase understeer?

I'd like to think I'm skilled enough that I could drive around the additional understeer in some situations, but ideally, this would HELP it, not cause more, wouldn't it?

utkinpol- V710 don't come in round shoulder in the sizes I need, just square.

Has anyone put a GT3 sway bar on a non-M030 986S? Also, what's this GT3 sway bar, and why is it so much cheaper than other vendors?

00r101

The sway bar you list does not include end links or bushings. Also it does not say it fits your Boxster.

Jim Michaels

sjfehr: In general, softening the front (e.g., via shocks, springs, and/or sway bar) relative to the rear decreases understeer. The exception is that stiffer front bushings help, but that's not stock legal anyway.

SCCA considers stock classes as the first level of preparation, but they often allow only about half what's really needed to go significantly quicker. For example, they allow wider tires (and R-comps!), but only on OEM width rims; they allow stiffer shocks, but only with OEM springs; and they allow non-OEM front sway bars, but the rears can't be changed.

Some of the stock legal changes that *might* help reduce understeer and excessive outside edge tire wear include: raising front tire pressure and width; lowering front tire aspect ratio, tread depth, and weight; lowering wheel weight (while keeping OEM sizes); increasing negative camber (yeah, we know); and reducing front toe-in, maybe to the point of having some toe-out. For some of these, one could opt to change the rear in the opposite direction (e.g., narrower tires and lower tire pressure) for better balance, but that seems to be giving up some good that already exists at that end.

sjfehr

I've already raised front tire pressure and tread width (running 225mm front vice 205mm OEM), threw front negative camber to the stops with subsequent increase in toe out (from tire wear, I think it's slightly toe out, but my DIY measurements show pretty much 0.) I haven't touched the rear, aside from tire pressure.

I autocross at 39psi front and 38psi rear with these star specs. I've been afraid to drop the cash on r-comps, in part for fear my soft suspension and lack of front camber would quickly ruin $1200 worth of tires. And in part because I'm having a hard time justifying dropping $2200 on wheels & tires...

Aren't C2 and Boxster front ends virtually identical, and all front suspension parts interchangeable? Bushings are shown in the picture; none of the other sway bars I've seen come with drop links either. (Edit: to clarify I mean 986/996)

BTW, if I haven't said it already, thanks for all your help guys/gals!!

00r101

sjfehr-

Try lowering your pressures to 36 all around - that's where I hrun my Dunlop Direzzas.

Pricing may have gone up but I got my GT3 bar, bushings and end links direct from Tarret at about $650.

Here's a link http://www.tarett.com/items/boxster~...1#ITEM_2249749

sjfehr

Do you have 18" wheels? I've got 17s, and arrived at these pressures through careful trial & error. I get too much rollover with anything lower; at 35psi, it was gripping well, but I was wearing right down to the sidewall. I'll probably have to raise them quite a bit in the front to account for the higher loads with the stiffer sway bar.

00r101

Well, you always have choices with setup. The question you have to ask yourself is do you want to go fast or do you want to have good tire wear? I don't think you can have both in a stock class camber challenged car.

Every tire has an ideal pressure for a given track surface and temperature. Anything above or below that temperature will reduce grip. My opinion is that you are outside the ultimate grip range of the Direzza at 39psi regardless of track surface and temp.

IMHO If you want to go faster, get a big bar, lower tire pressures and go slower into tight corners. Call up or email Greg Fordahl and ask him his opinion. He is probably the best expert on Porsche autocross car prep. http://www.fordahlmotorsports.com/contact.htm

sjfehr

I bought a GT3 swaybar and droplinks from Tarett, they came in yesterday. Went to put it on... and it didn't fit! Turns out, they mistakenly sent a 997 bar (oops!). Tarett was really good about it, super apologetic, and next-day shipped the right bar, which went right in, and I just got back from a test drive. I'm not entirely sure how much is placebo, but it feels more stable, and not a whole lot rougher over the bumps. I wasn't about to push the car anywhere near the limits on public roads, but I've got an autocross coming up this Sunday, so I'll soon see how much difference it really makes, and if my theory about reducing camber loss and decreasing understeer rather than increasing will pan out. It's on the 2nd to softest right now; I'll go from there depending how it goes on Sunday.

00r101: 18" are going to have a stiffer sidewall than 17", so they very well may require different pressures; you're in a 987 to my 986, too. There's also margin of error on air gauges, too; no 2 seem to ever agree, so we may be closer than we think. It might also be that I have to run higher pressures to account for always riding on the outside corner, and this sway bar will let me run lower pressures. I'll keep an open mind and re-chalk the next few races.

00r101

sjfehr - Glad you got the bar. A sway bar should not make the car ride rougher over bumps that go across the lane like expansion joints as the bar is decoupled when both front wheels move in unison. It only changes spring rates when one wheel moves but the other does not, or moves in the opposite direction - like when the car leans in a turn.

I also felt that the car was more stable with the stiffer bar. The back end is more settled and the car leans less both lead to a feeling of confidence.

I hope that you find the bar does keep the front tires more upright. I know it has for me.

I recommend when you start your serious testing next year that you start out with the bar on full soft (with the links closest to the end of the bar). Also make sure that you jack up both side of the front when making bar setting changes otherwise you will preload the bar when its static and the car will behave oddly.