In that case, I would think the max. tire width that will fit would be best for ultimate speed, then balance with the bars. What are the wheel/tire width limits ?

235/17 front 255/17 rear.. we run 255 square

The car ends up with more grip than power :)

No doubt! But 255 is the maximum width allowed by the rules ?

Yes, per our spec rules 255 RA1 or 255 RR,

On a 987 here in SoCal, we run 285 square (it fits 295 easily in the rear)

Testing 245 A6 square for 2 lap time trial format blast. It worked :)

http://986forum.com/forums/uploads01...1395691514.jpg

Brad:

What kind of camber are you guys running square?

I used to run square until I put in GT3 arms and cranked in about -3 deg. in front, at which point I had major oversteer. Ended up going 255 Front / 285 rear which calmed down the oversteer.

I guess I could have cranked in some more front bar, but that seems to fall under the heading of "unsticking the end that is working", which Caroll Smith taught us not to do.

Thanks for any info.

Camber depends on the driver and track. I change alignments for every track.

I've run upwards of -3.7 on the new RR (944 guys are talking about -4.0) in the front.

On my cars, I start with a .5 degree split between front and rear. I then take a ton of tire temps from all over the USA and adjust the cars per track per driver ability.

Not aiming this directly at you.. but you have to be INSANE :cheers: to think you can just bolt on square and go. 99% of the people who try square come back and say the same thing you said "I had a ton of front grip".. well.. NO SH_T!! :cheers:

Please note: I'm smiling when busting balls. I cannot tell you how many people have come to me saying exactly what you are saying.. LOL

FYI: Caroll is correct... BUT... Caroll's info was based in 1970. The cars have changed. A LOT. The tubs are so stiff now (with a cage) that minor adjustments to them give big results.

In the PRO world? (or SCCA AutoX) I have exactly NO time to make decisions. What if I need to adjust the wrong end because I don't have time to make a spring change? You damn well bet I'm adjusting the wrong end :)

I do whatever it takes to make the car work.... NOW. I can adjust a rear bar or remove it on the hot pit wall in less than one lap at most tracks. I prefer to use the rear bar for adjustments because I can reach it easily.

What rear bar?

I used to run around with it disconnected thinking that I would find some occasion to hook it up, but finally just pulled that dead weight out. I run just enough front bar for camber control in roll. If I ran more front bar, I would need more rear bar, but what's the point?

Good man! Multiple tracks here near SmellA that I run NO rear bar. I leave them in place and secure the drop link out of the way. If I need it in a hurry? break the zip tie and install the drop link in 2min. I consider disconnecting and reconnecting an adjustment :)

Something else we have worked very hard on.. changing the track width.

Add rear wheel spacers

(all my cars run screw in pro-style studs, I helped Tarett develop what I feel is the best on the market right now)

If you add spacers up front it makes the scrub worse.. on the rear? game on (I don't run them in spec) but if you need *just* a bit more grip in the rear? start with 5mm spacers.

The key is, don't use tire size to adjust balance unless there's no other option. Tires dictate the maximum potential grip, adjust geometry/alignment to get the tires working their best. The balance is (generally) adjusted with springs and bars. So to reduce the oversteer the easiest would be to stiffen your front bar, or you could install softer rear springs. Of course, if you don't have rules limiting you to 255's , stay with the 285's, and fine tune the balance in the same manner.

Caroll smith's quote doesn't really apply, you're not really taking away grip, you're just adjusting how much weight each end of the car has to "carry" via roll stiffness distribution.

Will do, let me know when youre in town!

please do, I'm having trouble finding an 8 or 9 X15 with the right offset.

... meant to give feedback a lot earlier. So...
I took the Boxster out to the local track High Plains Raceway on a square setup.
The car felt well balanced. The front was planted and the rear was easy to rotate.
I'm stil using the stock sway bar, so the rear bar is disconnected. Even so, the rear is a bit too tail happy if there is any surface bump under trailbraking. ...for my skill level anyway.
I have some other springs I'll be trying (600lbs/in F and 700R to replace the ~900F and ~1000R)

I was on very old R-S3s an corded two of them by mid day. Having a staggered setup definitely helped then :)
A couple of guys that race Spec Boxsters were out there and their choice is square.

https://dl.dropboxusercontent.com/u/...309-hpr-46.JPG

Could you tell me what the offsets are for those rims?

just got a box
 

just got a 99 boxster, want to run square. everything is stock, best way to try square is disconnect rear sway yes? i want to try toyo ra1. to get ultimate grrrripp hehe.

i have stock sized staggered michelin as/3 now and like them a lot, thinking to run square ra1 for autocross and track next year. any recomendations would be very welcome.

PS
my 1st post btw, just installed EPS eternal fix, only 700miles on new bearing now.
thanks

Boxster's are designed with inherent understeer. Most owners increase the front tire width from the stock 205 to 225 to reduce understeer. 235 is even better.

However, if you go the next step and install 255's up front, the car typically goes from natural understeer to natural oversteer (because now the front has a lot more grip). This won't be an issue while driving around town at normal speeds, but crank it into a freeway on-ramp with a set of RA-1's or take it to an autocross and at the limit the rear end is going to be loose.

Thus, most owners who go square install adjustable coilovers, adj drop links, and adj sway bars so the handling can be adjusted back to neutral (or however the owner likes it best).

If you wanted to try going square on the stock suspension, then yes, disconnect the rear sway bar and set front tire pressure slightly lower than the rear tire pressure. The car should still exhibit quite a bit of oversteer so be prepared to react accordingly.

Adjustable coilovers(pss9 2k $),
adjustable drop links (front/rear Tarret 1k $)
, and adjustable sway bars (gt3 front/Tarret tear 1k$)
And we havent got to lower controll arms and other bits.
Plus my time installing the stuff, sounds like about 4k of dollars and that much closer SPB build. 4k can buy a lot of tires of going staggered for $4k. Oversteers that bad huh if just doing square and no mods.. I do notice that bit of understeer a bit when pushing the car, its not that bad though.
Hmmm you made me think. Seeing that photo of Boxster on three wheels got me waay exited.
Hmm it sounds like ALL IN or nothing hehe

Welcome to the asylum :)

FWIW, my 986 ran faster on most tracks with 225/255 stagger. I ran this and 255 square over 8 years with a LOT of comparison data. With the 225/255 setup you don't need a sway change but either staggered or square, you will destroy the RA-1 outer shoulders quickly (1-2 days) unless you get more camber into the car. RA-1 feels best to me with -3 degrees F, -2.5 R.

R-Comp tires= suspension setup changes. GT3 arms and lowering springs are the poor man's track setup.