245's all around for AX?
 

It's almost that time of year when I start prepping for the autocross season. In looking at last years tires it is definitely time for new ones. I am going back and forth about using 245's all the way around (I have 8.5" wide front wheels) versus 245's up front and 275's in the rear. I have been using Victoracers and the fronts have worn out significantly on the outside edges (the rest of the tire is definitely worse than the rear tire wear). I am not willing to adjust the alignment for a competition setup as I would like my daily driver tires to last. Does anyone have any thoughts about the two different setups? I've heard the 245's all the way around should help balance out the understeer which I believe is causing the fronts to wear out a little faster; however, I sure would like to try the increased grip of the wider tires (this could be me being goofy about wider is better).

I had been using 225's in the front and 255's in the rear and felt I had a pretty good balance; however, the wear on the front has me thinking that maybe I am pushing the front a little too hard? I also noticed that in carousel style turns that I have a very hard time getting the car to rotate, instead I push like crazy until I induce oversteer with the throttle and this correction only lasts for a second or two.

Help???

:D

I think you are on the right track with non-staggered widths for AX. But I would pump up the volume a bit. If you are on 18" in a 987 then think about 285/30/18 Hoosier A6s. The Kumho 18s are just too wide and heavy. On 17" then 275/40/17 Hoosier A6 or a 275/40/17 Kumho v710. Either way 245s are pretty puny IMHO.

Regards,
Alan

245s all around has been talked about a lot. there are a lot of guys that like it. there is a guy named kenny jones that knows his stuff, you can find him on babblers and on the golden gate pca site.

for me, i am running 255/265 on 9.5s all around. i bet i could have gone with a widder wheel, but thats ok.

the first event for me isn't for another couple of months. i will miss the first event of the season cause I will be at the national tour with the SCCA in SD in our VW.

as far as alignment, what are your rear toe settings? an ever so slight change in that will help, and will not hurt st. tire wear that much either. I have found that a little change makes a big difference in the rear.

It depends on the courses you run and your driving style. The symptoms you describe may clean up with 245's. Graeme (Highlander) holds multiple SCCA National championships and runs 245's all around to good effect. You may want to give your alignment another look. I think Hoosiers run /wear best with lots of neg. camber. I am running 225/255 17 with no wear issues street or track. I find myself running faster times in cars and Karts with just a touch of threshold understeer on full throttle track out. It reminds me to drive the smoothest line.

I ran a 225/275 18 combo and wished I had gone to 245s all around. For me, I like a car to rotate and with the 225/275 combo, it just didn't happen. I won't say if 245s are faster, but they do feel more fun. 245s all around will help reduce understeer, but realize that the Boxster left the factory desgined to understeer - especially with the 205 stock fronts:) (plus, understeer is safer and limits lawsuits)...

If you are committed to a "stock suspension" then you will always chew up the outside edges of the fronts. R comps need at least 2-5 degrees of negative camber and the stock set up only allows about -1.8 at most (unless your car was in a collision ;) )

So, an advantage to 245s all around would be to spread that wear evenly around the car by rotating wheel positions.. and then flip tires on the rims as well.

I think I may stick with the 245/275 setup since the only problem I really have is the carousels (skid pad). I have spun my car numerous times and appreciate the grip and speed that I get going through slaloms and other higher speed corners that understeer is virtually non-existant. I am installing the lower stress bars on the rear and hope this will take a little of the understeer out.

I run 245/35/18 fronts and 285/30/18 rears (V710s) on stock-sized wheels. With the right alignment you won't be complaining about understeer, that much is certain. I ended up adding a GT3 front bar to the car to manage the oversteer.

We don't have issues with our stock suspension and chewing up front tires. The car is actually pretty easy on tires. We have gotten around a hundred runs out of a set of front V710s. Hoosiers are less tolerant, but they are a couple pounds lighter per corner. It's a tradeoff.

i kind of agree with john. there is so much caster built into the boxster's suspension geometry that you just don't need that much static camber to correct any understeer. even w/ 1.4 degrees camber up front i was wearing the INSIDE edges of the tires on a race track. i had to use my pyro to dial in less camber & even out the tire temps. generally now i run 1.0 deg on street tires w/ even wear. i run a P225 / P265 stagger with a stiff rear sway and GT3 front sway. with stock sways and a P245 / P245 setup, i imagine the car would be as easy to rotate as mine is now.

an important thing to note is that OEM alignment specs even say that some POSITIVE camber is okay up front. this means your car could come straight from the alignment shop with positive camber and be IN SPEC. if you're having understeer issues, get a more agressive alignment FIRST, then see how it drives before you start swapping parts. the first time i did a more sporting alignment on my car, i was really suprised in how different it drove. MUCH better.

Very true. Mine shipped with minimum front camber and a lot of rear camber. That can make a car pretty pushy. Getting rid of as much of the rear camber and toe-in as possible really helped. Adding the maximum front camber (-.7 on mine) helped as well. It's extremely well balanced.

You guys that are running a GT3 front sway bar. What is the difference between the GT3 and my stock S?

the GT3 bar is adjustable. on the softest setting, it's probably around 70% stiffer than your stock S. on the firmest setting, it's probably 150% stiffer. i never move mine off the first setting. when i go to the track, i only adjust the rear & leave the front alone.

Thanks! And where might I aquire such item(s)? (now that I have the lower stress bars I'm in the modding mood) ;)

you can get the GT3 bar and bushings from Sunset or Suncoast. you'll need a set of adjustable drop links; you can get those from me, Tarrett, or TRG. i use an H&R rear sway bar; it's available from ebay.

are we still talking AX or all performance driving including track days. and do all alignment shops understand a sporty set-up.

i would run staggered tires on a race track (i run 225/265). the sways are great for either, as is a performance alignment. not all shops understand what's required in a performance alignment, but if you give them the settings, any shop should be able to dial it in just fine.

sure; start with this:

front toe: 0.0
rear toe: 1/16" per side
front camber: -0.8deg
rear camber: -1.1 deg

that should be a nice start. if the tracks you run are tight and don't have many fast (>80 - 90mph) turns, you can go with zero toe in back.

I like insite's alignment suggestions. Very close to what I run for street and autocross use. The zero rear toe may be a bit much for some people, because it biases the car towards oversteer a bit. For more stability on throttle, run 1/8" total as he says.

I have insite's adjustable front sway bar links and I love them. They're the beefiest, best built links I've ever used and they haven't made a lick of noise in 500 miles of street driving.

JV

I pulled the trigger and went with the 245/275 setup on my 17" x 8.5" stock wheels. Does anyone know if I will need wheel spacers? I run a 2002 S with stock suspension.

:cheers:

Just did my first test and tune with the 996 GT3 front sway bar and 245/285 Kumho V710s on stock wheels. -.7 degrees front camber, -1.2 degrees rear, zero toe front and rear. Bar was set to full soft. On cold front tires, lots of understeer. But once the tires warmed up, the car was very well balanced. No understeer to report except in very tight turns. Slaloms are brainless now. Floor it and steer. No more inside wheelspin in slaloms. Nice lift-throttle oversteer characteristics, and neutral handling on-power.

31psi front and 33.5psi rear on 40-run-old V710s with a bunch of heat cycles on them. If it stays dry this weekend for our first local event I'll get some good data on how the car is relative to some of the best drivers in the country.