FFaust

Yeah, wish I could join you.

KOAN

I had a similar Hoosier failure, and sent it back to them for an analysis, and got the same response. Starting pressure too low, and cool temps. Have increased starting pressures, and have had no similar failures. I liked the feel at the lower pressure, but now use F34-36, R 37-39 with good result.

LVDell

Having those lower pressures really lowers the sidewall stiffness and I'm sure is a contributor to the failure. In the cooler temps, I start the pressures higher anyway as the temps don't increase nearly as much.

The tires seemed to work best from 38-40psi in these cars. Hoosier publishes their rec'd pressures as well and they state the same thing.

The biggest problem is drivers report a better "feel" at the lower pressures. The problem with that is they are nowhere near the limit of the slip angle and relying on that flattened feel (wider tire) of the tire to compensate for lack of feel of the tire at the proper pressure. The grip and performance of the tire is better at the higher pressure. It just takes much better feel to exploit it properly.

whylose

Just broke my 996 GT3 rear sway bar and this is the only non-ancient post on a similar topic I could find. I've got a nearly stock '00 C2 and I've had this sway bar on the car since 2004. I've done 3-4 track days, but always on street tires with this car. I decided to take it to an autocross and 2 weeks before the event I changed the settings to what I thought would be appropriate for autox vs street and visual inspection was fine.

On my first run, the car was very pushy and just awful to drive, exactly what should happen w/o a rear bar, but I just wrote it off as a tire pressure problem or maybe I read the course wrong or maybe I just chose a really poor setting on the bar. After the run, I changed pressure and driving style a bit, but had the same issue and finished only 0.05 seconds better. Third run, I was just gonna drive as "poorly" as I could to intentionally make the back end come around and it just refused to happen until I stomped on the brake in the middle of a sharp turn and floored it...and what a terrible jerking and bucking sensation after a delayed rear-end set and it was basically undriveable with any sense of performance. Finished within 0.05 seconds, again.

I was so beside myself to have done so poorly that I just let the car sit for a few weeks. I finally crawled under the car and found what you see in the attached pic.

Took it to my local welder this morning and he said that 100% of broken sway bars he's seen can't be usefully welded because they're all solid steel and treated and they just get more brittle with welding and break again. This was the first hollow bar he'd seen and he reckoned it should weld up just fine. He just called and it's all finished so I'll throw it back on and see what happens. Next event in 2 weeks. I'll let y'all know.