At an autox yesterday,with the Philly region SCCA we had a huge course (FTD was a 52 something in a Raptor (I believe)). My best time was a 69 and I should have been around a 66 for HS. Lots of fast technical slaloms and boxes. The rear kept wanting to step out and I almost spun a couple of time from all the trailbraking going on. I messed around with tire pressures
1st run: Front: 36 Rear: 38--Time: 72 (feeler run, it had been 3+ hours from my one and only walk through that took 20 minutes)
2nd: Fr: 36 Rr: 40--Time: 69 My best run, but the back end never felt planted
3rd: Fr: 38 Rr: 36--Time: 73 Damn near did a 180 during a fast L/R transition
4th: Fr: 40 Rr: 41--Time: 71--still no rear grip

Stock (RS1) 18" Yokos (which do have 17K on them) and I do realize that better tires would make a huge difference, but I'm more curious about the tire pressure tuning thoughts: What do you all run? How do you reduse OS with TP?

Thanks for any help....I'll post a pic or two later.

 

I haven't seen many courses where trail braking is beneficial, and if it is, the driver would know where and how to use it without upsetting the car. It's best to ONLY do one thing at a time, braking, turning or accelerating and in a straight line if you can, but you should always accelerate out of a turn which is an exception. Try to hold a steady throttle through a slalom, and if the back end suddenly gets loose from too much speed in a slalom, you can pound the gas to throw weight to the rear to save from a spin-out, but you can only do it once because it will throw everything else off. Also, the key to a Chicago Box is to treat the inside cone as just another cone and get out of there as soon as possible, if you go too deep you'll kill your times.

First off if you're taking your car to the track, I would tell you to get better tires and sell the stock ones while there's still some meat on them. because you'll still stay in stock class even on R-compound tires. The stock tires are good for just about not much, and asking them to hold grip at the limit of the car just isn't feasable.

I would suggest getting some way to measure the tire temperatures across the tread. Someone at the Auto-X probably has a pyrometer or a contact-free infared temp gauge they could let you use inbetween runs - If the temperatures are lower in the center of the tire then on the outsides, you don't have enough air in them. If the insides are hotter than the outsides, you have too much air. Every car is different and every tire is different because of the weight of the car and how you have it setup so there isn't a universal temperature, even for the same 2 cars unless they are identical.

If you want the rear to have more grip, you need more tire touching the ground. To do that you need to see what's touching from reading temperatures, and putting the rear pressures up too high will dramatically increase oversteer and cause spinouts. HINT: 40+ is too high.

BTW Hope to see you at a philly event, I'll be going to their next one. PM me if you need info on where events are in the area.

 

I appreciate the feedback: The 40+psi TP tip is what I wanted to hear. This course was so fast and technical that it was difficult not to trailbrake a little. There where so many quick transitions and slaloms.

Videos from "crewsfactor" posted down the page should give a good indication of the course (I can't get them to work on my Mac but you may have different luck).

I've been going to, and particpating in, Philly events for 4+ years, this is my first year in the tC. I ran in GS briefly in a couple other cars (with R compounds) before leaping into the SM world (big mistake) and the only reason I haven't taken that plunge for Rs for the tC is I haven't fully commited to HS (I am leaning toward STS with 140 tires and a couple mods).

My new employer [plug]JSC Speed[/plug] (see my mini-coverage here) is going to be an excellent source for parts (I'm generating a big shopping list for the Department of Economics seal of approval).

I won't be at the Boening event, though I'll be at the Time Attack at Summit (first weekend in August) with a friend and should be at the next event at Ripken. Maybe I'll see you there?

 

that course is pretty huge - and that driver did a dang good job too, great mounting position for the camera, felt like I was behind the wheel lol.

Unless something goes awry I'll be at the 2 auto-X's in Aberdeen at Ripken stadium (Philly and Autocrossers Inc.) and I'm trying to make it to the philly event in Boeing, but it's looking not so good for that event. Good to hear you've been at it for quite a while, much longer than me. I've got the knowledge in my head, I just need more seat time.

STS is a tough class, argueably one of the toughest. I'd be more comfortable in STX (which I'm in) because you'd mostly be running against slightly modded WRX's or IS300's, integra/RSX's, etc unless you come across an STX-prepped car (most likely a WRX) - those things are insane... watched a national STX prepped driver/car and he beat out almost everyone's time by 1/4 of their run (as in, ran a 40 when everyone else ran a 60)

Hopefully you'll get to meet my buddy in his STS Pontiac Sunfire (yes, a Sunfire) who consistently beats my times by 3-6 seconds and always runs in the top 5 of his class, and he's got right around the same mods as my car and less power.

EDIT: Found some pics for ya

 

wow ur really high there in the back!

 

That's because I'm braking and beginning to turn right and the weight is mostly on the left front....notice how the left front is closer to the ground?