2012 BRZ/FR-S Stock Class Autocross Discussion

[Evil86]

The Phoenix scca autox club (azsolo.com) runs summer events in Taylor, AZ (northern AZ between Flagstaff and the Border). My fastest clean run was 47.177. This one was dirty, I clipped the 2nd to last cone, but I felt good.
[ame="http://www.youtube.com/watch?v=IHyTjXonv1s"]fastest run Taylor.avi - YouTube[/ame]

sorry the vid sux, youtube said it was "shaky" and offered to "fix it," unfortunately it distorted the video.

Hankooks rs3 41psi front 37psi rear. Next tires will be star specs 225s.

Also I managed to spin the car on one run. I shifted into second as I went around the first slalom on a different run, and it got away from me.

The car is a blast autoxing. I have had three co drivers over three events, and they all dig the car.

[Kido1986]

Low turnout?

Our events are way too crowded lol

[NYC BRZ]

I'm on 225/45/17 star specs and they are fantastic. Had a bunch of great runs yesterday but needed to play more with pressures. It was about 105 on the Tarmac so I was spraying a lot of water. Once the edges were scrubbed in the car came alive.

[xwd]

Originally Posted by des

What are you running for pressures?

I'm on 235/45/17 Star Specs -- a lot more tire than most people are running -- but the rear really settled down and tire temps evened out when we dropped them to 30.

What tires are you on?

Is this on 17x7 rims? Why would you run 235/45 instead of 235/40 or is it just a typo? the 235/45 is a lot heavier than the 235/40 and the gearing is much worse...

I have heard the star specs have a stiffer sidewall so 235/40 on a 7" rim may not be terrible although it will be pinched.

[AlanLGuy]

Originally Posted by NYC BRZ

I'm on 225/45/17 star specs and they are fantastic. Had a bunch of great runs yesterday but needed to play more with pressures. It was about 105 on the Tarmac so I was spraying a lot of water. Once the edges were scrubbed in the car came alive.

What kind of pressures are you running? I'm on the same setup and have been playing with pressures as well. First event I ran 36F/ 38R and I think that was way too much. Second event I dropped down to 32 / 34 which worked better, but still think there is more to be had.

Honestly though, I need to be fixing my driving before playing with pressures too much. Coming from a front wheel drive celica GT-S, I find I tend to trail brake late into the turn to rotate the rear, rather than using the throttle to help it get around. The end result being too fast of an entry and a slow exit witha ridiculous amount of understeer. (I'm embarrassed to say my average PAX position has dropped slightly in the FR-S despite better tires and a MUCH quicker car)

[NYC BRZ]

Originally Posted by AlanLGuy

What kind of pressures are you running? I'm on the same setup and have been playing with pressures as well. First event I ran 36F/ 38R and I think that was way too much. Second event I dropped down to 32 / 34 which worked better, but still think there is more to be had.

Honestly though, I need to be fixing my driving before playing with pressures too much. Coming from a front wheel drive celica GT-S, I find I tend to trail brake late into the turn to rotate the rear, rather than using the throttle to help it get around. The end result being too fast of an entry and a slow exit witha ridiculous amount of understeer. (I'm embarrassed to say my average PAX position has dropped slightly in the FR-S despite better tires and a MUCH quicker car)

I was running 42F/38R. It was understeering slightly.

[des]

Originally Posted by dwx

Is this on 17x7 rims? Why would you run 235/45 instead of 235/40 or is it just a typo? the 235/45 is a lot heavier than the 235/40 and the gearing is much worse...

I have heard the star specs have a stiffer sidewall so 235/40 on a 7" rim may not be terrible although it will be pinched.

45s on the 17x7s. I would have gone for the 40s but they were backordered.

Not worried about the weight, but agree there's an oomph penalty to the 45s that would be exaggerated by a tight or power course. The upside is an additional 2 mph at the top of second.

It's not just about avoiding the shift -- it's staying off that rev limiter, which is pretty cruel. They don't roll over (stiff sidewall, as you point out), and pyrometer shows we are using all of the tire.

I probably will go for the 40s next set (soon) because our Bay Area venues are smaller.

[feldy]

So not sure why you guys are running such high pressures. Stock pressures work great on the stock alignment. Pryometer said so. I run 225/45/17s on rs3s. Been Acutally running 35 front 32 back for added rear grip. Now on my past car with -2 degrees of camber I had to run 45 front for roll over reasons.

[Biggins]

Originally Posted by feldy

So not sure why you guys are running such high pressures. Stock pressures work great on the stock alignment. Pryometer said so. I run 225/45/17s on rs3s. Been Acutally running 35 front 32 back for added rear grip. Now on my past car with -2 degrees of camber I had to run 45 front for roll over reasons.

Agreed. I thought these pressures seemed really high. I don't think you'd need more than 35F/33R on the Dunlops.

I'm still on the OEM tires and have run 35F/33R, and it's not even close to rolling over... I only ran 34F/32R with the Dunlops on my much heavier BMW for many years with success.

[mrazny]

While those are *probably* too high, remember that RS3's and not Star Specs, pyrometers are super useful but not a catch-all, still need to test, and size matters. Fatter star specs typically like less pressure. 17's will run a little different than 18's, etc.

If you have something this a -> b comparable, bmw on 17x7's in that same size, with hopefully the same camber, then pressure on a lighter car can possibly be dropped.

If pyrometers told the whole story, Andy Hollis wouldn't spend days testing various brands, or even fine tuning his selected one. Ideally you'd have a repeatable slalom and a skidpad at various pressures with recorded temps. Then see if the result helps your times. repeat. repeat. repeat. repeat.

[Evil86]

Originally Posted by Kido1986

Low turnout?

Our events are way too crowded lol

Delightfully so. Our Phoenix events vary between 90 to 150 people, but Taylor events are much smaller. This had the lowest turnout, 22 each day for a mini tour format. Six runs in the morning and six in the afternoon each day. Saturday we were done at 2:00 and Sunday at 12:30.. We could have had more runs each day, but 24 total runs were enough. With the exception of a few noobs, everyone was very experienced.

[Evil86]

I played with tire pressures at the test and tune for the SOPAC super regional at El Toro in Cali. I wanted to start with a stock size tire and see what happened. We ran 215 RS3s. We started high, 45/45 and worked our way down. We ended up with 41F/37R. Since then I have tried a few pounds lower in the tires, and for that specific size in RS3, it works pretty good. While I sucked, my co-driver did a very respectable 3rd in a field of 20 (RTR). This weekend, running the same pressure I was coming close to fast STR times. I tried lowering the pressure to around 36/33 and it sucked. The tires became unpredictable.

Optimum tire pressure is as high as you can go before performance falls off.

[xwd]

I'm still trying to figure out if I want to run RTR or CS.

If I do CS I'm probably going to bite the bullet and run the 245/40/17 BFG R1-S tires. If I do RTR I'll probably end up with the 235/40/17 Star Specs. I've raced on both Hoosiers and street tires before, but not for a few years.

Wheels show up tomorrow...

[Evil86]

Originally Posted by dwx

I'm still trying to figure out if I want to run RTR or CS.

If I do CS I'm probably going to bite the bullet and run the 245/40/17 BFG R1-S tires. If I do RTR I'll probably end up with the 235/40/17 Star Specs. I've raced on both Hoosiers and street tires before, but not for a few years.

Wheels show up tomorrow...

RTR at first. After I learn to drive it at its limits, it'll probably go STX. R-tires, as disposable items, are just too expensive.