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      04-28-2009, 03:17 PM   #1
axoid
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128i going Autocrossing this weekend

My local region’s first points event is Saturday and unfortunately the Camaro’s fuel pump is in a non-functional state , so I’m taking my 128 out.

I’m trying to decide to run in DS against a V6 Mustang or in ST against a Civic, Jetta and a RSX. I’m leaning toward ST.

I’ll be running on the stock RFTs. What are people running for air pressures with stock tires?

Thanks in advance,
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      04-28-2009, 07:24 PM   #2
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Those tires are going to kill your times. You may already know that
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      04-29-2009, 06:00 AM   #3
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Those tires are going to kill your times. You may already know that
That I expected. But since I'm not going to regularly campaign the one, I will just have to get by for now.
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      04-29-2009, 03:58 PM   #4
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I see Mustangs in GS and SMS.

I started @ cold 38F/36R (based on recommendations here) and bled to 42F/38R throughout the ~20 lap school on Saturday (based on my instructor's analysis/recommendations). He is a B-stock M3 guy. After cooling they were 32F/30R.

I think I did pretty well compared to the other novices and I'm coming back for more this weekend. Hopefully the "veteran" drivers will show me how it's done. See you there.

-Seth
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      04-29-2009, 06:18 PM   #5
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I ran 42/39 pressure on stock tires with my 135. That's what seemed to work out the best. Might be able to run a bit lower with the 128. People give the stock tires a lot of crap, but I had a LOT of fun on them. The BMW club I ran with on the west coast did a points-based classification system, and I just ran the stock 135 on stock tires and did reasonably well, considering my lack of skill :D

Will you be on concrete or asphalt?
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      04-29-2009, 06:33 PM   #6
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42/38? I was kind of the opposite when I took it to the track. I jacked up my rears more than my fronts to dial down the understeer. Being over 40 hot is kind of bad isn't it?
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      04-29-2009, 06:59 PM   #7
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Quote:
Originally Posted by scorcherjf View Post
42/38? I was kind of the opposite when I took it to the track. I jacked up my rears more than my fronts to dial down the understeer. Being over 40 hot is kind of bad isn't it?
Auto-crosses are typically not long enough to heat up the tire to their optimum operating temperature, hence often times auto-crossers will bump the tire pressure up to typical "hot" tire temps on track while the tire is cold to achieve maximum grip level quicker. That 42 Psi will read the same 42 Psi after a minute long autocross at 60 mph top speed (briefly), while that 42 Psi will likely read 50 on a 2 minute long road-course where top speed may exceed 120 mph.

So in this case, if 42 Psi creates the ideal contact patch size, running 42f/38r in an autocross may actually DECREASE under-steer since the front end would actually have more grip.
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      04-29-2009, 07:01 PM   #8
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Like all BMW MacPherson struts, the front end benefits greatly from additional negative camber. If you can knock out the alignment pin up on the front strut hat and bring both struts in as far as possible it will make your life easier.
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      04-29-2009, 09:21 PM   #9
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I'll be on asphalt this weekend.

Thanks for all the input guys.
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      04-29-2009, 09:31 PM   #10
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Quote:
Originally Posted by spk74 View Post
I see Mustangs in GS and SMS.

I started @ cold 38F/36R (based on recommendations here) and bled to 42F/38R throughout the ~20 lap school on Saturday (based on my instructor's analysis/recommendations). He is a B-stock M3 guy. After cooling they were 32F/30R.

I think I did pretty well compared to the other novices and I'm coming back for more this weekend. Hopefully the "veteran" drivers will show me how it's done. See you there.

-Seth
Is that your 135 on the ovr-scca galleries section? :-) would you guys ever entertain a passenger (i.e., me)? I plan to join a few non-points events later in the summer, but I'd like to ride a few times and understand the whole concept/procedure a bit better.
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      04-30-2009, 05:28 AM   #11
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Originally Posted by G5Ti View Post
would you guys ever entertain a passenger (i.e., me)? I plan to join a few non-points events later in the summer, but I'd like to ride a few times and understand the whole concept/procedure a bit better.
I would be more than happy to take passengers this weekend.
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      04-30-2009, 10:40 AM   #12
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Quote:
Originally Posted by G5Ti View Post
Is that your 135 on the ovr-scca galleries section? :-) would you guys ever entertain a passenger (i.e., me)? I plan to join a few non-points events later in the summer, but I'd like to ride a few times and understand the whole concept/procedure a bit better.
Yes, mine is in the most recent gallery. Yes, passengers welcome (but I'm a novice). Too bad you missed the novice school, it was an excellent intro, all of the "veterans" were there specifically to guide us through.

If you're just going to spectate, I'd recommend getting there ~8 AM so you can get a handle for how it goes early on. The inspection, novice meeting and walking the track are most important. The rest of the day just flows.

But once you're there, I think you'll REALLY regret not participating, especially after you go for a ride.
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      04-30-2009, 06:19 PM   #13
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I would be more than happy to take passengers this weekend.
I won't be able to make this weekend, sadly. But in the future, if the offer stands, I'll take you up on it!

Generally, it's almost impossible for me to have Saturdays off work; so I have to make some schedule adjustments literally months in advance. Even then, it can never be at all consistent. I always seem to forget the beginning of the autocross season, then I just stay away so I don't get the bug.
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