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FC AutoX Tire pressures

Old 05-24-09, 11:44 PM
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FC AutoX Tire pressures

After reading a bit, I figured that I would post with my specific " setup" and see if anyone could give me a good idea of where to start tweaking my tire pressure for AutoX.

NA FC Widebody

Suspension:

R.B. Sway bars
Corksport upper bars
Cusco lower ( rear ) control arm bar
Tein SS Coilovers ( set smack dab in the middle )
R.B rear steer eliminators
"aftermarket" camber adjuster ( set to minimal camber aka, as straight as possible)

Wheels/ Tires:

Rear: 285/35/18 Falken Fk-452
Front: 245/40/18


This is my first AutoX season and after a few events i think i should get a bit more serious about dialing in proper air pressure. Any feed back, or a good place to start?
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Old 05-25-09, 07:53 AM
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Have you tried taking white shoe polish and put a few marks on the shoulder around the perimeter of the tire? Do a run and then see how far you are rolling over on the shoulder. Adjust pressure so that you are using all the tread but not rolling over onto the sidewall.

I don't auto-x too much, but I have some friends who are fairly serious, and they've mentioned this method before.

-bill
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Old 05-25-09, 12:44 PM
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Use chalk on the sidewalls, the white shoe polish is a bitch to remove.
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Old 05-25-09, 08:35 PM
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Do the chalk thing for starters. It will give you a good idea of the minimum pressures you can run. I'm going to guess that you are really gonna have to jack up the rear pressures to get any sort of rotation. FCs tend to strongly dislike staggers.
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Old 05-26-09, 12:08 AM
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Ran with red shoe polish today at BSCC event 3... Spoke to a few tenured autoxers.. and got some good feedback. I ended up *liking* this setup very much

Front 41
rear 37
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Old 05-26-09, 12:12 AM
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Wow. With stock sized 205/55r16 Toyo RA-1s and BFG R1s I ran 32psi F/R or 32/30 F/R.

With the lower profile tires and bigger wheels I wouldn't have thought you'd bump the pressures up that much.
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Old 05-26-09, 02:37 PM
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Tire pressure depends on a lot of things. Camber, aspect ratio, tires.
My particular setup is very similar to yours in sizes, but I run hankook ventus rsII front 245/45zr16
Kumho XS 275/40zr17 Rear

My pressures were 31psi front 29psi rear

I have a weird setup according to a lot of people.
I run with -.6 degrees camber rear
-2.7 degrees camber front
I have the addco sway bar, polyurethane bushings everywhere, koni 8611-1257 struts front with bilstein hd struts rear. NO rear sway bar, awr spherical trailing arm bushings
430lb/ft springs front
280lb/ft springs rear
Car weighs 2645 with 1/8 tank (after a day of autox) full interior (yes it is a tII)

Depending on the tires you use, you ideally want those little rolls on the tire on the inside edges of every tread block. Most all season tires will not do this as they are too hard. Any tire worth a damn will do this. You can judge how well your camber works by feeling across (inside to out) the tread of the tire. Hotter inside means you have too much, too hot outside means too little. Tire roll over can be adjusted and fine tune this, but temps are the final say in how the setup is working together. A cheap 20dollar infrared thermometer will be a good investment to see closer what the tire likes.

Hope this was helpful
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Old 05-26-09, 03:53 PM
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Originally Posted by dpf22 View Post
Tire roll over can be adjusted and fine tune this, but temps are the final say in how the setup is working together. A cheap 20dollar infrared thermometer will be a good investment to see closer what the tire likes.
Unfortunately unless you can do this *immediately* after the run it's near useless. You're much better off spending a little extra money here and getting a probe type thermocouple, too. The inside/middle/outside temps are a great way to figure out your camber settings, but you need to get the them ASAP after coming it.
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Old 05-27-09, 01:22 AM
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^ +1.. i have digital laser thermometer.. which did me no good seeing as i left it at home that day........

These tires are monstrous. They evidently need all the air in the atmosphere. LOL
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Old 05-29-09, 08:29 PM
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I was speaking in generality. I autox and all of the national level ssm guys have told me that an info red thermometer is about all you need unless you like to spend lots of money that is. I just feel the tire. You get pretty close that way. Not perfect, yes the probes are going to be better I agree. For now, you have a lot of information to chew on.
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