Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure - Mazda3 Forums : The #1 Mazda 3 Forum
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post #1 of 25 (permalink) Old 09-17-2011, 02:08 PM Thread Starter
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Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Got my tires and wheels the other day and bolted 'em on. Fit great! As they're breaking in I realize they have a ridiculous amount of grip. It's awesome! And they squirm less than my old all-seasons already, even at full tread depth.

I used to run my Potenza Grid G019 205/50/17 tires at 40front/38rear psi on my gage, which according to everyone else's gage is reading low. I'm likely at an actual pressure of 47/45 front/rear.

Where should I start with the new tires? I can see the sidewall rolling just a bit on the street (I'm spirited) already. Not to the sidewall but further than I saw on my Potenzas at autocross, but my gage is reading at 25psi all the way around, which another gage read at 32.5psi. I'm going to at least pump them up to 30 on my gage as this worked well for tire wear on my old tires on the street, but for autocrossing should I go ahead and put them up around 40-45 again or should they need less pressure?

I was planning just to pump them up to 35-40 on my gage and reduce as necessary but if someone can give me a decent answer it's a little easier.

-Eric
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post #2 of 25 (permalink) Old 09-17-2011, 07:30 PM
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Id say 40 front and 38 rear is a decent starting point. I have noticed that I can post faster laps on certain surfaces with the rears over inflated but I think this is more of a drivers preference. The key is not to get married to your settings until your certain that you have optimized them. My club allows members to double enter their car to get a bit more seat time and I have found this quite helpful in dialing in my setup changes.

have fun!

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post #3 of 25 (permalink) Old 09-17-2011, 10:16 PM Thread Starter
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Thanks. I just went out and upped the pressure a little bit for street driving. There was a little more roll than I like even on the street. Had less pressure than my G019s anyway. Now they're up where I had them and I'll see how that works.

I'll probably just start where I was on my all-seasons and go from there. I found myself with a good front setting that didn't roll too much sidewall and then played with the rears a little bit to get it to rotate how I wanted it to. Usually end up about 40/38 so I'll just start there.

Thanks again!

-Eric
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post #4 of 25 (permalink) Old 09-18-2011, 09:16 PM
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

You're getting roll @ 25psi? I ran the older RS2's (which were great, my next set of tires will be RS3's once my Star Specs give out) and they performed substantially better at lower pressures a la the 20-30 range. My Star Specs are similar in that respect. It may the extra 0.5 inch of wheel that I have but all of my racing experience, track days or autoX says that lower pressures makes aggressive summer tires happy.
For reference, I ran 225/45 RS2 on a 17x8 wheel, and my current Star Specs are 235/45 on the same wheels.


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post #5 of 25 (permalink) Old 09-19-2011, 12:19 AM
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Start with more pressure than you think you need up front, chalk tires. See how much it's rolling over, adjust air pressure if necessary, repeat. Use same amount of pressure in the rear tires. If the is loose and wanting to spin out alot drop rear pressures until it feels more stable. If the car feels like it is plowing or understeering keep adding rear pressure until the car feels neutral or slightly loose.
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post #6 of 25 (permalink) Old 09-19-2011, 11:08 AM
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

What he said, and for heaven's sake, go buy yourself a decent tire gauge! They're not that much, and worth it to know exactly what
pressures are right for your car. Way cheaper than screwing up a set of tires.

Whoever stated 20-30# for pressures with 215x45x17 Dunlop Start Specs with "no rollover" must have massive front negative camber....... :shock:
On the Factory 17x6.5 wheels in H Stock/Street Tire (no camber) I have to run well over 40# in front to stay off the sidewalls...... On the street
I'm running about 38f/40r.

Note: Around here (Arizona) Hankooks are known for having much softer sidewalls than the Dunlops, requiring even more pressure.

[quote author=Adam3s link=topic=196877.msg4113974#msg4113974 date=1316405981][size=6pt]Start with more pressure than you think you need up front, chalk tires. See how much it's rolling over, adjust air pressure if necessary, repeat. Use same amount of pressure in the rear tires. If the is loose and wanting to spin out a lot drop rear pressures until it feels more stable. If the car feels like it is plowing or under-steering keep adding rear pressure until the car feels neutral or slightly loose.[/size][/quote]

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post #7 of 25 (permalink) Old 09-19-2011, 01:57 PM
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

I think I ran higher than 30 on 225 RS3's on a 7.5 wheel on a 1940 lb CRX.

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post #8 of 25 (permalink) Old 09-19-2011, 07:43 PM Thread Starter
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Thanks guys.

The lower pressure doesn't make any sense to me because I'm right about where I want to be on the street with 32f/30r.

For the pressure gage, I will be getting a decent one before I get too far along. I had figured out where the old tires were happy on the suspected 'off' gage so it didn't really matter what the actual pressure was. It worked.

Added bonus: I can't make them squeal on the street. That makes it exempt from 'exhibition of speed' in one of our suburbs. LOL

-Eric
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post #9 of 25 (permalink) Old 10-02-2011, 09:44 PM Thread Starter
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Welp, wound up at 48 on both ends, then lowered the front a little too much to 45 by the end of the day. I think 46-47 is the sweet spot on the fronts. The rear though, needs more pressure or less camber or something. It does NOT rotate any more! Too much rear grip! One of the local fast guys (who drives an Integra GS-R) suggested I start at 48/55 and see how it goes. I'm scared of putting 55psi of air in the tires, especially for the 50-mile trip to the course, but I may end up getting an air tank to push them up there after I'm at the event.

Anyone have suggestions as to how big of a tank I'd need to air up all four from 32.5 to 47/55?

Will update as to whether or not it hurt me once results are posted.

-Eric
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post #10 of 25 (permalink) Old 10-02-2011, 10:50 PM
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Re: Hankook Ventus R-S3 225/45/17 on 17x7.5 wheels - Autocross Pressure

Two things:

1. Work on maximizing front grip. If the rear is not rotating, it's not because something is wrong out back. Almost every car on the street is setup from the factory to understeer (because it is easier for the average driver to correct from an understeer situation than an oversteer situation). Unless you make significant changes to the suspension, the natural inclination of the car will be to push.

2. Buy a small air compressor instead of a tank. The tank is great for making small, fast additions to air pressure, but the compressor is better for adding large amounts of air. Plus, I cannot tell you how many nights I have loaded the car and remembered (at that point) that I hadn't gotten the tank filled.


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