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-   -   NeoGen air pressure (http://www.focusfanatics.com/forum/showthread.php?t=158867)

Blurvfocus 05-04-2008 08:30 PM

NeoGen air pressure
 
I just completed my 6th autocross and I'm not making any progress. The car is pushing badly and the front tires show drastic signs of rolling under, so I increased the pressure and they rolled under less but the car seemed to push even more and my time went even higher. (They thought I stopped somewhere for ice cream for pete's sake). I was up to 45 psi front.

Trouble is, I'm not consistant yet, so I don't know if the change in elapsed time is because of the tire pressure change or some ham-fisted thing I've unwittingly done.

I'm lost in the woods now- I need a good starting point. If anybody is having good luck with their neogens- can you suggest a pressure that I can set-and-forget (for now) so I have a consistant and reasonable performing car.

SVT Robzor 05-05-2008 08:24 AM

Your air pressure is one big piece to this puzzle, but I also suspect you need to slow down a little.

The Focus is kind of a big ass to get around a corner quickly. It's no Buick, but neither is it a 2200 lb. Honda. I've always had my best results with the SVT applying my inputs as slowly and gently as possible - there is a ton of mass over the front contact patch, AND we're FWD, AND we have an open diff, AND we're both running on street tires, AND (barring some nice camber plates) we're always going to be camber-challenged in front.

Also, make sure you're not trying to go and turn at the same time. Cars with trick front diffs can pull that off, it'll just make us push harder. Slow down your thinking and see if you can lead your inputs some more, and make sure you're not on the throttle too much until you're exiting the corner.

When I started autocrossing the Focus, I was slow because I was just plain slow. Then, I was slow because I tried to drive it way too fast. Now, I'm slow cause I'm just not that great a driver [:D].

45psi sounds like the right ballpark, I have Goodyear Eagle F1 DS-G3s on the SVT, which feature super-squishy sidewall technology (read: bad for turning), and I need to run them at 45psi or more COLD, I've seen 52psi after a run.

EDIT: When's the last time it was aligned? Some rear toe-in, or maybe a bent control arm giving you a tiny bit of positive camber, could ruin your day trying to go around a corner as well.

svtstu 05-05-2008 01:42 PM

Pressure responces vary greatly between tires, I had a set of 225 width conti-extreme contacts that liked 42 psi up front and 38 out back, now I am on a set of pirelli Pzero nero M+S and they like about 32 up front and 34 out back. My suggestion would be to go at forty front and forty rear and then bleed out the front if you are still pushing, if the tire rolling gets too bad try 44 in each and then bleed the fronts out as needed.

Blurvfocus 05-05-2008 08:54 PM

Quote:

Originally Posted by SVT Robzor (Post 2112604)
Your air pressure is one big piece to this puzzle, but I also suspect you need to slow down a little.

Yeah I had that thought too. "Go slow to go fast" type of thing, so I slowed down a little, and sure enough my line was better, more controlled, etc, but my time was slower still!

I've had a few days to think about this- I won't bore you with the details, they're tecnique issues I have to handle. And, I'll try going with 45 psi front and dropping 2 psi every run just to see what happens. (the back is good, btw. It never even hints at slipping out and the tires show no signs of distress whatsoever)

Thanks for your replies- both of you.

WD40 05-06-2008 09:49 PM

The first thing I'd do is save up for some new tires and ditch the NeoGens.
That's not a very good AutoCross tire at all.
The huge diagonal grooves are not conducive to very good cornering grip.
And...as you found out...they have a rather soft sidewall.

Check out Falken Azenis RT-615, Dunlop Sport Z1, Bridgestone RE-01R, Hankook R-S2, Kumho MX if you're going to stay in STS.
See here for a good discussion:
http://www.focusfanatics.com/forum/showthread.php?t=149887

Blurvfocus 05-07-2008 06:51 PM

Quote:

Originally Posted by WD40 (Post 2115483)
The first thing I'd do is save up for some new tires and ditch the NeoGens.
That's not a very good AutoCross tire at all.
The huge diagonal grooves are not conducive to very good cornering grip.
And...as you found out...they have a rather soft sidewall.

Check out Falken Azenis RT-615, Dunlop Sport Z1, Bridgestone RE-01R, Hankook R-S2, Kumho MX if you're going to stay in STS.
See here for a good discussion:
http://www.focusfanatics.com/forum/showthread.php?t=149887

I had high hopes for these, they were the only tires that had 100% favorable reviews on Edge Racing, and they are considered an all-season tire. But I noticed right away that they were much slower to respond than the crappy old Goodyears I had on there before. They're not wearing that well either, most likely I'll be ready for something else by the fall. Thanks for the tire suggestions (that was my next question).

DirtyDeeds 05-07-2008 07:34 PM

For every tire used in autocross, there is a sweet spot as far as tire pressure. Too low and you lose grip, too high and you still lose grip. Tread compounds, patterns, camber and alignment aside, how much pressure you run has quite a bit to do with how soft or stiff the side walls are on your particular tires. Tires can also handle only so much heat before they become greasy and start losing grip.

45psi is probably a little high to start with. Try starting out with the front tire between 38 - 40 psi and put the rears between 34 - 32psi.

Pick up some chalk and mark the tires where the side wall meets the tread. By seeing which tires are rubbing away the chalk, you can make a more informed decision on adjusting your tire pressure.

Is the car getting slower after a few runs? If so, the tires may be getting hot and greasy. If you think this might be the case, go over to Home Depot and pick up a cheap hand pump garden sprayer. Fill it with water and spray your front tires after the 2nd or 3rd run to keep them cool.

Are you trail braking? This generally the fastest way to get a fwd car through a turn.

Is it possible that you may be over driving the car? I'm only asking this because it's a common mistake for a new autocross driver. I know I did it.

The NeoGen isn't the best tire, but that doesn't mean that we still can't make you faster.

Dcl2049 05-07-2008 08:08 PM

I liked my NeoGens better than the G-Force sports on the track. It may have something to do with the concrete I race on?

In any case, I would run right around 38 up front and around 36 in back. They did seem to get a little greasy but I'm not a "pro" auto-xer so I just sucked it up. I would generally run fastest on my middle laps.

Do the thing with the chalk. ^
When mine was set right it would rub it off all the way to the end of the outside tread grooves and a tad further.

Blurvfocus 05-08-2008 08:37 AM

I've been tampering with the shock settings and seeing a drastic improvement. I set them hard in the back and soft in front (they were half-hard all the way around). So when I run next time I'll play around adjusting in small increments. In the meantime, you guys seem to be in substantial agreement on the pressures; I'll go with them.

Thanks for your help.

btw- I've got to travel for ??? long. So if there are any more thoughts, I'm not ignoring you, I'll respond as soon as I return.

Dcl2049 05-09-2008 04:38 PM

Yeah I use that setup for my Konis, be careful though because I had the car coming around on me big time just with braking in a straight line.


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