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Understeer...

Old 07-16-13, 05:23 PM
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Understeer...

Okay, while running on a road course and auto-x this weekend. My car had pretty severe understeer. I'm running 2* camber up front, 5* caster and 1.5* camber out back. Stock bars f/r.

Is it a tire balance issue, running 255's up front vs my 275's out back? Or something else? Or am i asking too much of what i consider a street tire in the NT05? They got greasy on my after about a dozen hot laps up front(air temps low 90's, track temps to match a clear sunny day that hot) and actually put me in the grass when i lost my front. Might have been able to save it, but chose 4 off in control vs fighting the car and likely dropping 2 out and hoping i stay pointed the right direction.

You can actually see me lose my front grip in this vid, good turn in and suddenly car pushed wide badly putting me in a bad spot.
RX 7 off - YouTube

At auto-x i noticed it pretty badly again, had 5-6 seconds left in the car if i had more front grip.

Do i need more tire or better tire or?

Any input is welcome.

Jason
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Old 07-17-13, 09:33 AM
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In that video it just looks like you turned in to early...

your tire stagger isn't helping... what is your suspension like? stock?

EDIT: just saw your sig. Tein springs are garbage you're probably hitting your bump stops in corners...
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Old 07-17-13, 10:29 AM
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It was a combo, got distracted by the corner guy and seeing that red car spin, turned ina little early(its a fast decreasing radius) and it literally pushed itself wide. I remember having plenty of time to think about it....lol

Jason
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Old 07-17-13, 11:42 AM
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Stock-ish suspension with staggered tires will understeer a bit. Your suspension settings seem reasonable, as long as toe in's are set right as well.

Going into a corner too hot and trying to turn can also feel like understeer - I haven't done that since last weekend's autocross. Slow in, fast out as they say. Understeer is safer than snapping the tail out tho - as you voted by doing.

I'm not familiar with the springs you are running, but it sounds worth considering an upgrade.
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Old 07-18-13, 07:18 AM
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What tyre pressures are you running? Do you drop the pressure after the tyres heat up? After a dozen or so quick laps the pressure would have come up a lot, maybe too much?
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Old 07-18-13, 08:55 AM
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30f and 27r when hot as best I could manage. I set the pressures after my previous runs when the tires were still pretty hot. Ended up dropping about 7-8lbs of air out of them through the day.

Jason
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Old 07-19-13, 07:24 PM
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Originally Posted by eage8 View Post
In that video it just looks like you turned in to early...
Turned in too early, and still a long ways from your chosen apex.

Recipe for mowing the grass.
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Old 07-19-13, 08:02 PM
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Yeah, it happens. Been years since I've been on a track. And watching that red car go round really distracted me. I knew i was off my line before opting to cut the grass, figured it was the safest option considering where i was on the track. Might have been able to bring it back on, but wouldnt have been very smooth and if i dropped two might have been pretty dramatic.

Still understeered horribly at auto-x. How much better is the 93 rear bar vs the 94/5 bar?

Jason
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Old 07-19-13, 09:11 PM
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Yes, you know what you need to do.

Stock FD understeers a bit and then you added staggered wheels and tires making it worse.

I hated the understeer when I raced my FD in stock class, but now it is banished with even front/rear spring rates and maintaining a square wheel/tire fitment with more width.
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Old 08-19-13, 03:06 AM
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stock shocks are the pits. staggered wheels will almost always understeer. better tires are always welcomed. trailing links help the rear track a little better. the FD is a funny thing, if something is off, the whole car throws a fit.
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Old 09-08-13, 10:22 PM
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Would adjustable rear sway bar help This? What is a good racing shock
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Old 09-08-13, 11:44 PM
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The Ohlins R&T series (with their DFV) are a great road and track shock, and will get rid of the understeer, as they have equal spring rates of 11k front and rear. You might even have to deal with oversteer like me with my new set!
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Old 10-18-13, 03:17 PM
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try a little testing on a constant radius skid pad, soften the end thats not working
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