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Old 01-19-2010, 10:55 PM   #1
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Default Stepping Out in Traction

I've been trying to conquer a setup issue recently without much luck, so I figured I'd turn to the crowd for some advice.

I'm running a touring car (13.5) on carpet with rubber tires. Generally, the grip is pretty good, but occasionally a few areas will develop and odd problem. Typically, these are the places where a lot of weight is transferred, like the end of a sweeper, or the first part of a sweeping turn. The car wants to get unstable in these areas, almost as if it's loose, where the rear end will kick out with surprising ease. But when you really watch closely, it seems more like the car is suddenly breaking traction after trying really hard to grip. And in fact, these very same areas can sometimes be problematic for traction rolling.

So what is that? And what kind of setup things can conquer it? Softening the rear of the car kinda works, but it feels more like you're solving the symptom rather than the problem. Stiffening up the front of the car seems to help quite a bit, as does using less camber.

To further complicate things, when this problem manifests itself, it seems to be the same time the tires want to get really dirty and "gunk" up during a run. Typically, traction will come up and feel great (nice dark groove) on a race day, but the next day during practice is when things start to feel odd. The grip will feel pretty good most places, and will be fairly dark, but the cars start to kick out kind of unpredictably. For reference, I've included a picture of our current layout. The issue is most noticeable at the end of the sweeper, and the first right hand turn after the first pole.
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Old 01-20-2010, 12:00 AM   #2
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Pave it over with asphalt and your problem will go away
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Old 01-20-2010, 12:13 AM   #3
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Originally Posted by linger View Post
Pave it over with asphalt and your problem will go away
I'd love to do some indoor asphalt, but I imagine it wouldn't jibe with the landlord.

How many runs can you get out of your tires on a track like West coast? I'd say were good for 20+ on the rug.

Alas, carpet is what I know and love, so I'd really like to solve this riddle so I can practice with more confidence.
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Old 01-20-2010, 12:19 AM   #4
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it sounds like a the carpet is rutted because thats where eveyone drives this could make it slick then when you reach the outside of the ru you get tracton and your car flips.

You could try slowing down. I find you shouldn't get back into the throttle untill you are ready to exit the turn with full throttle. Try to be a smooth as possible through out the turn fluctuations in throttle will throw your car off track.
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Old 01-20-2010, 12:20 AM   #5
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you lost grip at double S corners ? ( do you mean you lost cornering grip when the car transfer weight from left to right at the S corner ? )

In my case: rear suspension is too soft.... need harder springs at rear.
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Old 01-20-2010, 01:32 AM   #6
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Sounds like you're just at the edge of the groove. In the groove the car tries to grip-roll, at the edge of the groove the tires spin and it goes into a lazy side-step. That a fair summary?

Only thing you can really do is stay in the groove and set your car up for the high-traction areas, or keep running like you are and expand the groove out some. If you're not the only one having that kind of issue, the groove will widen out on it's own over the next few race days. If you're the only one, it'll take longer.
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Old 01-20-2010, 02:16 AM   #7
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Does the track use both Paragon and Jack?
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Old 01-20-2010, 03:39 AM   #8
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Perhaps try an extra 0.5deg of rear toe?
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Old 01-20-2010, 07:21 AM   #9
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Originally Posted by InspGadgt View Post
Does the track use both Paragon and Jack?
Jack. Well, sticky fingers now.

More rear toe doesn't seem to help unfortunately. Neither does anti-dive, which as been effective in the past with similar trouble.

Slowing down is the only thing that works, but it feels unnaturally slow. The car almost looks like it's skipping sideways, where the tires grab/release/grab/release/spin out. The carpet is 2 months old.

I appreciate all the feedback. The issue seems to affect everybody with all cars, though some more than others. We typically use Jaco blue, though I've experimented with Jaco green, Solaris medium & hard, and Sorex 28, and the issue persists. Maybe I'll try foams next.
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Old 01-20-2010, 10:25 AM   #10
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Quote:
The car almost looks like it's skipping sideways, where the tires grab/release/grab/release/spin out.
Any way you can get a little more damping in the rear? That has solved hopping problems for me in smaller scales, if that's what it is...

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Old 01-20-2010, 11:50 AM   #11
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everyone had the same problem (the car turns in and then suddenly the back end at times will slide out in a harsh manor, in slow speed or highly loaded corners) at the January Jam last weekend at RC Madness in CT in rubber 17.5... The solution everyone came up with was just drive it including 1000x race winner jeff cuffs, haha. The problem IMO is a few things...

1)Rubber tires on small tight tracks dont allow the car to work like it should and you will run into these issues when bite comes up

2)You are compormising set up always. And to get the car to steer enough for most of the track will make it probably overload right before the apex of long high load corners with generally decreasing radius where the load increases, you have less throttle to plant the rear end and eventually the rear tires break free.

So basically you either have to really compermise your set up and then drive around it, or learn to drive the car and anticipate it happening and figure out how to keep some load on the rear tires (trailing throttle into the corner) and steer accordingly. Easier said than done, but probably your best bet.
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Old 01-20-2010, 12:06 PM   #12
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Quote:
Originally Posted by stormperson View Post
everyone had the same problem (the car turns in and then suddenly the back end at times will slide out in a harsh manor, in slow speed or highly loaded corners) at the January Jam last weekend at RC Madness in CT in rubber 17.5... The solution everyone came up with was just drive it including 1000x race winner jeff cuffs, haha. The problem IMO is a few things...

1)Rubber tires on small tight tracks dont allow the car to work like it should and you will run into these issues when bite comes up

2)You are compormising set up always. And to get the car to steer enough for most of the track will make it probably overload right before the apex of long high load corners with generally decreasing radius where the load increases, you have less throttle to plant the rear end and eventually the rear tires break free.

So basically you either have to really compermise your set up and then drive around it, or learn to drive the car and anticipate it happening and figure out how to keep some load on the rear tires (trailing throttle into the corner) and steer accordingly. Easier said than done, but probably your best bet.
Interesting to hear we're not alone, kind of comforting actually. We've tried so many things to try and fix it with setup, and nothing really seems to work. The one thing that does fix it, however, is spraying the track with Paragon traction action. It brings up the grip quite well, and really makes things predictable. But that presents problems of its own.
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Old 01-20-2010, 01:13 PM   #13
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Have you experimented with the height of the lower arms to adjust roll center?
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Old 01-20-2010, 01:19 PM   #14
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Glue your front sidewalls and add back some of the turn in you lost.

I didn't have any issues at the Jam with my TC, my RCGT was doing exactly that, but rules prohibt me from gluing those tires. Even though I was a bmain driver, haynes drove my car to an 11.1 which meant it worked right if driven properly, lol.
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Old 01-20-2010, 01:31 PM   #15
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Quote:
Originally Posted by pejota View Post
Have you experimented with the height of the lower arms to adjust roll center?
Not much in the front, but quite a bit in the rear. I usually end up with the blocks low to keep the car drivable.

Gluing sidewalls is an interesting idea. I'll definitely give that a try and see how it feels.
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