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 Post subject: Launch
 Post Posted: Sun Sep 18, 2011 9:36 am 
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Joined: Thu Feb 12, 2009 7:52 pm
Posts: 348
Hello All,

Please take a look at my launch video and let me know what you think, I have having inconsistancy issues where the car seems to be breaking traction when the front wheels are up in the air. The first and last video, car spun knocking .02 out of the 60 foot. 2nd video it hooked pretty good. I have gone up on tire pressure and put a little more preload in the right rear which seemed to help. I plan on putting the car on scales this week.

Thanks in advance for your opinion.

http://www.flickr.com/photos/simpkinsfamily/6159047674/

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 Post subject: Re: Launch
 Post Posted: Sun Sep 18, 2011 3:05 pm 
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Joined: Tue Feb 05, 2008 6:45 pm
Posts: 248
what rear suspension do you have?

Don

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 Post subject: Re: Launch
 Post Posted: Sun Sep 18, 2011 3:22 pm 
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Leafsprings, with caltracs. Have the rancho 9 way shocks.

Thanks

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 Post subject: Re: Launch
 Post Posted: Tue Sep 27, 2011 11:16 am 
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Joined: Sat Nov 03, 2007 4:44 pm
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Location: Clawson, Mi.
4/10,

To me, it looks like a couple of things, but I am still learning also...my first thought is, that your I/C point is very far back in the chassis, like under your butt, or even farther back then that! 2nd thing I see is, once the car stops, it seems to do a little chassis bounce! and I am not sure if this is the tires or shocks, but I want to say both. Do you have any weight info on your Nova?

I see a few more things and I will watch the video's again and verify this, but it looks like the driver & pass side rear is seperating at the tire/body, which is a good thing, and on the rear. Hang on and I will be back.

I am assuming you are foot braking this right? as I see this chassis bouncing front to back and then it settles down... if you went up in tire psi, that may be your issue, try going lower and let the tire absorb some of the shock of the torque hitting them. If they are slipping, take away psi, and look at the pattern on the tires too, as this is one area of learning that can help you tune your car. Good looking Nova to btw \:D/

John

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 Post subject: Re: Launch
 Post Posted: Tue Sep 27, 2011 1:06 pm 
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Hey Elky,

Thanks for your input,

On that first video, according to the logger, It spins the tires one the front wheels are off the ground, front end sets down and it grabs and picks the front wheels up again.

I do have the weights for it, I think something is off. Here are the weights from the last time I had it on the scales

left front 857 right front 768
left rear 827 right rear 750

Car worked really good with these weights. I should have it on the scales tonight, last time this happen it got real light in the right rear.

Yes this is a footbrake car. Its a caltrac/leafspring car, so there is not much I can do with the instant center,

Based on the video and the logger, what I think has happen is there is not enough preload in the caltracs on the right side and too much in the left side. To me it looks like it is rolled over on the right rear a little to much. The car used to leave level. I plan on weighing the car first, Then take all the preload out of the caltracs and get it all leveled out. Then put the preload back in it.

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 Post subject: Re: Launch
 Post Posted: Tue Oct 25, 2011 12:42 am 
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Joined: Thu Apr 28, 2011 12:25 am
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Location: COLORADO We got no air!!!!
I believe the Cal-Tracs should be just about parallel to the ground when car is at rest. I had to get front brackets with three holes instead of just two. They sent them to me at no cost! Here is my letter to Calvert with some pics. using the two hole brackets. I had WAAAAY too much rear-end lift! http://www.calvertracing.com/gallery/page16pic14.htm

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 Post subject: Re: Launch
 Post Posted: Tue Oct 25, 2011 5:25 pm 
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Thanks for the advice, I will keep that in mind.

I think my problem is in the front end. It is rising too quick unloading the chassis. When I go to a track where the car makes alot of power, I have no issues, but when I race at my normal track, car doesn't make as much power and it is more sensitive to the front end travel rate. Last time out I tightened up the front end, and it seem to make an improvement. I am going to continue to tighten them up till it stays hooked.

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 Post subject: Re: Launch
 Post Posted: Wed Oct 26, 2011 11:48 am 
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Joined: Wed Dec 06, 2006 9:24 pm
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Location: Elizabethtown, KY
This is a friends of mine that has stock suspension with caltracks, TRZ anti-roll bar. It has taken a while to get this to work like this. he runs a 525 BBC w/nitrous. It has taken two years and a engine and tranny rebuild. Normally it blows the tires off on launch or a little further down track. Prior to this run they found that the the hole was not big enough fo the down arm on the anti roll bar and it was binding.

http://www.youtube.com/watch?v=9KiGbPWzxAk&sns=fb

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 Post subject: Re: Launch
 Post Posted: Wed Oct 26, 2011 6:38 pm 
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Location: COLORADO We got no air!!!!
After watching the video(didn't do so before first post), I think you should have more travel on the front end if possible. Try removing the A-arm bumpers if you have not done so already. This along with slowing the rise may be all you need. Your rear-end seems to be good, no lift or squat.

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 Post subject: Re: Launch
 Post Posted: Sat Oct 29, 2011 8:44 am 
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Joined: Sat Nov 03, 2007 4:44 pm
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Location: Clawson, Mi.
One thing I have learned about my hotrod is that, SHOCKS AND SPRINGS are very important when trying to setup any hotrod. The more you can afford on shocks, the better you are going to be able to control the chassis provided it is a strong stiff door car chassis. I have found out that, double adjustable shocks are the BEST tuning tool for any chassis. You can dial in or dial out power to the tires on any track surface and keep up with the pack as well.

Do you have an Anti Roll Bar in the back?

Have you been out agin since this thread started?

What kind of power are we talking about here also? Do you know what your pinion angle is? Do you know where your I/C point is on your car?, or where it is vertically?, high, low????

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 Post subject: Re: Launch
 Post Posted: Sat Oct 29, 2011 8:53 am 
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Location: Clawson, Mi.
410,

After watching your video's more, have you tried giving the front suspension more travel??? The car initially hooks, and then the front end is coming down rapidly and then you spin the right rear tire!!!!
Try letting the front end travel a bunch more and tighted up your comp. on the front shocks if you can and tighten up the extension on your rear shocks if you can. My car did this same thing for a long time. I had coil springs and control arms also so we have different suspension systems but they can both be setup to work per the torque and hp available.

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