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Discussion Starter #1
I know this should be posted in tech section, but i need to hear the racers advice.

3150# sonoma pick up, 4 link, 33X16 hoosiers on 16 wide rim, afco da coil overs in rear, QA1 coil over converstion on front w/350# springs, rear air pressure has been set from 7.0 to 8.5 in 1/4# steps, 60% nose weight, nitrous set up with 1st kit on at the hit and 2nd on at 4 tenths out.

Truck leaves decent, rides the bars for awhile, sets down and goes real good til about 400ft, then all hell breaks loose and tire shake takes over. We played with the air pressure, front and rear shocks, added 90# to the truck.

Our last settings seemed to be the best... front shocks set real loose, rebound on rear shocks set all the way tight, 90# against tailgate, air pressure @ 8#. It didn't shake them as hard, but more less calmed it down to a bounce/shake.

I hate the thoughts of adding weight cuz we all know that end result, slower et. Anyone have any suggestions or thoughts on what needs to be done to get this thing down the track without the tire hop/shake???? I know i'm prolly fogetting vital info, so any questions, please ask.

 

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Has this been a ongoing issue or did this problem just come about:confused:
because I know the truck has been together for awhile.
Retrace your steps as far as what you have changed before the tire shake started happening and up untill It started and start putting stuff back like It was one change at a time to try and pinpoint the problem.

But like said above It could be something as simple as old worn out tires causing the problem;)
 

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I know this should be posted in tech section, but i need to hear the racers advice.

3150# sonoma pick up, 4 link, 33X16 hoosiers on 16 wide rim, afco da coil overs in rear, QA1 coil over converstion on front w/350# springs, rear air pressure has been set from 7.0 to 8.5 in 1/4# steps, 60% nose weight, nitrous set up with 1st kit on at the hit and 2nd on at 4 tenths out.

Truck leaves decent, rides the bars for awhile, sets down and goes real good til about 400ft, then all hell breaks loose and tire shake takes over. We played with the air pressure, front and rear shocks, added 90# to the truck.

Our last settings seemed to be the best... front shocks set real loose, rebound on rear shocks set all the way tight, 90# against tailgate, air pressure @ 8#. It didn't shake them as hard, but more less calmed it down to a bounce/shake.

I hate the thoughts of adding weight cuz we all know that end result, slower et. Anyone have any suggestions or thoughts on what needs to be done to get this thing down the track without the tire hop/shake???? I know i'm prolly fogetting vital info, so any questions, please ask.

You state that the rear shocks rebound is all the way tight or no rebound. I am somewhat surprised it doesn't shack at the hit. You need rebound or have the shocks extend at the hit to plant the tires. Then go tighter on compression to help keep them planted. You may want to recheck your pinion angle. Should be set at -1 to -1.8 deg.
 

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Discussion Starter #7
It started when the new motor was installed and progressively has gotten worse. Its had 2 new sets of tires put on it. It has a small jet in the first kit and a not so much bigger jet in the second kit. I tried stepping both kits up to try and keep it on the bars longer, but it shook so bad it deployed the chute on that run. I can pull timing out to take power away and it'll go down threw there with minimal shake, but end results are slower et.

I kept adding timing threw out the night and it kept picking up. But listen close to the last pass (the one w/ the rear facing camera), I had to peddel it three times because it was shaking them so bad.
http://youtu.be/nTdhvK3GzBk

This video is with the bigger jets in it. 1st pass the chute came out...2nd pass is with a bunch of timing out
http://youtu.be/aRz18S9oMcg
 

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I used to run that tire and weight with a blown powerglide and it was shaky before the shift a lot of the time on shitty tracks. Shortshifting helped a lot. I found that it usually was shaking even on the hit but it never really set in until downtrack a ways.
I assume you don't have a computer to check the wheelspeed so it's hard to see when it's starting to piss the tire off.
One of the biggest lessons for shake on a converter deal is it WILL go away if you soften the power up. Don't listen to anybody saying it will get better if you throw more at it...
It might be happier if you get aggressive earlier in the run and then back a little timing out at the shaky spot on the track.
It took me a lot of years to figure out that almost any track has a usable starting line but very few will allow you to throwdown a lot of power 400ft out. If you run at Noble you know what I mean.
 

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Tire shake is generally the result of too little or too much wheelspeed. Normally it's a matter of not enough power and results in coming off the tire and into shake. If it spins the tires then shakes, it's too much wheelspeed as a result of too much power or the chassis isn't getting it to the ground. It took me a while to understand it often needs more power to prevent shake especially early in the run.

Do you know the driveshaft speed at .25 & .5 seconds into the run? 8# of tire pressure seems high...we run 34.5's and run anywhere from 5# to 5¾#. To get more wheelspeed I lower the pressure, to get more grip, raise it. 60% over the nose is a lot. We run a lot of ballast over the front to get it to 54% which seems about optimum and I run the front struts at almost full tight. How far out is your instant center? How much height difference is there between the front & rear of your lower 4 link bar? Pinion angle? If there's a bad spot in the track I've pulled a couple degrees of timing out right before that spot and put it back in uring a gear retard curve.
 

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I tried to help Outonyou this weekend and didnt have much luck every shock setting front/rear is as tight as it will go. And we added the 90lbs. to the rear. I havent had a chance to map the 4 link out but the, 4link spread on the back is 8in, "which is as far as it will go with the brackets" and the front spread it like 5in. Bottom bar is running downhill about 1-2 degrees.
 

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Im actually wanting to try a stiffer spring in the rear, i think it might have to much stored energy and it starting to lift the rear on the truck and unload the tires, the last pass it shook hard then blew them off. However i have recently found out that several local guys are experiencing the same problems at this track in the same spot. Either way we gotta find a way to make it down the track.
 

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Im actually wanting to try a stiffer spring in the rear, i think it might have to much stored energy and it starting to lift the rear on the truck and unload the tires, the last pass it shook hard then blew them off. However i have recently found out that several local guys are experiencing the same problems at this track in the same spot. Either way we gotta find a way to make it down the track.
coupled with no rebound?...I guess
 

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How much power does this thing have?? Does it really need that much tire? How heavy is it? If it don't have enough power to stand that tire up, somewhere within 60ft, and keep it up, you'll always have some shake or vibration issues.. Quick and easy band aid, would be... Put in some "Liners and Tubes".. Or.... Put some 33X10.5 W's on it.. It'll probably go faster... More consistantly..
 

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Discussion Starter #18
Not sure on the HP, never dyno'd it. Fulton 632 with 3 guns. I've had smaller motors that I know make less hp in the truck, and never had this issue. I use to have 15 wide wheel on it and if my memory is correct, it didn't shake as bad if any. But with this new motor I figured a 16 wide would work better to aid in getting more contact path. Could going back to 15 help???
 

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Not sure on the HP, never dyno'd it. Fulton 632 with 3 guns. I've had smaller motors that I know make less hp in the truck, and never had this issue. I use to have 15 wide wheel on it and if my memory is correct, it didn't shake as bad if any. But with this new motor I figured a 16 wide would work better to aid in getting more contact path. Could going back to 15 help???
Probably be worse... That creates more flexibility in the sidewall..
What's the best 60ft it's had?
Never heard any short times ever mentioned...
 
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