Slow Motion Tire Shake

Two videos taken in slow motion with my new camera. So using the video, how the hell do I get rid of the shake. Over the last two years we have changed a bunch of things but nothing gets rid of it. That second video it went 4.436 @172mph with the driver pedaling it twice. Its went 4.23 @165 so we have made the top end better.

http://www.youtube.com/watch?v=z2oH34dHYUI
http://www.youtube.com/watch?v=vVDrLD_Gmr0

1/8th mile racing, 402 sbc with 14-71, powerglide, MSD 10

 

When are you going to post the rest of those clips ?

Bob Frigon

 

do you have a data recorder? I look for wheel speed at half a second and one second. It looks like you are overpowering the race track when it spins that early in a run. Try raising your tire pressure a quarter of a pound. Tire pressure has a lot to do with tire speed. If you had a clutch I might suggest a little less static and less tire pressure. Dave Germain

 

Man Bob, you got to do everything fast! Your slo-mo video is now on You Tube too.
More slo-mo to come tomorrow night. Be sure to change the setting to HD for best viewing.


http://www.youtube.com/watch?v=cyJSvy2_1vE

 

The last video posted, you can see the tire 'dead hook' (common with initial hit of a converter car) and then the wheel speed picks up. In the first two videos, there is no 'dead hook' and in the second one you can see it unload the car before it goes into tire shake. How much tire pressure are you running? Have you played with the just the tire pressure in the past, everything else being equal? What RPM do you leave at? Are you leaving off of the converter stall? I am also curious if you have a data recorder, it looks like something is happening with the fuel system at the launch as there is visible 'puffs' out of the exhaust. Maybe the ports are coming in as you are trying to take off making the engine lazy at that exact moment?

 

Did you have more air pressure on the last run? The first two runs you can see the car wad the tire and drop the car onto the wheelie bar before the chassis has had a chance to get loaded, it seems like adding more tire pressure to keep it from bouncing off the bar so hard and quick (the first two runs) would be a big help.

 

If you look at the first 2 videos, the car goes into shake when the wheelie bar hits the ground. The bar is unloading the suspension. The 3rd video the bar never hit the ground. Raise the bar.

 

In the first two videos, the tire never gets to full squat height. Either the bar is hitting the ground too early and not letting the tire squat, or the tire itself is trying to keep itself from doing that.
I have seen similar dragsters that have too little tire pressure squat the tires too hard, then spin and shake when the tire rebounds after squatting too far, but yours looks like it is the other way. Like the bar is way too low, or the tire pressure is a bit too high.
The Hemi car has it right. On a draster, you have to let the bar fly the nose a little. If the bar hits the ground that hard and the front end is not hiked, then you are hydraulicing the rear tires off the ground, and unloading the chassis. The the car just plum can't work. Also, the flexibility and length of the wheelie bar on the hemi car is what I would like to see on a car more like this. The longer the bar, the more room for minute adjustments, and the "softer" the hit.

 

yes raise the bar

 

What is your wheelspeed at .5 and 1.0? With tire psi. do you have in the car?

Brandon Booher
NHRA TAD #35

 

Am I missing something? The first two videos and the third are not the same car, correct? So comparing to the third is like me compared to Frank Manzo.

 

I am not gonna comment on the tire shake issue directly....but I had all kinds of shake problems and all of the clutch guys say "down on power" and "no wheel speed" - but it seemed like more power with a converter car just made more violent tire shake....so my suggestion is to talk with Mick Snyder (Snyder Motorsports, DeMotte, IN) about converter car shake issues....he has the most experience in this area with Lencodrive cars....he sure helped us in the shake dept....

 

Tireshake/spin that early is from too much power and/or too low tire psi.. I too would be interested in your w.s. @ 0.5 and 1.0 secs.? Also rear gear, tranny gear, launch RPM, timing etc. all factor into this; it surely isn't as simple as "raise the wheelie bar". I'd say since a person has posted on here who's the quickest dragster with a converter in alcohol dragster history, I'd message him, just my .02.

Steve

 

Not Wheelie Bar

This video is from this past weekend. Wheelie bar never touches.

http://www.youtube.com/watch?v=Y9dn3NGuOxk

We have went from 4.25 psi to 9 psi. Low pressure will cause as big a wheelie as the wheelie bar will along. About 2 ft high is as far as we have gone and it then shook while in the air. On the high psi side, little wheelie and will go up in smoke if in the 8 - 9 range. The 3 videos are all in the 7 - 7.5 psi range.
Since you get so few hits in a dragster like this, usually we make a couple changes. I know thats bad but to try one at a time would take forever. Most of the low psi passes where made with a higher launch rpm. Around 4k then, 3k now. Also have pulled as much as 20 degree timing from it at the hit, nothing now till .2 out when the convertor grabs it. Yes I can get rid of the shake then and probably could make a good Jegs Super Quick car out of it but it sucks for heads up.
As far as wheel speed, its tough to say as we are in the shake zone so early and the driver pedals it.
On the 2nd Night Under Fire run, .5 sec it was 3646, pedaled at .62 when it was at 4104. On the video above .5 is 2825 and pedaled at .74 when it was 3964.

 

Ron , thanks for posting the clip of my car (The third video)

Give me a call 315-436-6653

 

You are hitting that car way too hard. I would recomend lower launch rpm or a stator convertor change. What is the .25 sec wheel speed?

 

Now it looks like you don't have enough wheel speed. The tire doesn't even spin, it just goes into shake. I'm no convertor guy, but what does the convertor stall at and what RPM do you stage at?

 

Correct. But a wheelie bar that's too low on any car will unload the tire.

 

What 1st gear and rear gear do you run? What does the car weigh?