As the others said it could be a variety of items, but I would try tightening the extension. After shock fully compresses, if the extension is too loose it will try to return to ride height too fast and not keep the tire planted. Tightening the extension will slow that process down and could keep the tire planted longer.

quote:

Originally posted by Bob Payton:
Light blue line is 02. Tires are are 7 5psi and brand new. To me it looks like a shock change just not sure which way to go.

I run 10psi on the Shevelle

quote:

Originally posted by N2Ofrog:
As the others said it could be a variety of items, but I would try tightening the extension. After shock fully compresses, if the extension is too loose it will try to return to ride height too fast and not keep the tire planted. Tightening the extension will slow that process down and could keep the tire planted longer.

I have the extension pretty tight currently and compression pretty loose.

Im going to play with shocks and Tire pressure and see what happens

Sometimes it can also be the compression is too loose and causing the tire to unload.

ok here are my w a g's
compression needs set 1/2 way
extension need 3/4 from soft
air is close
instant center appears to low and possibly to far out if 4 link
loosen front end

quote:

Originally posted by rusty:
ok here are my w a g's
compression needs set 1/2 way
extension need 3/4 from soft
air is close
instant center appears to low and possibly to far out if 4 link
loosen front end

I agree with Rusty on this one but would add with those changes the suspension would work the tire harder and may need more air then. As it is right now you are not getting much suspension front or back. The car drops in the rear but that is almost all tire squat.

I would also take shocks off and move rear end all way up and down and see if there is any binding or anything not right.

On a door car I like seeing the shocks 2-5 from loose on ext and 3/4 tight on comp depending on settings to make it separate and hold it there. Really fast door cars need stiffer settings. Tire psi can be used to remove or add bite just like shocks and the 4-link. More air more bite, less air less bite. Bobs car has a ton of hit in it and needs more air. I’m running 3190 bubbas on mine with way more air than is being recommended.

Thanks for the info guys. When I got the car the shocks were all full loose. I will try going more on compression and less on extension & some more air pressure. If it ever stops raining maybe we can get out and test.

How old are the shocks and are they working correctly is honestly one of the first questions that need addressed.. Also mentioned above, does the rear end move up and down freely without bind or bad heim joint? I had a set of shocks that had a burr on one of them, causing them to now move freely together on the rear of my dragster. Sent them back to Strange over winter and got them back and the back of my dragster has way more movement and doesn't hop off the starting line any more. It actually lets the entire setup work together now.

Also having the same issue. At galot there was no issue, but came home and have that same hop. I went down in air psi and it got smaller. Adjustable struts up front all the way loose. Extension set on 6 (1/2) and comp set on 2 of 12, strange doubles. Its still pretty consistent, but would love to get it to go away.

Went out this weekend had the tires at 9psi which seemed help. The range of the rear shocks are 18 clicks. I set the comp at 9 from soft and rebound at 4 from soft. Car still spun .25 off the line at its normal spot but had another spin after it. You can see on the video the front end bobbling up and down. Im looking into front struts for this thing. Seems like its not weight transferring like it should.

https://drive.google.com/file/...2hB/view?usp=sharing

Set the rebound 2 from loose and the compression 2 from tight.

It'll have one hump/spike in the driveshaft at the hit instead of two or three down track. Then you fine tune those settings to zerox driveshaft graphs in comparison to each other over several laps. If it'll zerox driveshaft graphs, the capacity to zerox timeslips exists. It's either that or put some anti-squat in the bars.

This message has been edited. Last edited by: Mike Rietow,

Air psi helped so your going in the right direction. Still to much wrinkle in the tires for me

quote:

Originally posted by C Hodge:
Air psi helped so your going in the right direction. Still to much wrinkle in the tires for me

Better on the time slip (more consistent 60 ft) worse driveshaft graph with two humps and visually worse bouncing. The reason the 60 ft is more consistent (better) is because the car spends more time trying to get up on the tire before the 60 ft. You can see in the groove, the tire track get narrow 2-3 ft past the starting line and then again 6-7 feet out from there. That's the two humps in the driveshaft graph. I'd raise the ride height in the back a hair to raise the IC for anti squat and run the shocks like I suggested. Raising the ride height will give a good indicator on if the car needs anti-squat without taking anything apart to raise the IC.

I'm not sold on the tire pressure adjustment being the reason for more consistent 60ft's. Added tire pressure is traction (bite). The tire looks more wound now (more bite), that adds up with more pressure. Although the OP needs less bite (traction) at the hit, not more. The OP needs a lil wheel speed off the trans brake to speed up the front end, and get the car up on the tire. He went the right way on the shock adjustments, this is why it was better (more consistent 60ft times) I believe. Adding pressure definitely went against the grain of fundamentals pertinent to the original video/driveshaft graph.

This message has been edited. Last edited by: Mike Rietow,

I went through last night and measured the 4-link. Bottom bar is 2.8 deg down.

Raise the top bar on the housing end a hole or two. needs more leverage

Bob, Front end has no lift as you already know.After messing with a nose heavy doorslamer I feel your pain although I got lucky in the front strut area and worked through it. Unill you get transfer out of the front do not be afraid to add weight to the rear. Even a 50 pound bag of any thing for a run. 30 lbs in the back of my 3200 lb car made it right. 60 lbs would carry the wheels forever. Loose 6400 converter 4.30 gear 29.5 tire leaving at 3200 perfect. 3600 almost too much.

Still working on this. I believe some/most of the problem is in the front struts like a few others suggested. I figured out how to adjust these last weekend. These struts are old and you need to remove the spring and collapse the strut to adjust it. I believe these were topping out at launch. i lowered the front end some to allow for some more travel before they top out. I was not able to get out again because of rain. Hopefully this weekend.

Update on this:

Spent some time going thru the car and found out the corner weights were all funky. I fixed all that and went to the final the next weekend. The hook spin was still there but consistent. In the final the car bogged real bad on the shift. After some investigating and talking to a bunch of people figured out it was the sprag in the converter. Purchased a new converter and now the hump is gone. Dont know really how the converter could affect that but it is totally gone now.