Why does the suspension look like i drove over a rock?

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Cudafever

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Ok so first, we got rained on 3 different times and all thow we dragged the track after each rain shower, the track was just plain cold.
The butt odometer said the tire hopped and slipped off the line. but my gopro shows no tire slip at all. But the suspension bumps like it just drove over a rock.
This is a 2 minute video that shows the launch once at regular speed. Then super so mo, the 2nt time.
It make it super blurry and the sun reflecting off the inside of the rim dont help the quality any better. Take a look and tell me you thing is happening here.
Thanks
 
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Looks to me like its squatting during the shift. That's all I see? Maybe I'm missing something.
 
The hop is during the first revolution of the tire.
I shift into 2nt just past the tree.
 
for some reason the video starts late. You have to back it up to see the full speed launch from the start. At least that what's happening to me.
 
Try running more tire pressure adding a 1/4 lb. at a time until your 60 ft. starts to slow then go back to the best 60 ft pressure. Just a thought.
 
Maybe the shocks are topping out or hitting the axle back support , any witness marks? Looks close in the video.
 
TomMoparMan said:
Try running more tire pressure adding a 1/4 lb. at a time until your 60 ft. starts to slow then go back to the best 60 ft pressure. Just a thought.
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That's a good thought and i may try just that.........however, it 28x10.5x15 MT Slick. I have 15 pound in them already

Mr. Sinister said:
Maybe the shocks are topping out or hitting the axle back support , any witness marks? Looks close in the video.
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Topping out the shock, no. You can watch the shock and suspension expanded way past the hop. HOW EVER

You made me go out and look on the shock versus back support. I have two fingers (just under 2") of clearance. My fresh painted housing/support has no marks on it.
That was a Great thought, considering the rear diff, rolls back and caused the shock to get closer. That I never considered!!!:thumbsup::thumbsup:
 
Could be as simple as shock adjustment. Or even the front portion of the springs flexing a little causing the slight wheel hop. Could try clamping the front segments and see if it affects anything.
 
These are Brand new 3800 pound SS Springs that have maybe 20 passes on. and the video don't show the front segment bowing like my old SS Spring were doing, With clamps on the front segment.
 
I went from 28X10.5 MT to 28.5X10.5 Pheonix they have much stiffer sidewalls. The bounce / spin at hit is the tire being hit too hard and crushing the sidewall. Leafsprung Mopars have a very short instant center (spring eye) which causes this. Stiffer sidewall slicks, tubes if you're not running them, more air, GOOD double adjustable shocks, taller gears, wider rims, will help. Unfortunately if the track is crap its gonna spin.
You might also try less RPM on the start line. It looks like you've killed the chassis reaction coming up too high on the converter.
 
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Screws is right. You're beating the hell out of the tire. Another reason to not use SS springs. You need a DA shock and set the bump (compression) much stiffer to not let the tire bounce back. You can also slow the rebound (extension) so it isn't quite hitting the tire so hard.
 
Cudafever said:
These are Brand new 3800 pound SS Springs that have maybe 20 passes on. and the video don't show the front segment bowing like my old SS Spring were doing, With clamps on the front segment.
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That's a really heavy spring in an A body.

That said, I don't see how anyone can tell a thing from your video. It's just too slow.
 
I never try to send any one down the same path as me, for the chance of learning something new that i had not thought of. MR Sinister did that for sure.

skrews said:
I went from 28X10.5 MT to 28.5X10.5 Pheonix they have much stiffer sidewalls. The bounce / spin at hit is the tire being hit too hard and crushing the sidewall. Leafsprung Mopars have a very short instant center (spring eye) which causes this. Stiffer sidewall slicks, tubes if you're not running them, more air, GOOD double adjustable shocks, taller gears, wider rims, will help. Unfortunately if the track is crap its gonna spin.
You might also try less RPM on the start line. It looks like you've killed the chassis reaction coming up too high on the converter.
Click to expand...

I'm running drag tubes already and the other problem is my car is heavy! 3860 with me in it.
I don't have the double adj shock. they were to price for my budget. I did buy some Competition Engineering 3 way shock that i have not Yet installed.
As far as coming to high on the converter, you are right. Was trying to get a better 60 foot time.

The other thing, i have notist with these videos, is that the left tire is getting hit/wrinkle sidewall more than the right rear slick.

yellow rose said:
Screws is right. You're beating the hell out of the tire. Another reason to not use SS springs. You need a DA shock and set the bump (compression) much stiffer to not let the tire bounce back. You can also slow the rebound (extension) so it isn't quite hitting the tire so hard.
Click to expand...

This is for you both......well any and every one.

Do you think i should set the new shock up initially equally? such as in a 50/50 setting(compression/Rebound). I have 3 settings 30/70 40/60 and 50/50.
Would you stagger the setting from left and right and if so what would you recommend for my first initial setting.

Also i bought some 3 way shock for the front end as well. My choice is 90/10 80/20 and 60/40 I basically have worn out front shock up front right now.

Thanks for all you thoughts so far, Keep then coming.....
 
RustyRatRod said:
That's a really heavy spring in an A body.

That said, I don't see how anyone can tell a thing from your video. It's just too slow.
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Agreed!!!
It is 3860 with me in it......... and it's not a A body.
Here is the 5 minute video that i have been avoiding showing you all.:)



the two launches that don't sound right were when i changed squirters and didn't get all the air out of the system. The first one i thought it was going to die right there on the track.:eek::D
 
That thing sure isn't leaving very hard is it? It almost looks like the springs aren't working.
 
A couple things you have to add into the mix.
It's a heavy car and it a naturally aspirated 408 trying to breath at 6600 foot elevation. That day the adj alituted was 8500 foot........which is and above average air day. have see the adj go to all most, 10,000 foot elevation

1.70 to 1.75 60' a best of 7.76 at 97 mph (1/8 miles)
 
Did you watch the hole video?
two of them launches were aquirter/ bog failures.
 
Cudafever said:
A couple things you have to add into the mix.
It's a heavy car and it a naturally aspirated 408 trying to breath at 6600 foot elevation. That day the adj alituted was 8500 foot........which is and above average air day. have see the adj go to all most, 10,000 foot elevation

1.70 to 1.75 60' a best of 7.76 at 97 mph (1/8 miles)
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Well, that does it for me. No offense, but I hate it when I have to piece meal something over the internet. You left out everything. What it was, that you are at altitude........next thing it'll be a 408 Chevy motor.

We're big boys. We can take all the info at once. It always works better that way.
 
Nope! NO ****-ro-lay in my mopar.
Let me catch you up to speed then
Its a 12.8:1 408 Hyd Roller cam .562/.550 lift 243/247 @.050" duration, 4200 stall, reverse manual shift 727, shift at 5800 rpm, Brand New SS Springs, 4.56 rear gears w/clutch style sure grip. 28X10.5X15 Mickey Thompson slick with tubes. Stock old shock up front and MP long rear shock(also vary old)
I think that brings us up to speed...... o yeah its a 70 plymouth Barracuda.

After watching my video. I realized that some may have not seen the hole video because, the last launch from under the car is in "slow mo" and it take a minute before i launch the car. There is three more from up front of the car.
 
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Cudafever said:
I never try to send any one down the same path as me, for the chance of learning something new that i had not thought of. MR Sinister did that for sure.



I'm running drag tubes already and the other problem is my car is heavy! 3860 with me in it.
I don't have the double adj shock. they were to price for my budget. I did buy some Competition Engineering 3 way shock that i have not Yet installed.
As far as coming to high on the converter, you are right. Was trying to get a better 60 foot time.

The other thing, i have notist with these videos, is that the left tire is getting hit/wrinkle sidewall more than the right rear slick.



This is for you both......well any and every one.

Do you think i should set the new shock up initially equally? such as in a 50/50 setting(compression/Rebound). I have 3 settings 30/70 40/60 and 50/50.
Would you stagger the setting from left and right and if so what would you recommend for my first initial setting.

Also i bought some 3 way shock for the front end as well. My choice is 90/10 80/20 and 60/40 I basically have worn out front shock up front right now.

Thanks for all you thoughts so far, Keep then coming.....
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I won't speak for screws because he can hold his own, but all 50/50 means is it has the same compression and rebound dampening. A better what to say what it's doing is to use an example of a 90/10 front shock.

All that means is it comes apart 9 times easier than it goes together, or, the extension has 9 times less dampening than the rebound.

Those numbers really mean nothing.

The issue is you need to use the shock to control the motion of the spring, and it's that way for any spring type suspension.

If you can't control the spring in extension and compression (or bump and rebound as I like to say) then you are going to fight your chassis until the cows come home, although I've never learned how long that is.

Like I posted, you are beating the **** out of the tire, and the tire isn't happy about you handing it its *** so it is bouncing back. You control that by slowing down the rebound (more dampening) and slowing down the bump (more dampening. That slows the hit on the tire, and then slows down the tires equal and opposite reaction to getting its brains smashed out.

There is no way a 3 position or 9 way type of shock can do that.

You also need DA shocks for the front end, because what happens up front affects what happens in the rear.

You really need DA shocks on both ends, and then rent the track and spend the day just tuning the chassis.
 
I could be wrong here.......God knows it's been a while since I've set up a rear suspension in a Mopar race car, but the way I remember it is, you don't choose the spring based on the vehicle's weight.........in other words, say your car weighs 3800 pounds, I don't "think" that's how you choose the spring. I believe you chose based on spring rate, not the weight. I believe you may have too much spring under that car.

Now, I could be so far off base I'm a lunatic......wait, I am a lunatic, but I could be slap wrong. But something sticks out in my mind about that. I can tell you this. I know someone with an almost 4K pound 73 Charger in north Georgia running 9s. He has the 002 and 003 SS springs in his car and it LEAVES FROM HERE. lol
 
I fully understand that a double adj shock are much more tunable then what i have.....But this is what i can afford for now.
So what your saying is that i need to leave my new shock in the 50/50 position just like the MP drag shock is set up like(not adjustable.
In my mind if i had it in the 30/70 setting it would soften up the hit more then if i had it at 50/50 right? so there would be less of a need for the stiffer compression..........am i thinking thru this correct???
 
RustyRatRod said:
I could be wrong here.......God knows it's been a while since I've set up a rear suspension in a Mopar race car, but the way I remember it is, you don't choose the spring based on the vehicle's weight.........in other words, say your car weighs 3800 pounds, I don't "think" that's how you choose the spring. I believe you chose based on spring rate, not the weight. I believe you may have too much spring under that car.

Now, I could be so far off base I'm a lunatic......wait, I am a lunatic, but I could be slap wrong. But something sticks out in my mind about that. I can tell you this. I know someone with an almost 4K pound 73 Charger in north Georgia running 9s. He has the 002 and 003 SS springs in his car and it LEAVES FROM HERE. lol
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I wish i would have understood that before i bought my springs.:(
A 9 sec car probably weighs a lot less them my full body car thow right?(curb weight)
 
Cudafever said:
I wish i would have understood that before i bought my springs.:(
A 9 sec car probably was a lot less them my full body car thow right?(curb weight)
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It's not a hollowed out shell, but it's no street car either. Don't take my word as gospel yet. Like I said, I could be wrong. It just seems I remember something funny about how to choose what spring for the rear of these cars.......for racing anyway. For a street car it's easy. @72bluNblu will know. I tagged him. He'll come in here and tell me how wrong I am. LMAO
 
Cudafever said:
I fully understand that a double adj shock are much more tunable then what i have.....But this is what i can afford for now.
So what your saying is that i need to leave my new shock in the 50/50 position just like the MP drag shock is set up like(not adjustable.
In my mind if i had it in the 30/70 setting it would soften up the hit more then if i had it at 50/50 right? so there would be less of a need for the stiffer compression..........am i thinking thru this correct???
Click to expand...


IDK how to answer that. I doubt 50/50 will help you so you either need to slow the spring down on extension, or on compression.

IOW, the way I understand that shock is you also have a 60/40 and a 70/30 setting. If so, I'd make it so it is on the 70/30 side and try and tune that.

By that I mean you are either going to slow the spring down in extension or compression. That's what you'll have to deal with. But damn, if you slow the spring down in extension, but it's actually less dampening in compression you still might have an issue with the tire unloading.

Can you see the corner you are painted into? One way or the other you are going to compromise spring control. You can work with tire pressure and the other stuff skrewssaid, but still, you are showing up to a gun fight with a pan of noodles.

It would be better if you can slow everything down in both directions, but at this point you are going to have to deal with what you have.

FWIW, when I bought my car it had some junk KYb shocks up front and that 50/50 shock on the rear. So I beat on it awhile, because before I bought the car and it belonged to my cousin so I drove it a bunch.

Anyway, he didn't want to buy a good shock, so that's what he bought and that was on the car when I got it.

I replaced the fronts first with Viking DA shocks. Then the rears. When I pulled the rear shocks off, the one on the right side was toast. It had beat the valving out of it. It had no dampening in either direction.

You get what you pay for.
 
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