spastic rear suspension

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To me it sounds like what most solid axle cars do when they hit a sharp bump mid corner, they do this little skip/hop. My 2012 Mustang Gt does this just like an old Mopar does, but the new car has balanced suspension and settles back quickly.
Looking at what you have done to your Duster I would guess ( because it could be anything causing this ) that the front is a lot stiffer than the back and when the rear skips over something mid corner it starts whipping around due to the suspension not being balanced, stiff front, soft rear. So the first thing I would do is install the rear sway bar that goes along with your kit suspension system.
Low profile tires do change a lot of the characteristics of a car but I don't think they are the problem in this case, but you might feel the problem more because of them.
Let's us know how the test drive goes and report back!
 
RustyRatRod said:
Thanks. It's nice to see someone else got my point. That tires ARE a part of the suspension system, no matter how much you might not want them to be. LOL
Click to expand...

What point? You completely missed the point.

The original rear suspension on these cars was designed for use with bias ply tires, which have even softer sidewalls than the radials that everyone runs without bothering to change the OE springs. And that would be relevant IF the OP was using stock suspension.

But he's not. He's using Hotchkis springs that were designed to be used with modern tires, and have different spring rates and leaf construction than the OE springs. They were intended to be used with the tires like what the OP is using, and therefore the "low profile" tires aren't the problem. Take a look at the Hotchkis Challenger, that's the whole package.

The fact that the Hotchkis springs were designed for use with a rear sway bar, on the other hand, could be an issue.

Dr dan said:
'67 autocross has good counsel.
Click to expand...

He does! I said the same thing in post #5. The OP's front suspension is very stiff, the rear is not. The mismatch could definitely cause problems with settling the car after a big suspension input like a manhole cover.
 
72bluNblu said:
What point? You completely missed the point.

The original rear suspension on these cars was designed for use with bias ply tires, which have even softer sidewalls than the radials that everyone runs without bothering to change the OE springs. And that would be relevant IF the OP was using stock suspension.

But he's not. He's using Hotchkis springs that were designed to be used with modern tires, and have different spring rates and leaf construction than the OE springs. They were intended to be used with the tires like what the OP is using, and therefore the "low profile" tires aren't the problem.

The fact that the Hotchkis springs were designed for use with a rear sway bar, on the other hand, could be an issue.
Click to expand...

Leaf springs have rate,and bias,they do not know nor care whether you have
mounted bias or radial nor 75 or 40 series tires. What they do know is that they are
either stiffer,resisting motion at a given load ,or softer offering less resistance to that
motion.More resistance means motion transferred to the(in our case unibody)for a
given impact,necessitating more rebound distance to regain contact w/the road,or..
TRACTION. A tall compliant tire regardless of construction will transfer less motion to
said spring,which in turn will transfer less to the chassis, and will always do less of the
"dance". No doubt a rear bar will help suppress and recover the axles roll,and again,
I have a feeling the shocks may have too much resistance in rebound. I believe the OE
skins on My swinger were D75-14's and my fading memory says the sticker said 26psi.
That will absorb a lot of manhole cover my friends. After adding a few leaves, a 3/4"bar
& I believe they were 215/55VR15 potenza somethings(lol,whatever they had late '80's
early '90's) My swinger would "step out" more regularly for sure,but cornered great all
in all. Shocks however, were routinely marketed in the early '80's up till it was a moot
point,as "radial tuned" precisely because of the difference in the tires effect on the
suspension. Modern low-pro gummies are better and more accommodating than ever,
but a W-Y rated 245/40 vs a 175/75r14 over a manhole cover? C'mon man........
 
No, I didn't miss the point. You're on ignore now since all you can do is be a total *** lately.


72bluNblu said:
What point? You completely missed the point.

The original rear suspension on these cars was designed for use with bias ply tires, which have even softer sidewalls than the radials that everyone runs without bothering to change the OE springs. And that would be relevant IF the OP was using stock suspension.

But he's not. He's using Hotchkis springs that were designed to be used with modern tires, and have different spring rates and leaf construction than the OE springs. They were intended to be used with the tires like what the OP is using, and therefore the "low profile" tires aren't the problem. Take a look at the Hotchkis Challenger, that's the whole package.

The fact that the Hotchkis springs were designed for use with a rear sway bar, on the other hand, could be an issue.



He does! I said the same thing in post #5. The OP's front suspension is very stiff, the rear is not. The mismatch could definitely cause problems with settling the car after a big suspension input like a manhole cover.
Click to expand...
 
its been a while since I got on here but basically the issue was the hotchkis front eye bushings are junk so I replaced them with poly bushings that have a side wall to them and aren't just a cylinder that the spring slides all over. All is well now other than the stupid squeak I took the advice of using blue marine grease with the understanding that the bushings wouldn't do that.........lol oh well the car handles very well so I will deal with it. thanks for all the responses
 
Guy hits a bump.
Long discussion and arguing over suspension components.
Nobody is an actual suspension engineer.
Fact: Guy hit a bump.

Recomendation: When you hit a bump, how your car reacted and what you should do next time is information that makes you a better driver.

I hit in the past few years; 2 deer, a german shepard, a sink hole, 100's of huge pot holes, a muffler, an exhaust system, a fat *** racoon, a few squirells...

Can someone explain to me why my solid axle rear end slid a little bit, I didn't like my *** wiggling in the seat when it happened?
 
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oi81b4uu812b4 said:
Guy hits a bump.
Long discussion and arguing over suspension components.
Nobody is an actual suspension engineer.
Fact: Guy hit a bump.

Recomendation: When you hit a bump, how your car reacted and what you should do next time is information that makes you a better driver.

I hit in the past few years; 2 deer, a german shepard, a sink hole, 100's of huge pot holes, a muffler, an exhaust system, a fat *** racoon, a few squirells...

Can someone explain to me why my solid axle rear end slid a little bit, I didn't like my *** wiggling in the seat when it happened?
Click to expand...

Some of us have in fact engineered suspension systems. Not professionally and a long time ago, but none the less you're assuming things you obviously don't know. The point was always that the OP thought his car reacted in an unusual way, and since his car has been modified significantly from stock that is a real concern. Live axles have their limitations but you can obviously make them better or worse by how they're set up.

Sounds like you should take your own advice, apply what you've learned, and stop hitting so many things.
 
oi81b4uu812b4 said:
So 72bluNblu... I should rebuild my entire suspension is what you're saying.
Click to expand...

Well, based on your own argument that hitting things makes you a better driver you might want to look into it. After all, you've hit more things in "the last few years" than I have in the last 20. So, by your logic you should be an amazing driver. I would think at some point you'd be such a good driver that you'd stop hitting things, so maybe your suspension is what's holding you back.
 
Well thank you. I am amazing driver!
It's good to see we agree on things again.
You're so full of compliments today I'm getting all warm and fuzzy inside.


Psssst... These aren't all arguments people post here. Not everyone is here to battle internet warriors.
 
hobbsza said:
its been a while since I got on here but basically the issue was the hotchkis front eye bushings are junk so I replaced them with poly bushings that have a side wall to them and aren't just a cylinder that the spring slides all over. All is well now other than the stupid squeak I took the advice of using blue marine grease with the understanding that the bushings wouldn't do that.........lol oh well the car handles very well so I will deal with it. thanks for all the responses
Click to expand...
Glad You found an issue to correct for an improvement in stability, not sure why they wouldn't have a side thrust control of some type, being used for improved cornering &
all LOL!! As for the unfortunate squeaking, check with Energy Suspension or FABO sponsor PST for the Vaseline-like paste specifically for that app, hopefully will help.
 
oi81b4uu812b4 said:
Well thank you. I am amazing driver!
It's good to see we agree on things again.
You're so full of compliments today I'm getting all warm and fuzzy inside.


Psssst... These aren't all arguments people post here. Not everyone is here to battle internet warriors.
Click to expand...

Says a guy that dug up a 6 month old thread to add a bunch of sarcasm that didn't add anything to the discussion. Nevermind that the OP actually found a problem with his car that turned out to be causing the issue he was describing, fixed it, and now has a better handling car.

Killer6 said:
Glad You found an issue to correct for an improvement in stability, not sure why they wouldn't have a side thrust control of some type, being used for improved cornering &
all LOL!! As for the unfortunate squeaking, check with Energy Suspension or FABO sponsor PST for the Vaseline-like paste specifically for that app, hopefully will help.
Click to expand...

Best bang for the buck is Energy Suspension's poly grease. Comes in an 8 oz tub though so not exactly grease gun friendly, but that doesn't really matter for spring eye bushings
https://www.summitracing.com/parts/ens-9-11104

14oz Prothane supergrease, they're really proud of this stuff
https://www.summitracing.com/parts/ptp-19-1751/overview/

Hotchkis supergrease in 14 oz. Probably the same stuff, and if you have a bunch of poly bushings you can throw this in a grease gun easily to simplify your life.
https://www.summitracing.com/parts/hss-3101/overview/
 
Well 72blNblu the compliments didn't last long. We'll have to work on it more.

Actually I got on here to look at why the new XHD leaf springs I got came from two different manufactures. One really poor quality

Then as usual, I got to read about how you put offset shackles on your car to fit 295's on the back about a 1,000 times. Oh, and how your leaf sprung Plymodge is the best handling car ever made. And you claim to design an build your suspension, with stuff you just purchased stuff.

Still can't find the info I'm looking for other than posters confusing XHD's with SS springs.
 
oi81b4uu812b4 said:
Well 72blNblu the compliments didn't last long. We'll have to work on it more.

Actually I got on here to look at why the new XHD leaf springs I got came from two different manufactures. One really poor quality

Then as usual, I got to read about how you put offset shackles on your car to fit 295's on the back about a 1,000 times. Oh, and how your leaf sprung Plymodge is the best handling car ever made. And you claim to design an build your suspension, with stuff you just purchased stuff.

Still can't find the info I'm looking for other than posters confusing XHD's with SS springs.
Click to expand...

Ok, I have never claimed that I designed the suspension on my Duster. I have designed suspension in the past, built from scratch for FSAE competitions. But like I said, that was a long time ago. Ma Mopar designed the suspension on my Duster, I've just used aftermarket parts to tune and improve it. And yes, I've bought all of it because everything I've wanted so far is being manufactured. I've modified some of it myself, but hey, whatever. There's absolutely no mention of my tires in this thread, or my offset shackles. I do post about them a lot because there's a new "will this tire fit on my car" thread every day on this forum. The "search" function is an underused tool here for sure.

As far as your XHD's go, Mopar Performance has been making them in Mexico for about a decade now, and the quality control has suffered. Beyond that, some guy in the warehouse at the place you bought them might not like you for some reason, or maybe you're just unlucky. But you should still return them for a refund if they aren't matching springs. Seems pretty obvious, way easier to just call the place you bought them from for a return than try to find an answer here that still won't solve the problem of your springs being from different manufacturers.

And, if you're tired of reading about my car, just put me on your "ignore" list. :thumbsup:
 
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