Late model suspension under 69 Coronet

[69Vorhaden]

Im fishing for information and opinions.

Im at a decision point in my restomod build......My body guy is finishing up on the body. I'm not good with body work and body mods so it's the one thing I've outsourced. My body guy also fabricates, and he saw my donor 2018 charger and wants to put the late model rear suspension under my 69 coronet. Mixed about it...Seems to be alot of fabrication and may cause more problems than it's worth. I think the late model charger rear end is 3-4 inches wider. The car is a roller right now and this would mean more time in someone else's shop. I want to get may car back and start in on the drive train swap. Anybody seen or done a late model rear suspension swap?

I found a thread on here that does something similar with an aftermarket kit that still needed ALOT of fabrication. 69 road runner on new rear suspension

My original idea was to keep the 8 3/4 till I could upgrade to a Dana 60. Any input on how well the 8 3/4 rear holds up to the 6.4hemi?

Anybody done one of the aftermarket QA1 coil over or Ridetec air ride kits.

Thanks in advance

Don

 

[kramer]

My personal opinion is to keep the front and rear suspension stock or modified stock, its actually a pretty good design with everything new and some upgrades along the way, I believe Kerndog has a good write up on doing his 70 Charger. I would leave the aftermarket suspension systems to people that do some type of rallying or racing.

 

[69Vorhaden]

My personal opinion is to keep the front and rear suspension stock or modified stock, its actually a pretty good design with everything new and some upgrades along the way, I believe Kerndog has a good write up on doing his 70 Charger. I would leave the aftermarket suspension systems to people that do some type of rallying or racing.

That is what I'm leaning toward. Ill look up kerndog

 

[radical rob]

I have the ride tech air bar 4 link under my 69 rr. Is working pretty well and with the coilovers the rear ride height is now adjustable.

 

[dfrazz]

What are your goals for the car? Auto-cross, strip, cruising? Without knowing your body guy, it sounds like he is trying upsell you because that is a ton of fab work. There are plenty of aftermarket performance suspension options out there including 4-link, mono-leaf, etc without a ton of modification.

 

[Kern Dog]

Modern suspensions will ride better and handle better than what our cars were built with but.....
Is the juice worth the squeeze?
Will you ever see the benefits of the expense to do it?
I'll admit, much of my reasoning to retain a stock design is rooted in the balance of dollars spent versus value received.
There are some things that we do that cost a LOT but don't feel like they added much improvement.
I can't clearly compare between the two in regards to the modern suspension when installed in a classic car. I've driven a new Challenger and have driven plenty of old classics. The ride of the new cars is a lot easier to live with but hey...you'd expect a newer car to have some improvements, right?
In short, I've found that good shocks really make a difference.
Years ago, there was a company that tried hard to revolutionize the classic Mopar market. XV Motorsports invested a lot of money developing suspension systems to improve the handling and ride of these cars. They built a chassis jig to monitor and measure how the chassis reacts to "real world" road and race conditions. They found that in most cases, these cars were too soft in the front spring rate and too stiff in the rear.
As an aside, They were the ones that developed those chassis stiffening pieces that later were sold by US Cartool.
To the point of suspension. it can be argued that what makes any suspension better is to mount it to a rigid platform so the frame/unibody structure does not act as another spring. If the platform is solid, the springs can actually be softer and lighter due to there being less lost motion.
I am no expert, I just know what I have personally witnessed. I have reproduction Mopar Performance leaf springs that were supposed to be replacements for Hemi and 440 4 speed cars. Six leafs per side. They have left and right sides, I chose two rights that also had a half leaf that was supposed to reduce right spring wind-up under launch.
I don't know the spring rate. The front spring eye is rubber, the shackle bushings are urethane.
I have a 3/4" rear sway bar and Bilstein shocks.
The front has BIG torsion bars, 1.15". No, the car does not have a harsh ride. It is firm, but no more so than the Wife's 2015 Challenger R/T. Personally, I prefer a firm ride. I have a tubular 1 1/4" front sway bar and Bilstein shocks. I used rubber bushings in the lower control arms but have aftermarket upper control arms with urethane bushings. The car handles better than any other car that I have driven and rides great.
A former member of this forum chose to go with the RMS front and rear suspension and had problems with it. The components used for the rear suspension look beautiful but were not durable for a street car. Within a few thousand miles, he had to replace several components and he wasn't much of a "hands on" sort of guy. He paid others to work on his car.
That can be expensive and inconvenient.
Adapting the rear suspension from a late model Mopar would be way outside of anything that would interest me. I could understand the appeal though.
Good luck.

 

[69Vorhaden]

Modern suspensions will ride better and handle better than what our cars were built with but.....
Is the juice worth the squeeze?
Will you ever see the benefits of the expense to do it?
I'll admit, much of my reasoning to retain a stock design is rooted in the balance of dollars spent versus value received.
There are some things that we do that cost a LOT but don't feel like they added much improvement.
I can't clearly compare between the two in regards to the modern suspension when installed in a classic car. I've driven a new Challenger and have driven plenty of old classics. The ride of the new cars is a lot easier to live with but hey...you'd expect a newer car to have some improvements, right?
In short, I've found that good shocks really make a difference.
Years ago, there was a company that tried hard to revolutionize the classic Mopar market. XV Motorsports invested a lot of money developing suspension systems to improve the handling and ride of these cars. They built a chassis jig to monitor and measure how the chassis reacts to "real world" road and race conditions. They found that in most cases, these cars were too soft in the front spring rate and too stiff in the rear.
As an aside, They were the ones that developed those chassis stiffening pieces that later were sold by US Cartool.
To the point of suspension. it can be argued that what makes any suspension better is to mount it to a rigid platform so the frame/unibody structure does not act as another spring. If the platform is solid, the springs can actually be softer and lighter due to there being less lost motion.
I am no expert, I just know what I have personally witnessed. I have reproduction Mopar Performance leaf springs that were supposed to be replacements for Hemi and 440 4 speed cars. Six leafs per side. They have left and right sides, I chose two rights that also had a half leaf that was supposed to reduce right spring wind-up under launch.
I don't know the spring rate. The front spring eye is rubber, the shackle bushings are urethane.
I have a 3/4" rear sway bar and Bilstein shocks.
The front has BIG torsion bars, 1.15". No, the car does not have a harsh ride. It is firm, but no more so than the Wife's 2015 Challenger R/T. Personally, I prefer a firm ride. I have a tubular 1 1/4" front sway bar and Bilstein shocks. I used rubber bushings in the lower control arms but have aftermarket upper control arms with urethane bushings. The car handles better than any other car that I have driven and rides great.
A former member of this forum chose to go with the RMS front and rear suspension and had problems with it. The components used for the rear suspension look beautiful but were not durable for a street car. Within a few thousand miles, he had to replace several components and he wasn't much of a "hands on" sort of guy. He paid others to work on his car.
That can be expensive and inconvenient.
Adapting the rear suspension from a late model Mopar would be way outside of anything that would interest me. I could understand the appeal though.
Good luck.

Thanks for the verbage. Improve and beef up the OEM layout was pretty much what I was thinking before I got bit by the novelty of a late model suspension under my 69 coronet.

 

[69Vorhaden]

What are your goals for the car? Auto-cross, strip, cruising? Without knowing your body guy, it sounds like he is trying upsell you because that is a ton of fab work. There are plenty of aftermarket performance suspension options out there including 4-link, mono-leaf, etc without a ton of modification.

Good point---cruiser with ocasional trips to the strip. Not an autocross guy with this car but might if I had a smaller platform

 

[dfrazz]

Good point---cruiser with ocasional trips to the strip. Not an autocross guy with this car but might if I had a smaller platform

Even more reason to spend your money on just improving the stock suspension. A lot of guys have gone with the combination of Bilstein shocks, Hemi rear leaf springs (espo.com) is a great source, 1.03 or bigger torsion bars (PST or FirmFeel or Hotchkis have these), front and rear sway bars. I also would suggest frame rail connectors. There are fancy ones from US Car Tool, tubes from Hotchkis, or I just welded in 2" sq tubes that are cut into the frame.

One thing to note on @Kern Dog's details above, he is running bigger wheels with thin sidewall tires and that makes his combination different that a lot of others still running 15" wheels.

 

[Kern Dog]

In some ways, yeah.
Steering response with the shorter and stickier tires is better. Ride quality on bumpy roads is not. It isn't bad, just a bit firmer than what some people might prefer.
I have to run a 17" minimum wheel to clear the front brakes but I had these 18" wheels with the 12" Cordoba discs. I liked how they looked and wanted a good handling setup.