Auto-X / Roadrace rear suspension 1969 Valiant

[go-fish]

I would like to find someone with experience on the 3 link rear suspension. I am looking at XV Engineering. Art Morrison has one but it is for Chevy and could be made to work but XV is a Mopar specific company so I'm pointed toward them.

Preface: This will NOT be a discussion about whether the OEM leaf spring rear is good enough, as good, or better than the direction I choose to go. Don't come in here and try to change my mind. I believe in the OEM suspension but not for 9/10's road racing and auto-x. I need quick and highly adjustable rear suspension. The car will race on multiple road surfaces (rocky asphalt/ smooth cap, big apex/small apex, big track/short course) at different parts of the country (weather) so there will be changes to the suspension setting for every track. Nothing against leaf springs but they just aren't in the Valiants future.

The back story is that I thought my 1969 Valiant project was dead in the water after being at a chassis shop for 4 years. There was a bunch of excuses like the shop was sued, they lost a bunch of employees, the office lady scammed customers out of money, Covid, lost the employees again, .... I was going to pull my car on a few occasions and they would get it in the shop and do something and then it would get shoved back in a corner. I didn't have anywhere to store it at home for one. Also, I got balls deep on my deceased friends Duster "Arthur's Duster" and that took my mind off the Valiant. Arthur's Duster is damned near wrapped up so my mind has been going back to the Valiant. I went to the chassis shop today to tell them to get my damn car mobile and I'm taking it home and I want my money that I have already given them back. They promised to finish out some work that will be worth the money that I've already paid. They were supposed to paint it as well but that isn't happening now so they do have quite a bit of my money already paid in advance (huge mistake paying a shop up front). I will never use anyone who wants payment in full or even half up front again. After meeting some trustworthy shop owners afterwards I have found out that working off a draw the customer and shop owner are usually happier. You give the shop enough money to start, they bill you in stages. They don't go to the next tage without getting paid and the customer doesn't pay until a sta is complete.

What has been done over the 4 years is sub-frame connectors, mini-tub, fender modification for 18x10, Aeromotive fuel cell install in a fabricated fuel cell enclosure, and tunnel work for the T56. Work left to do is J-bars from firewall to front frame rail, lower radiator support stiffening, torque boxes, Roll bar, and what was supposed to be an in-house 3 link build. I will then get the car back and finish it with the front suspension I have put together with all the go fast goodies like SPC UCA's, boxed LCA's, delrin pin bushings, Hellwig 1-1/4" sway bar, Viper disc brake kit, along with Forgeline ZX3 3 piece wheels in 18x10 and 18x11, Quick Performance floater 9" rear ..... Also I have a 510 hp IMM built stroker 340 with Pro Flo 4 and a Tremec 6 speed ready to go.

While at the chassis chop (same guy that did work to Tom Kaman's purple Valiant) the guy told be he didn't feel like he wanted to build the 3 link. He has built some in the past for Pro 4 trucks and Camaros but he has admitted that his 3 links have not been performing like he expected at the Goodguys, NMCA autocross, and Optima OUSCI in Vegas. He actually suggested the Reilly Motorsport 4-link. Now, I do have the 4-link in my '70 Cuda and it really does handle great but I was always under the impression that the 3-link was the way to go for max effort road racing and autocross. I told him about XV and he said he was open to it if that's what I wanted.

I kinda get the feeling he just doesn't want to fabricate on my car (a Mopar) and he's just trying to bend some tubing up and slap on a suspension kit to get me out of the shop. It has always seemed like he didn't want to work on my car because he has been building 6 figure pro-touring GM cars and this is just side work (the real excuse for not working on my car start to finish?). They pretty much do complete builds and my car IS just some fab work and I'm doing the rest. It's a partial build and they make big money on rich guys builds and building cars for SEMA and the big auctions.

I really haven't seen any XV 3-links on A-bodies. Like I said, I have a triangulated 4-link and it does handle great but that is the Ride Tech kit. It has bushings and no swivel links. The Street Lynx from Reilly does have a heim type swivel link that I like better than bushings for race cars. Bushings for a street car is great but with limited use and frequent inspections I like the swivel links on a race car due to less bind. So, it looks like XV or Street Lynx. If I settle on the Street Lynx I will just do it myself. The whole point of taking it to a chassis shop was to do work that I didn't feel I had the capabilities to do (rear suspension designing, bend tubing, painting, and welding on safety items). The 4-link kit on my 'cuda was a fairly easy installation. For that matter, the 3-link XV kit seems like about the same amount of work.

FWIW, I have already seriously considered special built fiberglass monoleafs and a panhard bar but feel like I need more adjustability from event to event.

 

[go-fish]

Some pics

 

[go-fish]

More

 

[go-fish]

More

 

[go-fish]

More

 

[go-fish]

This was Tom Kaman's Valiant that this shop worked on. Check out the pic of the car with the rear wheel openings cut out. That wasn't due to rust in the wheel lip. Dan Weishauer at Hotchkis Suspension thought it would be a cool idea to make the wheel opening round? That was when Tom pulled his car from Hotchkis and took it to the shop I am using. George had to weld the cut out section back in when he did the widening on the rear panels.

 

[72bluNblu]

Alright, I'll bite. If nothing other than to see some of the other responses and learn some more! Maybe @HemiDenny will chime in...

Your vote is tough, kinda needs a none of the above.

So in general, 3 links are best for road racing and other racing disciplines because of how adjustable they are. The problem with them is the location of the upper link. On an A-body if you run the upper link off the top of the housing it ends up being really short, or it ends up being inside the cabin space and running into the rear seat. If you're building a full on race car you're probably not worried about the rear seat or running structure back there to mount the upper link. But the XV kit is worried about that stuff, and the upper link is too short on account of it. If you think about how the axle will move, you see how the length of the upper link compared to the lower links will control how much pinion angle change there is. The XV set up will have a ton of pinion angle change, which isn't great. Here's an install on an E-body...

XV Level II Suspension Installation by jvike | plymouth | diys | DIY

You can offset the upper link to the right, and if you match the offset distance to your rear axle ratio you can get the tire balance equal on acceleration (counteracting the torque wrap). But you still might get a load balance issue in the back under braking. Regardless, that would mean a different upper link than what the XV kit has, which basically means you're designing and building your own 3 link. Which, if you're hell bent on the 3 link, is the way I think you'll have to do it. The XV kit isn't really a racing 3 link kit, if you want what I think you want you'll have to design and build it yourself.

The RMS Street Lynx is a triangulated 4 link, so, it actually doesn't have all that much adjustability. And because of the angles on the links and the relatively short upper links you can get binding with longer travel. I kinda think that's didactic, a lot of people run the RMS or versions of it that amount to a triangulated 4 link. But for all out racing, you lose adjustability compared to a 3 link and possibly even some suspension travel compared to a leaf spring set up. It works better than a 3 link with the stock chassis and floor locations, but it's still designed around the install and not cutting stuff up, and geometry is sacrificed for not cutting up the bodywork.

The fiberglass leafs with a panhard bar doesn't do much of anything different than a metal multileaf set up with a panhard. You lose some unsprung weight, but that's really the only difference and the axle housing itself is the lions share of the weight. Everything else will work almost exactly like a mulitleaf set up. Maybe a slightly faster spring reaction because you aren't sliding leafs on each other? Pretty theoretical at that point.

The Dan Gurney AAR's rear suspension ( to be taken with a grain of salt, because they run according to vintage race rules, not by what's "best")

And of course, Tom's car did very well with its Hotchkis rear leaf springs. He wasn't even running spring sliders in the back, which can help reduce a little of the resistance you get from the rear shackles and a little better side control too

 

[jos51700]

For the requirements you're listing, I can't really figure out why you're wanting to stay with a solid axle.

 

[go-fish]

If you're building a full on race car you're probably not worried about the rear seat or running structure back there to mount the upper link.

Not worried about intrusion at all really. I share your concerns with the XV stuff. There are some other things I don't like about it. The lower bars for one would need to be put in the frame rail like the MP inboard relocation. The Reilly Motorsports has an option for OEM mounting location at the front spring hangers or inboard, for which they sell the the frame cut-out. I had seen right off the bat where some changes to the XV kit would be needed. Illiminates a lot of the allure for me.
Not really keen on the triangulated 4-link due to what you stated. Binding, less articulation. It does fine on a street car where an off ramp or clover leaf is as tight as you get but I am after optimum track suspension. I do see than Reilly went to a swivel-link (rebuildable greasable heim joint) that may help a fraction with binding but the articulation is still limited by the uper bars and their angles.

The fiberglass leafs with a panhard bar doesn't do much of anything different than a metal multileaf set up with a panhard. You lose some unsprung weight, but that's really the only difference and the axle housing itself is the lions share of the weight. Everything else will work almost exactly like a mulitleaf set up. Maybe a slightly faster spring reaction because you aren't sliding leafs on each other? Pretty theoretical at that point.

Great point on using sliders. Some of the reasons I like the composite monoleafs: Cheaper, can buy multiple spring rates. Lighter, can lug multiple sets to the track and swap them out. With a panhard rod you eliminate the side to side movement of the rear axle. I totally forgot about the sliders, thank you.

BTW, I thought the Gurney cars ran composite monoleafs. I was mistaken.

For the requirements you're listing, I can't really figure out why you're wanting to stay with a solid axle.

For all these years I was under the assumption that the chassis man was going to do a 3-link. George (my chassis guy) won NMCA-West autocross in 2021 in his torque arm rear / Total Cost Involved front suspension 69 Camaro so he said he wasn't recommending the 3-link anymore. If you pay attention to NMCA West and OUSCI you would see many cars that are way up there in refinement.
Tom Kaman ( Purple Valiant) , who just had his bad *** 70-71 Firebird built by George is running the same TCI/ torque arm suspension and has been winning this year. To my knowledge none of the cars in NMCA Classic American Muscle class are running an independent rear. All solid axle with various rear suspensions. I do believe Mary Pozzi is running an Art Morrison IRS but she is sponsored ($13,000 rear suspension) and runs in SCCA and OUSCI.

If I had F@(% YOU money I would be running the suspension she does, front and rear. IT is way above the capabilities of a torsion bar/ leaf car.

One of the foundational principles of this Valiant build was to continue on with a Valiant that would have been the result of Tom's car if he had continued refining it. I talk to him often about his thoughts on taking it further. We are friends and I see him every once in awhile at the shop. He had an 833 and said he would have gone T56 had he continued so I put that on my shopping list. He would have went with a bigger torsion bar so I went with 1.24" bars. Brakes? He likes my Viper kit. His engine was underpowered so I made sure to have Brian at IMM build an engine specifically to tackle not only autocross but big tracks as well. His car was pretty balanced but he said he would have liked to get a little more weight off the nose so I got a fiberglass hood and may get a fiberglass front bumper.
I have an Alter-k-tion car but I really wanted to stay away from a coilover suspension and build an OEM suspension Green/Red Brick inspired Valiant. Then I met Tom and saw him coming onto the San Diego SCCA scene. By the time I was close to done collecting parts and ready to get chassis work done he had told me that he would have liked to try George's 3-link before selling it. The whole reason he got out of that car was to move onto a different platform that would be more competitive. GM F-bodies. His Valiant was competitive for a moment in time but this sport is ever changing and where we are today, if you want to be at the top of the heap you have to be in a platform that is well supported and be a damn good driver (which Tom is). He could not be competitive in the purple car today. I won't be able to ever be #1 in my Valiant but my particular goal is not to be class winner but to have the fastest Mopar to compete in the class and take out as many brand X cars as possible. I would have to spend $50,000 on suspension and chassis work to be competitive in a Mopar and it would mean not using ANY Mopar parts other than the body and perhaps engine.

 

[BergmanAutoCraft]

I worked at XV the during the whole run. I'm not sure what "XV Engineering" is actually offering...

The big issue is bind with any link suspension. I don't consider a triangulated 4 link something that is designed for handling, so we can leave that out of any discussion. We do like and sell the parallel four link from Detroit Speed. Its from the Gen X series and offers bushings, not bearings for quiet operation. It has links that rotate to articulate and high quality mono tube shocks in a good length from JRI. I consider this levels above any other offerings for this application. Some of the best sports cars have offered parallel 4 links for years with some type of locating device, panhard or watts links.

PM for any information

 

[72bluNblu]

Not worried about intrusion at all really. I share your concerns with the XV stuff. There are some other things I don't like about it. The lower bars for one would need to be put in the frame rail like the MP inboard relocation. The Reilly Motorsports has an option for OEM mounting location at the front spring hangers or inboard, for which they sell the the frame cut-out. I had seen right off the bat where some changes to the XV kit would be needed. Illiminates a lot of the allure for me.
Not really keen on the triangulated 4-link due to what you stated. Binding, less articulation. It does fine on a street car where an off ramp or clover leaf is as tight as you get but I am after optimum track suspension. I do see than Reilly went to a swivel-link (rebuildable greasable heim joint) that may help a fraction with binding but the articulation is still limited by the uper bars and their angles.
View attachment 1716005318



Great point on using sliders. Some of the reasons I like the composite monoleafs: Cheaper, can buy multiple spring rates. Lighter, can lug multiple sets to the track and swap them out. With a panhard rod you eliminate the side to side movement of the rear axle. I totally forgot about the sliders, thank you.

BTW, I thought the Gurney cars ran composite monoleafs. I was mistaken.



For all these years I was under the assumption that the chassis man was going to do a 3-link. George (my chassis guy) won NMCA-West autocross in 2021 in his torque arm rear / Total Cost Involved front suspension 69 Camaro so he said he wasn't recommending the 3-link anymore. If you pay attention to NMCA West and OUSCI you would see many cars that are way up there in refinement.
Tom Kaman ( Purple Valiant) , who just had his bad *** 70-71 Firebird built by George is running the same TCI/ torque arm suspension and has been winning this year. To my knowledge none of the cars in NMCA Classic American Muscle class are running an independent rear. All solid axle with various rear suspensions. I do believe Mary Pozzi is running an Art Morrison IRS but she is sponsored ($13,000 rear suspension) and runs in SCCA and OUSCI.

If I had F@(% YOU money I would be running the suspension she does, front and rear. IT is way above the capabilities of a torsion bar/ leaf car.

One of the foundational principles of this Valiant build was to continue on with a Valiant that would have been the result of Tom's car if he had continued refining it. I talk to him often about his thoughts on taking it further. We are friends and I see him every once in awhile at the shop. He had an 833 and said he would have gone T56 had he continued so I put that on my shopping list. He would have went with a bigger torsion bar so I went with 1.24" bars. Brakes? He likes my Viper kit. His engine was underpowered so I made sure to have Brian at IMM build an engine specifically to tackle not only autocross but big tracks as well. His car was pretty balanced but he said he would have liked to get a little more weight off the nose so I got a fiberglass hood and may get a fiberglass front bumper.
I have an Alter-k-tion car but I really wanted to stay away from a coilover suspension and build an OEM suspension Green/Red Brick inspired Valiant. Then I met Tom and saw him coming onto the San Diego SCCA scene. By the time I was close to done collecting parts and ready to get chassis work done he had told me that he would have liked to try George's 3-link before selling it. The whole reason he got out of that car was to move onto a different platform that would be more competitive. GM F-bodies. His Valiant was competitive for a moment in time but this sport is ever changing and where we are today, if you want to be at the top of the heap you have to be in a platform that is well supported and be a damn good driver (which Tom is). He could not be competitive in the purple car today. I won't be able to ever be #1 in my Valiant but my particular goal is not to be class winner but to have the fastest Mopar to compete in the class and take out as many brand X cars as possible. I would have to spend $50,000 on suspension and chassis work to be competitive in a Mopar and it would mean not using ANY Mopar parts other than the body and perhaps engine.

Yeah honestly I don't think the "kits" that are out there are designed for what you want to do. I'm not saying that the RMS 4 link kit couldn't be made to work, obviously there are guys out there that have run them in various autoX and track events.

The other thing to consider is the amount of horsepower you're running. 3 links don't usually do great with loads of horsepower, a parallel 4 link might be a better choice. And since you're not worried about cabin intrusion the parallel 4 link wouldn't be an issue for installation (like can be for those that want to retain the rear seat).

The Gurney AAR may have run composite mono leafs at some point, I'm sure it has gone through multiple configurations. That's a good point about being able to have a few different spring rates made and being able to swap them out, getting good quality multileaf springs has definitely been an issue lately and getting more than one spring rate that's in the same ballpark is getting downright difficult. That said, I think setting up a tubular splined sway bar system would probably solve a lot of the spring swapping issues. That's one thing in that XV kit that's a really good idea.

As for not being able to be competitive, I call BS. There's nothing "more competitive" about a GM F-body, other than there being more aftermarket support. The factory motion ratio is abysmal, I mean, running a 900 lb/in spring to get a decent wheel rate? C'mon.

Tom's car beat the stuffing out of modern Mustangs, C6 Corvette's, etc. And to be completely fair, Tom's car was not set up perfectly. He was still undersprung for his tire choices with a 1.06" torsion bar. He was definitely under powered compared to the other competitors at the time, he was running undersized brakes for most of his outings and his transmission/rear end gearing was not ideal. And he still came in second only to Mary Pozzi at an SCCA national event.

I'm not gonna defend the leaf spring rear suspension too hard, a properly set up IRS system is a better deal. But that's not as easy as it sounds, especially given the constraints of putting it into a car designed for something else. All things equal and the IRS wins out, but I do think that A LOT can be accomplished with a leaf spring rear if everything is set up and tuned properly.

The torsion bar suspension is just an unequal length control arm set up, just like EVERYTHING ELSE. Whether or not it works better than some mega bucks aftermarket suspension comes entirely down to tuning. Not all that long ago the tuning advantage other suspension systems had was significant, but that's not the case anymore. With a set of SPC UCA's you can dial in changes in just about every suspension geometry metric there is. Slapping on a set of tubular control arms with a corvette spindle on an F-body does not, in and of itself, make for better suspension. You're still just running parts designed for a different car, and like aftermarket suspension kits designed for the Mopars not all of those kids are really designed for competition, they're designed for rich guys that like shiny things.

There are plenty of cases of torsion bar and even torsion bar/leaf spring Mopars besting cars with much more modern suspension designs. The Hotchkis Challenger pulled a higher skid pad G loading than a modern Challenger SRT. The Hotchkis Taxi lapped faster on TireRack's test track than the 3 series Beemer's they usually use for testing, driven by the TireRack test driver that drives the Beemer's all the time and had never driven a pro-touring Mopar before. And yeah, Tom had a ton of success against modern cars too. Mary Pozzi was fast in the Hotchkis Challenger also, and I think the majority of Mary Pozzi being fast has more to do with her skills as a driver, rather than the megabucks ride she drives.

The biggest advantage to any race suspension is tunability, and you don't need to speed $50k on suspension to get a tunable Mopar suspension.

 

[go-fish]

@72bluNblu I agree. When I did the Cuda up with Reilly Motorsports stuff the choices for UCA were slim and they really weren’t a huge improvement over stock geometry. Overall, there just wasn’t a lot of marketing and performance oriented front suspension parts out there. Of course, there were parts in the Mopar world that could have worked well for a performance handling car because racers have been tuning the torsion bar system for a long time but they weren’t at all as prevalent and common knowledge. We didn’t have BAC, Hotchkis, SPC, Borgeson…..

Nowadays, I’m with you @72bluNblu . I have no doubt that a torsion bar suspension can handle with or, really, outperform a “kit” suspension. It comes down to tuning and driver skill. I am not thrilled with the choices for the rear “kits”. As stated I thought I was going to get a custom built 3-link for the longest time now. That is what Tom said he would have went to if he kept trying to be competitive with the Valiant. I have talked with him at length and made the moves he would have. Power, brakes, transmission, suspension, and was going to do the 3-link.

What can you tell me about optimizing the angle of the leaf springs in conjunction with sliders? Something akin to the angle that the E-body springs are at. Would that help. Would the sliders bind when leafs are angled?

Also, I will be calling two different composite spring manufacturers and getting quotes on 115# and 125# springs. I love the idea for the splined sway bar. All the pieces can be bought from Speedway for not a huge amount of money. Just have to measurement right the first time so you don’t have to repurchase links or brackets.

What is your thought on the panhard rod? I tend to think it would help. What are other ways to keep the rearend from going left to right?

Thank you very much for your patience insight.

 

[72bluNblu]

So this is by far the best information I have on leaf spring sliders, and actually some really good info just on leaf spring handling in general...

It's from the AFCO instructions, and getting it easily readable is a pain in the ***. So I pulled the text out of it....

"Leaf mounting angles

The geometry of a leaf spring suspension appears to provide the best overall handling whenever the front eye is mounted below the rear eye. If you lower the front eye of the leaf 1” or more and readjust the chassis back to its original ride height, you can expect the following:

1. More "tight" roll steer (may tighten handling)
2. Increased rear suspension stiffness
3. Lowered roll center (increases body roll and rear side bite -handling tightens)
4. Less body / tire separation during acceleration (may reduce forward bite)

You can expect results opposite to the above when you raise the front eye of the leaf and adjust the chassis back to its original ride height.

Mounting the leafs so that the front eyes are slightly inboard of the rear eyes will cause the leafs to have more lateral stiffness. This can make the chassis feel tighter and may help prevent the rear suspension from binding due to excessive lateral deflection of the leaf. However, if the leafs are offset too much the suspension becomes too stiff laterally and rear side bite is lost.

Whenever the body slides over the rear end during cornering, the splayed leafs can cause rear steer that will help the car to turn. Also, if the right front spring eye is mounted more inboard than the left eye (measured from the corresponding tires), the right rear tire will tend to be loaded less than the left rear tire during acceleration. As a result, the chassis will tend to be tighter off the corner. Corner exit handling tends to be loose under opposite conditions.

Generally, moving the front spring eye 1-1/2” laterally will produce a noticeable effect in corner exit handling.

ILLUS. 2
SUGGESTED LEAF MOUNTING ANGLES
(CHRYSLER TYPE LEAFS)

55” TO MIDDLE OF SLIDER
ONE INCH SPACING
6 1/2"
SLIDER EQUPPED 14”

54 1/2”
SHACKLE EQUIPPED 14”

1 1/2” TO 3”
BOTH LEFT AND RIGHT

YOUR COMBINATION OF VEHICLE WEIGHT AND LEAF SPRING RATE MAY REQUIRE THIS DIMENSION TO BE ADJUSTED. SLIDERS SHOULD BE MOUNTED SO THAT THE REAR SPRING EYE IS LOCATED 1/2" REARWARD OF THE CENTER OF THE SLOT. SHACKLES SHOULD BE MOUNTED TO PROVIDE A SHACKLE ANGLE OF 90° OR LESS."

 

[72bluNblu]

As for the other stuff, if you mounted the springs splayed you'd have to mount the sliders so they were at the same angle as the springs to prevent any binding. So parallel to the springs and not the frame rails if you mount the springs at an angle.

As far as keeping the rear end from going left and right, there's a few things. First is just the design, the flatter the springs are the less likely they are to deflect laterally. Hence the "zero arch" spring design from Ma Mopar. Then there's a few other things, like the spring sliders. The spring sliders allow for less side to side movement than the shackles would. And if you did composite mono-leafs, they would tend to flex less laterally than a multi-leaf spring because you won't have the leafs sliding around. So just that would help improve that. But the panhard bar should help a lot too, you just have to make sure you're mounting it properly so you're not inducing more binding with it too. To me the panhard bar is something you might not add right out of the gate, like if you determine when you're actually racing that the rear end is still moving around too much you could add it. But I think that will depend a lot on what you're doing, what tires you're running and at what tracks.

Yeah I've looked into the splined sway bars before, at some point I may get into doing that. But I'm pretty happy with my Hellwig bars for now, at least on the street. I have a lot of geometry and suspension math calculations to do to really blueprint my current set up before I get too crazy with things like splined sway bars.

I'd definitely ask some questions about the spring rate ratings from the companies and how they compare. In general I think 120-130 lb/in is a pretty good ballpark, but composite mono-leafs will have a different reaction time than a traditional multi-leaf so the rates might be a little different too. I haven't run them myself but I've heard it's not necessarily a 1:1 deal, like if you thought your current traditional leafs were right and they were 130 lb/in it still might not mean buying 130 lb/in monoleafs. But that could even vary one company to another.

 

[go-fish]

A little info on composite leaf springs. Huge weight savings, much more in the article.

Composite leaf springs are not new to the automotive industry. In fact, the leaf spring itself dates back to the horse-drawn carriage. By design, leaf springs absorb vertical vibrations caused by irregularities in the road. Variations in the spring deflection allow potential energy to be stored as strain energy and then released more gradually over time. Composites are well suited for leaf-spring applications due to their high strength-to-weight ratio, fatigue resistance and natural frequency. Internal damping in the composite material leads to better vibration energy absorption within the material, resulting in reduced transmission of vibration noise to neighboring structures.

The biggest benefit, however, is mass reduction: Composite leaf springs are up to five times more durable than a steel spring, so when General Motors (GM, Detroit, Mich.) switched to a glass-reinforced epoxy composite transverse leaf spring (supplied by Liteflex LLC, Englewood, OH, US) on the 1981 Chevrolet Corvette C4, a mono-leaf composite spring, weighing 8 lb/3.7 kg, replaced a ten-leaf steel system that weighed 41 lb/18.6 kg. This reportedly enabled GM to shave 15 kg/33 lb of unsprung weight from the Corvette, yet maintain the same spring rates. The leaf spring was transverse-mounted; that is, it ran across the car’s width at each axle. This eliminated the coil springs that sit up high in a spring pocket on the frame. Thus, the car can sit lower to the ground, which improves car handling.

Today, GM continues to employ transverse GFRP composite leaf springs on the front and back of its Corvette models. The 2014 Chevrolet Corvette Coupe includes a double-wishbone suspension, which, at GM, goes by the name short/long arm (SLA). SLA refers to the fact that the upper control arm is shorter than the lower one. A transverse composite leaf spring presses against the lower arm and spans the width of the car. In fact, the spring is always loaded against the subframe. This design directs shock loads into the frame side, eliminating the standalone rear antiroll bar that must be incorporated into models with standard suspension packages. The spring’s camber curve also is said to improve tire contact with the road during cornering.

Composites also have the potential to replace steel and save weight in longitudinal leaf springs (see “Building a stronger longitudinal leaf spring,” under "Editor's Picks," at top right). These run parallel to the length of the vehicle, providing suspension as an integrated part of the wheel guidance system. “Longitudinal leaf springs have a higher safety factor,” claims Frank Fetscher, head of business development, Benteler-SGL (Ried, Austria), a joint venture of Benteler Automotive and the SGL Group – The Carbon Company (Wiesbaden, Germany, see “SGL Automotive Carbon Fibers opens new plant in Washington,” under "Editor's Picks"). “They can have a linear spring rate or a progressive spring rate — multistage springs — and must perform better with respect to torsion and side stiffness than transversal springs.”

Composite leaf springs: Saving weight in production

 

[racerjoe]

I'm by no means a guru on suspension, but I have ready that many people are using torque arm style. (I know you mentioned it above.) Here's my opinion, which is worth nothing. You started by saying you wanted lots of adjustability, but it appears the 3 link won't give you that. So why spend the money on it? Art Morrison makes a torque arm setup that looks like it could be easily adapted to an A-body with some amount of fabrication. The adjustment seems endless on that thing. As with all things in the automotive industry, it comes down to how much money you want to spend. A set of leaf springs will get you on the track right away instead of waiting for the car to come out of fab shop jail.

 

[go-fish]

I'm by no means a guru on suspension, but I have ready that many people are using torque arm style. (I know you mentioned it above.) Here's my opinion, which is worth nothing. You started by saying you wanted lots of adjustability, but it appears the 3 link won't give you that. So why spend the money on it? Art Morrison makes a torque arm setup that looks like it could be easily adapted to an A-body with some amount of fabrication. The adjustment seems endless on that thing. As with all things in the automotive industry, it comes down to how much money you want to spend. A set of leaf springs will get you on the track right away instead of waiting for the car to come out of fab shop jail.

Currently, as of starting this thread, I am hot on the information gathering trail of the composite monoleafs. I am running that idea down hard as we speak. I have two companies identified, one contacted, that may possibly be able to build a couple of composite A-body spec spring sets in different rates cheaper than a "custom" rear suspension or kit. Now, this wouldn't just mean no fab, put springs on. The car is mini-tubbed and I am looking at toeing the springs in up to 1.5" in front so that means a Mopar Performance style full relocation. I would put the Calvert angled rear sliders at the proper place and in the front would cant the frame boxes appropriately. Also, per the attachment @72bluNblu posted above, I would try to achieve an 8" rake in spring mounting points front to back (6" front and 14" read). Also, note the spring toe in on that attachment.

I like the composite idea because they are light. Light for the weight savings of the car. Composites can weigh around 10 lbs whereas OEM's weigh 45 plus lbs. Also, I can buy a couple different spring rates and carry them around easier to make changes on-site. My track options are not local and are multiple days so if something needs to be tuned like leafs I can do it at the end of Day 1. (I do have San Diego SCCA but they lost their venue in San Diego and actually run up in Inland Empire). The Hotchkis adjustable front shocks are already purchased so I would also be purchasing the rear adjustable Hotchkis Fox shocks to add adjustability in the rear. I have contacted Hotchkis about their big front sway bar and they said you can only order it over the phone and you have to buy front and rear as a set. I already have the Hellwig 1-1/4" bar in front so I may skip the Hotchkis front bar and do a NASCAR style splined bar in rear. @72bluNblu brings up a great point about the 0 arch springs keeping the rear centered and with the addition of spring toe I think it would help further so I would take his advice and not add a panhard rod until I felt it was warranted.

I don't know what the cost of custom composites are but the shelf ones are hundreds cheaper than Hotchkis or other multi-leaf manufacturers.

One thing that is at the top of my concerns (other than if I can even get a custom composite made) is leaf spring pad on the axle with toed in springs?

 

[BergmanAutoCraft]

Hi guys, I don't have too much to add here, but geometry and ride quality may play into your decision making. I like things super quiet and smooth, so my options may vary.

The reality of available parts vs theory is also part of this. The one guy who could supply composite leafs is out of business. I've tried all the AFCO springs without success.

The roller shackle is interesting, but I'd bet it makes a hell of a racket. This is similar to any torque arm style rear setup.

The AFCO spring notes are interesting, but their parts are geared to oval tracks. Also remember, the amount of roll is partially dependent on the distance of the roll center to the center of gravity. This is why raising the rear height is instant destruction to handling on any leaf spring vehicle.

Lastly, the Mopar road race manuals suggested raising the front eye position where possible. The flatter the mounting points, the more neutral the toe steer will be.

Having many open track days under my belt, I can say that stabilizing the spring laterally is of great importance. I destroyed shackles by side loading them. The pins, if they are the old MP ones, should be welded in place to avoid wallowing out the holes in the side plate.

Once again, if you were thinking about an aftermarket suspension for the back, I wouldn't consider anything else than the DSE Gen X. I will most likely be doing this on my Dart in the future. If I do, and have to make specific parts for them to fit, I would do so.

I recently moved to NC from a lifetime in NY and am finishing up a new building as we speak. 2023 will be a fun year as a result.

 

[racerjoe]

Currently, as of starting this thread, I am hot on the information gathering trail of the composite monoleafs. I am running that idea down hard as we speak. I have two companies identified, one contacted, that may possibly be able to build a couple of composite A-body spec spring sets in different rates cheaper than a "custom" rear suspension or kit. Now, this wouldn't just mean no fab, put springs on. The car is mini-tubbed and I am looking at toeing the springs in up to 1.5" in front so that means a Mopar Performance style full relocation. I would put the Calvert angled rear sliders at the proper place and in the front would cant the frame boxes appropriately. Also, per the attachment @72bluNblu posted above, I would try to achieve an 8" rake in spring mounting points front to back (6" front and 14" read). Also, note the spring toe in on that attachment.

View attachment 1716005749

View attachment 1716005750

I like the composite idea because they are light. Light for the weight savings of the car. Composites can weigh around 10 lbs whereas OEM's weigh 45 plus lbs. Also, I can buy a couple different spring rates and carry them around easier to make changes on-site. My track options are not local and are multiple days so if something needs to be tuned like leafs I can do it at the end of Day 1. (I do have San Diego SCCA but they lost their venue in San Diego and actually run up in Inland Empire). The Hotchkis adjustable front shocks are already purchased so I would also be purchasing the rear adjustable Hotchkis Fox shocks to add adjustability in the rear. I have contacted Hotchkis about their big front sway bar and they said you can only order it over the phone and you have to buy front and rear as a set. I already have the Hellwig 1-1/4" bar in front so I may skip the Hotchkis front bar and do a NASCAR style splined bar in rear. @72bluNblu brings up a great point about the 0 arch springs keeping the rear centered and with the addition of spring toe I think it would help further so I would take his advice and not add a panhard rod until I felt it was warranted.

I don't know what the cost of custom composites are but the shelf ones are hundreds cheaper than Hotchkis or other multi-leaf manufacturers.

One thing that is at the top of my concerns (other than if I can even get a custom composite made) is leaf spring pad on the axle with toed in springs?

I've always been curious if leaf springs moved inboard to the frame rails would be a detriment to handling. In my mind you lose leverage and may need stiffer springs. I'd be curious to hear about the composite springs if you find a decent supplier.

 

[72bluNblu]

Currently, as of starting this thread, I am hot on the information gathering trail of the composite monoleafs. I am running that idea down hard as we speak. I have two companies identified, one contacted, that may possibly be able to build a couple of composite A-body spec spring sets in different rates cheaper than a "custom" rear suspension or kit. Now, this wouldn't just mean no fab, put springs on. The car is mini-tubbed and I am looking at toeing the springs in up to 1.5" in front so that means a Mopar Performance style full relocation. I would put the Calvert angled rear sliders at the proper place and in the front would cant the frame boxes appropriately. Also, per the attachment @72bluNblu posted above, I would try to achieve an 8" rake in spring mounting points front to back (6" front and 14" read). Also, note the spring toe in on that attachment.

View attachment 1716005749

View attachment 1716005750

I like the composite idea because they are light. Light for the weight savings of the car. Composites can weigh around 10 lbs whereas OEM's weigh 45 plus lbs. Also, I can buy a couple different spring rates and carry them around easier to make changes on-site. My track options are not local and are multiple days so if something needs to be tuned like leafs I can do it at the end of Day 1. (I do have San Diego SCCA but they lost their venue in San Diego and actually run up in Inland Empire). The Hotchkis adjustable front shocks are already purchased so I would also be purchasing the rear adjustable Hotchkis Fox shocks to add adjustability in the rear. I have contacted Hotchkis about their big front sway bar and they said you can only order it over the phone and you have to buy front and rear as a set. I already have the Hellwig 1-1/4" bar in front so I may skip the Hotchkis front bar and do a NASCAR style splined bar in rear. @72bluNblu brings up a great point about the 0 arch springs keeping the rear centered and with the addition of spring toe I think it would help further so I would take his advice and not add a panhard rod until I felt it was warranted.

I don't know what the cost of custom composites are but the shelf ones are hundreds cheaper than Hotchkis or other multi-leaf manufacturers.

One thing that is at the top of my concerns (other than if I can even get a custom composite made) is leaf spring pad on the axle with toed in springs?

So, on the E-bodies I can say the following- the front hangers are not angled, neither are the spring perches, or rear shackles. What that means is that the angle on the springs is taken up by the rubber bushings front and rear, which is not a great idea if you get rid of the rubber bushings. But the E's don't have very much angle either. Forr what you're planning, I would suggest angling the spring sliders in the back. The perches probably don't need it as long as the angle is fairly shallow. The front hangers, I dunno. I would try to set at the same angle if possible, especially with the 3" relocation spring boxes because of the amount of leaf spring tucked into the box.

Hyperco makes Chrysler springs, they still show them as available so you might look into them. I didn't do a quote to see what the stock and price looked like. These were made for oval track originally, and they should have the 20.5" front section
Shop Composite Leaf Springs - Buy Online | Hyperco

There are a few threads about them on some of the other forums, a member named "Brads70" uses them and has a detailed write up over on the old cuda-challenger forum. He used Hyperco springs in a #175 and then a #225 lb/in rate, although it's worth noting that the Hotchkis E-body springs are 160 lb/in, the A-bodies are 130 lb/in. He had to use extended front hangers on his E-body like you do with the SS springs which also have the 20.5" front section (E's used a 22" front section and longer spring). Mopar Mitch, who also races a Challenger pretty extensively, was also using the 225 lb/in Hyperco's

Anyone in here using composite leaf springs?

There's also a thread over at Moparts...
Fiberglass Springs any good?

Seems to me like there is definitely a "conversion" factor in the spring rates, I ran SS springs on my Challenger with 1.12" torsion bars (270 lb/in) and they were pretty darn stiff, although they also changed the rake on the car substantially. I went to XHD's later which are a much lower spring rate.

Also from the DC rear suspension bulletin, E-body spring angle was only 1.67°

Hi guys, I don't have too much to add here, but geometry and ride quality may play into your decision making. I like things super quiet and smooth, so my options may vary.

The reality of available parts vs theory is also part of this. The one guy who could supply composite leafs is out of business. I've tried all the AFCO springs without success.

The roller shackle is interesting, but I'd bet it makes a hell of a racket. This is similar to any torque arm style rear setup.

The AFCO spring notes are interesting, but their parts are geared to oval tracks. Also remember, the amount of roll is partially dependent on the distance of the roll center to the center of gravity. This is why raising the rear height is instant destruction to handling on any leaf spring vehicle.

Lastly, the Mopar road race manuals suggested raising the front eye position where possible. The flatter the mounting points, the more neutral the toe steer will be.

Having many open track days under my belt, I can say that stabilizing the spring laterally is of great importance. I destroyed shackles by side loading them. The pins, if they are the old MP ones, should be welded in place to avoid wallowing out the holes in the side plate.

Once again, if you were thinking about an aftermarket suspension for the back, I wouldn't consider anything else than the DSE Gen X. I will most likely be doing this on my Dart in the future. If I do, and have to make specific parts for them to fit, I would do so.

I recently moved to NC from a lifetime in NY and am finishing up a new building as we speak. 2023 will be a fun year as a result.

Yes, you definitely have to consider the source of the information when looking at the geometry and set up. A lot of the information out there on Mopar rear suspension is either drag race or oval track. And while the oval tracks springs themselves are very useful, setting up the geometry is a little different. You don't want to stagger side to side for sure for autoX or road race since you'll want your turn in to be the same. And you definitely want to be careful with roll steer. On an oval all your transitions are turning the same way. On an AutoX course you may have to change direction quickly, so a bunch of roll steer on the exit will not be a good thing.

I run the leaf spring sliders on my Duster. They definitely don't make a "hell of a racket". Occasionally over speed bumps or things I can hear them click, but realistically at any kind of speed or RPM I can't hear them over my exhaust.

I've always been curious if leaf springs moved inboard to the frame rails would be a detriment to handling. In my mind you lose leverage and may need stiffer springs. I'd be curious to hear about the composite springs if you find a decent supplier.

Yep, moving the springs away from the contact patch will change the roll couple, and stiffer springs would be needed to maintain it.

 

[BergmanAutoCraft]

I run the leaf spring sliders on my Duster. They definitely don't make a "hell of a racket". Occasionally over speed bumps or things I can hear them click, but realistically at any kind of speed or RPM I can't hear them over my exhaust.

What is your exhaust comprised of?

 

[72bluNblu]

What is your exhaust comprised of?

Doug's headers, a summit 2.5" kit and 2.5" DynoMax Ultraflo's. It's fairly loud.

 

[go-fish]

All, good points to consider. Hyperco is the company that I have already contacted. No reply yet but I did the quote sheet they have online.
Preliminary thought is that the spring perches will be at 41-42” spacing (right under the frame rail). The slider will be placed on center of the frame rail and the relocation boxes in the frame will be canted to be in alignment with the toe. What I need to research is how much toe.

The AFCO attachment posted says toe should be 1.5” - 3” in. Right off the bat I am thinking no more than 1.5” for this application (non oval track car). I want to find the proper toe in. Possibly look at the measurements for E-body and see how they compare with the 1.5” - 3” suggestion for oval track setups.

Something that is a recurring ponder is if the spring perches need to be canted in-line with the toe’ed spring. If I come to the conclusion that a lesser toe-in suffices (maybe a 3/4” toe) then I think they would be fine being straight. Thoughts on that?

 

[Phreakish]

1.67 degree angle from the E body in @72bluNblu 's post equates to about 1.66" of taper (per side) with a 57" spring (which seems to be E body length). The amount of taper is about .03" per inch: 0.291 at 10" of length.

If you want 1.5" of taper over a 57" spring, the spring toe angle would be 1.507 degrees
If you want 1.5" of taper over a 55" spring (a body), the spring toe angle would be 1.562 degrees

If you are going to attempt to taper the springs at all, I would try to match the relocation box and sliders to the angle of the springs. Doesn't take much angle to subtend some measurable distances.

 

[72bluNblu]

All, good points to consider. Hyperco is the company that I have already contacted. No reply yet but I did the quote sheet they have online.
Preliminary thought is that the spring perches will be at 41-42” spacing (right under the frame rail). The slider will be placed on center of the frame rail and the relocation boxes in the frame will be canted to be in alignment with the toe. What I need to research is how much toe.

The AFCO attachment posted says toe should be 1.5” - 3” in. Right off the bat I am thinking no more than 1.5” for this application (non oval track car). I want to find the proper toe in. Possibly look at the measurements for E-body and see how they compare with the 1.5” - 3” suggestion for oval track setups.

Something that is a recurring ponder is if the spring perches need to be canted in-line with the toe’ed spring. If I come to the conclusion that a lesser toe-in suffices (maybe a 3/4” toe) then I think they would be fine being straight. Thoughts on that?

Yeah I don't think I'd worry too much about the spring perches with that little angle. The E-body 8 3/4 perches aren't angled.

Like anything, I would do some more research on the spring angle. As Peter pointed out, the AFCO instructions are for circle track, which definitely has some differences for desired handling compared to autoX or road racing. You don't want a ton of rear steer response, although a little more resistance to lateral movement would be nice.

But, if the plan is to add a panhard bar, you don't need the springs to be angled since your lateral movement will be limited by the panhard bar. And you don't want to compromise your thrust angle or forward bite too much for autoX, since you'll want to be able to accelerate hard on a short track.

1.67 degree angle from the E body in @72bluNblu 's post equates to about 1.66" of taper (per side) with a 57" spring (which seems to be E body length). The amount of taper is about .03" per inch: 0.291 at 10" of length.

If you want 1.5" of taper over a 57" spring, the spring toe angle would be 1.507 degrees
If you want 1.5" of taper over a 55" spring (a body), the spring toe angle would be 1.562 degrees

If you are going to attempt to taper the springs at all, I would try to match the relocation box and sliders to the angle of the springs. Doesn't take much angle to subtend some measurable distances.

Nice! Was gonna do that calculation, you beat me to it.

I think if I was going to do this at all, I wouldn't go past the E-body numbers.