Leaf spring question

[jaybee]

OK, I've spent some hours going through posts and searching topics. I've picked up that a leaf spring suspension can be tuned to work well on the street with the right spring rate, shocks, and MAYBE a mild sway bar to fine tune the balance. Sounds also like adding a panhard or watts link is wasted effort for a street car (please feel free to correct me if I have any of this wrong). Also that there's a certain amount of disagreement over using Delalum or Polygraphite bushings

I'm also getting the impression that traction bars such as CalTracs or slapper bars at best have no impact on handling and at worst could be pretty detrimental, depending largely on preload. How about simple underride or override traction bars such as on early Shelby Mustangs?

[wendell]

Over rider bars are frequently used on gt350s for vintage racing. They are effective. That said, the amount of developement and tuning that goes into them is staggering. Trust me, there's a LOT more to it than meets the eye. The motivation behind all this inovation is the 9.5" spec tire. The most sucessful set ups involve spring loaded links and or biscuits to manage the forces.(think dirt late model). For a street car I wouldn't even consider it. A lateral locating device would have a larger possive impact on performance and be a lot easier to develope.

Regardless, a well speced spring driven on the street will need neither traction bars nor a lateral locator. KIS.

[jaybee]

Sounds like a whole bunch of track testing. I keep reading that the right springs are all you need. How do I recognize the right springs?

[astroracer]

It really depends on the end usage of the car. If it is a street car what is your performance goal? Straight ahead? Cornering? If both, a good set of handling springs from Hotchkiss or Gulstrand is probably all you'll need. There are so many variables on the street how do you determine if one spring is worth 2 tenths on the drive to the store over another set? Looking at it from a street aspect the stock springs may work better as they will probably be less harsh then a performance version and provide less "skip" going around lumpy-bumpy gravelly corners.
Something else to think about is street driving versus track driving. How good does your suspension have to be to get you around a big sweeper entrance ramp to the expressway as compared to hot lapping around a race track. A street car will NEVER get pushed to it's limits on the street as compared to a track only car on the track.
I did a lot of research when I was conceptualizing my Bad Ast Project and I finally realized this is a STREET oriented vehicle. I didn't have to spend thousands of dollars on a race oriented suspension to make the van handle exceptionally well on the street. Granted it probably won't be a barn burner going around a track but that is a moot point when it boils down to street versus track time... It will see much more street time and that is where I need it to work...
Mark

[steemin]

I am subscribing to this thread as I am having issues with my leaf spring rear end.
My car will primarily be street driven with an occasional trip to the drag strip.
The car is a 65 Mustang Fastback.
I have red Koni shocks,4 leaf springs and Shelby under rider traction bars. My car will not spin the tires.
I just get an insane amount of wheel hop


So I am looking for answers as well.
Scott

[jaybee]

My understanding of springs and shocks is built on what I learned from dirt bikes, so the philosophy for a fast road car could easily be different. In that arena the target spring would be just strong enough to keep the suspension from bottoming on the largest bumps the bike is going to encounter. Shocks are soft on compression to let the springs work and stronger on rebound to keep from overshooting ride height. Too much rebound damping is to be avoided as the suspension will pack down over washboard or repeated bumps. Shock valving has to be sophisticated enough to provide correct response on large wheel motions while at the same time remaining supple on stutter bumps, without which the machine will get skittish as the wheels lose adhesion.

First of all, does ANY of this relate at all to a hot street car, second, it tells me absolutely nothing about the correct specs and construction of a leaf spring suspension.

[chicane67]

Sounds like a whole bunch of track testing. I keep reading that the right springs are all you need. How do I recognize the right springs?

By their design and construction. There is more to spring science than meets the eye..... and there are many factors that need to go into the 'correct' spring build. There are very few individuals that have taken the time to learn, understand and build spring for exactly what is in question here.

I got the majority of my experience while working for the godfather of F-body roadrace/autocross/ProTouring. **** Guldstrand. His "FIA" spring designs are still packed full of surprises. I since then, have built several designs from a simple street spring to a full blown 24hr Daytona roadrace spring. And all I really have to say is... that a properly designed spring in a hotchkis type rear suspension does not need and or require a stay-bar or any type of forward location device, ie, a traction bar/CalTrac/under/overbar.

The only thing that traction bars are need for are for IC location because of soft, weak and poorly designed leafsprings. A correctly designed spring will also take into consideration IC location, braking force axle tramp, wheel hop and keeping the chassis off of the bump stops. We'll leave the subject of spring, frame eye bushings and shackels out of it right now..... because there is really only one solution to this issue.

Jaybee's understanding is just about point on. The truth to most of this is really in the shock and spring package combined and unfortunately, on the shock side of this, it comes down to an expensive shock set-up. Which at a minimum, means a double adjustable. In reality, a bypass triple. But lets get out of the stratosphere for now and talk springs.

[Mean 69]

I am not a leaf spring kind of guy due to the products we are marketing, but I can also state, without any doubt, that leafs can work. If done well. And, as some form of fate may have it, THE two dudes that I would refer anyone with a leaf question to, are both in this thread. They both happen to be good friends of mine though they have never met each other, both highly intelligent, and could dominate the leaf world if working together. Bar none.

Wendell (Jensen), meet Chicane (Tom). And vice versa.
\Mark

P.S: Wheel Hop? Under acceleration, or braking? Full throttle, part throttle? Details please!

[Slow Ride]

By their design and construction. There is more to spring science than meets the eye..... and there are many factors that need to go into the 'correct' spring build. There are very few individuals that have taken the time to learn, understand and build spring for exactly what is in question here.

I got the majority of my experience while working for the godfather of F-body roadrace/autocross/ProTouring. **** Guldstrand. His "FIA" spring designs are still packed full of surprises. I since then, have built several designs from a simple street spring to a full blown 24hr Daytona roadrace spring. And all I really have to say is... that a properly designed spring in a hotchkis type rear suspension does not need and or require a stay-bar or any type of forward location device, ie, a traction bar/CalTrac/under/overbar.

The only thing that traction bars are need for are for IC location because of soft, weak and poorly designed leafsprings. A correctly designed spring will also take into consideration IC location, braking force axle tramp, wheel hop and keeping the chassis off of the bump stops. We'll leave the subject of spring, frame eye bushings and shackels out of it right now..... because there is really only one solution to this issue.

Jaybee's understanding is just about point on. The truth to most of this is really in the shock and spring package combined and unfortunately, on the shock side of this, it comes down to an expensive shock set-up. Which at a minimum, means a double adjustable. In reality, a bypass triple. But lets get out of the stratosphere for now and talk springs.

I need you to design me some leaf springs for my Blazer. I broke the stock ones because of axle wrap, so now I run traction bars with beltech leaf springs, but would love to gain back the ground clearance and still have the thing launch correctly. I don't even have the good motor built yet and I'm breaking stuff.

As you can see things are a bit tight under there with 315/60's

http://i56.photobucket.com/albums/g1...4/DSCN0361.jpg

http://i56.photobucket.com/albums/g1...4/DSCN0353.jpg

[patriot68]

how do the dse 3" drop springs compare to hotchkis and others??

[Norwoodx55]

We'll leave the subject of spring, frame eye bushings and shackels out of it right now..... because there is really only one solution to this issue.

Well I am ready for this part now. The suspense is killing me.

[wendell]

The word on the street is that Chicane's brain is big. I'd definately differ to him on all things leaf. That said, I made this one car go pretty good one time...

[steemin]

P.S: Wheel Hop? Under acceleration, or braking? Full throttle, part throttle? Details please![/quote]

Thanks for the response..
In attempting to launch the car hard from a dead stop or a roll and even when I try to really nail 2nd gear I get zero tire spin.
All I get is wheel hop...
I obviously avoid doing this as it is brutal on the rear end.
FYI the car is a 5 speed with a 3.89 Ford 9" rear end
(2.95 1st gear) and has 382 RWHP. It also has a Meirer racing sub frame connectors welded in. For tires I have Bridgestone Potenza Pole Position 245X40X18's. I have had the pinion angles checked and I was told that they are okay..
I am not sure but it is possible that my leaf springs are old and
tired and are the cause of my problems
Scott

[wendell]

That's a good description of the problem. Does it hop with out the under riders? What type of bushing material is used in the spring eyes and in the bars?

[jaybee]

I don't know if anyone builds a true performance spring for a 57 Chevy. Before discovering this site I had pretty well decided on a 3" drop Posies Super Slide spring which comes with moly/nylon buttons for reduced friction and Polygraphite bushings. I'll admit to knowing absolutely nothing about controlling spring behavior through design beyond the old MOPAR Super Stock springs of the early 60s which used an extra, partial leaf to control spring wrap under acceleration. I'm eager to learn and grateful for your assistance, however, please school me!

[steemin]

That's a good description of the problem. Does it hop with out the under riders? What type of bushing material is used in the spring eyes and in the bars?

I have not ever ran the car w/o the under riders.....
So I do not know if the wheel hop would still occur...
Rubber bushings in the spring eyes and traction bars..
Scott

[wendell]

I don't know the lay out of the under riders but the first thing I would do is take them off. If that didn't fix it... hell, I don't know. Ask Chicane.

[jaybee]

"The truth to most of this is really in the shock and spring package combined and unfortunately, on the shock side of this, it comes down to an expensive shock set-up."

Sometimes you spend the money one place to save it someplace else. Good shocks cost money, but so do CalTracs or good-quality slapper bars.

[Bandit]

I agree with astroracer's comments: "It really depends on the end usage of the car. If it is a street car what is your performance goal? Straight ahead? Cornering? If both, a good set of handling springs from Hotchkiss or Gulstrand is probably all you'll need."
In my case I wanted a great all-around street setup, that handles flat in the twisties.
I have a Hotchkis Total Vehicle (TVS) setup, 600lb 2" lowering springs front, 1.5" lowered rear, on my '80 TA and I can say that this kit has met all of my expectations and then some, and it's not really expensive (about $1400 with shocks). I wanted to maintain the stock configuration and mounting points, which the kit does (no crazy fabrication), except for a different rear swaybar setup (at least on my car). I used Bilstein shocks. The first thing I noticed was that the suspension is QUICK! Meaning that at high speed on the highway, when I go over a slight inclination, there is no more of that scary "floating" sensation that forces you to slow down, the car just lifts, then quickly plants itself back down, with no hint of bouncing afterwards. The other thing is that it is a noticeably rougher ride, but who cares, right? If we wanted a soft ride we would all drive '76 Buick Electras.
I will include a link to an excellent article that helped me alot when I was researching suspension options, some of you might know the author but I don't, anyway it is really well written and worth the read:

http://racingarticles.com/article_racing-9.html

The main thing I got from it was: pick one reputable company, and buy all of your parts from them as a system. That way, you know you are getting a good system that has already been proven to work; otherwise, there are just too many variables to piecing a system together from scratch, which could be a frustrating process.

Anyway, good luck with your selection. Sorry this post turned into a novel.

Paul
"If at first you don't succeed, get a bigger hammer"

[jaybee]

Don't worry about writing a novel, This has all been extremely interesting. One thing that stood out from the linked article was the phrase "the center line of the front spring eye level with the centerline of the main spring leaf." Now we're getting into geometry. What exactly is determined by this relationship, I'm guessing instant center? If so that could be a huge contributor to how the car behaves under power.

In that case it throws out the concept of determining stance with lowering springs. As I think that through it looks like chassis package would need to be determined as follows:
1. Determine what size FRONT tire you can run. You'd do that first because space for fronts is normally more restricted than rears.
2. Decide on a size split front to rear. That's the reason for step 1, so you don't unbalance the car with an enormous tire size difference.
3. Now you have the rear axle centerline. If "the center line of the front spring eye level with the centerline of the main spring leaf" is correct, the front spring eye needs to be at the height of the spring pads on the axle. The sping selected needs to be rated and arched such that this relationship is preserved at ride height.
4. If that doesn't give the visual stance you're looking for, or you wish to lower the center of gravity, the shackles and front eye need to be moved upward. If that provides insufficient wheel travel you're potentially into major surgery.

I have a feeling I've made this more complicated than it needs to be, but potentially correct setup could be anything from relatively simple to very complex. Looking at my own project the spring pads are several inches below the front spring eye. The car also has long shackles that will need to come off. It looks as if a set of stock-length shackles and a reversed-eye spring providing 3" drop total could be just about right.