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Old 06-28-2010, 10:46 AM
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Spring Question for Mr. Billy Shopes

Hey Mr. Billy, I'm building a 1957 Chevrolet 3100 P/U. It will be powered by a '97 LT1 w/t56 six speed mildly hopped up. I would like your input on my spring and suspension package.

Here is the basic approach I'm taking;
1) Leaf springs at all four corners as stock, I refuse to butcher up the truck w/IFS. Reversed eye front for 3" drop, stock ride height rear.
2) Add on sway bars, front and rear.
3) QA-1 single adjustable shocks.
4) Power rack & pinion steering mounted to the straight axle w/telescoping shaft.
5) Probably a 235/70/15 front, 255/70/15 rear 7"f, 8"r wheels.
6) Add on traction bars, slide link or slapper bar.

Here is what I want;
1) Haa, to borrow the ad slogan, Ride like a Cadillac and handle like a slot car.
I realize this is all about compromise.
2) Decent traction without wheel hop issues for an occasional drag strip run.
3) Rear spring setup for superior ride quality(will never carry any load in the bed)
4) Want to work with Detroit Eaton Spring for the package.

Here is what I know from research;
1) Curb Weight 1995#front, 1365#rear. Payload rating 1555#/100% rear.
2) Factory spring specifications; FRONT-Semi-elliptic, chrome carbon steel,6 leaves, load @ opening height 826-906#@1.70", average rate of deflection 304# per inch, rated capacity 1000# on the pad-1170@the ground. REAR- Semi-elliptic, chrome carbon steel, two stage, 7 leaves, load @opening height 1100-1200 @ .440", average rate of deflection(pounds per inch)(1st stage-175# @140-425(2nd stage-237@ 800-1050), rated capacity-1100#on the pad, 1250#on the ground.
3) Detroit Eaton has on the shelf springs and can custom build. On the shelf springs available; FRONT- 6 leaves w/304# spring rate & 865# load rate. OR
7 leaves-410/950#
REAR- 4/3 leaves w/1150# load rate(no spring rate given) OR 8 leaves w/248# spring rate-1425# load rate.
4) 114" wheelbase, 60.5" track width front, 61" track width rear (wheel c/L to c/L)

With requested requirements and the information supplied, how would you set up the old buggy? olnolan

Comments welcome from others too, especially if you've worked with four wheel leaf spring packages. olnolan

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Last edited by OLNOLAN; 07-01-2010 at 07:38 AM. Reason: more detail
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Old 06-28-2010, 02:20 PM
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Gien the weights involved I would go this way..And it is a given that tuning a suspension involves some guesstimatation so here we go..

On the steering box i would order a repalcement item from borgeson and ditch the rack and pinion..I know I know the rack and pinion is the fad of the moment and in fact workss fine with a suspension designed from the get go for rack and pinion..but yours was not..you can get several different ratios including some fast steer boxes suitable for autocross or road course and of course I would have power steering.

Spring rates i would run a 350# spring up front and about a 150# rear..Ladder bars would be good but mount them close together up front like a modified truck arm..aftermarket sway bars make the front one fixed rate and the rear one adjustable rate in order to help tune the oversteer/understeer character of the car..On your truck I would plan a pair of auxillary air bags just in the event that you need to haul something.

Most of all get yourself some good books like Tune to Win by Carroll Smith and there are several good ones from Steve Smith Autosports that go into depth on suspension tuning..Most of those are for the circle track guys but if you can tune it to turn left then you cam balance the car to go right as well..one just forgets the special circle track stuff such as wedge in that case..

In any case take a hard look at the primary use of the vehicle and plan accordingly..

Sam
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Old 06-28-2010, 08:21 PM
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'57 chevy p/u

Hey Sam, I appreciate your reply. I like the way you're thinking, soft spring, big bar. I think I like the way I think it will ride. Sound crazy? Well, the plan has to move forward, the rack & pinion has to stay, its the most viable solution to alot of integration required to use all the Camaro donor parts.The engine and associated wiring and computer components including the steering column are being used to keep cost down. I'm trying to pin down the spring rates to avoid having to second guess my spring choice. I don't want to re-invent the wheel, I just want to improve the original design.

On the thought of ladder bars in conjunction with leaf springs, would the front mount have to slide a bit or solid helm joint mount? You got me curious?

Lets talk more about this while waiting for Mr. Billy to reply. olnolan
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Old 06-29-2010, 08:01 PM
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Bump

Bump,bump, Bump Bump Bumb
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Old 06-29-2010, 08:19 PM
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Ladder Bars

Hey Sam, I have never tryed ladder bars on anything. Which set up are you suggesting. Heres some traction setups;http://www.competitionengineering.co...s/chassis2.asp

Not sure I understand how the housing floaters work?
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Old 06-30-2010, 04:16 AM
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Those guys build a good setup and know what they are doing..The floaters serve to end the issue of suspension bind when using leaf springs..myself I would just bite it and use coils..BTW replacement coils from stock car products are only 40/50 each if one misses on the spring rate so it is not an overwhelming budget bender to change a coil if one needs to do some tuning..we used to take a whole box of those as well as extra shocks to tuning day at the track in order to tune the suspension to the drivers liking..Just an FYI..

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Old 07-01-2010, 06:35 AM
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Missed your new thread after the PM. Sorry.

For your application, I'd stick with basically the stock suspension.

If you feel you must change it, I would agree with OMT: Ditch the leafs and go to coils. Unless your sponsor is a leaf spring supplier, there's little justification in attempting to adapt ladders and such.

Wouldn't exceed 125 pounds per inch WHEEL rates.
http://www.racetec.cc/shope
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Old 07-01-2010, 06:56 AM
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Quote:
Originally Posted by BillyShope
Much appreciated that you've made all that information available.
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Old 07-01-2010, 07:23 AM
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Spring Rate/wheel Rate

Hey Man, Thanks for looking at my setup. So, you're saying to stick with the factory spring rates? How do you calculate the WHEEL rate versus the SPRING rate. Or visa versa?

The general plan is to just improve what the General(GM) put in it to begin with. I'm just hard headed and stubborn about cutting the suspension out and starting fresh, I want to keep the stock design and improve it to eliminate some of bad attributes.

When these old trucks are well lubed(solid leaf spring bushings) and with taller sidewall tires the front ride is not too bad. The rear on the other hand is way too stiff and jouncy without any load. Bumpsteer and steering box slop, along body roll are the other poor attributes.

The rack & pinion assembly I'm going to use is supposed to eliminate a great deal of the bumpsteer and make the steering more precise. The front and rear sway bars will eliminate alot of the body roll. I'm close to what I want, but need help in choosing the proper SPRING rates.

This is a street cruiser, its not like I'm going to try and run an autocross course with it. The ladder bar thing was just a discussion, I'll very likely run a slide-link traction bar system to prevent wheel hop and get a half decent holeshot if I want to bring it to the drags on Friday night.

Sorry about the long wind, but I'm trying to get help it the areas that I'm not too knowledgeable about. Nolan

Last edited by OLNOLAN; 07-01-2010 at 07:39 AM.
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Old 07-01-2010, 07:50 AM
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With the springs bearing directly on a beam axle, the spring rate is the wheel rate. Obviously, lateral spring spacing affects the roll stiffness.

With an IFS (or in the case when the spring is mounted on a trailing arm attached to a beam axle), the linkage ratio must be taken into account. If the linkage ratio is, say, 1.5 to 1, the wheel rate is the spring rate divided by 2.25 (or 1.5 squared).

Stopped to do a little googling and found this:

http://www.miracerros.com/mustang/t_wheel_rate.htm

His "motion ratio" is my "linkage ratio." Also, rather than work with trigonometric functions, it's usually easier to measure the distance from the pivot to the spring centerline on a line perpendicular.
http://www.racetec.cc/shope
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Old 07-01-2010, 08:19 AM
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Spring Rates

Okay, So the wheel rate is the spring rate on a beam axle. With that understood, are you still suggesting no more than 125# spring rates at all four wheels?
Seems like the 125# would be too soft for the front given the 1995# curb weight of the front end, 1365# rear curb weight could definitely use the softer spring to get more of a car type ride considering I'm never going to put anything in the p/u bed.
Help me understand this. I'm going to have the springs custom built by Eaton as per this information. I appreciate you taking the time to discuss this.
Nolan
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Old 07-01-2010, 01:01 PM
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Personally I think I would go for about 300 or 350 in the front..the 125/150 in the rear is fine..you may wish for some aux airbags in order to stiffen things up a bit if you need to..this suspension stuff has lots of compromises to it in order to get a decent ride and it sthandling..Myself I like them a bit stiffer than some to get the cornering that I like..

You might wish to use the field expediant method and just remove some leaves from the stock springs and give it a test hop or two..if all the bolts are clean and well lubed changing a leaf spring is not all that hard.



Sam
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Old 07-01-2010, 02:13 PM
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Thank You Sam

Thanks for the help Sam, You advice is greatly appreciated. I think I'm getting closer to having enough information to at least talk intelligently with the spring manufacturer. With the stock springs having a 304# spring rate in the front and the 1st stage of the rear having a 175# spring rate(adds a 237# spring rate when you get on the 2nd stage overload section) total of 412#. I may be closer than I thought, with just the second stage of the rear being a bit too stiff.

I don't know what happened to Billy, he left me somewhere between leaving it stock and no more than 125# WHEEL rate, which I gather is my SPRING rate.

Again Sam, thanks for taking the time to discuss it. When you mention leaf spring suspension with a straight axle in most circles, people just tell you to whack that crap out with a torch and get IFS, then whack out the rear and get a four link. I just march to the beat of a different drummer, I'm gonna make this old buggy spring truck drive and ride good with the original design. No cutting torch required. Nolan
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Old 07-01-2010, 03:33 PM
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With a beam axle, both wheel rate and roll stiffness must be taken into account. When one wheel drops into a pothole, the situation is quite different from hitting a speed bump. The speed bump situation is akin to that which I referenced when I said the spring rate is equal to the wheel rate. Unless a hefty sway bar is used (which increases manufacturing cost), however, a compromise is necessary. This results in spring rates which cause you to lose your fillings when you hit a speed bump, but are otherwise acceptable when a pot hole is encountered. At the front of the car, steering requirements move the leafs close to the car's centerline, resulting in a greater compromise (and higher spring rates) than at the rear.

Since I hate trips to the dentist, I'd go to a lower rate at the front and sneak in a sway bar.

The following is a post from another thread:

A very popular reference book among suspension engineers is Race Car Vehicle Dynamics by William and Douglas Milliken. (It can be purchased through Amazon.)

On page 582, ride frequency ranges for different vehicle types are given. For a sports car, the range is from 70 to 90 cycles per minute. For a passenger car, 30 to 50 cycles per minute.

With an 800 pound corner weight, the 150 pound per inch wheel rate would put you right in the middle of the sports car range.

For greater convenience, the ranges can be expressed as a multiplier, which, when multiplied by the corner weight, gives you the wheel rate. For sports cars, from 0.139 to 0.23; for passenger cars, from 0.026 to 0.071 .
http://www.racetec.cc/shope
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Old 07-01-2010, 04:53 PM
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If this were mine and I had to turn this into something doable in the shop I would stick with the stock springs up front..remove some leaves in the rear to get me close to 125/150 in the rear..add the slide-a-links and some sway bars.

Once that is done we can now work on shock valving I have found that alot of issues with ride and handling are traceable to shock selection..

Sam
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