Leaf vs coil springs

[CG]

I have a couple of C20 72's, one with leaf springs and one with coil springs. Curious why someone would want to order up leaf over what I assume is the normal for stock coil springs.

[Mike80D]

Curious as to what other optional equipment your leaf spring truck has. It might have been set up for a slide in camper.

[kwmech]

My personal preference is for a leaf sprung truck. Better and more stable loading. Easier to upgrade with either an airbag or overload. I had a coil sprung short bed years ago with a big block in it and it wanted to hop all the time when I got on it. I converted to leaf and it got rid of the problem

[CG]

Originally Posted by Mike80D

Curious as to what other optional equipment your leaf spring truck has. It might have been set up for a slide in camper.

Pretty basic truck without air

Plain Cheyenne package Z84
leaf spring
350 CI (3OTT)
4.10 rear gears
tach
belt molding
sliding rear window
white dark olive
tinted glass
am radio
black vinyl custom trim
chrome rear bumper

[Mike C]

Originally Posted by kwmech

My personal preference is for a leaf sprung truck. Better and more stable loading. Easier to upgrade with either an airbag or overload. I had a coil sprung short bed years ago with a big block in it and it wanted to hop all the time when I got on it. I converted to leaf and it got rid of the problem

Odd. That is backward over most peoples experience. One of the benefits of the trailing arm suspension is the arm prevents axle rotation which is what leads to wheel hop. Leaf spring “wrap” or windup is what causes wheel hop. You must have had terrible shocks and maybe some other geometry issues going on on that coil spring truck. I have CalTracs on my own leaf spring truck making it behave more like a coil spring truck…

For heavy loads I am in agreement that the leaf spring is the better tool, but for unladen drive ability the coils seem the better choice. For running exhaust, the leafs win far and away.

[factorystock]

Most people would agree the leaf spring system is more durable than coils, the reason it is used on 1 tons as standard equipment. From an engineering point of view, the leaf spring system attaches the axle to the frame at 4 points, the coil system attaches the axle to the frame at 3 points. When it comes to stability, 4 points is better than 3.

[garyd1961]

Leaf springs are cheaper to manufacture and install, probably better for hauling heavy weight also. Coil springs and trailing arms have a better ride and handling. Nascar uses a coil spring trailing arm setup also drag racers like a modified coil spring trailing arm setup. When it comes to pickups I believe the main reason for leaf springs was cost, cheaper and faster to install.

[GMCBubba]

My grandfather's 69 GMC C25 has leaf springs and Dana 60 rear axle. It is otherwise low option. It was a farm truck and routinely used for hauling a bed full of grain or hay. I assume he desired the leaf springs for load handling.

[Mike C]

NASCAR did use the trailing arm suspension for nearly half a century but the ‘car of tomorrow” or whatever they call it no longer has it.

And the new Ram 1/2 ton trucks are coil in the rear…

Clearly there are merits to both but I think the leaf wins out for load control with reasonable height and ride compared to the coils in an HD application, but the coils win the ride and drive in the 1/2 ton world.

[garyd1961]

As I said before I believe leaf springs were mainly a cost saving thing. You will be surprised at what a auto manufacturer will do to save a few bucks. I remember seeing brand new trucks coming into the dealership with rusty spindles, balancers, an other parts just to save a little paint. I thought it was pretty cheap of them to be able to open a hood of a brand new truck and see rusty parts with no paint. I even had to rattle can a few trucks before the customer would buy them. I believe I remember chevy going back to coil springs around 2011 but I don't think it lasted long,$$.

[CG]

Pretty sure all the Chevy 67-72's came with coil and trailing arms (not 4x4), leafs were an option as noted on the spids. Spids dont mention coils because thats how they came.

GMC may be a different animal though. More upscale than your Chevy and while Im not positive I thought Ive seen mention here on the board that leafs were very common on the GMC.

And now that Ive posted these two thoughts I'm sure someone will let me know how wrong I am haha!

[jgrote]

My 72 lists almost nothing on the SPID, but it does list leaf spring. It's originally a 307, th350 PS, PB truck.

[Accelo]

Originally Posted by jgrote

My 72 lists almost nothing on the SPID, but it does list leaf spring. It's originally a 307, th350 PS, PB truck.

I could assume your truck is a GMC. I believe leafs were standard on the GMC's.

[Bob B.]

For the most part, all '67-'68 U.S. built GMC pickups had rear leaf springs and Dana-Spicer rear axles. Chevy 4X2's had coil springs and Corporate/Eaton rear axles but leafs were optional. Starting in '69 it seems that you could order either truck either way. Remember that a SPID label lists what was optional, so you may not see leaf springs listed on a '68 GMC but you would see leafs listed on a '68 Chevy so equipped.

[jgrote]

Originally Posted by Accelo

I could assume your truck is a GMC. I believe leafs were standard on the GMC's.

Nope, it's a Chebby.

[sloGMC]

Originally Posted by CG

I have a couple of C20 72's, one with leaf springs and one with coil springs. Curious why someone would want to order up leaf over what I assume is the normal for stock coil springs.

I think it is similar to the more recent automotive debate of aluminum bodied F-150s vs more conventional steel bodies GMs and Dodges; there's pro's and con's to using either material and no clear winner. I'm guessing that trailing arm suspension was new in trucks at the time, so GM offered both and allowed the consumer (or more likely, the dealer) to select what they wanted.

To my knowledge there remains no physical evidence that GMCs were standard with anything other than coils, and instead there is evidence that GMC dealerships did not fully understand the different suspension/tire options available and how those played into GVW calculations.

[Accelo]

From the 1970 Chevy brochure.
It looks like the leaf springs were something like a heavy half ton option.

[sloGMC]

Originally Posted by Accelo

From the 1970 Chevy brochure.
It looks like the leaf springs were something like a heavy half ton option.

...except that the leaf springs always had the same base load ratings as coil, and coil springs could actually be ordered from the factory with a higher load rating using the G50 option, and/or G60 which wasn't even available with leafs. If you wanted a "heavy half", it would be smarter to order coil springs.

The exception of course is C30 where coils were not offered.

[Accelo]

I was attempting to use some type of logic.
Should have know better. LOL
Thanks for the education/information.

[factorystock]

Originally Posted by sloGMC

To my knowledge there remains no physical evidence that GMCs were standard with anything other than coils, and instead there is evidence that GMC dealerships did not fully understand the different suspension/tire options available and how those played into GVW calculations.

I would re read Bob B comments. He has the knowledge. Also, when it comes to '67-'72 GM pickups, generalizations are generally useless. Being year specific makes all the difference in the world, not to mention if U.S. or Canadian build truck. A good truck salesman would recommend leaf springs for heavy duty loads and coils for light duty loads if and when available.

[sloGMC]

I don’t doubt that “most GMCs came with leaf springs”. Mere popularity of equipment is not proof alone of it being standard equipment, however. I’m all for someone producing pages from a GMC Data Book to prove me wrong. I was looking at the ‘71 info kit and have no reason to believe the other years are much different. As for my comment on the salesmen, maybe they were different in years passed, but these days I wouldn’t count on them knowing every available option for each vehicle on the lot.

All this speculation and talk is in good fun, and I enjoy it. I want the record to be just as straight as anyone else.