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stiffer? a quick google search shows fiberglass' elastic modulus is 17.2 GPA, steel is 200GPA, so steel is 11.6x stiffer. to get the same effective stiffness, for a same length & width beam segment, the fiberglass spring will need to be approx 2.25x thicker (taller) to have the same spring rate as a comparable steel spring the way the equations work out.

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stiffer? a quick google search shows fiberglass' elastic modulus is 17.2 GPA, steel is 200GPA, so steel is 11.6x stiffer. to get the same effective stiffness, for a same length & width beam segment, the fiberglass spring will need to be approx 2.25x thicker (taller) to have the same spring rate as a comparable steel spring the way the equations work out.

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I can't dispute your numbers, they sound correct, but two points, he might have meant comparable weights regrading stiffness, and a "leaf" is not a solid member, but sliding members, where a composite spring is obviously solid.

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Okay, i gotta ask...

I've always seen the tremendous weight-reduction factor for FG leafs, that one is obvious, but FG just seems like an unlikely material for a spring. Do these things not break? Thats a LOT ov stress, and even more on a race car in corners. Are these safe? Sure, some here have track cars that never see real streets, but how about for a street car? or do you people drive these things (and abuse these things) on the street as well...???

I would love to save a massive chunk o' weight, but i'm leery. I'd also be leery about ordering them, as if they're not quite the rate, or height, load, whatever you wanted, there is no adjustment. How do you make SURE you order the right one...???

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Okay, i gotta ask...

I've always seen the tremendous weight-reduction factor for FG leafs, that one is obvious, but FG just seems like an unlikely material for a spring. Do these things not break? Thats a LOT ov stress, and even more on a race car in corners. Are these safe? Sure, some here have track cars that never see real streets, but how about for a street car? or do you people drive these things (and abuse these things) on the street as well...???

I would love to save a massive chunk o' weight, but i'm leery. I'd also be leery about ordering them, as if they're not quite the rate, or height, load, whatever you wanted, there is no adjustment. How do you make SURE you order the right one...???

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then don't buy any corvettes made in the last, oh 30 years or so, as IIRC they all used transverse fiberglass leaf springs in their IRS

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stiffer? a quick google search shows fiberglass' elastic modulus is 17.2 GPA, steel is 200GPA, so steel is 11.6x stiffer. to get the same effective stiffness, for a same length & width beam segment, the fiberglass spring will need to be approx 2.25x thicker (taller) to have the same spring rate as a comparable steel spring the way the equations work out.

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I can't dispute your numbers, they sound correct, but two points, he might have meant comparable weights regrading stiffness, and a "leaf" is not a solid member, but sliding members, where a composite spring is obviously solid.

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true, guess I'm a stickler for details I guess....there are 2 components to a part's "stiffness"--material properties and geometry. fact is, from a material property stand point, steel is MUCH stiffer. but a part can be stiffer with changes to the geometry to give more cross section.

but even looking at just a steel main leaf, which is what, 5/16" thick? the thinnest part of a fiberglass leaf would need to be approx 11/16" thick to get a comparable stiffness....

didn't bother looking at densities, steel is 7.85g/cm^3...a quick google search shows fiberglass as 2.5g/cm^3 or less (depending on glass to resin ratios), so you could have 3-4 times the volume of fiberglass in your part before it weighed more than the steel part.

so yes, stiffness per weight can be much better for fiberglass, if the space allows for the geometry differences.

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Okay, i gotta ask...

I've always seen the tremendous weight-reduction factor for FG leafs, that one is obvious, but FG just seems like an unlikely material for a spring. Do these things not break? Thats a LOT ov stress, and even more on a race car in corners. Are these safe? Sure, some here have track cars that never see real streets, but how about for a street car? or do you people drive these things (and abuse these things) on the street as well...???

I would love to save a massive chunk o' weight, but i'm leery. I'd also be leery about ordering them, as if they're not quite the rate, or height, load, whatever you wanted, there is no adjustment. How do you make SURE you order the right one...???

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FWIW, somewhere I have a flyer around promotingFG springs for class 8 semi's (80K stuff), and that would be huge weight savings, but I don't know if they are still marketed for that application. I have high confidence, except for situations that have extreme spring wrap up, and that means 1/4 mile, heavy car , slicks, 4 speed, etc, and that opinion is only based on gut feeling, not real world experience.

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Okay, i gotta ask...

I've always seen the tremendous weight-reduction factor for FG leafs, that one is obvious, but FG just seems like an unlikely material for a spring. Do these things not break? Thats a LOT ov stress, and even more on a race car in corners. Are these safe? Sure, some here have track cars that never see real streets, but how about for a street car? or do you people drive these things (and abuse these things) on the street as well...???


i bought the hypercoils leafs but not until i did some research on them and asked around on forums before buying them - their are guys using these springs on street. dirt. roadcoarse. and scca racing with great success - punishing them in the corners and never having one crack or break. They are pricey but i do like the fact i can pick my own spring rates...
I would love to save a massive chunk o' weight, but i'm leery. I'd also be leery about ordering them, as if they're not quite the rate, or height, load, whatever you wanted, there is no adjustment. How do you make SURE you order the right one...???

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I would love to save a massive chunk o' weight, but i'm leery. I'd also be leery about ordering them, as if they're not quite the rate, or height, load, whatever you wanted, there is no adjustment. How do you make SURE you order the right one...???

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Hmmm... more good answers. I'm sold.

Now, if i go better than give the manufacturer the rates/specs i want, and just give them a steel spring i would like duplicated in FG, that would be easier for them, yes?

And the last question... how much (ballpark) do a set o' Mopar style FG leafs run?

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I would love to save a massive chunk o' weight, but i'm leery. I'd also be leery about ordering them, as if they're not quite the rate, or height, load, whatever you wanted, there is no adjustment. How do you make SURE you order the right one...???

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Unless you're real sure of what you want, I'd avoid swap meets and online auction buying of the springs. Talk to a reputable supplier to verify what you want is what you get. They have been doing this a long time and can probably get you what you want. Sure you can't change the rate of a fiberglass leaf, but changes in mounting position are the same as a steel leaf.

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Hmmm... more good answers. I'm sold.

Now, if i go better than give the manufacturer the rates/specs i want, and just give them a steel spring i would like duplicated in FG, that would be easier for them, yes?

And the last question... how much (ballpark) do a set o' Mopar style FG leafs run?

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Depends on the manufacturer. Most can get you within the ballpark of what you want with their off the shelf product of few different rates and a few different arches. Creating an exact duplicate of a steel spring isn't necesssarily the best way to go because of the different properties of the materials, but they can give you better info than I could on the details.

Ball park price for fiberglass springs is around $300-400 each. If you want to get into any custom work the price would go up from there. FWIW, a truly custom spec, steel race leaf spring would be comparable in price. I'm not talking about the Espo style, bend em up +1 over stock leafs, but true custom built racing springs with teflon interliners, diamond point tips, hardened, and with consistent taper through each leaf.

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i bought my hypercoils a couple months back - they were 618 shipped. ; bought them through amazon s they have a bit of a discount:

http://www.amazon.com/HYP10231-Hyperco-Hypercoils-COMPOSITE-LEAF/dp/B003PNW8CW

refer to their website for the part numbers with the spring rates you want on page17-18 in the catalog:

http://www.hypercoils.com/leaf-springs.html

they offer spring rates up to 225 lbs

I'll post some pics of them if I get a chance tonight...

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Nice! curoius to hear how they work for you!

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sorry it took so long:

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Could you weight one before you put them on the car?
How did you decide what rate to choose?
When mounting them do they just slip in place of the steel springs or do they have to be mounted in rubber or something? Is there a maximum tourque spec when tightening up the u-bolts or anything like that?

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Could you weight one before you put them on the car?
How did you decide what rate to choose?

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Could you weight one before you put them on the car?
How did you decide what rate to choose?

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I weighed one on a car scale - 10 lbs! I'm gonna weigh them on a more accurate scale soon to see if thats correct

I choose the rate based on my previous experience with spring rates:

8kg (448lbs)on the front and 6kg(338lbs) on the rear - Max I'll ever go on the street again - not so great on the lower spine but awesome on the track - little to no body roll

6kg(338lbs) front and 4kg(224lbs) on the rear - tolerable on the street (barely bearable for the wife) - still great on the track - little body roll

now these were on a car 800-900 lbs less than my big old bbody

so I figure that with a 5kg (270lbs) front I figure a good match would be a 3.5kg (200lbs) rear in a heavier car should still have the firm feeling and roll I want but not so harsh of a ride that the wife would want to stay in the passenger seat!

This is all speculative right now - I'll see how well its put into action this summer - I also based this on the hotchkis setup for the ebodies which are running a 4kg(225lbs) front and a 3kg(160lbs) rear
and they are anywhere from 600-800lbs lighter than the bbodies...

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Thanks for the reply! Wow 10 LBS!!!! that IS light! When you ordered from Hypercoil did you or were you able to specify the lenght and segments. Like for my e-body I'd need 22 in the front and 35 in the rear to be able to bolt in?

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Thanks for the reply! Wow 10 LBS!!!! that IS light! When you ordered from Hypercoil did you or were you able to specify the lenght and segments. Like for my e-body I'd need 22 in the front and 35 in the rear to be able to bolt in?

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