Good reproduction rear springs

3321 Views 38 Replies 11 Participants Last post by yellow73sb, Jun 6, 2007

yellow73sb

Discussion Starter · Jun 2, 2007

Are there any good reproduction rear springs that sit flat when mounted? Seems like all of them have an arc after they are mounted. Mine has to be perfectly flat

1 - 20 of 39 Posts

gtr1999

· #2 · Jun 2, 2007

I haven't found any yet. I was told there were only 2 mfgs and maybe Eaton Spring now. I used ones made in Canada, Mexico, and even one a well known vendor said would work fine. They all required the 8" bolts to level the body. Some are a little wider and the 4 bolts hit them requiring grinding a radius in the spring to mount it. The glass ones require new shocks and had them same issues in addition to breakage.

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redvetracr

· #3 · Jun 2, 2007

have you tried Guldstrand??
....redvetracr

PS: I have a NOS/GM Daytona rear spring but I am afraid to give you a price...your 16 year old heart couldn`t take it.....and I wouldn`t want to be accused of killing you before you get to race your car.....:thud:

yellow73sb

Discussion Starter · #4 · Jun 2, 2007

I don't really want to spend the 300 on gulstrands spring

TwinTurbo

· #5 · Jun 2, 2007

rule #1, the good stuff costs $$$$

turtlevette

· #6 · Jun 2, 2007

TwinTurbo said:
rule #1, the good stuff costs $$$$

Rule 2

smart dudes can figure out how to make cheap stuff work. I revised the mount on my trw spring to get it up 1" and cut it to shorten it.

Yes you CAN cut a fiberglass spring.

TwinTurbo

· #7 · Jun 2, 2007

exception to rule #2, some cheap junk just won't work, no matter how hard you try. See, he wants a spring combo that is uncommon, and uncommonhard to come by stuff is expensive. How can he make a cheaper spring perform the same way? glueing 2 together maybe?

MYBAD79

· #8 · Jun 2, 2007

TwinTurbo said:
How can he make a cheaper spring perform the same way? glueing 2 together maybe?

No, you have to weld them together... the process is similar to welding three flexplates together to make a flywheel.... but the two springs must be clocked perfectly !!!

:rolling:

turtlevette

· #9 · Jun 2, 2007

TwinTurbo said:
exception to rule #2, some cheap junk just won't work, no matter how hard you try. See, he wants a spring combo that is uncommon, and uncommonhard to come by stuff is expensive. How can he make a cheaper spring perform the same way? glueing 2 together maybe?

do some welding on the trailing arms adding bolt mounts 2-3" inner. Then cut the fiberglass spring. The rate goes way up when you shorten it.

just an idea.

TwinTurbo

· #10 · Jun 2, 2007

That would be doable yes but there's no sure telling where to drill and what the rate would be. Anotehr thing is, this offset mounting way distort the flimsy stock trailing arm.

turtlevette

· #11 · Jun 2, 2007

TwinTurbo said:
That would be doable yes but there's no sure telling where to drill and what the rate would be. Anotehr thing is, this offset mounting way distort the flimsy stock trailing arm.

who cares if you measure the rate? You tune until you get the car handling the way you want. Make small changes then test the car on a track.

A moment arm of a couple 2 -3 inches is not going to twist the trailing arm that bad. Lots of this kind of stuff is done all the time in racing. Its not bubba. Even though the NCRS show n' shine guys think so.

I've not seen any of these guys laughing at this stuff doing anything at all that requires any brainpower.

BBShark

· #12 · Jun 2, 2007

turtlevette said:
do some welding on the trailing arms adding bolt mounts 2-3" inner. Then cut the fiberglass spring. The rate goes way up when you shorten it.

just an idea.

I'm not saying you are wrong but shortening a spring a few inches does not change the moment or the section modulus of the spring. Not sure I follow how your rate would go way up.

turtlevette

· #13 · Jun 2, 2007

BBShark said:
I'm not saying you are wrong but shortening a spring a few inches does not change the moment or the section modulus of the spring. Not sure I follow how your rate would go way up.

The section modulus is not constant across the length of the TRW. The spring action takes place in the last foot or so at the end. Cutting off the end has a significant effect on the overall rate. Make sure to cut equal amounts off each end or you will end up with a higher rate on one side.

You don't understand how shortening a section of anything makes the strength go up be it a steel beam, pencil or anything? Get out your statics book.

BBShark

· #14 · Jun 2, 2007

turtlevette said:
You don't understand how shortening a section of anything makes the strength go up be it a steel beam, pencil or anything? Get out your statics book.

I was not aware that you were talking about a spring of non-uniform cross section.

As for understanding how beams deflect, I have a very good understanding of that and stand by my statement that shortening a beam does not make the stiffness go "way up" as you describe. The moment does not change (in this case track width), the load does not change, the section modulus does not change. The only thing that changes is the deflection. If you were to measure the beam deflection at 2 inches in from the current spring mounting hole, I believe the difference would be negligible.

turtlevette

· #15 · Jun 2, 2007

BBShark said:
I was not aware that you were talking about a spring of non-uniform cross section.

As for understanding how beams deflect, I have a very good understanding of that and stand by my statement that shortening a beam does not make the stiffness go "way up" as you describe. The moment does not change (in this case track width), the load does not change, the section modulus does not change. The only thing that changes is the deflection. If you were to measure the beam deflection at 2 inches in from the current spring mounting hole, I believe the difference would be negligible.

The moment DOES change because the spring is shorter after being cut. Have you seen a TRW spring?. If you have you wouldn't be arguing with me. I also have the VBP fiberglass spring and that one is also much thicker at the middle and tapers towards the ends, so cutting off a inch or 2 will make a big difference on that one as well.

Raise and lower the car and watch which part of the spring deflects.

yellow73sb

Discussion Starter · #16 · Jun 2, 2007

TwinTurbo said:
rule #1, the good stuff costs $$$$

How do you know? Have you tested the parts on your car yet

I think I should just get coil overs. How much would they be. I think some cheap ones from speedway are 150 each. They should be fine. I would have to copy the one kit thats made over seas somewhere.

http://www.speedwaymotors.com/p/218...iPro-Carrera-Monroe-QA1-and-Bilsteinandi.html

http://www.speedwaymotors.com/p/556,148_Monroe-Racing-Oval-Track-Shocks.html

http://www.speedwaymotors.com/p/396...oil-Coil-Over-2-1and2andquot;-ID-Springs.html

BBShark

· #17 · Jun 2, 2007

turtlevette said:
The moment DOES change because the spring is shorter after being cut. Have you seen a TRW spring?. If you have you wouldn't be arguing with me. I also have the VBP fiberglass spring and that one is also much thicker at the middle and tapers towards the ends, so cutting off a inch or 2 will make a big difference on that one as well.

Raise and lower the car and watch which part of the spring deflects.

I am not arguing with you at all. I have not referred you to a textbook, questioned your understanding of the relative strength of pencils etc. etc. I have merely questioned your logic, without sarcasm.

However, I (again) stand by my statement and welcome you to offer proof that I am incorrect. The first issue that you must understand is that the moment DOES NOT CHANGE regardless of the length of the spring. The moment (statically and dynamically) is the force of that portion of the cars weight, on that wheel at the distance set by the distance between where the spring is fixed and the center of the tire. These are fixed, nothing changes regardless of the length of the spring. The moment is the same without the spring installed in the car!

This is my last post on this subject. If you would like to debate this further either email me or start a new topic. I doubt if the original poster is interested as he begaan this one looking for a spring that was flat when it was installed.

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turtlevette

· #18 · Jun 3, 2007

BBShark said:
This is my last post on this subject. If you would like to debate this further either email me or start a new topic. I doubt if the original poster is interested as he begaan this one looking for a spring that was flat when it was installed.

I'm giving him a way to lower the car with his existing spring, so it is very pertinent to his question.

you are confusing moment of the car itself with the moment placed on the spring. Shortening the spring places the same weight at a inner portion of the spring thus lowering the torque on the spring. Torque = force X distance. The spring becomes effectively stiffer when the force acts on a shorter moment arm on the spring itself.

The other added benefit is that most of the arc of the spring is in the last foot or so. Cutting off an inch or two lessens the overall arc which is the problem with new springs. The mounting point becomes higher allowing a shorter bolt.

I really don't want to continue with this tutorial either. I spend many hours training engineers and technicians and get weary of it.

OK...? Ok

P.S. I'm not being condesending or sarcastic. Going back to a statics text is a good way to refresh your understanding and the pencil is a visualization tool to get an intuitive understanding. If i decide to be sarcastic you will know and it won't be subtle. Didn't you see my posts on the other forum.?:laughing: Actually i suggest all posters in this section keep a statics as well as dynamics text handy for future C3 handling discussions.

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TwinTurbo

· #19 · Jun 3, 2007

I'll just add this, it's for a multi leaf but should give an idea based on what variables are in there

multi leaf spring rate (roughly) = (((leaf width * # of leaves)/12) * (((1000 * thickness) / length longest leaf eye to eye)^3))

Well, the fiberglass one isn't a multileaf, msot have a variable thickness and width...but the length....

Those dual mount leaf springs do exacty what Jim says, but the other way aroudn. They move the 2 mounts in and outboard to change the free length sticking out on the sides, this does change the spring rate.

TwinTurbo

· #20 · Jun 3, 2007

yellow73sb said:
How do you know? Have you tested the parts on your car yet

Have you ? :rolling: How do you feel over and understeer when daddy's driving :laughing: :laughing: :laughing:

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