Leaf Spring Change 5 leaf to? - Vintage Mustang Forums
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post #1 of 19 (permalink) Old 05-14-2019, 11:22 PM Thread Starter
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Leaf Spring Change 5 leaf to?

Like lots of us, funds dictated the purchase of budget-friendly leaf springs many years ago.

I purchased the Grabatrack 5 leaf reverse eye springs. As the car evolved, especially the front suspension, the stiffness of the rear suspension is noteable.

So there are two things I want when I change out the rear springs. Day to day driveability (a little less harshness) and better overall handling. (more compliant)

I don't want to lose any ride height and I have caltracs that fit the reverse eye springs. I think I can get a different front bracket, from calvert if I want a pair, butI'm not sure that's necessary yet.

In reading the 5 leaf springs that I have now are rated at 195 lb/in
TCP claims their 5 leaf is 140 lb/in
or 4 leaf at 112 lb/in

So if those numbers are correct, what do you think, is the 195 to 140 enough of a change?


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post #2 of 19 (permalink) Old 05-15-2019, 12:12 AM
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Here's another one I'll throw into the mix...GLOBAL WEST 150 RATE, REVERSE EYE

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post #3 of 19 (permalink) Old 05-15-2019, 01:35 AM Thread Starter
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Originally Posted by Mustmatt View Post
Here's another one I'll throw into the mix...GLOBAL WEST 150 RATE, REVERSE EYE
Yes, thanks, Global is good stuff as well. I guess I am asking if the rate difference will be that significant, or what rate I should be shooting for?


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post #4 of 19 (permalink) Old 05-15-2019, 06:23 PM
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I have the global west L-11 rear springs which I think are 165#
Its stiff but not super stiff....
What is your front setup?
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post #5 of 19 (permalink) Old 05-15-2019, 07:34 PM
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I just went from 4 leaf standard eye Grab-A-Trak (with KYBs) to 5 leaf reverse eye TCP (with Bilsteins). Other than lowering the rear a good 2", the ride is only a bit stiffer...but I need the control for the track. My car also has a Watts link that controls the rear end to the 9s...so you need to add that to the equation.


I'm of the belief that each vintage car reacts differently to identical setups, but that's just me (and my car is possessed, so take that with a grain of salt lol). You may just have to bite the bullet and buy a new set of 4 leafs and see if you like the difference.


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post #6 of 19 (permalink) Old 05-15-2019, 09:04 PM Thread Starter
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Quote:
Originally Posted by Jsams View Post
I have the global west L-11 rear springs which I think are 165#
Its stiff but not super stiff....
What is your front setup?
Front is a Hybrid, started with TCP UCA's and LCA's then Shaun came out with his system, so it's his coil-overs and Bilstein shocks, The front is about 1 3/4"-2" lowered, quite firm, It's necessary as with that much lowering, one does not to be bouncy. The front shocks make the difference there. TCP R&P



Quote:
Originally Posted by Sparky66 View Post
I just went from 4 leaf standard eye Grab-A-Trak (with KYBs) to 5 leaf reverse eye TCP (with Bilsteins). Other than lowering the rear a good 2", the ride is only a bit stiffer...but I need the control for the track. My car also has a Watts link that controls the rear end to the 9s...so you need to add that to the equation.


I'm of the belief that each vintage car reacts differently to identical setups, but that's just me (and my car is possessed, so take that with a grain of salt lol). You may just have to bite the bullet and buy a new set of 4 leafs and see if you like the difference.
After having had my car on the track and street, it's demonstrated a noteable enough oversteer to try and look at options. The other issue is day to day driveabliity.

You mentioned Watts link etc. I am not ruling that out, but want to get the right balance with the rear spring. I'd guess with the 5 leafs that I have now, they are about the stiffest that I can get, and contributing to the jumpiness of the rear set up
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post #7 of 19 (permalink) Old 05-16-2019, 03:28 PM
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Leaf Springs are really a crap shoot. I have 5 leafs that really are not that stiff at all. In fact I clamped the front half of the spring and that didn't really change the spring rate that much surprisingly. It did make the car handle fantastic especially noticeable under trail-braking into a turn.



If you spend any time on the hairy edge of traction (autocross or track), a watts link is game changing in terms of letting you know exactly what is going on back there and if you break loose, you can gather it up without any drama. Its easy to find and hang on the hairy edge of traction. If not, you probably won't really notice its there unless you jerk the wheel from side to side quickly to wag the tail so-to-speak.
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post #8 of 19 (permalink) Old 05-16-2019, 05:08 PM
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I went a bit cheap as well with the SD reverse eye 5 leafs that i think are rated #155 on a '66. I wouldn't call them stiff at all. Firm but compliant motion to me.
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post #9 of 19 (permalink) Old 05-16-2019, 06:11 PM
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Originally Posted by dobrostang View Post
If you spend any time on the hairy edge of traction (autocross or track), a watts link is game changing in terms of letting you know exactly what is going on back there and if you break loose, you can gather it up without any drama. Its easy to find and hang on the hairy edge of traction. If not, you probably won't really notice its there unless you jerk the wheel from side to side quickly to wag the tail so-to-speak.

Game changer indeed. The Watts (Fays2, in case you're wondering) *completely* changed the driving attitude of my car. It's scary how much that rear end used to move left & right. Now it stays centered, where it's supposed to be. Nice and predictable, like dobrostang said. It has little effect on "up/down" though, so it doesn't stiffen the rear. It just makes it behave lol.
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post #10 of 19 (permalink) Old 05-16-2019, 10:43 PM
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Quote:
Originally Posted by ripped View Post
Yes, thanks, Global is good stuff as well. I guess I am asking if the rate difference will be that significant, or what rate I should be shooting for?
The rear is light. It responds well to something a bit stiffer than the "GT"
spec rear spring rate. We ran a 150# rate in 65-68's.
In direct answer to your question, a 10-15# change in the back is a
significant one. I think you'll find 160's are absolutely the stiffest rate
you would EVER want to run in the back.

ex-Global West GM
1991-1995
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post #11 of 19 (permalink) Old 05-16-2019, 10:52 PM
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Quote:
Originally Posted by Jsams View Post
I have the global west L-11 rear springs which I think are 165#
Its stiff but not super stiff....
What is your front setup?
L-10 are 150#
L-11 are 160#
L-12 are 170#
These rates aren't posted anywhere that I'm aware and not widely discussed.
150's are the ones generally recommended unless you're talking purpose-built
race car. The 170's are really not intended for 65-68's. We used them on the
later cars that were like B302 race cars and 71-up race applications.
They're super stiff, even with a low-drag bushing like a del-a-lum.

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post #12 of 19 (permalink) Old 05-17-2019, 01:42 AM Thread Starter
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Quote:
Originally Posted by Jsams View Post
I have the global west L-11 rear springs which I think are 165#
Its stiff but not super stiff....
What is your front setup?
Thanks

Quote:
Originally Posted by dobrostang View Post
Leaf Springs are really a crap shoot. I have 5 leafs that really are not that stiff at all. In fact I clamped the front half of the spring and that didn't really change the spring rate that much surprisingly. It did make the car handle fantastic especially noticeable under trail-braking into a turn.



If you spend any time on the hairy edge of traction (autocross or track), a watts link is game changing in terms of letting you know exactly what is going on back there and if you break loose, you can gather it up without any drama. Its easy to find and hang on the hairy edge of traction. If not, you probably won't really notice its there unless you jerk the wheel from side to side quickly to wag the tail so-to-speak.
I've looked at quite a few different iterations but am leaning to making the leaf spring suspension as good as I can, including looking at a watts link (if I can get the tailpipes past it)

Quote:
Originally Posted by Sparky66 View Post
Game changer indeed. The Watts (Fays2, in case you're wondering) *completely* changed the driving attitude of my car. It's scary how much that rear end used to move left & right. Now it stays centered, where it's supposed to be. Nice and predictable, like dobrostang said. It has little effect on "up/down" though, so it doesn't stiffen the rear. It just makes it behave lol.
Thanks

Quote:
Originally Posted by GT289 View Post
The rear is light. It responds well to something a bit stiffer than the "GT"
spec rear spring rate. We ran a 150# rate in 65-68's.
In direct answer to your question, a 10-15# change in the back is a
significant one. I think you'll find 160's are absolutely the stiffest rate
you would EVER want to run in the back.

ex-Global West GM
1991-1995
Thanks that's helpful


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post #13 of 19 (permalink) Old 05-17-2019, 08:31 AM
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Quote:
Originally Posted by ripped View Post

(if I can get the tailpipes past it)

Thanks that's helpful

That's a big if, most of them I looked at recommend dumps. I designed and fabricated my own WL in such a way to make room for the exhaust.


BTW, are you sure its not your shocks driving the stiffness? Try backing off if they are adjustable or if they are airshocks dump em...
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post #14 of 19 (permalink) Old 05-17-2019, 01:58 PM
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My exhaust guy hates me, as he had to custom route my exhaust over/around the Watts. But the Fays2 isn't terribly obstructive, IMHO.
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post #15 of 19 (permalink) Old 05-17-2019, 08:49 PM Thread Starter
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Quote:
Originally Posted by dobrostang View Post
That's a big if, most of them I looked at recommend dumps. I designed and fabricated my own WL in such a way to make room for the exhaust.


BTW, are you sure its not your shocks driving the stiffness? Try backing off if they are adjustable or if they are airshocks dump em...
I just have the very stock generic hydraulic shocks on there right now. I broke one of the bilstien rear shocks about a year and a half ago, so the remaining shock was taken off.
Due to the lowered stance there is quite an angle on the shock, so I wanted to rethink the mount before replacing them.
The car is so hideously loud that I would not be able to just dump the pipes. I need the tailpipes and resonators to help keep my sanity.

Quote:
Originally Posted by Sparky66 View Post
My exhaust guy hates me, as he had to custom route my exhaust over/around the Watts. But the Fays2 isn't terribly obstructive, IMHO.
Sounds promising. I'll definitely look at that once I decide on springs.


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