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Discussion Starter · #1 ·
Rebuilding the rear on my 65 fastback.. going to replace among other things the tired rear leaf springs.
They sell them as what I assume is stock, and then for extra money you can buy 5 leaf heavy duty springs..
Are these worth the money or needed? Anyone have experience with these?
 

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only if you need them.
i put on Eaton OEM set and car rides smooth
 

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Discussion Starter · #3 ·
Read the article on leaf springs. Lots of mention of steel grades. It nothing about 4 leaf vs. 5 leaf. I was afraid the 5 leaf may make it too tall
 

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What sort of ride quality do you want? Everything else being equal, 5 leafs would lower a car a little vs. stock, not raise it.
 

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Sure, if you planned on adding a hitch for towing, carrying extra heavy loads in the trunk, or maybe giving my sister a ride.... otherwise I think it'll ride pretty rough (ok if that's your goal, right?)
 

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The last set of standard 4 leaf springs I bought, jacked the car up almost 2in. I had to install lowering blocks.
 

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I went with the 5 leaf HD springs (C5ZZ-5560-HD)

Pros
I can have 4 adults in the car (all my boys are in their 20s) and not have the a$$ end sitting low driving on our crappy roads out here. Since I am running an 8.8 Exploder rearend, it has an offset pumpkin which would hit the floor pan if using normal 4 leaf springs.
I have zero wheel hop and not running any slapper bars, CalTracs or anything.
Reduces body roll.

Cons
Rougher ride when just me in the car

When I decided to go with the HD springs, I was thinking that we would go on a lot of rides together so the car would be loaded often. The fact is it rarely happens and usually just me these days in it driving. So, would I do it again, not sure.
 

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I desperately needed new springs on my 66. I really, really, really wanted Eaton springs. However life gets in the way, got laid off from work and had the opportunity to buy some like new mid eye 4.5 leaf Scott Drake. Rated at 195# they are much stiffer then I wanted from Opthos so I bought them. They look well made. They really seem to compliment my Street or Track front suspension and springs.

While I would still prefer Eaton and the Eatons are the gold standard and what I would recommend. I would recommend the Scott Drake as the next option if cost is a concern. The SD leafs are made in India.
 

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are they worth it? that depends on a number of things;

what do you consider heavy duty
who makes the springs you are looking at
what do you want form the car
what are you willing to put up with

one option to consider is going with a 4 1/2 leaf spring. not as much spring rate addition, and you get the advantage o the 1/2 leaf to help prevent wheel hop.
 

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I've ran both 4.5 and 5 leaf in my 66. You should at a minimum run a poly or del-a-lum bushing up front to help the leaf rotate. The 4.5 has a tendency to squat on hard acceleration, but has a very nice ride quality, firm but not jarring. the 5 leaf is stiff, and does not give. The rear half leaf as compared to the 4.5 does allot to prevent the rear of the car from squatting. Just my $.02.
 

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4.5 reverse eye is what i run.
 

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For reference, with 235/60-15 tires on the rear with C5ZZ-5560-HD standard eye 5 leaf springs and 1'' longer GT shackles, I'm sitting at around 28-3/4'' to the wheel well lip. I don't find the ride too harsh at all, but may need to swap to a mid or reverse eye as I now have a 3'' difference in rake from front to back after changing to GT coils, 215/60-15 tires and Arning drop.
 

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Essentially you don't want overly stiff springs in back. These cars are light in the rear. You want the rear suspension to be compliant to the road surface and not stiff where it bounces over bumps and the tires loose contact with the road. You want to pick the parts to work with how you use the car. The Eaton mid eye is rated at 138# I think that's probably a good reference point. The SD springs I have are 195#. That's why I was questioning them. As I said before they seem to work ok. Maybe the 195# is rated differently from the Eaton or maybe my shocks which are Bilsteins have something to do with it. If your stocks springs are working fine, leave them
 

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If you are really cheap you can find a set of old leafs that are the size of yours and just add a leaf. You may have to experiment to fine tune the rate and ride height you want. This only works if you want stock ride height.

Another option (again if you are really cheap) is to add a set of helper springs for a compact truck like a ranger. Again you may have to experiment to get the ride height you want and the rate. A lot more work but cheaper.
 

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I got 4.5 mid eyes from Opentracker Racing, with Del-a-lum bushings. Ride is good and the bushings keep the rear under control in turns.
 

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Read the article on leaf springs. Lots of mention of steel grades. It nothing about 4 leaf vs. 5 leaf. I was afraid the 5 leaf may make it too tall
Properly arched 5-leaf springs won't make the car too high, but they will make it too stiff. Even the mighty 428 SuperCobraJet and BOSS 429 had 4-leaf springs.

The question is, what sort of driving do you do? If you are hitting cruise night at Dairy Queen, or even the occasional autocross, stock GT 4-leaf will do just fine. If you are track racing, get the 5-leaf. Worried about wheel hop? Get Traction Masters™. Not the fakes, the real thing.
 

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