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My car is a mostly street driven 65 Mustang fastback with a stroked 351W (about 475FWHP), G-Force (T5) 5spd. and drag radials. I was running a 4.33:1 ratio but will be changing to a 3.89:1 ratio when my new N-case and 31 spline axles are ready in a few weeks.

I am planning to replace the very tired (2.5&quot
rear leaf springs, and am trying to decide what spring and spring rate to use. The car sits about an inch lower than stock, and has the Shelby A-arm mods, big sway bar etc. I realize this is far from ideal for straight-line traction, however I am looking for a balance between traction and a car with decent road manners. When I take it to the strip I will run a real slick, and hope to run somewhere in the 11's

From what I have read the Flexi-Form springs and Cal-Tracs make a great combination for drag racing. Is anyone using this combination on the street? Are they okay? Will they last?

Perhaps these are over-kill??? and stockish steel leafs would be fine??? I would like to hear your opinions, and recomendations for spring rate.
 

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Replace the second spring with a longer spring from a spring shop that will extend forward past the center line of the front spring bolt by 1 inch. If you use slapper bars extend the bar so that the snubber lines up with the center of the eye(front spring bolt) and has 1/4 inch clearance on pass side and 1/2 on drvs side......the combo works good for 11.20s and up!
 

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I went from a 5 leaf to the mono leaf, better ride and responce. the mono leaf has no binding and fits great with the caltracs. I think your suppose to take all the preload out for street driving but I havent tried that yet, I run the bars loaded at all times.
 

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Re: Rear leafs - what spring to use for good launch & good street manners

Where do you get the Flexi-form springs?

Are they safe for street use?

Thanks
 

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Re: Rear leafs - what spring to use for good launch & good street manners

I'm running Caltracs, stock leaves (41 years old), Rancho shocks. I'm in the low 1.6 60's foot range. The car drives fine, either with the Cals set for the track or loose for driving around.
 

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Re: Rear leafs - what spring to use for good launch & good street manners

Jeff,
A buddy of mine is running Cal-trac mono's and swears by them.
He went from a 1.59 to a 1.54 with ONLY switching from superstock mopar leafs to the mono's in his 67 Barracuda.
It made me raise my eyebrows too.
He drives the car about 1000 miles a year and says he has not noticed anything in terms of ill street manners with the mono's.
Next year, I'll be switching to the mono's.
 

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Re: Rear leafs - what spring to use for good launch & good street manners

Jeff, I went through the same last year on my 70. I decided on three reasons
1.needed new springs
2.talked to a friend ( an auto body man ) he said that any new supports under these older cars will help hold them together and make other improvements. He also said I would need them to run with his 12.0s chevy
3. I wanted to go faster and straighter, so talked with calvert racing then bought their mono springs and bars.
Results after installing them: the car improved in ride, stance, performance, and smoked the 12.0s chevy. I have no complaints of using mono springs on the street!:D
 

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Re: Rear leafs - what spring to use for good launch & good street manners

Of course you all know that this is a 2 year old thread and Jeffstar now runs in the low 11's??? :rolleyes: Maybe he will come back and tell us what he did.

Old springs can work well with the Caltracs and some adjustable shocks (such as the Ranchos.) At least in my case, the 4 speed car did its best with a fairly soft suspension. I got fairly consistent low 1.60's (1.60 flat was best) after I swapped in the Mono-leafs (from 5 leafs) and set the Ranchos to "3." Automatics would probably use a stiffer setting.

I did try the 5 leaf springs before I bought the Mono-leafs and the car went nearly a tenth slower and the street ride was teeth chattering unless the shocks were set at "1" or "2". No thanks. At the track, this route might have been fine with other types of suspension improver's, such as slapper bars.
 

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Re: Rear leafs - what spring to use for good launch & good street manners

New stock rear springs, Shelby underride traction bars, KYB gas-a-just shocks, Global West subframe connectors and a rear sway bar. 60 foots in the mid 1.50s. Should 60 foot better this Spring with the increased boost.
 

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Re: Rear leafs - what spring to use for good launch & good street manners

Good eye Dennis,

I went with a set of BOSS 302 leafs (re-arched 2 " higher). I bolted on my old Lakewood slapper bars after breaking the front bolt on one of the Shelby under-riders.

Of course you all know that this is a 2 year old thread and Jeffstar now runs in the low 11's??? :rolleyes: Maybe he will come back and tell us what he did.
 
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