leaf springs gone bad? - Vintage Mustang Forums

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post #1 of 26 (permalink) Old 03-27-2010, 04:56 PM Thread Starter
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leaf springs gone bad?

How can I confirm if my leaf springs are shot?

I was driving the 66 yesterday and hit a bump in the road at speed and my rear bottomed out hard. Drivers side rear took it hard. Tire got sliced up by the tire well.

Shocks are about 6 years old but only have about 10k miles on them. The car is begining to sag in the rear.

Thanks

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post #2 of 26 (permalink) Old 03-27-2010, 05:06 PM
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When we put those shocks in I seem to recall you have spring over shocks we took out. That was an indication back then that the springs were a little 'dated'

Nick
1965 Fastback 410c AOD - DT
1967 Fastback 347 FMX - Cruiser
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post #3 of 26 (permalink) Old 03-28-2010, 04:05 PM
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Nick knew my leafs were shot the moment I pulled into his driveway for the first time...

1965 convertible, 289 C-code upgraded to 4bbl
1965 coupe, 200, T5 - daily driver
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post #4 of 26 (permalink) Old 03-28-2010, 04:12 PM
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Don't confuse shocks and springs. The springs are OK if they sit at stock height. They can't go bad and still sit up there. Shocks can cause easy bottoming if worn. Cutting the tire on the fenderwell means your tires are too wide. The axle will go all the way to the axle snubber if you hit a big enough pothole, regardless of what springs and shocks you have, so if the tires contact, they are too big.

Since you say the rear is sagging, you do need springs. You can get "show correct" GT springs from Glazier Nolan for $185, including U bolts, eye bolts, and shackles.

Those yellow traction-action bars are killing your ride quality. Toss them and install a pair of genuine Traction Masters (not the cheap fakes), like the 66 GT350 had, when you replace the springs. You won't believe the difference.

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post #5 of 26 (permalink) Old 03-29-2010, 09:42 AM
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IMO with a warmed over 302 you don't need traction bars. Put in a set of 4.5 or 5 leaf springs and you will not have a problem with wheel hop and the car will still hook up OK.

I don't like the Traction Masters because of the welding and if you get the geometry wrong they will rip loose.

If you really, really want traction then (1) get a set of state-of-the-art summer (sticky) tires or (2) give Calvert racing a call. Calverts springs and traction devices are the absolute best bolt on traction devices made. Period.

John Bednorz

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post #6 of 26 (permalink) Old 03-29-2010, 10:09 AM
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Quote:
Originally Posted by 68RCodeConv View Post
IMO with a warmed over 302 you don't need traction bars. Put in a set of 4.5 or 5 leaf springs and you will not have a problem with wheel hop and the car will still hook up OK.

I don't like the Traction Masters because of the welding and if you get the geometry wrong they will rip loose.

If you really, really want traction then (1) get a set of state-of-the-art summer (sticky) tires or (2) give Calvert racing a call. Calverts springs and traction devices are the absolute best bolt on traction devices made. Period.
Hmmm… Stiff rear springs for that pickup-truck ride quality would not be my choice for traction control. Besides, wheel hop is not actually up-and-down, it's a twisting action of the axle. Traction Masters prevent this, without stiffening the ride at all.

Getting "the geometry right" on Traction Masters is dead easy. You install the bars on the rear plates, and clamp them to the rail at the front, and weld in place. Can't go wrong.

Then you have NO wheel hop, and a car your wife won't complain about the harsh ride.

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post #7 of 26 (permalink) Old 03-29-2010, 11:04 AM
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I agree with using a traction control leaf spring. (5 leaf, with 2nd leaf under the main
being nearly full length) Lots of history with that design, going all the way back to
WWII Jeeps which used a "military wrap" on the 2nd leaf around the main leaf's
bushing eyelet. Works really well. I've built many sets of these springs. They ARE
the better mousetrap. Most of the other solutions out there are ok for drag use but
don't compliment ride or handling.

You can't help but introduce bad geometry with Traction Masters. When welded in place
they lock up the front spring segment. Every time you hit the gas pedal the spring goes
to infinity for spring rate. They're one of the "features" that make Shelby's so interesting
to drive.

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post #8 of 26 (permalink) Old 03-29-2010, 11:48 AM
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I disagree. I have had TM's on my 66 for 20 years. Actually rides smoother with them than without. "Infinity" spring rate? nope. Doesn't work like that.


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post #9 of 26 (permalink) Old 03-29-2010, 01:53 PM
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Wow! I bow to your experience.
Not.
I'm not here to make it personal, so just the facts.....
Look at your diagram.
What you've got there is a parallelogram. The front segment will lock under torque
application. This is caused by unequal pickup points between the spring and the
traction bar. For practical purposes the spring rate the car sees then goes up significantly.
Since anything over 160#/in is too stiff, let's say it's safely way over that rate. Using high
durometer bushings in the traction masters makes the effect even worse. The result is "throttle on" oversteer. (conflicting angles would be the reason in summary)
These are all factual statements. Just because Shelby used something, doesn't change
the physics and doesn't mean it's the best.

I have a significant resume full of suspension and brake experience at GM, Ford, SVO, Global West and Akebono. I won't post unless I know that things work the way I say.....

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Last edited by GT289; 03-29-2010 at 01:56 PM.
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post #10 of 26 (permalink) Old 03-29-2010, 02:16 PM
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The limitations of the under rider design and the binds that they introduce into the system are well known/document in the annals of this site and hundreds of other locations.

However, in terms of street use, the positives almost always out-weigh the negatives because a street driven car is rarely pushed to the point where the limitations become apparent. Heck, my 410c powered 65 took 4 years before the limitation of the design reared its head in the form of a broken bar.

Nick
1965 Fastback 410c AOD - DT
1967 Fastback 347 FMX - Cruiser
1968 Fastback 408w T5 - Brute
1996 Dodge Viper GTS

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post #11 of 26 (permalink) Old 03-29-2010, 02:21 PM
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I have also installed them in maybe a dozen cars.

The parallelogram will NOT lock under torque, whoever told you that should be ashamed.

The pivot points of the parallelogram are free to pivot at all times. Really.


Quote:
"I won't post unless I know that things work the way I say..... "
I think you'll need to prove it at this point. Documentation of "infinite spring rate" when using Traction Masters would do.

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Last edited by 22GT; 03-29-2010 at 02:38 PM.
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post #12 of 26 (permalink) Old 03-29-2010, 02:36 PM
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Quote:
Originally Posted by dodgestang View Post
The limitations of the under rider design and the binds that they introduce into the system are well known/document in the annals of this site and hundreds of other locations.

However, in terms of street use, the positives almost always out-weigh the negatives because a street driven car is rarely pushed to the point where the limitations become apparent. Heck, my 410c powered 65 took 4 years before the limitation of the design reared its head in the form of a broken bar.
Were they Traction Masters™ or imitation? The fakes are typically made with much thinner tubes.

That said, anything can be broken, at some point, else you'd never hear of race cars dropping out, or tanks broken down on the battlefield. I haven't broken my Traction Masters, in maybe 200,000 miles of driving, but I'm running a blueprinted and port-matched 289 High Performance. A 428 CJ, or even a 351C 4V might be enough to tip the balance.

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post #13 of 26 (permalink) Old 03-29-2010, 03:48 PM Thread Starter
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Thank you all for the input. I think I'm going to take a little bit from everyone here...

Replace the leafs with some Eatons from NPD
Replace the rear shocks
Dump the traction bars (ugly anyhow)
Install the trac-loc or tru-trac
Replace the rear tires. Currently 245x40.

Sounds good to me.

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post #14 of 26 (permalink) Old 03-29-2010, 03:53 PM
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Sounds like a good plan.

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post #15 of 26 (permalink) Old 03-29-2010, 03:57 PM Thread Starter
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So how does replacing leaf springs rate as a driveway job?

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