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unit91 06-20-2013 06:31 AM

Springs or Shocks ?
I have a 68 base convertible. How do you tell if the rear leaf springs are weak, or if it's the shocks and not the springs. I did the old test of pushing down on the rear bumber and letting go to see how many times the car bounced and it only bounced once. Springs are originals as far as I know, and the shocks are about 5 years old. When I drive I'm feeling a floating sensation in the rear end when I go over a rise in the road. Feels like the rear end is kind of hanging up in the air and then floating back down, if that makes sense. Never felt that before until about 2 weeks ago.

Helo-tech 06-20-2013 08:16 AM

contrary to popular belief, the shocks don't actually hold any of the cars weight (unless they are air shocks), so if the back is sagging, it's the springs that are week.

28HopUp 06-20-2013 10:30 AM

^^^Good Info^^^

If the rear springs have never been replaced, then chances are that the rubber bushings in the fore & aft positions of the leaf springs are original too. They may be totally shot, allowing the entire rear suspension to shift as you drive over the peaks and valleys of today's roads. If the rear-end is not sagging, then I would check out the bushings, and make sure all other attachment points are tightly secured. Check to make sure the mounting holes for the rear shackles are not elongated or rusted/rotted.

unit91 06-20-2013 12:07 PM

Good to know! What do the rear shocks actually do then?

Will check bushings, mounting holes, shackles, etc.

The rear end does sit lower than the front. All I have in the trunk is a tool box, spare tire and rim, and a' miscellaneous' box. Not too much weight.

AzPete 06-20-2013 01:59 PM

The shocks keep the car from bouncing numerous times after a bump has been hit with a tire. The springs control ride height, load capacity and assist in overall stability.

unit91 06-20-2013 02:32 PM

OK. Makes sense. I'm starting to put all this together and I'm thinking that by the way the car feels I need to replace the springs.

Thanks to all for the input!

unit91 06-20-2013 06:21 PM

Checked everything and all appears to be tight. I parked on a concrete floor and measured the distance from the floor to the springs and the shock supports, and the left side is more than an inch lower than the right. I'm wondering, will new stronger shocks solve this? Would they raise the car, or would new springs be needed to do that?

petrock 06-21-2013 07:14 AM

Shocks do not effect ride height. They are there to prevent harmonic oscillation that occurs when a spring is compressed/released. In other words... They help suppress the springs natural tendency to go 'boing-boing-boing' and keep the tire on the road. Ever drive down the highway and see another cars tire bouncing up/down or appearing to vibrate up/down? That is what happens when your shocks are bad. When the tire is bouncing like that, you will feel the car walk/wonder all over the place. Especially at highway speeds. If that is what you feel, then most likely your shocks are bad.

As for the different heights on each side, make sure your rubber bushings are all good. They are rubber and deteriorate over time. So if they have started to squish/crack/turn-to-dust/deform, then it will effect your ride height. Before changing the springs I would check out all the suspension bushings and replace any that look bad. I’d recommend polyurethane bushings (Energy Suspension or Prothane). If the springs are original, then chances are so are the bushings. Most rubber bushings don’t last more then 10-15 years in good climate weather.

The control arm bushings on my wifey's ’98 mustang were almost completely shot, and we live in an area with really nice weather. I replaced them all with Energy Suspension’s poly bushings a few months back and the ride height went up about an inch (rough estimate). Just sayin’...

Helo-tech 06-21-2013 08:07 AM

it's not unheard of to have one leaf spring sag more than the other over time, they are not always tempered the same way and at the same time. and the fact that the drivers side is sagging more may be because most of the time, there is only the driver in the car. so more time with more weight on one side can do it. you would be best to do some research and see what the factory ride height is supposed to be, it seems to me that the rear ends on that era cars was lower right from the factory. if so, getting new springs probably won't help the sag much because they should be built to give the factory stance, you may have to use some longer shackles to get a more agressive rake to the car.

unit91 06-21-2013 10:30 AM

This is all GREAT info! I noticed that a couple of the brackets that wrap around the springs are so loose they move around. Could that affect the strength of the springs?

What about getting the longer shackles and leaving the springs on?

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