1961-63 Stock ride height?

[UGW]

Does anyone know how to determine if the REAR height of a 1961-63 Imperial is correct? I'm trying to figure out if my rear leaf springs are worn out. I like the way the car sits, visually, but yesterday I scraped the frame on a speedbump when I had 3 adults in the back seat. Same bump never scrapes when I am alone. That doesn't seem like it should happen. I replaced all the shocks last fall, but the car still feels a little "bouncy." I don't have anything to compare it to that would help me understand if it's just how an Imperial should be.

The service manual gives a procedure for measuring the front suspension and correct height range, but it doesn't say anything about the back except that both sides should be the same on level ground. It does note that even if the springs look flat or even slightly reversed, that necessarily doesn't indicate a problem.

 

[CBODY67]

Perhaps the best thing to do is to look at actual photographs of the cars when they were new to see where an imaginary line from the bottom of the rocker panel extends to the wheel cover, which can be done with the front and rear wheel covers.

As to the rear springs, it is perfectly normal for the "loaded" ride height to be less than when there is only somebody in the front seat. It should also be noted that the passenger weights (quoted as the "number of passengers" in the car as to tire pressure and loading, in the owners and factory service manuals) are more like 150lbs each, which is NOW a bit light, all things considered.

A TOTALLY KEY thing is that the rocker panel should be parallel to the road surface, by design, when the car is unoccupied with no significant additional weight in the trunk. NO droopy front ends or rear ends, by design!!!

In the factory-provided specs, there should be a spec for "Ground Clearance". Which means the minimum amount of space between the car's body/frame and the flat road surface. In general, it seems like it was usually between 5"-6.5" for USA cars, back then. This spec has always been presumed with the car unoccupied.

Just some thoughts and observations.
CBODY67

 

[UGW]

Re: rocker panel to wheel cover line. I thought of that, but the angle of the picture can make that so subjective, and in the promotional material from the time, the Big 3 were always distorting proportions to make cars look lower or wider.

I like the idea of the rocker panel parallel to the ground! I have the procedure to confirm the front, so if the front in in spec, the distance from ground to rocker should be the same front and back. I didn't find a blanket "ground clearance" spec when I was looking, but I do know it's just high enough I can shimmy under the car without a jack.

 

[CBODY67]

Re: rocker panel to wheel cover line. I thought of that, but the angle of the picture can make that so subjective, and in the promotional material from the time, the Big 3 were always distorting proportions to make cars look lower or wider.

I completely concur with the "drawn art" of the time inconspicuously doing some work on proportions. GM and Buick seemed to be the masters of that art in the middle 1950s! Which is why looking at PHOTOGRAPHS instead is what should be sought out and found.

Whether it is the top of the rocker panel "line" extended or that of a solid piece of molding in that area, the "line extension" can work, too.

Enjoy!
CBODY67

 

[Boydsdodge]

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What I have found to be the correct ride height is stand back looking at the side and the bottom edge of rocker panel should go through the centre of the rear wheel. you can pull a string by tying or having a friend hold it at the front and then you pull it so it is just contacting the bottom of rocker panel with out drooping or bending up, now see where you are through the rear wheel. For the few times you are loading friends you can install airshocks and pump them up for the rowdy dates. Starting in 74 Chrysler offered self leveling rear suspension, it was a small compressor with a switch attached to rear axel and frame, when car loaded, the switch would trigger the pump to inflate the shocks and when emptied the compressor would release air to level. There are mondern air bag systems for self leveling that sit on rear axel and the side of frame rail with switch compressor setup. I have been looking into it for my Imperial, just gathering up the parts to make the switch set up. Then there is the modern self levelling shocks.

Nivomat Shock Absorbers: Self-Leveling Monotube Ride Control Units https://www.brakeandfrontend.com/nivomat-shock-absorbers-self-leveling-monotube-ride-control-units/​

 

[1962 Crown Conv]

A way to know for sure that your '61-'63 Imperial has correct rear spring height, is to get a new pair of leaf springs from Eaton Detroit Springs. They have the exact specifications.

All Imperial rear leaf springs eventually sag, in my experience, especially after 60 years. Previous owners may have put in an extra leaf to compensate for sag. Then the rear end sits too high. New springs restore the original ride, and they are great.

 

[UGW]

A way to know for sure that your '61-'63 Imperial has correct rear spring height, is to get a new pair of leaf springs from Eaton Detroit Springs. They have the exact specifications.

All Imperial rear leaf springs eventually sag, in my experience, especially after 60 years. Previous owners may have put in an extra leaf to compensate for sag. Then the rear end sits too high. New springs restore the original ride, and they are great.

That's actually my exact dilemma: I like the way the car sits now, visually. Looking at the eaton catalog, I'm trying to decide if I should go with stock springs (6 leaves), heavy duty springs (7 leaves), stock height, or 1" drop. (If I went with a drop, I'd probably use HD springs, because less travel should require more resistance.)

If the car is already sitting lower than stock, and I install new, stock springs, it may sit higher than I'd like. On the other hand, if it's currently near stock height, and I install dropped springs, making it even lower, the car might scrape. There are a few places around my neighborhood where clearance is already close - see original post.

 

[1962 Crown Conv]

Heavy duty springs are for towing a boat. Stock springs with 6 leaves are perfect. 1" drop will make the car look like it is going uphill.