1963 Ride Height & Gas Charged Shocks

[Frederick H.]

Just got one of the rear shocks installed (gas charged AC Delco or whatever brand it was before they stamped it) on the driver side and not surprisingly, the ride height increased by over 1/2 inch. The car already sat too high at 28 inches in the rear before the install and still an inch too low in the front (the front has the same new gas charged shocks installed). The rear should lower a bit after I get the spare tire & carrier back in and drive it a bit but am concerned that it won't lower by 2 inches (specs from the ASM). Other than the crazy expensive repros from Zip and Corvette Central, are there any new shocks that aren't gas charged? Would that even make a difference?

Thanks in Advance,
Fred

[Duke W.]

Re: 1963 Ride Height & Gas Charged Shocks

There are low pressure and high pressure (deCarbon type) shocks, like Bilstein. I assume the "Delco" are low pressure type. How much force does it take to compress them?

Are the front and rear springs OE? If not, what are the spring rates?

I don't understand how you measured ride height to get 28". What is the D dimension as explained in the shop manual and AIM relative to spec? The D dimension is independent of tire diameter. Other "ride height" dimensions depend on tire size. The inflated OD of the OE 6.70-15 tires is about 27.4". What size tires are installed and what's the inflated OD?

Duke

[Frederick H.]

Re: 1963 Ride Height & Gas Charged Shocks

1) I do not have the tool (shock dynomometer) to accurately measure force required to compress the new shocks. Manually depressing them results in a travel of approximately 4 inches.
2) Front and rear springs are not original to the car but are original springs. (I checked leaf measurements some time ago after referring to threads in this forum to confirm proper width & thickness).
3) Rear springs: I measured floor to top of wheel well opening as described in the AIM for Dimension R, showing 26.03 inches at curb weight photos attached).
4) Current tires are UniRoyal Tiger Paw 205/75 with inflated OD approximately 26".

Would prefer non-gas charged shocks if any non-repros are available.

[Stephen L.]

Re: 1963 Ride Height & Gas Charged Shocks

Fredrick, I assume you have a AIM for your car. Look for pages that are titled "FRONT TRIM HEIGHTS" and REAR TRIM HEIGHTS".
On those pages you should see tables that identify dimension "Z" for the front and dimension "D" for the rear. These are the dimensions "as shipped from the factory. You will note that these dimensions are NOT affected by the tire size, inflation etc. (There is a +/- table for options)
These dimensions are taken when the car has full curb weight on the suspension.
The front dimension can be influenced by the front springs (rates etc.) and shocks (if the shocks are doing some of the support work.)
The rear dimension can be influenced by the spring rate, the long bolts and rubber donut condition on the spring ends as well as the shocks (again, if the shocks are doing some of the support work)
If you suspect the shocks are influencing the ride height, disconnect the shock on one end and check the "D" dimension against the spec. This will indicate if you have a spring or shock problem or a combination of both.
The original shocks were not meant to support some of the car weight..... only prevent excessive bounce.....

Good luck.

[Frederick H.]

Re: 1963 Ride Height & Gas Charged Shocks

Thanks Stephen. The AIM sections I was using are Section 3 Sheet 6 for the front height and Section 4 Sheet 6 for the rear. Let me know if you are referring to a different section. The long bolts are the originals but cushions could use replacing. As I mentioned, it rode high before adding the shocks. I don't think I will have a true result until I get a full tank of gas, installed spare tire & tub, and drive it regularly. Thanks.

[Stephen L.]

Re: 1963 Ride Height & Gas Charged Shocks

I don't have a '63 AIM. Mine is a '67. That is why I refered to the page "titles". It sounds like you are using the correct pages and information.
IMHO measuring from body to floor introduces many variables; tire size, inflation, body abnormalities etc.
So by using the procedure I described you eliminate those variables. If the "Z" and "D" measurements are within spec then you have a possible problem elsewhere causing the body to be hi/lo........

[Duke W.]

Re: 1963 Ride Height & Gas Charged Shocks

1) I do not have the tool (shock dynomometer) to accurately measure force required to compress the new shocks. Manually depressing them results in a travel of approximately 4 inches.
2) Front and rear springs are not original to the car but are original springs. (I checked leaf measurements some time ago after referring to threads in this forum to confirm proper width & thickness).
3) Rear springs: I measured floor to top of wheel well opening as described in the AIM for Dimension R, showing 26.03 inches at curb weight photos attached).
4) Current tires are UniRoyal Tiger Paw 205/75 with inflated OD approximately 26".

Would prefer non-gas charged shocks if any non-repros are available.

You don't need a shock dyno to answer my question. High pressure Bilstein deCarbon type shocks come with the shocks compressed with a very strong string to aid installation. If you cut the string the shock will expand, and I recall it may take 30-50 pounds of force to compress them, and if you release them, the gas pressure force causes them to expand back to full rebound length. These type of shocks can raise the ride height slightly, but only a small fraction of an inch.

I don't think your Delco shocks are deCarbon type. They are probably low gas pressure type, and I don't know if they expand to full length when unconstrained, but if so I expect it takes much less force to compress them, so they should have little effect on ride height.

Total shock travel of 4" is too short, especially at the rear where shock travel is not much less than wheel travel that I recall is a total of about 7" inches. Front shock travel is less because the shock is subjected to a longer lever arm.

205/75R-15 tires have an inflated OD of slightly over 27". The OE 6.70-15s are nominally 27.4". Of course the "R" dimension is affected by "static loaded radius", which is a function of both load and tire pressure. This is why I prefer using the Z and D dimensions as they are independent of tire dimensions.

Whenever your Corvette is up in the air the front and rear wheels assume significant positive camber, and when it's let down to the ground it will sit high because lateral friction of the tires will prevent the car from initially settling to normal ride height. Normal ride height cannot be achieved until you "roll the car out", which means moving it at least several car lengths.

You should check for other potential issues like too short rear spring link bolts. Shorter than OE length rear spring link bolts will raise rear ride height.

"Curb weight" is with all normal equipment (spare tire, jack...) and full fluids including fuel, but no driver, passengers, or cargo.

Duke