72 Buick Coil Spring Question

[72Buickguy]

Does anyone know where to find the original spring rate for the front and rear coil springs on a 72 Riv GS? My local shop doesn't have a listing for aftermarket springs, so I'd like to get something close to original.

[56Roadmaster]

Hi,<BR> You might get an approximation by using F=kx(Hookes Law) put an known load on the spring and measure how far it compresses and use F/x=k where F=force(weight) and x=Length change from load which gives spring constant K (which is essentially stiffness) if you do this with them in the car divide the weight by 2 and position weight over which ever set you are trying to find.<BR> Of course if the spring are out this much easier and accurate and the spring shop should be able to determine the k that way.<BR> just a thought

[Guest]

I would see if similar full size GM cars had available springs. Cadillac's and Caprice's are probably similar in weight.

[72Buickguy]

Thanks guys, but what I'm really looking for is the spec Buick used when they selected the springs for my car.

[NTX5467]

The way that replacement springs were determined (in the "Computer Selected Spring" era of GM) was with a chart in the GM Parts Manual. You started with the basic model, then went to the appropriate front spring or rear spring chart. Then you added to the basic weight capacity from the list of optional equipment to arrive at the weight each wheel would have to support. There were charts for the standard suspension and also for the upgrade "performance" (usually F41) suspension option (when offered) too. <P>Once you had the total weight figure, you went to another chart with the part numbers for particular weight ranges. That's where you found the GM part number you needed.<P>In the later '70s, you used the GVWF/GVWR rating on the door decal. At that time, the weights was in "kg" instead of "pounds". Same scenario though, you went to the chart where the weight ranges and the part numbers were.<P>GM never did release the "lbs/inch" deflection rating in their parts number specs. You'd probably have to get the SAE specs that were filed each year for that figure. "Car Life" magazine used to publish them, but they were absorbed by "Motor Trend" by the time your Riviera was built.<P>TRW, Moog, and other suppliers do have all of the spring specs in the back of their coil spring catalogs. Quite an interesting list, especially when you look at what certain springs fit other than their original application. <P>Eaton/Detroit Spring is a GM Restoration Parts vendor so, if you can determine the correct GM part number you need (from the GM Parts Manual, as described) they can supply it. The GM Restoration Parts Catalog has a long list of spring part numbers in it, but applications are not listed. Eaton/Detroit Spring claims to have blueprints of OEM springs back to whenever. I suspect that what they would supply would be as close as you will come to the factory correct spec items. I believe they also have a website for inquiries. The springs from the other aftermarket suppliers will be more general in application than what GM specified.<P>Enjoy!<BR>NTX5467