Did RockAuto screw up these descriptions?

[saxart]

I'm putting 1/2 springs in my C-10 to replace the 50yr old "Heavy Duty" springs so that the truck rides better. I went on RockAuto and ordered AC-Delco "Variable" springs. The correct part number arrived, but when I compared them, they looked exactly like my old springs (2 or 3 coils closer together) and the spring wire actually measures slightly THICKER on the new springs!



Here is a screenshot of how RockAuto describes them. Do the springs at the top (more open coils) look more like 1/2 ton springs even though they're described as "Heavy Duty"? (I think they have the descriptions flip flopped)



I've never actually seen 1/2 ton springs in person, so I'm just trying to confirm which is which...

[jkeady]

The top Rock Auto pic would seem to show a constant rate spring and what you have looks like a variable rate spring (rate increases as spring compresses). What actually is ‘heavy duty’ about either would have to be determined by their specs (that is, I don’t think a constant rate spring is necessarily more ‘heavy duty’ than a variable rate spring).

[saxart]

Originally Posted by jkeady

The top Rock Auto pic would seem to show a constant rate spring and what you have looks like a variable rate spring (rate increases as spring compresses). What actually is ‘heavy duty’ about either would have to be determined by their specs (that is, I don’t think a constant rate spring is necessarily more ‘heavy duty’ than a variable rate spring).

Thanks for commenting Yes, I agree about your "variable" rate comments. What I'm really interested in knowing, is which spring is a 1/2-ton spring and which is a 3/4-ton spring. (I suspect their descriptions are incorrect) My truck has the "HD Springs" listed on the SPID. These new springs are made of even thicker material, yet have the exact same number of wraps, so I gotta think they're going to ride as stiff or stiffer.

What we need is for some of the guys who part out these trucks to tell us which looks more like a 1/2 ton spring in the pic I posted, the top spring or the bottom. The new front springs I received in this same order had a slightly thinner spring wire thickness, so I do believe those are correct lighter duty spring.

Any and all thoughts are appreciated...

[saxart]

I think I may have just answered my own question.

If we can trust Amazon's descriptions they list the 45H2011 springs as weighing in @ 28.7lbs per pair and the 45H3018 springs weighing in @ 40.2lbs per pair. If that's the case, then the 45H2011's are definitely labeled incorrectly has "Heavy Duty".

I'm curious if someone who's parted any of these trucks can tell us if the 1/2 ton springs are visually different from the 3/4 ton springs. I think the 3/4 ton springs have that "variable" look to them with some coils closer together, correct?

[rechinca]

I have a 71 C10 (1/2 ton) with the HD spring option in the rear. As far as I can tell, the rear springs are original and they look exactly like the original ones you pulled out.

Now in looking at the set you received, they look to have 2-3 coils with closer spacing toward one end. I don’t think that the 3/4 ton springs necessarily are different from the 1/2 ton HD springs. I thought I read somewhere that the 3/4 ton and 1/2 HD springs are actually the same spring. I could also be wrong but it seems to me that is what I gleaned from a thread here.

In fact here is the thread, post #6. Not sure if it apples accross all years, but it’s a good point of reference.

http://67-72chevytrucks.com/vboard/s...d.php?t=369355

[lowrollin70gmc]

What matters is the rate of the spring. If you click on the blue ”Info” button you can see the load rates. This is different from the commonly used spring rate. Load rate is the weight that the spring is designed to carry at it’s intended height. (https://www.eatondetroitspring.com/s...-vs-load-rate/)

45H2001 “Heavy Duty”

Load Rate: 1700 lb

45H3018 ”Variable”

Load Rate: 950 lb


So, the heavy duty spring is designed to carry more weight at it’s intended height, thus “HD”.

As far as HD having less coils: “Increasing the wire diameter, decreasing the outer diameter, or decreasing the number of total coils are all ways to increase the strength of your spring and produce a stronger rate and load.” (https://www.compressionspring.com/spring-load-and-rate). Therefore, by decreasing the number of coils the top spring (HD) is stiffer than the bottom spring (variable). Decreasing the number of coils also has a side effect of reducing the weight of the spring, so spring weight doesn’t have a direct correlation to spring rate (as stiffening by increasing wire diameter has the opposite effect of increasing weight, and it gets complicated).

Where the problem comes in is that GM likely used a dozen different spring rates based on GVWR and options but the aftermarket has combined part numbers to only 2 options (and the same options show for a C20 as a C10). None of this likely helps determine if the new is the same as the old, but you do have the softer of the two options that RockAuto offers.