Rear Leaf Load Rating Question

[Kilian]

I found these rear springs for sale locally and think they'd be good for my K20 project...I'm converting a 1985 K10 frame to K20 and trying to max out the load rating for use around the farm. They are 52" springs, which will fit the K10 frame that came with 52's so I won't have to move the rear hangers back 4". Anyone have any idea on what the load rating would be/what model they came on originally? I would call it a 8/1 set...8 leafs with a second stage. I've looked through the part catalogs for 1973-78, 1979-84, and 1985-1991 and couldn't seem to find something similar that is 52.

I know that the 52" springs will bounce the rear end around more when empty, but it would be good to get a heavy load rating without having to move the rear spring mounts.

 

[MarineOne]

Both frames are identical. K30 had a beef chassis

That said these appear to be k30 springs I'd say your capacity would be around that of a modern 1500 pickup
2, 800 payload
8,000 towing

Your biggest limit will be axles

 

[Bextreme04]

Those don't look like 52" springs. I've never seen a heavy duty 52" spring either. You could get a 52 or 56" rear spring on a 1/2 ton, but as far as I know all 3/4 ton and up came with 56" springs. My 8600GVW K20 had a 56" 8/1 leaf pack that looked just like that.

52" and 56" GM springs have the same front eye to pin distance. The pin to rear eye distance is different though. It should be a 26" front eye to pin distance for both and the pin to rear eye will be 26" on a 52" spring and 30" on a 56" spring. It's super easy to move the rear hanger. The holes are already in the frame, you just need to cut out the old rivets.

https://www.truckspring.com/products/truck-springs/replacement-leaf-spring-22-485.aspx
The closest thing I've ever seen would be something like this 6/1 pack that has almost the same rating as the 8/1 pack but is for a 52". It was probably OE on a Big-10 or C6P equipped C10, maybe a camper special?

 

[Kilian]

Thanks for the replies so far. I've got a 14-bolt full floater that will be the rear axle.

Owner says that they are 52" springs, but will take along my measuring tape to make sure. Either way it sounds like they'll provide the hauling capacity for the truck.

 

[Kilian]

Hello, picked up the springs and they are 52". As far as restoring them, what's the best way to separate the leaves to derust and paint etc? Is there a good thread on this board somewhere? Thanks

 

[Old Guy Bill]

My original ‘78 K20 has 52” springs…
As for removing rust, the spring pack can be disassembled.
Depending on how bad it is, either a hand held grinder/sander or sandblasting.

 

[Kilian]

Thanks. Upon closer inspection, it would appear that they started life as 6/1 springs and someone added two leafs (leaves?) at some point. I'm going to check the arch to see if it's still around 4.75" which is specificied for the 6/1 sets.

 

[Craig Nedrow]

Killian, grind a radius on each spring where is rides on the next spring so that is rides smoothly and doesn't "dig in the the lower spring. If the lowers have a small groove, grind that out. I use teflon between, made a HUGE difference as my springs were really gouged.