Rear Suspension question. Drop spring or combo of spring & block?

[1964FarmFreshC10]

Howdy folks.

I’m currently installing 2.5” drop spindles and 1” drop springs on the front of my ’64 C10, for a total front drop of 3.5”. I’ve already picked up CPP tubular trailing arms for the rear, but I haven’t ordered the rear springs yet.

From what I’ve read and been advised, with a 3.5” drop up front, I should be aiming for around a 5” drop in the rear to achieve a proper stance.

My original plan was to go with a straight 5” drop coil, but I’ve recently come across recommendations suggesting a combination of drop springs and lowering blocks instead.

I’d appreciate your thoughts on the best approach.

[SkinnyG]

In theory, the 5" coil spring should be engineered to be stiff enough to handle full bottoming of the suspension with 5" of less travel. This should keep you from hammering the bumpstops all the time.

A shorter spring (let's say 3") should be engineered to work with its reduced travel - a 3" spring should be stiff enough to keep you off the bumpstops with that 3" less travel. If you add blocks (let's say, a 2" block), that spring thinks it has 3" less travel, but discovers it actually has 5" less travel, and you hit the bumpstops hard.

That's the engineering behind it. In practice it might just be fine. I recommend AT LEAST 4" suspension travel in the back.

Many "lowering springs" are just plain not stiff enough to account for the amount of drop they provide. If you are going low, you MUST go stiffer.

[Grounded63]

That's exactly what I did on my 63 fleetside long bed, 3.5/5 drop. Stock rear arms.
To me it had way to much rake. And ended up also putting 2" blocks in the back also. Which got it about perfect. But I'll note that my bed wood was just about completely rotted out at the time. And maybe the back end didn't settle down. As much as it should have, with springs only.

At this point " 7 inches " down in the rear it really kinda needs a pipe, or small full notch. Also at even just 5" down you are going to need to realign the pinion angle and shorten the drive shaft. FYI.

[1964FarmFreshC10]

Thanks folks.

Well i do still want to be able to use the bed for hauling things so maybe i am better off going with CPP 4” HD Rear Coil Springs (RCS603-4HD).

If needed i guess I could always add air shocks to stiffen things up a bit.

[hewittca]

I think the HD springs are a good idea. I ran those on my last truck and they are definitely stiffer than the standard springs. With nothing in the bed they are great. I was also able to put several hundred pounds in the bed without even noticing a difference. More than 600 or so and I would start to hit rear to frame over bumps. Keep in mind, I also had 2" drop blocks and no notch so my suspension travel was limited.

Before the 4" HD spring/2" block combo I had standard 5" drop springs and they were way too soft, even with nothing in the bed.

[Chevy Fleetside]

These are my trucks. They both have 2 1/2 drop spindles up front. The blue truck has 255/75/15 tires up front and 275/60/15 in the rear. The green truck has stock 235/75/15 all around. The blue truck has 4" drop springs in the rear and the green has 3" drop springs in the rear. I did this because I was going to be hauling things in that truck. Not the best pictures but maybe give you an idea. I miss that dog.

[SCOTI]

Originally Posted by hewittca

I think the HD springs are a good idea. I ran those on my last truck and they are definitely stiffer than the standard springs. With nothing in the bed they are great. I was also able to put several hundred pounds in the bed without even noticing a difference. More than 600 or so and I would start to hit rear to frame over bumps. Keep in mind, I also had 2" drop blocks and no notch so my suspension travel was limited.

Before the 4" HD spring/2" block combo I had standard 5" drop springs and they were way too soft, even with nothing in the bed.

Another vote for the HD 4" drop coils. Adjust w/blocks as needed from there.

I also want a minimum of 3" clearance for travel. Once drops start to get to the 'it needs a frame c-section' realm, another thing rarely mentioned is clearance @ the differential to the bed-floor. On my swb trucks w/c-notches, the pumpkin would beat the floor above it so measure & verify for that as well.

[AcampoDave]

For the way I drive, I've found a 4" rear drop to be the limit of practicality. I like a 2.5 x 4 inch drop best.

[SCOTI]

Originally Posted by AcampoDave

For the way I drive, I've found a 4" rear drop to be the limit of practicality. I like a 2.5 x 4 inch drop best.

This is why I started down the path of modding things further. When you want that 4" drop practicality but desire more drop, you have to create the room/clearance to allow it. A 2.5/4" combo is a great call for a good-looking ride w/minimal extra effort.