69 c20 lowering questions

[Adam4pt6]

1st off I'm sorry, I know this is beat to death, and I did search but most everything is referring to a c10. But my question is pretty straight forward. How low can I go with out a c notch? I won't be hauling anything at all with the truck. I plan on Staying 8 lug and keeping the rear (eaton I believe?) I have. It's also coils all around. Will the larger rear limit me any?

The plan is drop spindles (disc conversion), Springs and new shocks all around, and a block in the rear if need be. I'm assuming I'll need an adjustable Panhard bar and rear shock relocations as well. I can switch to smaller bumpstops if needed. I'll be running steel wheels off of a 90s suburban, and am flexible on tire size (open to suggestions).

So what's the lowest I can go? Am I missing anything in my parts list? Thanks guys

[demian5]

Measure the distance between the top of the axle and the frame rail. Then subtract at least 2 inches for suspension travel and that would be a safe way to estimate.

[Adam4pt6]

That's a good point, and obviously easy to do. I won't be around the truck unail later so I'm just curious what every one else has gotten away with

[JustToxic]

GMC Pauls makes drop springs for our C20 trucks and POL make disc brake drop spindles for our trucks as well. So with that, you can drop as much as your heart desires. I personally wouldn't drop it lower then 4" in the rear without a c-notch. For the front if you drop it 3" or more with springs then you'll need a camber adjustment upper control arm cross shaft. Without doing more modifications to the C20 best bet would be doing a 2/4 drop with springs, or a 2 1/2" front drop with spindles and a 4" drop rear with springs.

[Adam4pt6]

Originally Posted by JustToxic

GMC Pauls makes drop springs for our C20 trucks and POL make disc brake drop spindles for our trucks as well. So with that, you can drop as much as your heart desires. I personally wouldn't drop it lower then 4" in the rear without a c-notch. For the front if you drop it 3" or more with springs then you'll need a camber adjustment upper control arm cross shaft. Without doing more modifications to the C20 best bet would be doing a 2/4 drop with springs, or a 2 1/2" front drop with spindles and a 4" drop rear with springs.

Just checked them out. What's the difference between c10 and c20 Springs? I was under the impression I could just run Springs marketed for the c10, is that incorrect?

[northerngmc]

Originally Posted by Adam4pt6

Just checked them out. What's the difference between c10 and c20 Springs? I was under the impression I could just run Springs marketed for the c10, is that incorrect?

I used C10 springs in my C20 when I lowered it. Worked well. 2" front, 4" rear. Left it with stock drum brakes.

Biggest problem I had was most threads said to simply pop the lower ball joint open and swing the brakes out of the way to swap the front springs. Popping the ball joint took some work and then the brake backing plate would not clear the suspension and come out. So I ended up unbolting the lower control arm from the frame.

Pics for reference on 2" front and 4" rear C10 Springs.

Before.....



After....



I did take measurements on the top of the fender lip to the garage floor before and after and it was close to 2"/4" on the tape.

[JustToxic]

Originally Posted by Adam4pt6

Just checked them out. What's the difference between c10 and c20 Springs? I was under the impression I could just run Springs marketed for the c10, is that incorrect?

If you still want to use the C20 as a C20 then you'd want the slightly heavier duty springs. But if your like most of us with C20's then you can use C10 springs. The C10 spring will give you a smoother ride compared to a C20 spring.

[Adam4pt6]

Originally Posted by JustToxic

If you still want to use the C20 as a C20 then you'd want the slightly heavier duty springs. But if your like most of us with C20's then you can use C10 springs. The C10 spring will give you a smoother ride compared to a C20 spring.

So basically a c20 lowering spring will be stiffer and have less travel then a c10 spring?

[Adam4pt6]

Also, on the measurement idea...how accurate is that really? Think about it... 50 year old springs...there's probably some sag going on there. It may already sit a little lower then factory...making the measurement for new lowering Springs possibly off... right?

[Adam4pt6]

Thanks man those pictures are helpful

[Jose's 69]

I used c10 4" lowering springs and a 1.5" block in the back. 2.5" drop spindles and 1 inch drop springs in front. Converted to front disc brakes in the process. I would like to go another inch lower in the back but not sure if I can without the rear end hitting the bed.

[Adam4pt6]

Originally Posted by Jose's 69

I used c10 4" lowering springs and a 1.5" block in the back. 2.5" drop spindles and 1 inch drop springs in front. Converted to front disc brakes in the process. I would like to go another inch lower in the back but not sure if I can without the rear end hitting the bed.

Any chance you can snap a few pictures of your truck for me? I like the stance of yours, but do you have a picture of a straight on side view? And would you be able to take a picture showing axle to frame clearance?

[Jose's 69]

Originally Posted by Adam4pt6

Any chance you can snap a few pictures of your truck for me? I like the stance of yours, but do you have a picture of a straight on side view? And would you be able to take a picture showing axle to frame clearance?

Sure no problem. I'll try to get some pics uploaded later.

[Adam4pt6]

Originally Posted by Jose's 69

Sure no problem. I'll try to get some pics uploaded later.

Thanks man I appreciate it

[JustToxic]

Suspension travel will be close to the same it'll just be a stiffer ride.

[Adam4pt6]

What I'm getting at is, with the c20 spring there will be less of a chance bottoming out on smaller bumpstops and such as there would be with the softer c10 spring...correct?

[JustToxic]

Since your not wanting to do a c-notch, yes the C20 springs would be less chance of bottoming out.

[azle]

That is rear differential sitting on frame on 1 inch rubber blocks and front A arms sitting on modified rubber bushing, also about 1 inch. That is fully slammed not driving stance. Kind of new to the BAG world but I run 60psi on both front and back to drive, it is still low. Hope that helps.

Azle