85 K15 rear spring swap from 52" to 56" W/ 6" lift

[J-SQUARED]

I'm looking to get a 6" rough country lift. It has an option for either 52" or 56" rear springs. Mine currently has 52". From what I have read, the 56" actually has a lower spring rate and the added length makes it ride a bit better. Additionally, some trucks are already drilled to move the rear hangers back 4". I have also seen where they get swapped side to side to change the angle of the shackle backwards allowing for the longer spring. My question/concern is if the truck is drilled to move them back and I do that, what does it do to axle centering in the wheel well? I have read plenty of posts on multiple forums where guys do this but nobody says if the rear axle is now set back further and not centered in the wheel well.

Does anyone here have experience with doing this modification or pictures of before and after? Seems like it would be 2" further back.

That would also negatively impact turning radius as well, correct?

Thanks!

 

[legopnuematic]

The front spring hangers remain the same, from a factory 52” or 56” spring, the springs themselves have the center pin the same distance from the front spring eye (with aftermarket springs it may be different due to spring arch, but the effective distance will be the same), with the difference in length being rear of the center pin.

Now the centering can be off depending on what method is used to lift, like a shackle flip with stock springs will likely result in needing a spring perch that has offset holes or a zero rate with an offset hole to re center things up. As the distance from the center pin and front spring eye are a constant and move on an arc, so if the rear moves down, the center will move forward.

But lift springs intended for use with stock hangers and shackles should have this factored in already.

 

[1lejohn]

Off Road Design has a nice write up with the pros, and cons of doing this on their web site. You might want to check it out.

 

[Bextreme04]

Off Road Design has a nice write up with the pros, and cons of doing this on their web site. You might want to check it out.

I haven't seen that, are you sure it isn't for the B52 swap for front springs? I can't think of any Con's to going to a 56" rear spring. Its quick, easy, and greatly improves ride quality.

If you don't mind a bit more fab work, you can move the front hangers and crossmembers forward 4", move the rear hangars to the 56" location, and then run factory GMT-400 or newer 63" K1500 leaf springs. They will ride MUCH better than even the 56" springs will and it gives you a 4" lift without doing anything else. I have factory GMT-400 K2500 suburban 62" springs on mine with a 2" ORD shackle flip. I'll probably switch those to K1500 springs with airbag helpers instead to smooth the ride out a bit more.

 

[J-SQUARED]

I haven't seen that, are you sure it isn't for the B52 swap for front springs? I can't think of any Con's to going to a 56" rear spring. Its quick, easy, and greatly improves ride quality.

If you don't mind a bit more fab work, you can move the front hangers and crossmembers forward 4", move the rear hangars to the 56" location, and then run factory GMT-400 or newer 63" K1500 leaf springs. They will ride MUCH better than even the 56" springs will and it gives you a 4" lift without doing anything else. I have factory GMT-400 K2500 suburban 62" springs on mine with a 2" ORD shackle flip. I'll probably switch those to K1500 springs with airbag helpers instead to smooth the ride out a bit more.

This wont be a DD for me so I will likely stick with the 56" mod for ease and convenience. I like the idea though! Thanks for the info!

 

[J-SQUARED]

The front spring hangers remain the same, from a factory 52” or 56” spring, the springs themselves have the center pin the same distance from the front spring eye (with aftermarket springs it may be different due to spring arch, but the effective distance will be the same), with the difference in length being rear of the center pin.

Now the centering can be off depending on what method is used to lift, like a shackle flip with stock springs will likely result in needing a spring perch that has offset holes or a zero rate with an offset hole to re center things up. As the distance from the center pin and front spring eye are a constant and move on an arc, so if the rear moves down, the center will move forward.

But lift springs intended for use with stock hangers and shackles should have this factored in already.

This is the exact info I was looking for. I never considered they were built with that regard and just figured the perch was in the middle of the spring. thanks for you help!

 

[legopnuematic]

The 52” are 26/26, 26” inches in front of and behind the pin, the 56” are 26/30, so still 26” in front, but the 4” extra is rear of the center pin.

If you do go 56” springs, make sure not to put them in backwards, then you’d have some wheel centering issues lol.