OE rear spring rates?

[KidWgn]

I've been searching the Googles for half an hour or more and cannot find ANYTHING detailing the OE rear spring rate. Everything I can find is from aftermarket manufacturers touting "30% stiffer!" with no actual measurement. I'm putting together my own drop kit, and want to be sure I order enough spring rate for the rear.

Its the last component to order; help!

 

[iamdub]

I've been searching the Googles for half an hour or more and cannot find ANYTHING detailing the OE rear spring rate. Everything I can find is from aftermarket manufacturers touting "30% stiffer!" with no actual measurement. I'm putting together my own drop kit, and want to be sure I order enough spring rate for the rear.

Its the last component to order; help!

When I was comparing drop springs, I never found any specific ratings for the springs. What I did find were calculators that factored the wire size, length and diameter to determine the spring rate. It calculated based off a standard and common spring metal alloy. For my 2008 LTZ with ALC and Autoride, that calculator showed my rear coils to be 263 lb/in. I compared this to some McGaughy 3" coils and stock Jeep Wrangler (TJ) rear coils, which I ended up staying with.

How much drop are you looking for?

 

[KidWgn]

When I was comparing drop springs, I never found any specific ratings for the springs. What I did find were calculators that factored the wire size, length and diameter to determine the spring rate. It calculated based off a standard and common spring metal alloy. For my 2008 LTZ with ALC and Autoride, that calculator showed my rear coils to be 263 lb/in. I compared this to some McGaughy 3" coils and stock Jeep Wrangler (TJ) rear coils, which I ended up staying with.

How much drop are you looking for?

5 inch rear drop. Looking at Hyperco springs.

Our stock spring is 16" long with an OD of 5.7".

A Hyperco spring is available in an 11" or 12" free length with an OD of 5.5", in everything from 175 lbf-in to 1300. I'm thinking that if the OE spring is around 260 lbf-in, I should probably go to something like a 300 lbf-in spring to make up for the loss of the air ride.

 

[swathdiver]

I searched for YEARS and came up empty.

 

[justchecking]

You could measure them. I measured my fronts using a trailer tongue weight scale (see my post New Front Struts Question). But you could measure the rear by measuring the height to the wheel well with and without 10 bags of water softener salt over the rear axle.

 

[iamdub]

I searched for YEARS and came up empty.

If YOU don't have the info, then it's virtually inaccessible.

 

[iamdub]

5 inch rear drop. Looking at Hyperco springs.

Our stock spring is 16" long with an OD of 5.7".

Never heard of Hyperco.

I have a 4.5" rear drop with the TJ coils. They're a little softer than stock, but perfectly fine for my uses. I've towed an electric golf cart 750 miles and a car on a dolly about 100 miles, road trips with loaded cargo hold, consistently huck it around corners, etc. They were a hair too soft for the corner carving, but upgraded sway bars fixed that. I plan to reinstate the ALC system so they're definitely fine.

Also, I'd like to go a little lower one day, maybe to ~5" in the back. According to that calculator, cutting one coil off the TJ coil would put it right around the same spring rate as the stock coil, but be lower than the 4.5" drop it's at now. So, it might be a viable ~5" drop coil while maintaining stock capacities and characteristics. Dirt cheap if not free, too. I have a second set of TJ coils I'll experiment with when I'm ready to go lower.

A Hyperco spring is available in an 11" or 12" free length with an OD of 5.5", in everything from 175 lbf-in to 1300. I'm thinking that if the OE spring is around 260 lbf-in, I should probably go to something like a 300 lbf-in spring to make up for the loss of the air ride.

My stock coil is 16.25" height, 5.5" OD, .594" wire diameter, 8 total coils and 5.75 active coils. You're correct about the ALC difference. The models equipped with it have a slightly softer coil. My ALC never worked and I thought the ride was still much too stiff for how their flagship model should ride. Turns out, it was the shocks. IMO, the rear rides great and my issue is with the front, which will be addressed with different struts. I'm on a journey to make it ride like a Cadillac, tow like a truck and handle like a sports car.

 

[KidWgn]

Never heard of Hyperco.

They make springs for all sorts of applications; NASCAR, F1, etc. Super high end stuff, but priced very reasonably. They also block their springs 5x before they leave the factory, ensuring all the "sag" is already removed, and eliminating any springs that don't pass their +/-3% QC standards.

I'm on a journey to make it ride like a Cadillac, tow like a truck and handle like a sports car.

We're on the same journey

I came from a world of sporty vehicles, and I'd like this one to handle quite a bit better. I don't really tow with mine, but I'd like it to still have the ability.

 

[iamdub]

They make springs for all sorts of applications; NASCAR, F1, etc. Super high end stuff, but priced very reasonably. They also block their springs 5x before they leave the factory, ensuring all the "sag" is already removed, and eliminating any springs that don't pass their +/-3% QC standards.

We're on the same journey

I came from a world of sporty vehicles, and I'd like this one to handle quite a bit better. I don't really tow with mine, but I'd like it to still have the ability.

I figured they were a high-end manufacturer.

I rarely ever tow as well. Just want the ability to tow at or near its factory-rated capacity. I plan to do so with Air Lift bags (installed), controlled by the factory ALC sytem.

Handling, you say? I can't speak enough for these sway bars. Back when I bought 'em, they were $400+ cheaper than the Hellwigs, which they are very comparable to. Now, they're even $65 cheaper than that! Totaled with tax, they'd still be cheaper than what I paid before tax.

I used to keep about 7psi in the Air Lift bags to make up for the slightly softer springs. After the sway bars, I drained the bags cuz their help wasn't needed. The bars make that much of a difference. I gained 1/4" more rear drop from draining the bags, too.

The Tahoe is much more fun to huck around and very predictable. Instead of being limited by the body wagging around, I'm limited by the tire's grip and my ability to stay in the seat. No understeer, and I can predictably toss the back end out in a high speed turn. The Pirelli P-Zeros haven't let me down at all.

 

[KidWgn]

Handling, you say? I can't speak enough for these sway bars. Back when I bought 'em, they were $400+ cheaper than the Hellwigs, which they are very comparable to. Now, they're even $65 cheaper than that! Totaled with tax, they'd still be cheaper than what I paid before tax.

Just did some research on that company. Turns out they're a sister company to Whiteline, owned by the same parent company! Found some reviews on other forums (for other applications) saying the bushings are subpar, but no complaints about the hard-parts.

Previously I was looking to the Hotchkis Sport kit, as it uses larger diameter bars (1.5F 1.25R) than most kits, but these are the same size and are quite a bit cheaper!