Factory Spring Part Numbers & Associated Lift

[Trail X]

I beleive a stiffer spring will help somewhat to reducing the downward travel of the vehicle into the trail... but you bring up an interesting point. Shocks need to be tuned somewhat to the spring stiffness or else you get over or under dampening. In this case, I beleive you'd be under damping the system, so you would find that the may take a couple extra bounces to settle if you are at the stock damping constant.

I'm sure the designer will take that into account though. They realize they want close to critical dampening for optimum ride quality.

[The Roadie]

I'm still waiting for Johnny to find the missing parts from Icon to complete the prototype coilovers so I can start evaluating them. After I get them, THEN I'll contemplate a return to Sedona.

On the "shocks are better to prevent nosedive" issue. I totally agree, but you already know the problem. NOBODY makes a larger, stiffer, or more adjustable shock for our current strut/spring mounts. I think the ONLY way to get in there and start experimenting is to get a coilover platform like Icon's that comes with some manufacturer support like a stockroom of springs and shock valving to choose from. Once the mount issue is solved, then I'll be able to experiment with spring rates and shocks. I have to assume that the ones they adapted from the Tacoma will be close. The new Tahoe product they offer looks like the spring choices are all on the heavier side, but the shock is at least 2.5" dia.

Hey, Johnny. Calling Johnny.....

[bgwolfpack]

God those are gorgeous. I'm soo excited that you are doing this sir. Please keep us updated amap. Some of us still need to live through others vicariously.

[OregTrailBlazin]

I'm still waiting for Johnny to find the missing parts from Icon to complete the prototype coilovers so I can start evaluating them. After I get them, THEN I'll contemplate a return to Sedona.

He said they sent them on the 10th, and doesn't know why they never made it. So he supposedly shipped out another pair yesterday, which unfortunately puts us yet ANOTHER week away

On the "shocks are better to prevent nosedive" issue. I totally agree, but you already know the problem. NOBODY makes a larger, stiffer, or more adjustable shock for our current strut/spring mounts. I think the ONLY way to get in there and start experimenting is to get a coilover platform like Icon's that comes with some manufacturer support like a stockroom of springs and shock valving to choose from. Once the mount issue is solved, then I'll be able to experiment with spring rates and shocks. I have to assume that the ones they adapted from the Tacoma will be close. The new Tahoe product they offer looks like the spring choices are all on the heavier side, but the shock is at least 2.5" dia.

Hey, Johnny. Calling Johnny.....

Theoretically you shouldn't have a problem with firmer GM stock springs since the Billy HD's are supposed to have a firmer valving rate. I still see that as a very viable option. Remember the aftermarket shocks have to fit the same application that all those different springs do, they should do just fine keeping up with the slight increase in spring rate.... (OF course not nearly as nicely as a set of 2.5" diameter shocks.. )

It will take Bill a little while to get the coilovers where he likes them. But looking at the "offroadTB big picture" the idea is to get enough of you together that want them, so I can hand ICON a order for ten of them, and send somebody up there with a TB/EV and have them find the perfect valving/spring rate.

I can say this Bitch'n sight sure helps people take us more serious in this industry.

[Philberto]

Hmmmm.... so apparently, compnine has different RPO codes listed for many of those spring part no's than you guys have... you suppose they're different by year? Also, could anybody help me distinguish between T155, ST155, and ST158? What do those stand for in the RPO fields on the compnine site? I'm guessing year and swb vs lwb, but not sure... It also appears that we have different shock options stock, or at least there are different part no's, and there's other spring part no's not listed here... It's all so complicated

[The Roadie]

ST155/158 are indeed wheelbases. The equivalent of GMT360/370.

For more data to make your brain explode, search the OS (advanced search) for posts by "zibby", a GM insider who leaked the initial charts of the spring choice complexity.

[Philberto]

ST155/158 are indeed wheelbases. The equivalent of GMT360/370.

For more data to make your brain explode, search the OS (advanced search) for posts by "zibby", a GM insider who leaked the initial charts of the spring choice complexity.

So with all that said, are there stiffer springs than the 15125889 ones on the chart? Just a matter of curiosity.

[Trail X]

Not that I know of, but there could be. I don't believe the 89 springs were used on any standard production vehicles. They may have produced them for purposes of creating a Z71 package at one time... or possibly for armored vehicle aftermarket mfgs.

The RPO codes I listed may just be from 2005... there may indeed be different suspension RPOs by year. Maybe we need to get the Compnine guy over here as a vendor... he has access to all the raw data and seems willing to help us understand them.

[The Roadie]

Just looked on parts4chevys.com. Odd.

15125887 - List $73, Cost $52
15125888 - $78, $56
15125889 - $129, $92

[bgwolfpack]

Just looked on parts4chevys.com. Odd.

15125887 - List $73, Cost $52
15125888 - $78, $56
15125889 - $129, $92

I just checked gmpartsdirect.com
15125887 - Cost $43.26
15125888 - Cost $45.95
15125889 _ Cost $76.50

[The Roadie]

I've heard bad things about gmpartsdirect.com high shipping prices, so after a couple of comparisons, I just quit even looking. I have called the Internet guy a few times with questions at parts4chevys.com, and he says I drive a lot of business to him from trailvoy, especially for HVAC resistor packs.

But except for very small cheap things, they BOTH have to be better than my local dealers.

[bgwolfpack]

Thanks for the heads up. I actually think I read you saying that on the os awhile ago, but I forgot. Must be why we keep you around. Just another noobish moment on my part.

[mikek3363]

out of curiosity what is the spring rate of the stiffest "89" spring?

[Trail X]

Hehe

Its all actually listed in the 3rd post in this thread. But I'll list it here... 77 N/mm.

[The Roadie]

And since this is offroadtb.com and not the OS, it should go without saying that if you want the English spring rate number, you can find the conversion factor on your own.

[mikek3363]

sweet thanks

[rgraboske]

I don't know if this is helpful to anyone, but I noticed that Rock Auto lists a Moog front spring for Trailblazers. The part number is 81110, and the price is $78.87. I was curious about how they split the difference from all the different spring rates offered from the factory, so I made a few phone calls. Eventually I made it to the manufacturers Techincal Support line where I was told the spring rate is listed as 66 N/mm.

It seems that for now, we can get heavier duty springs from the factory for similar or less $$$, but as they discontinue parts, this may be helpful.

[HARDTRAILZ]

Just paid for a new pair of 15125888's from gmpartsdirect.com. Just under 110 for the pair delivered. Hopefully they get here soon. I need them on in the next 2 weeks.

[Gordinho80]

Just paid for a new pair of 15125888's from gmpartsdirect.com. Just under 110 for the pair delivered. Hopefully they get here soon. I need them on in the next 2 weeks.

MEASUREMENTS!!!! Befores and Afters please! And lots of pics!

[Trail X]

I hope they work out for you. My springs are sagging pretty good now, new springs are on the list of "eventually need to fix".