Moog Front Coil Springs

[nuclearnavajo]

I am in the process of lifting my truck (2002 Envoy SLT 190k) with Mark's 2.5' kit. I have Z71 springs in the back and am looking to lift/level to around 3". I figured I should do front struts and new coil springs while I have them off for spacers. I will probably flip UCA's while it's apart also. My question is concerning replacement coils springs for the front struts.

I current have 82's and was looking to do something in the 87/88 range about 70n/mm for spring rate however they are unavailble. I was wondering about the Moog 81112 and 81114 spring rates/ride heights. I have emailed the manufacturer but have recieved no reply on the spring rates. The 81110 is the only spring I can find the rate for, 375 lbs/in. That puts it around the 85 range, but I was hoping for a bit more lift on the front of the ride.

Does anyone know what the rates for Moog springs that might fill the void of the discontinued 87/88 springs?

 

[stormsurge]

Im close to level with the 85 springs. I used the stock springs in the back. With the tires i got a totel 4" lift.

 

[The_Roadie]

We're trying over at offroadtb.com to get a definitive answer on the spring rates from Moog's manufacturer, Federal Mogul. No data yet.

 

[nuclearnavajo]

Yeah thats kinda what I understood from reseaching the problem. I can't get a straight answer either. It is a shame that replacement front springs are this tough to find. I don't really have time to go junkyard picking for springs at the moment, but I don't want to pay for something only to replace them. It is also my understanding that the Moog springs are not longer than stock, only thicker, so the only thing would be eliminating front sag. Is this correct ?

 

[The_Roadie]

Even if the springs were longer, you'd have to compress them more to put them in the strut. The shock and top mount define the total exterior length of the strut, and that can't grow by more than about 1/2" from OEM length before we get into binding of the inner CV joint at full extension.

Lifting our platform is not making it permanently higher in the normal sense of spring spacers used on other platforms. It's just changing the REST HEIGHT of the front strut. You essentially trade up-travel for more resting height and down-travel. But the strut stays the same length. Stiffer springs and spring pre-load are two ways to accomplish this.

A drawback we're discussing and analyzing now on ORTB is the problem of a long COMPRESSION stroke being able to store up a LOT of energy, and on the next extension stroke, if you jump or go to almost zero G, all that energy is used to accelerate a heavier-than-stock tire downwards very quickly. The shock has a bump stop on the shaft (the orange thing) for compression, but there is NO structure meant as a bump stop for extension. Some of us have been breaking shock shafts and damaging the upper polyurethane bushings, both on Mark's and on BDS style lift kits. More news when we discuss it more on ORTB. Only a worry for folks who occasionally unweight their front ends just after full compression, and who have heavier tire and wheel combos.

 

[navigator]

I received a PDF from Federal Mogul but the springs we are interested in (81110,12,14,16) are not listed in the PDF.
The email was from one of those do not reply emails.

They also listed a phone number (800-325-8886) but I have not had time to call them yet.
From the research on offroadtb.com the 81110 seem similar to an 85/86 and the 81114 seems to be close to an 89.
I think most would expect the 81112 to be ~87/88 but we really don't know.
Be careful if you order from ebay, some listings are for 1 spring and some are for a pair of springs.
We had one member on offroadtb.com end up with 3 sets of springs(81114)

 

[nuclearnavajo]

Funny thing was I was thinking about this earlier. How we are limited to the front struts by design geometery. I was thinking some adapter for our odd shaped yoke to something a bit more universal. I don't really like being so limited on products

 

[navigator]

I just got off the phone with a guy at Federal Mogul, he should be emailing me the specs on those springs.
I'll post them once I receive them.

 

[nuclearnavajo]

Thanks man! I appreciate the help! ...BTW what's the best 22" rim for off-road ...jk

 

[navigator]

I was able to get some info from Moog about their springs, it seems they all have the same spring rate but different free lengths/loads. I can neither confirm nor deny any info below.

Spring 81110
Bar Diameter .671
Inside Diameter 3.7
End 1 PT-103
End 2 Tang.
Spring Rate: 375 B/T 9.5 & 11.5in.
Design Height 10.5
Design Load 1940
Free Height Ref 15.674

Spring 81112
Bar Diameter .671
Inside Diameter 3.7
End 1 PT-103
End 2 Tang.
Spring Rate: 375 B/T 9.5 & 11.5in.
Design Height 10.5
Design Load 2145
Free Height Ref 16.22

Spring 81114
Bar Diameter .671
Inside Diameter 3.7
End 1 PT-103
End 2 Tang.
Spring Rate: 375 B/T 9.5 & 11.5in.
Design Height 10.5
Design Load 2340
Free Height Ref 16.74

Spring 81116
Bar Diameter .671
Inside Diameter 3.7
End 1 PT-103
End 2 Tang.
Spring Rate: 375 B/T 9.5 & 11.5in.
Design Height 10.5
Design Load 1765
Free Height Ref 15.180

here is the link to the google doc
https://docs.google.com/file/d/0B66ibZBJzyfYbjlzai11SS1WS28/edit

 

[nuclearnavajo]

So if the factory springs have different spring rates it is due to construction and material differences. The Moog springs seem to just add compressive force due to changing spring height.

 

[navigator]

I think the member from offroadtb said that his 81114s were a little longer than stock.