Rear lift blocks on composite leaf springs?

[KRAS]

Has anyone been able to crack the nut from an engineering perspective on why you’re not supposed to put a lift block under the composite springs (which my dealer did). Oddly enough- RC & Fabtech don’t have any warnings, just Chevy

and Readylift.  My theories are:

1- steel will continue to flex but not rebound when it hits its load limit but composite/carbon snaps 

2- they are tuned for the trucks specific factory angles

3- GM figured out that this truck looks a lot better at 2”+ taller and wants more money

[topgear1224]

It's leverage on the spring that's why GM says don't do it. Yes it will snap with hard enough use.

Also because of how it's designed it's really only designed to flex sort of towards the ends and kind of give you a variable spring rate,

whereas the steel one the whole thing can flex and as you flex more of it it's sort of variable.... it's kind of hard to explain.

Anyways now you can get the conversion to steel springs from GM I think it's $600 and that includes both the springs and u-bolts. Just look at the 2021 accessories

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[AJMBLAZER]

I dunno.

 

The surface area of the lift blocks won't be any smaller than the surface area of the spring perch on the axle so not sure what difference it will make.

[Travis26]

Following this post.  I ordered a Moto Fab 2.5" front 2" rear leveling kit last week.  I'm now contemplating whether or not to install the lift block in the back or not since I have the composite leaf.  I emailed Moto Fab and they say there are no issues using it.

[topgear1224]

it really just depends on how hard you drive the truck if you're sitting there jumping it all the time you're probably going to snap them.

if you just drive them on the road it'll probably never fail

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[Travis26]

I have a 6,000 lb travel trailer that I tow probably a dozen times through out the year.  I will be installing a Air Lift system before I tow though. That's my main concern. 

[Gangly]

As far as I can tell through my research on the boards, there are no known instances of mechanical failure, degradation, or diminished  materials performance as a result of using the blocks with the composite springs.  GM has a reason for what they are saying, but I don't know if anybody outside of GM knows why.  

 

 

[Grumpy Bear]

On 11/8/2020 at 2:14 PM, AJMBLAZER said:

I dunno.

 

The surface area of the lift blocks won't be any smaller than the surface area of the spring perch on the axle so not sure what difference it will make.

The difference is that extra inch to the compression bump stop. Extend the bumper an inch and all is good. Otherwise the spring can be extended an extra inch. Question is.....how big a jump empty would equal 2000 pounds in the box or who at full load is running the dunes? 

[AJMBLAZER]

Might be but yeah, it’d take some beating to do it. 

[Travis26]

Thanks for the all the input!!

[pewterliftedz]

The composite springs have a shim that should be removed before installed a block, Superlift has a kit that provides a new pin to remove the shim

[Travis26]

I didn't see any kit like this listed on their website?

[1Silverado9]

Dumb question here...

How do I know if my leaf springs are composite or steel ones? 

[AJMBLAZER]

The composite is thick and looks obviously different. Also I don’t think a magnet will stick to it. 
 

I’d take a picture but my truck is 2 hours away from me. 

Edited November 12, 2020 by AJMBLAZER

[Duramax3oh]

Along a similar path, could there be a problem of using an Add-a-leaf in lieu of rear block? If the composite is made to flex different would mixing that with an AAL be bad?