rear lift with bilstein 5100s and icon AAL

not a pressing question, just something that's been eating away at me lately...

so when i added billys to the rear of my 05 AC i got about an inch of lift or so. YES i realize this is weird, and from what many are saying IMPOSSIBLE, but the numbers didn't lie nor did the reach over height of the bed.

furthermore, when i later added the icon AAL and removed the factory overload springs, as recommended, i got almost no gain in lift whatsoever (the ride was killer though).

wtf happened here? is this impossible? did some weird anomaly give me lift when i swapped out the struts and that was the max the icons could provide for? i can't wrap my head around it.

i have definitely read a number of threads of folks saying they gained lift with new struts in the rear, with every thread having a number of people in it saying no way sorry not possible.

why did i gain lift with new struts? why did i gain zero lift with the new AAL's? anyone???

 

thanks for the reply! makes sense to me and kinda what i was thinking. just so many folks were telling me that it'd be impossible for the struts to effect the lift in the rear.

 

I guess it could be possible. Bilsteins are a floating piston shock with a nitrogen pre charge. They do have a decent force on them that makes them want to extend completely at all times. Stronger than a twin tube shock.

I had a 1st Gen and the springs seemed pretty flattened and worn out around 150k ish. If yours were so worn out as well, the Bilstein could possibly provide unintended lift helping the worn springs. Then, as mentioned, when you installed better springs that had the 1" lift, the shocks adjusted and could not overcome the stiffer springs.

 

slightly off topic. When you say killer ride do you mean that in a good or bad sense? Just curious!

 

I had the exact same thing happen when i put icon shocks on the rear of my gen 2

 

Ha, killer meaning good! It rides amazing with the stock overload off and the AAL. But I haven't towed or really loaded up the bed too heavily yet so TBD on that.

 

Out of curiosity, for scientific purposes ha, how old were the struts on your gen 2 when you did that?

 

60 miles lol. But it got an extra 3/4 inch in measurement or so. Im guessing them being under pressure did it

 

ahhh interesting. must be the pressure then!

 

This anomaly happened to me, as well. I gained some height out of the rear after 5100’s were installed. It was at least a half inch in gain, but not sure as I didn’t measure before the install. My trailer hook ups required extra height to get the tongue to engage is how I noticed.

 

Well dang, now you guys are making me want to install some on the rear of mine. I could use even a half inch of lift maybe. Towing with all my gear makes my truck squat a bit.

 

im so glad i've been validated here, ha. thanks for all of your responses!

 

I had someone here tell me its impossible for shocks to lift a truck last year after doing mine so I understand your need for validation.

I didn’t measure before so my guess is 1/2” minimum. Maybe an inch max. The rear on my 2002 is stout for sure. Those rear 5100’s are great for tow/haul and street driving. I may switch to another type of front shock in the future as the fronts are a bit stiff. Good shock, but looking for softer up front.

 

It wont add any carrying capacity, it sags down with load the same. I think oe shocks have nearly 0 pressure so it makes sense a little bit of pressure in the shock could push up an empty truck bed a tiny bit

 

Shocks don’t lift vehicles.

 

Yeah my ride up front was really rough after I went to the 4th notch. I actually wound up swapping my springs up front for Eibachs from Toytech, which at the lowest notch on the 5100's was supposed to add the same lift as the the top or second to top. Toytech and my mechanic friend said that would provide a better ride but also gain the lift I needed. Ride was great but, weirdly, I lost about a 1/2'' to 3/4'' of lift and rub. So now I have to go back with 1/2'' top spacers or mess with a different notch. This is like the 7th time I've re-coiled these things by hand playing with ride and height feel. Kinda wanna shoot myself.

Retrospectively, with the time and effort I've put into messing with them, I would have probably have gone with coil overs ha...

 

Ok. Explain why two people here say they have gotten lift. Remember, I am not an expert on suspension and have nothing to gain by being right in my observation. Is it an optical illusion that I am seeing?

I get the entire premise of old shocks sagging and when replaced with new shocks the sag disappears explanation made by others above. What is your explanation why I am seeing a lift that is not suppose to happen? My front coils and rear leafs are the originals. Only things that were replaced were shocks. Front 5100 shocks set at one notch up from stock height.

Again, I did not set out to achieve lift in the rear. As you know from my style, I do not care for all the suspension accessories/lifts etc as I like the way the truck sits naturally OEM.

Please explain why I have a lift of at least 1/2” when its not suppose to happen.

Or, explain what else may have happened that made the lift happen that isn’t suppose to happen.

 

My payload max is about 1600lbs. The old shocks would bottom out on the bump stops when hauling that weight. The 5100’s keep the stops about 1” off the frame and will only bottom out when hitting big dips/bumps carrying 1600lbs.

 

I agree, they are not intended to lift vehicles. If you have ever played with a 5100 shock that is not installed, it naturally wants to extend completely. With quite a bit of force at that. More so than a twin tube shock at that. I can see it over coming worn out springs slightly.

Now if someone were to bet me that it would lift the truck I would bet against it. But I have to believe multiple guys that say it happened.

 

The 5100’s brought the rear end back up to where it should be. You lost a 1/2” of ride height over the lifetime of those worn out shocks, which doesn’t help support the vehicles weight anymore. A worn out shock doesn’t aid your leaf springs in dampening the ride/payload. I’m sure a 4600 or a stock replacement would do similar to a 5100. The leaf springs aren’t the only culprit for a sagging rear end. If the shocks are blown/old, you’re riding mostly on the springs.

Bust out your measurements from when you bought the truck new and then we can compare numbers.

 

The stock shock can be pressed down with finger strength. A 2.5 inch shock needs to be pushed with your grip and muscles to move the same amount

 

I can agree with that. I would be curious to see the brand new stock height numbers vs now with the new shocks.

 

Those numbers I do not have. The new shocks do add lift by your admission. I already understood your point about the shocks bringing the height back to OEM. I also understand your point about shocks not being designed to add lift.

The point is a new shock will add lift even though its not designed too. @timesinfinity was perplexed as was I on this matter last year. Regardless, its all understood.

For us to gain 1/2”-1” in height with new shocks there has to be some strong force behind these shocks. I wonder what would happen if the springs were removed?

 

Your axle would rip out. You seriously need to do some research on suspension. I’m done wasting my time with you.

 

Obviously the axle would rip out if you tried to drive it.

This is an exercise in understanding what shocks do to a suspension per the OP Title.

Chock the wheels. Remove rear springs. Would the 5100’s shocks hold the rear weight? Would they push even (a just a little) higher? Probably yes. Legit questions.

 

They would completely bottom out. With the help of the springs they might be perking up the ride height a little bit. But with no spring to assist. they would completely bottom out. Example, I recently installed pro shocks on the rear of my truck. Without even jacking the truck up I am able to compress the shock into place. It is difficult but it’s not impossible by hand. With shocks and springs connected, lay underneath your truck and push up. You’ll be surprised how easily you can lift the back of your truck by hand. It may be only a 1/2”-1” but it is probably comparable to the amount of tension a good shock is doing for the height of the rear end.

Another test would be taking the shocks off but leaving the springs on. Push up on the back of the truck and watch it rise easily. That’s what the shock is doing.

 

The shocks would not hold up the truck.

The spring is not assisting the shock to pull up the truck. It is the opposite. With no shock, 100% of the trucks weight is just on the spring. With a charged shock maybe just 95% of the trucks weight is on the spring. Enough lbs of assist to maybe allow the springs to push harder against the weight

 

Interesting explanation as I’ve never had a shock in my hand to be able to compress as you’ve explained very nicely.

I wonder then what is the reason for the ‘lift’ (thats not a lift)? There is something going on to raise the rear.

So far I’ve learned:
The shock raises the rear (not a lift), but can be collapsed by hand. An old shock sags the rear. A new shock raises the rear back up. Shocks can’t hold the weight of the truck because springs do this but for some reason the new shock boosts the springs higher.

 

Kind of goes back to my explanation of there is some amount of back pressure on the shocks. So when you collapse them they always go back to fully extended. There is a certain amount of foot pounds being exerted from the shock itself. So I imagine that is just enough pressure coming from the shocks to slightly perk up the ride height of the truck. Similar to barely lifting up on the back of your truck by hand, somehow we are able to slightly lift our trucks with just human strength.

Think of it like this. With the springs removed and the truck just laying on the axles, you wouldn’t be able to lift the back of the truck. But with assistance from the springs, you could lift up on the truck to the point where the springs are no longer helping you. The shocks kind of take up that slack. Especially if they are new. Since the shocks have a small amount of outward pressure they are basically perking the suspension back up. Sorry that’s the best I can explain it. I’m definitely limited on my vocabulary.