What shocks with air lift bags?

leathermaneod · April 29

Hi all,

I just got back from my first camping trip after upgrading to load range e tires and installing airlift 5000 air bags. Definitely a good improvement, but now I’m on to my next upgrade, shocks. I know I want to go with bilstein 5100’s, but I’m having a hard time choosing between the normal 0-1” of lift, or the 2”. Reason for this is I did not measure my stock height right before adding the bags and consequently do not know exactly how much lift they added at minimum pressure. My front height with stock size tires at 60 psi is 36 1/4” inches from ground to bottom of fender centered on the hub. My rear with minimum 5 psi in bags and stock size tires at 70 psi is 39 5/8. I really thought my rear before was about an even two inches higher than the front, but that would mean the bags added 1-3/8! I called bilstein to see what they recommended and they immediately said my warranty would be void if I’m at 1-1/2” over stock and I use either option because it’s out of spec. I asked if they don’t have any leeway in either direction and the guy said yes, a little, but 1/2” is a lot. He did send me directions on how to measure, but it feels like I’m making this more difficult than it needs to be. Anyone else been through this?

mikeyk101 · April 30

When normal conditions (not towing, etc...), the Airlift 5000 bags as suggested, should be at 5 psi like you did and which should have no height difference whatsoever. And if you went with stock tire size, even with going to a different load capacity, the rear hight should not really change.

I have my front end leveled up about 2" with Rancho Quick lift struts and went with 275/60R20 instead of 275/55R20. This changed the stock tire size from 32" to 33" overall but that works out to about only 1/2" higher. It will slightly change based on air pressure aand I usually run them around 40 psi. Cold Max is 51 psi. I also changed my rear shocks out to Bilstein 4600 (not adjustable like the 5100's) as they were recommended as a better choice for towing. (I occasionally pull my 25' toy hauler which when loaded comes in around 6300lbs.) I just checked rear height on my Silverado 1500 LT and it is very close to 39".

But in reality, even if you change tire size and add the airbags but run them at the recommended 5 psi, there should be very little change between the space between the axle mount for shocks and frame mount. That's what needs to be considered. Unless you added or removed the rear suspension blocks, there should be very little if any change. The rear height of ground to the fender actually only comes in to play when making sure the the camper load distribution is properly set.

I added the Airlift bags after towing my toyhauler a few times. Because I leveled the front of mine (2" higher) I ran into a different situation. My load distribution hitch called for adjusting by checking front wheel well height. As far as that went, I had it dialed in perfectly. And like just about all 1500 trucks, when you have a 3 ton trailer connected in rear, the rear had the normal 2" sag. When in stock configuration, the front end will normally be roughly 2 or so inches lower than rear (raked) unhitched. So when trailer hitched up and wdh adjusted, the rear ends up about the same height as front. Mine unhitched has about the same height front and rear already but hitched, that 2" rear sag, although completely normal, caused an issue with truck front and rear angles. The front end even though correctly adjusted, still had the headlights pointed slightly upwards which was a problem at night. The solution was to add the air bags and adjust the rear height back up a bit after trailer hooked up. I think when towing, I raise airbag pressure to between 25-30 psi IIRC. It didn't add any extra load capacity, it just made sure that the very front end where headlights and bumper are, were now at proper angle.

Sorry for long post and I hope it made sense. But like I mentioned above, the shock height is in relation to difference between axle mount and frame mount of shock. If you don't change anything suspension related, you are still stock height. And all shocks are meant to go in and out some so IMHO, I wouldn't be really concerned on the 0-1" or the 2" stated with the Bilstein 5100's . Tire size difference will only affect height of axle to the ground so no effect on shock. The Airlift bags especially when at 5 psi, will have very negligible impact on the space between axle and frame. I would say it's up to you and what you want. I went with Bilstein 4600 because several said that they are cheaper than 5100 and good choice when towing, they just weren't adjustable.

mikeyk101 · April 30

TL;DR...

I do go overboard at times...

Tire size will make no difference to the 0-1" or 2" when choosing a rear shock. The space between the shock mount in frame and shock mount on axle doesn't change because of tire size. It only changes if you change or remove the rear suspension blocks. Airbags will also have very little affect on this as well unless you bump them up considerably higher than the 5 psi. And that really only needs to be done when hitched to heavy camper or a heavier load in the bed. I believe you are confusing how to ensure and measure that truck is adjusted after adding a load and picking appropriate shock size.

leathermaneod · April 30

I appreciate the long post and yes it made sense. I also appreciate your advice and the time you took to reply. I understand what you’re saying about the height and the tire size and the fact that the air lifts should not affect height, but I’m almost positive that they have. I gathered some more data to add this afternoon. My actual tire size is 275/65/r18, so .2 larger in diameter. I understand that works out to .1 of an inch of lift over stock. I remeasured my height on a flat surface with 6.9 psi in both bags, I use a digital gauge and leave a small buffer to the 5 psi required because I don’t want to risk damage to the bags. With no weight in the bed, driver side is 39-7/8”, passenger is 40-1/8”. Fronts are 36-1/4” and 36-5/16. With no air in the bags, driver rear is 39-1/2 and passenger is 39-3/4. My shocks measure, from center of bolts to center of bolt, with 6.9 psi in bags, 21-5/8” driver and 22-1/4” passenger. I’d be very curious to hear others measurements.

leathermaneod · April 30

As far as shocks go, I was planning on using Bilstein 5100s for the 0-1” lift in the rear and for about 1-1/2” in the front. I thought I had been told that the 5100s and 4600s are basically the same except for the height options. Maybe I should try lift blocks in the front instead.

mikeyk101 · May 1

Forget about tire size and distance from ground to wheel well. Whether you have 25" tires or 35" tires, that will have no effect on the distance from top shock bolt to bottom shock bolt. That remains consistent unless suspension modifications are made. That is what you should pay attention to. The Airlift bags will change that bolt to bolt distance slightly but not a great deal when at 5 or 6psi. The thing to pay attention to is the extended and compressed length on the replacement rear shocks.

I have the Airlift wireless compressor kit on mine and have it set at 5psi. I also have a cap on bed that adds maybe 200lbd on rear suspension. I measured my 4600 shocks bolt to bolt at both 5psi and 15psi. I don't have completely flat ground but pretty close. Drivers side at 5 was about appx 20-3/4 and at 15 was about 21-1/4. Passenger side was appc 21-1/2 at 5 and just shy of 22" at 15. My lengths without the cap would probably be about the same as yours.

The 5100 rear shocks (0-1" lift) have an advertised eye bolt to eyebolt compressed length of 16.18", an extended length of 25.79" and overall travel of 9.61". The 4600 ones have compressed length of 15.98", extended length of 24.8" and overall travel of 8.82"

And after looking into it, you are correct in that the internals between the 4600 and 5100 are identical.

From specs on the rear 5100 shocks and your measurements, you should be just fine. I would say you would also be fine with the 4600's as well.

And as far as lift blocks on front, I would caution you on those. If you were thinking about something like the Rough Country leveling blocks, putting them in wasn't too terribly bad. But the bolts that came with the kit are something else. I had them on for a couple years and then wanted to replace the factory struts. The bolts rusted so bad that it was a nightmare getting bottom of strut removed. Never again. I learned my lesson and would only use a strut like the 5100 to level. I ended up going with the Rancho Quicklift struts and accomplished the same thing.

And if you do go and use the 1-1/2" setting on the 5100 struts, don't get concerned when rear of truck ends up lower than front slightly after hitching up your camper. It is supposed to sag because of the added weight even with a weight distribution hitch. It's normal as I explained in post above. With my Equal-I-zer weight distribution hitch, it only instructs you adjust it so the distance from ground to front wheel well back down as close to unhitched height as you can. It (wdh and adjusting) doesn't have much affect on the normal sag in rear end after hitching up. The Airlift bags will help raise the rear so that your rear can be close or even with front. That's why I have them.

Edited May 1 by mikeyk101

leathermaneod · May 2

I really appreciate all the time you took to reply and to take those measurements! I think I'm starting to get what you’ve been saying all along. I really didn’t change anything as far as suspension goes. I was focused too much on actual height because I was trying to determine if the bags had raised it or not. I ordered the Bilstein 5100s for the rear. I will almost certainly end up doing the same for the front, just not right now. I appreciate your input on the front lift blocks as well. If I go that route, it will only be temporary to determine what height I want to permanently set the Bilsteins at. I’d hate to go through all the work of setting them for 1.5 and wishing I’d gone lower.

leathermaneod · May 2

By the way, how do you like the airlift compressor system? Was it much work to install?

mikeyk101 · May 3

I think it's a bit pricy but works very well. I got it as a warehouse Amazon special so I saved a few bucks. I got the 25980EZ system as it was simply a bolt on setup. I installed it on the passenger side frame rail toward rear of cab. I picked up some corrugated split loom wire cover for the power wires to conceal them and ran the red and black wire right to the battery. I zip tied the wiring and cover along frame rail to keep it up. I didn't connect the pink aux wire and haven't had any problems. The wireless feature comes in handy and makes it so simple to check present pressure and to adjust the bag pressure as needed. I can also use the Airlift app on my phone.

When I first installed the bags, each bag was on its own hose and I ran it towards rear bumper. I installed the Schrader valves in bumper footwells on each side. This kept each bag independent when adjusting. With compressor, both bags are tied in together and adjusted equally now. I did keep the one Schrader valve and hose on passenger side as a backup in case the compressor ever fails but so far, so good.

I was also concerned about water getting into the compressor when using. The system comes with an air filter and hose so I was able to mount the air intake just towards top of frame rail. So far it has been fine. I just make sure not to drive through any deep water which doesn't happen often anyway.