Springs and shocks are strong--will airbags improve ride comfort?

[daveemac]

I've been planning to install load-lifters, but recently read a comment in a Toy group stating that they make no improvement in ride quality.  The author says they help with sag & carrying capacity, but do nothing for comfort.

My Americana already has re-arched & beefed up springs, plus brand new KYB gas-ajust shocks, so I'm not worried about sag or capacity.  But I do wish that the rear absorbed road bumps better, was less tank-like.  If I set airbags at a lower pressure will it help offset my very stiff springs and brand new shocks, smooth out the ride?

Thanks!

[WME]

Adding air bags won't make the ride any softer than just the spring. You would have to remove a spring leaf and then add the airbag.  Adjusting the air pressure could keep the same ride height and a softer ride 

 

[daveemac]

11 hours ago, WME said:

Adding air bags won't make the ride any softer than just the spring. You would have to remove a spring leaf and then add the airbag.  Adjusting the air pressure could keep the same ride height and a softer ride 

 

Thank you.  Wow, so zero ride improvement?  Is there anything else I can do to smooth out the ride but keep my stiff springs?

[daveemac]

Is there nothing to be done to cushion the ride in the rear, except for removing springs?  Thanks !

[extech]

if your shocks are really stiff they can make the ride rougher. cheap shocks will give a softer ride, but handling will suffer. mostly your springs control how soft the ride is, but you have to have enough to hold the weight

[linda s]

Your shocks are brand new. They will soften up some. I hated the ride on mine when I got new Bilsteins to replace the very old KYB's but now they have softened up and seem much smoother. I think your springs will relax the touch to. Give it some time

Linda S

[IdahoDoug]

One of my areas of interest in my auto career was suspension development.  It's actually extremely complex, and the factory ride quality we experience in our daily drive is the result of a HUGE amount of development.  The suspension must perform at all load levels, all emergency handling and braking conditions, and on all the hugely varying road conditions atop all that.  

 

Air springs will actually improve the ride, especially in the way it seems you are asking about - that hard hitting initial response that makes small bumps and broken pavement edges rattle your fillings.  This is because they are progressive - soft at first and then exponentially stiffer - and it's the reason high level vehicles from Mercedes, Lexus and others have air suspensions.

 

Unfortunately, that's for an "air only" setup whereas you have leaf springs and their harsh ride in the mix, so you can't benefit anywhere near that extent.  However, you can get relief from some of that initial movement I *think* you are speaking off simply by installing air springs and then pumping them up so they raise the vehicle.  Now, the air springs are largely the reaction to those smaller initial movements.  Since there is no free lunch, now the combined rising stiffness of the air springs may conspire with the stiff steel springs to create a sharp reaction to medium bumps as both their spring rates conspire to resist movement against the moving axle.  So you'll trade reduction of that initial stiffness for perhaps an annoyance at another bump frequency.  I'd raise the vehicle an inch and see how that feels.

 

The good news is air springs are infinitely tunable in seconds and you can find something you like. I'd also suggest you alter your tire pressures to change that harsh reaction to small bumps and broken road edges. Just be mindful of not underinflating.  The good news here again is the tires are essentially air springs, and therefore also tunable in just a few seconds to achieve what you want.  I carry auto deflaters in my LandCruiser and drop the E rated tires (harsh) pressures in half on washboard gravel and forest roads, then use my onboard air to inflate when speeds rise.  DO NOT do that with your tires as offroad tires like mine are designed for operation at low inflation and road tires are emphatically not - it will damage them.

 

Having said all that, you may have embarked on this path to harshness with those beefed up leaf springs.  As I said, the factory springs were painstakingly tuned initially, and then may have sagged in your case.  Had the spring maker been very good and used the original springs' spring rates as his goal, you might not be in this situation.  But he may have gotten guidance from you that he was to create a beefy suspension that doesn't sag, and any spring maker knows how to do that - overbuild it so the customer can never come in and complain of sag.  Which unfortunately means teeth rattling ride. 

Edited July 1, 2023 by IdahoDoug

[linda s]

Well technically we could run our tires at far lower pressures than we do. Derek posted this years ago

Load Inflation Table - 185R14 - Load Range C & D

Inflation (Psi)....       26 ... 29 ... 32 .. 35 ..  38 ...  41 ... 44 ..  47 ... 51 .. 54 ..  58 ... 62 ..  65

Singe (Lb)........... 1080 1147 1213 1279 1345 1400 1466 1532 1599 1665 1731 1786 1874

Dual (Lb)............. 1036 1102 1158 1223 1279 1334 1389 1455 1521 1588 1643 1709 1764

 

Our rigs usually weigh 2000lbs or less in the front and 4000lbs in the back. 

I always lowered my pressure to 30 when I went to Pismo beach. Max load on sand is not a good thing

Good idea for daveemac to try a lower pressure. Maybe 40 in the front and 50 in the rear. At least until your new springs and shocks settle in.

Main problem with the Toyota dually is they are not deep dish. Too low and the tires will rub. My Nissan has an inch more room between the tires.

Enough that I could run off road tires. 

Linda S

[extech]

is this lbs per tire-- like at 27 psi the load can be 4400 lbs for duals?

[WME]

Spring rate=lbs to deflect the spring 1". Adding an airbag can only add to the rate. KYB and Bilstein are DeCarbon style shocks and ADD to the initial stiffness. It takes about 60 pounds of pressure to move this style of shock. Time and miles will help smooth things a bit.

The basic problem is the stock spring have a certain spring rate you have added more springs so the total rate goes up.

P.S. Were the spring bushings replaced?

[WME]

1 minute ago, extech said:

is this lbs per tire-- like at 27 psi the load can be 4400 lbs for duals?

Yes for the entire rear axle

[extech]

i found on my rig the dually installer put the rear spring hanger a little too far forward reducing the ability of the spring to extend horizontally when deflecting. this caused a really harsh ride on rough surfaces.  my fix was to add 2 inches to the shackles. really smoothed the ride and gave about 1 inch lift

[fred heath]

Shackles are supposed to move with the leaf spring. If your shackles were too far forward, they were installed too tight.

As a leaf spring flexes up or down, its length from main eye to shackle eye changes. Since one end is mounted solidly (the main eye), and cannot move, the length changes happen at the shackle end of the leaf pack. When this movement can’t happen it can cause binding and a poor quality ride.

A longer shackle will allow the spring to drop down farther while in its resting state. At this point, the shackle will be going inwards toward the axle. It may also allow the spring to flatten out more as it compresses (but this can be limited by the frame side mount, or a rear crossmember). During compression the shackle will be going away from the axle. 

It will also add a slight change in ride height.

 

You probably lucked out when you installed the longer shackles. Not that they increase the ride quality, but they can now move as expected.

 

 

Edited July 1, 2023 by fred heath

[extech]

not luck. i knew what to do

[fred heath]

1 minute ago, extech said:

not luck. i knew what to do

Your first fix should have been to loosen the shackle bolts. Adding the 2” to the shackles is not what smoothed out the ride. Allowing the shackles to move as designed did that.

[extech]

loosening them wouldn't put the mount where it should have been. longer shackles is a fix that doesn't involve cutting off the badly welded mounts and repositioning them

[IdahoDoug]

WMW,

 

By raising the vehicle with the air springs above its normal ride height with just the leaf springs, you are now using mostly the air spring's spring rate/response. The leaf springs relax an inch or whatever you raise the vehicle. We do it all the time towing our heavy boat with our LandCruiser and it's a softer ride - especially that initial shock of small bumps that rattle teeth. As I said, he's still dealing with the leaf springs as well, versus removing them and using just air.  But the first bit of (now harsh) movement will be eased considerably as the air springs have less friction to initial movement and a softer initial movement.  

 

On the DeCarbon comment, I'm not aware that there is an intentional designed-in characteristic with that conventional shock to increase stiffness of initial movement. That would be a bad thing for suspension design, which seeks as little suspension system friction as possible. The gas charge's purpose is to reduce aeration of the hydraulic fluid, and neither Bilstein nor KYB shocks are unique in that respect.  It's now a common feature.  Happy to start a separate thread on shocks if you've more to share in that area.

[linda s]

Removing the leaf springs and just using air? You crack me up

Linda S

[IdahoDoug]

A lot of vehicles use just air, but not what I'm advocating.  To get the full benefits of the ride quality of air springs, he WOULD have to remove the steel springs.  However, that's not a practical solution here, where obviously it's common to use air along with the original steel springs.  My point is if he does that (add air), he'll be able to achieve a softer ride by using them to raise the vehicle so the static load is supported largely by air, and thus the initial movements of the suspension are going to be felt more as the characteristics of air.  Make sense?

[WME]

2 hours ago, IdahoDoug said:

On the DeCarbon comment, I'm not aware that there is an intentional designed-in characteristic with that conventional shock to increase stiffness of initial movement. That would be a bad thing for suspension design, which seeks as little suspension system friction as possible. The gas charge's purpose is to reduce aeration of the hydraulic fluid, and neither Bilstein nor KYB shocks are unique in that respect.  It's now a common feature.  Happy to start a separate thread on shocks if you've more to share in that area.

Try taking a gas charged Monroe and see how much force it takes to collapse it and then take a Bilstein and do the same.

 

[WME]

P.S. Linda here is a leaf spring to air bag conversion. Way to much $$$ for this crowd.  

https://hutchswelding.com/product/universal-rear-air-suspension-kit-for-leaf-springs/

[linda s]

Damn, off road only. 

Linda S

[IdahoDoug]

WME - you've got me curious, I"ll see if I can do that.  So let it extend, then measure resistance to move it?

Edited July 2, 2023 by IdahoDoug

[Gary_M]

I want to try the zuk mod when I decide to replace my airbags. Easy enough to try, back it out if it doesn't work.

 

[WME]

11 hours ago, IdahoDoug said:

WME - you've got me curious, I"ll see if I can do that.  So let it extend, then measure resistance to move it?

Yep, put it on a scale and push. 

[daveemac]

Thank you for all the replies so far, very helpful and appreciated.

 

The KYBs have <30 miles on them, so it's good to know they'll soften up some.

If I understand right, the airbags will compress partially before the springs do, which sounds like it will noticeably smooth out the ride.