HerNameIsSway

Hey guys,

I was unable to find any threads on VaD in the first 10 pages of searching "lowering trucks."

I have a 1976 Dodge D100 pickup 2wd and I use it for towing my race car long distances, so it is seeing a lot of highway miles. One of my small concerns is the gas mileage (I've basically done everything I can possibly do) and I thought lowering the truck would help with aero, but I want to make sure I'm keeping the truck "purpose built" and keep it reliable and safe.

I have already installed a tonneau cover to reduce truck bed drag. I have also installed load-leveling airbags in the rear (to improve the sag for extra weight in the truck bed and pulling a trailer) as this somewhat helps the angle of my truck reduce underbody drag. I have also installed new struts on all 4 corners so the ride is much stiffer/smoother and not so bouncy. This makes towing more stable and feels safer.

Since I already have airbags in the back, I was thinking about adding some in the front. I am still researching how they are installed up front, but here are my questions:

Are there any handling benefits while using airbags up front?

Do airbags replace the struts and/or coils up front? If no, where exactly do the airbags go?

What is the most effective/suitable way to combine the ride height adjustibility and stability of a tow truck?

Here are my goals:

-Drop the height of the truck in both front and rear for better aero on highway driving, but have the opportunity to raise it up for any reason (such as dirt roads or driveways with changing elevations) using onboard air
-Modify/improve this antique truck rather than buy some other truck that is newer/better/more suitable
-*NOT* to slam the truck like most slammed trucks that you are thinking

This truck is not destined to be a show truck, but it would be neat to have a few tricks up its sleeve, but my biggest thing is to merge height adjustments with suspension that is safe and suitable for long term towing.

I saw this thread, where swapping D-series control arms for B-series control arms automatically lowers the front of the truck 3 inches, which sounds great, but I am having trouble figuring out how I can raise it back up 3 inches and still keep the performance aspect of the suspension above par.

http://www.dodgetalk.com/forums/showthread.php?t=328611

Pics of his mod:


Anyone able to shed some knowledge to help me piece this plan together?


Cliffs:
Edit: Changed "biggest concern" to "One of my small concerns is the gas mileage (I've basically done everything I can possibly do)"

Flinch

What kind of mileage are you seeing now?

What size motor, what trans, etc.?

JETSWU87

you're going to spend more money trying to improve the gas mileage...then the savings from getting 1-2mpg better.

HerNameIsSway

I have a carb'd 318ci V8 with a 3-speed auto. I am running on steelies with 235/75 R15 non-aggressive all season tires.

I get about 12-14mpg average with an empty bed and no trailer doing typical city/highway driving.

When towing with a full bed, tonneau cover, and trailer with car, I got 9mpg driving up and down the Allegheny mountains (of course, the steep incline was killer) but on the boring flats of Ohio I was getting 15-16 mpg on a fully loaded truck and trailer. O_O

HerNameIsSway

Well yeah I understand that, but if I want to get into mods and making the truck look more "flattering." I think lowering the truck would be sweet, but I'm wondering how airbags work with the suspension system.

I just realized I started this thread as a concern for gas mileage and not suspension capabilities, haha.

I was making a point that lowering the front would help underbody drag, thus effectively helping aero/mpg of the whole towing rig (although minimal, but that's not really helping my case here).

This thread is strictly for asking about how airbags work and finding out if they are good for what I am doing with the truck, as not all airbags are strictly for show/lowering, but they're supposed the help trucks somehow, right?

Fabrik8

Functionally, air bags just take the place of a coil spring. So you're just replacing a coil spring with an air spring. The big difference is that an air spring is obviously adjustable by changing air pressure to change spring rate and also changing ride height for a given spring rate as a consequence. It would be better if air pressure could change spring rate independently of ride height, but oh well.

I was going somewhere with that train of thought, just can't remember where.

HerNameIsSway

So you're saying that airbags operate on the same level as the coil springs they replace? If I just remove the coil springs and throw in air bags, they're going to function just the same? What about when it's lowered, the stiffness of the airbags is much less, in terms of PSI. I dont see how the airbags can keep up with the coils' performance, as the pressure never changes in coils, but they do in airbags.

Computer_Nerd

i put a 6" abs plastic air dam under my front bumper of my diesel f350. helps tremendously. there is a reason tractor trailers have those low bumpers up front -- to keep the air from going under the truck -- plus you still have clearance for speed bumps and stuff.

use 3/16" thick abs plastic (eBay has some decent sellers that can sell you sheets) and two joist hangers (made for 2x6" wooden deck beams, home depot/lowes has them cheap) mounted upside down. the joist hangers can use the bolts under your truck bumper and can mount the abs by pre-drilling and putting machine screws with washers and nylon locking nuts on them.

works amazingly well and you can take it off when not towing or when you want it to just look original.

Fabrik8

You're re-stating my post, yes.

Pay close attention to the spring rate independent of ride height part....

With a coil spring you have a spring rate and a spring length, and you have the same thing with an air spring but only fordo a givenspring air pressure. So just like a coil spring, the starting point for height at a certain pressure with a air spring is important.

HerNameIsSway

I had thought about this and started researching this right before you posted this. I really liked the tractor trailer front air dam idea, so I could some up with some way to integrate that into the vintage look of the truck, or as you said, have it installed for long distance towing.

Got pics of your air dam work on your F350?

Regardless of MPG improvements, I initially created this thread to understand how the performance works between coil springs to air bags. So the air bag is 100% a real possible replacement for the coil spring?

I dont know much about suspension geometry and the variable changes in spring rates of a constant changing airbag. I dont know how to read spring rates and stuff, so I gotta try to find and learn that stuff. Mind teaching me a few things about it? I'm still trying to get my head wrapped about your post so I can go down that path and continue research and learn more about it.