The Stovebolt Site Forums The Parking Lot Big Bolts Independent air front suspension idea

Just found out about the independent front suspension used in some Freightliner RV chassis.
Here is a link to some info, in this link is another link to a PDF brochure with some good pictures of it.
http://www.freightlinerchassis.com/mhMain.asp?page=xcbrochure

The front suspension is made by, or designed by, ZF, here is a link to some info from them.
http://www.zf-mediacenter.de/sea_view_v2.php?id=380&pos=0&pRubA=35&lang=e

It looks like a regular A arm coil spring suspension, but bigger and with air springs.
Also uses 17" air disc brakes.
Available in 12,000 lb or 14,000 lb capacity.
10 lug wheels (semi truck size).
Hydraulic assist rack and pinion steering.
And perhaps the best part, 60 degree steering angle, (read really really tight turning radius)

I have not seen one in person yet, but will be looking for one to inspect.
Also don't know the track width, and the frame rail spacing, but theoretically it could be used under about a 3 ton truck with a little narrowing of the front cross member, think about making a modern Cannonball (big AD GMC COE)...
The rear suspension on the same chassis are also air ride, and could be more simply swapped to something older.

Just ideas, as I don't need another truck or project for a long time.
Anyone else think I am crazy?

Grigg

not crazy just a cool idea

Grigg sometimes I think you are running around in my head.

That turn radius is crazy, with that on my old dump truck I could turn tighter circles than my hot rod! Would sure beat the acre & a half I need to turn it around now.

peterbilt was using airride front axles in the 90's they weren/t too popular. western star was using them in 2003 drivers were praising the set up haven't heard anything recently. considering the improvement in ride with airride on the tractor rears and on trailers it's worth pursueing. stabilty and alignment could be issues freightliners system proably has addressed this.used to be a western star dealer there by the leehi maybe they could answer some of your questions if they are still there.

Yes, they still have some sort of Western star dealer at Lee-Hi, but never any RV chassis, and hardly any trucks, 2 or 3 at the most. I buy parts there, but I'll have to go somewhere else to see one of these front suspensions.

Grigg

I'll try to remember to take my boost off then, may be less painful :/

Would it matter? Would it be a bad thing?

Build it and we'll come admire it.

Grigg, I had a 1999 Discovery Motor Home up until last summer, with a Freightliner Chassis with that suspension and it would turn really tight with the 60 degree steering. You might keep your eye out for a wrecked or damaged rig and salvage the suspension.
Cleon

Hello Grigg,

I work at Freightliner Custom Chassis Corporation, in Gaffney, SC. I work on Line 2, RV chassis. I install 2 or three of the exact ZF IFS assemblies every day. Let me know what kind of measurements or info you need.

Seth K. Pyle

Thanks Seth, that's great!
Perhaps I saw you on TV? I forget the channel, the show was about about the Winnebago RV factory, started with the chassis assembly at FCCC.

Curious what the outside frame measurement is at the front suspension, then what is the approximate track width center of tire to center of tire?
What is height of assembly, like from bottom of frame rail to top of air bag mount?

Any chance you could take some pictures? Or is that frowned upon where you work? would be great to see some details before the whole thing gets covered with a body. Also, how does the front suspension cross-member look from the top before you put the air tanks in, where the engine would sit if it were a conventional drive-train layout?

Thanks,
Grigg

Seth would be really cool if they would let you have some access to engineering drawings, take your boss some pictures of the work Grigg has done and that he has a genuine interest in this suspension and maybe they will give you copies but don't get in trouble

Hello Gentlemen, I have PM'd the both of you, and we will go from there.

Seth K. Pyle

Seth I really want to see what Grigg would do with one of these suspension systems this could be the start of truly functional street rod Big Bolts. Grigg is the guy who could make all the pick-up guys who tore apart Big Bolts for their sound cabs wish they had their big fenders back. Ok maybe not but I know it would be cool

Grigg, You might also check with Billy Marlow -- Isn't that the front suspension under his RV?

And despite what the rest of these guys say, you are crazy. Love ya like a brother, though


John

And despite what the rest of these guys say, you are crazy. Love ya like a brother, though


John [/quote]
But John arn't we all :crazy:

Yep, We got the Freightliner chassis under the motor home. It is IFS and quite possibly the ZF. If you need them I can take picks, or measurements. Let me know.



I don't think you are crazy, I just think you project is totally cool.

Hi Bill,
I did not realize yours had the independent front, all that RV over it makes it hard to see.. And to think I was so close, and missed looking at one.

Seth has some info on the way, so unless you just want to crawl under your RV and take a peek, no need for measurements quite yet, and I doubt you can get any meaningful pictures with the RV in the way, it's not the tilt cab model is it? It does have all the other bells and whistles right? but no tilt cab??

Looks like wheel mounting surface to wheel mounting surface is about 97", and frame outside to frame outside is the standard 34" for big trucks.

All this info, so readily offered, means I may have to do something with this sooner than I thought..
The big problem will be finding a front axle assembly at a good price, as I bet it cost a bunch if ordered as an assembly form the Freightliner dealer, and if the 1997 or newer model is the one to have, because they use standard bolt pattern truck wheels, then a used/wreck will be hard to find too.

Apparently the older ones had a larger bolt circle on the front wheels, not sure what the measurements are, but traditionally busses can have an extra large bolt circle, and wheels are more expensive/harder to find, as this is just a bus thing. Another possible reason for the different bolt circle is the axle is European design, (and perhaps construction?) they may primarily use a different bolt circle than we use on trucks over here?

About being crazy, numerous times I have had people at truck shows question my sanity, It usually starts with "how did you get disc brakes under there"
My reply "I used an axle from a newer truck"
Them "But new axles are to wide right?"
Me "Yes, but they can be narrowed..."
Them "you must be crazy, I hope I never see you on the road!" :mad:

I have successfully put about 20,000 combined miles on the two axles I narrowed, from the beginning I had no doubts it would work.

This air sprung independent axle is interesting,
I'm headed to the shop with a tape measure
Grigg

Some quick measuring and figuring on my AD 6400.

Rear frame width is 36", 2" more then the current standard of 34"

Front frame is tapered, and I could see just barley getting an engine to fit if it were 24" and parallel. So, the Freightliner suspension could theoretically be narrowed 10", wheel surface to wheel surface would shrink to 87" and that's still around 10" to wide for an AD truck.

So, to fit an AD truck it could be narrowed until the frame rails were a box, touching each other, that leaves no room for an engine. So, a COE could work, engine completely behind the front suspension, and partly under the bed. I don't think that's a good idea..

So, to use the independent front a larger truck is needed, obviously the ideal project truck will have a front wheel mounting surface measurement of 97". If narrower, then only 6", possibly 8" would leave room for an engine.

I can't think of a good truck for this? possibly a GMC Cannonball, what's the front wheel mounting surface measurement on one of those?

When I am ready for a new project (many many years form now) I think it will be a late 40's Autocar single axle with a Cummins NHS (supercharged) probably an original restoration, or pretty close to it. This independent front would look wrong in that truck...

So, I still want to play with one, anyone have a project it fits, can find/buy the new front axle, and wants to pay me to make it happen?

Grigg

Hey Grigg,

Minor correction to one of your replies. The 2007 and newer IFS units have the standard 10-bolt pattern. Earlier units have the larger bolt pattern. There might be some 2006 model IFS's that have the standard bolt pattern, but I can't be absolutely sure.

Also, the info I am sending you will give you lots of good data, but it might be worth your effort to try to crawl under Bill Marlow's RV. Nothing beats seeing the IFS in person to get a feel for how massive it is.

Seth K. Pyle

Hi Seth,
I thought that was how I understood it, the new axles use the more common 10 lug pattern, old ones are larger.

The new "pictures" I have of the front axle assembly answer a few questions.

1. The axle can not be narrowed, as the bottom A-arms meet at the centerline of the vehicle, they can't be any closer to one another.

2. The Freightliner setup has a traditional steering gear mounted in the center, where the oil pan would be if there were an engine over the front axle.

I still need to do some more looking at the new information I have, but it looks like the Freightliner independent front is not a good candidate for swapping into a front engine truck, and if it were, it would have to be used full width.

I think I found pictures of a bus chassis with another perhaps more swappable version of the ZF independent front axle, with an engine over it, and rack and pinion steering. I'll try to find those pictures again, and some more info on that chassis.

Grigg

Hey Seth thank you got them today. Hey Grigg are there bigger AD trucks that used wider front axles I think that the cross member on this suspension could be notched at the top rear for the sump of an oil pan a guy may be able to mount a motor above it without a problem.

Billy;
Here is a thought. Why don't you just give Grigg your set up off your motorhome, isn't time you upgraded and and buy a new one. I know if John had a motorhome with IFS he would do it. You know, it is what brothers do.

John Gott