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Old 04-19-2011, 09:06 AM   #1 (permalink)
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Peterbilt air suspension

i did not want to hijack/clutter this thread : http://www.pirate4x4.com/forum/showt...=933305&page=8 .... so i post the pics over here

maybe this info is useful for guys with U-haul/MDT/HDT trucks that would like to convert from leaf spring to air suspension.

the popular Peterbilt "air leaf" (AL) and "low air leaf" (LAL) are a prime candidate (and can be found at bigrig wrecking yards)
here are pics to illustrate the difference;

note that the AL (left) is made out of large forget aluminum parts where the LAL is all steel

the LAL is riding significant lower with a low hanging air bag cross beam






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Old 04-19-2011, 02:16 PM   #2 (permalink)
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here is a pic of the low hanging LAL inflated to ride height ...



... and a pic of the LA on my (very dirty) 379 with the air deflated



notice the better departure angle and the well protected air bags....
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Old 04-19-2011, 02:42 PM   #3 (permalink)
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What is unique to the "pete" air leaf suspension? This design looks the same as about every other truck I've driven except Kenworths. Does Peterbilt just have the patent? Maybe some of the others were SUA.

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Old 04-19-2011, 06:40 PM   #4 (permalink)
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How much does a LAL setup cost from a wrecking yard? I'm wanting one mostly so I can drop the truck down for loading stuff. Don't think I've ever seen it on a semi, but school buses often have air front suspension too.
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Old 04-19-2011, 06:44 PM   #5 (permalink)
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New model 587 Petes and Freighshaker Cascadias have optional air fronts. I think Columbias and Coronados might as well.

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Old 04-19-2011, 10:54 PM   #6 (permalink)
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A lot of the lowrider semis have removed most of the leaves and install air bags over the front axle, as well as using auto transport front axles, they are built with more of a drop in them than "regular" semi front axles.
CSM now builds an air flip up front bumper kit for the lowriders, for when they get into a bad spot, they can flip the bumper up (hinged at the top and air cylinder about 1/2 way up the bumper, hinges bumper out at about 90 degrees)
And thanks to the OP for posting up the pictures showing the differances!
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Old 04-20-2011, 05:42 AM   #7 (permalink)
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Great thread Rooster. Pete AL suspension is the best, IMO. Never had the honor to ride on a LAL tho. Started out with air ride on a Pete 352 (110" cab) bought(1974) from what is now Rush down on McDowell. Never much cared about KW 8 bag. Can't remember the name of the place there in Phoenix, but when I was picking up some fuel tanks 4 bag Neuways(spl?) cut-offs were selling for $2K. Minus tires/wheels of course.
Harold
Learn something new every day. About those "Texas snow plow" bumpers being hinged and flipping up with air ram.
Back in the mid 60's IIRC some of the old cracker box GMC's had an air set-up on the steer axle. Didn't last long.
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Old 04-21-2011, 02:25 PM   #8 (permalink)
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lal is the king of over the road suspension. it's like riding in a 1959 caddy that corners like a vette.
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Old 04-21-2011, 02:58 PM   #9 (permalink)
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What is unique to the "pete" air leaf suspension? This design looks the same as about every other truck I've driven except Kenworths. Does Peterbilt just have the patent? Maybe some of the others were SUA.
i think the extensive use of aluminum is unique to the Peterbilt LA ....
yes, IIRC Kenworth uses a somewhat complex 8 bag push/pull arm suspension on twin screw trucks that is difficult to convert to single axle ... and for that reason also difficult to retrofit to another frame.
i have no clue about other brands like Freightliner and Volvo ....never worked on one ....
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Old 04-21-2011, 03:24 PM   #10 (permalink)
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How much does a LAL setup cost from a wrecking yard? I'm wanting one mostly so I can drop the truck down for loading stuff. Don't think I've ever seen it on a semi, but school buses often have air front suspension too.
"dumping the air" for loading or easier access when camping is very nice... but the biggest difference is the smoothness of the ride.
my old rig...

(the red one in the back) was also air suspended (International's version of the LAL ) and i towed a trailer behind it for at least 50k miles and never had a single issue with it ...
but my buddy with the leaf spring chevy MDT in that pic was having a lot of problems; his hitch developed cracks and he needed to have the tongue of his toybox trailer fixed a couple times and finally re-enforced due to flex issues.
the ride in his truck was also significant rougher then in my rig.

i personally would never drive a (MDT/HDT) truck without air susp (i guess i'm getting old and soft)
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Old 08-24-2011, 05:15 PM   #11 (permalink)
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I am also interested in the cost of this setup complete from a yard vs a Kelderman for my MDT F750 that is only air assist in the rear and rides like a jack hammer.
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Old 08-24-2011, 07:40 PM   #12 (permalink)
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I am also interested in the cost of this setup complete from a yard vs a Kelderman for my MDT F750 that is only air assist in the rear and rides like a jack hammer.
Any of the above for $400 less the bags in my neck of the woods.

Nat
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Old 08-25-2011, 10:42 AM   #13 (permalink)
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Any of the above for $400 less the bags in my neck of the woods.

Nat
That is pretty cheap... has anyone done a build thread on putting one in a MDT?
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Old 08-25-2011, 10:46 AM   #14 (permalink)
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That is pretty cheap... has anyone done a build thread on putting one in a MDT?
i sold the LAL to Machinos .... so hopefully he will provide us with a build thread soon
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Old 01-05-2012, 04:12 PM   #15 (permalink)
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The OP's pic no longer work..

I really want to do away with my leafs front and back.
A LAL is available but I don't know if a AL would better suite my needs on a F750.

I can't see this being terribly difficult to retrofit, but I have not seen another 650 or 750 done I am probably missing something...
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Old 01-05-2012, 04:53 PM   #16 (permalink)
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Here's the setup on Rocky's F700. All pretty simple.


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Old 01-05-2012, 05:44 PM   #17 (permalink)
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Thanks for the pics.

That is the LAL I take it... pretty low but looks like a no brainer to put in.

I was wondering how bad the anti-squat might be.. especially unloaded.. I have been driving this truck alot lately as a DD.
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Old 01-05-2012, 05:49 PM   #18 (permalink)
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Why is there a leaf there at all wouldn't an arm work just as well. Whats the benefit to the leaf if you have the bag
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Old 01-05-2012, 08:26 PM   #19 (permalink)
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Quote:
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Here's the setup on Rocky's F700. All pretty simple.
He did a very good job on that. Slick
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Thanks for the pics.

That is the LAL I take it... pretty low but looks like a no brainer to put in.

I was wondering how bad the anti-squat might be.. especially unloaded.. I have been driving this truck alot lately as a DD.
That's Pete Air Leaf. LAL has re-curved springs. In the shape of a "C". When pulling empty trailer, or bob-tailing, the rear-end does rise some. IIRC my Pete would come up about 3"s

"Neuway" is another brand of air-ride suspension. But, Peterbilt is considered the 'top shelf' of them all. KW's 8 bag system is more complicated and seem to
roll from side to side more. At least on the ones I've driven. FreightLiners' air ride is similar to Petes' air-leaf
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Old 01-05-2012, 09:07 PM   #20 (permalink)
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Why is there a leaf there at all wouldn't an arm work just as well. Whats the benefit to the leaf if you have the bag
Axle articulation. If you use solid arms mounted solidly to the diff you get a wide swing arm suspension.
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Old 01-06-2012, 05:25 PM   #21 (permalink)
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The Pete Air Leaf and Low Air Leaf have minimal travel, only a few inches and suck if you do get into the dirt but will be ok on a 2 axle. Air trac is the way to go for a taller bag that will give you more suspension travel.
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Old 01-06-2012, 06:02 PM   #22 (permalink)
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The Pete Air Leaf and Low Air Leaf have minimal travel, only a few inches and suck if you do get into the dirt but will be ok on a 2 axle. Air trac is the way to go for a taller bag that will give you more suspension travel.
Can't the bags on the LAL or AL be changed out to a taller bag?
Of course bag size would have to be figured out before mounting to the frame.. lower/higher the mounting point = able to use taller/shorter bag?

I have been doing ALOT of reading on the inernets about all the various setups, the AL, LAL, Flex Air, Air Trac, some aftermarket setups like silent drive.. but they are way to pricey.. the consensus being the LAL is not a very good setup for anything rougher than flat gravel roads and with any air setup a locking diff is essential for anything off the pavement. I don't have a locking dif but its not often my rig goes off road as its 2wd. I have on occasion been down some rough shit with the trailer to get to the trail which would have been brutal on a air ride I'm thinking.

I am just pretty determined to get rid of these leafs, but looking for the most beneficial and cost effective setup. You can get these LAL's fairly cheap from what I am seeing... still trying to figure out why this swap isnt done more often, if ever, on these F-650/750's. Everyone seems to use the Kelderman rear bag setup with the leaf which mine has and still rides like a pogo in the rear when not loaded.


Edit: This would be the shit if money were no object..

http://www.hendrickson-intl.com/prod...has_single.asp

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Old 01-06-2012, 06:27 PM   #23 (permalink)
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Edit: This would be the shit if money were no object..

http://www.hendrickson-intl.com/prod...has_single.asp

There are tons of suspensions like that in the wrecking yard. Go search and you'll be rewarded.
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Old 01-06-2012, 07:09 PM   #24 (permalink)
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sorry ... yes, unfortunately the pics of my original post are gone

yes, the "Low Air Leaf" is a heavy but great riding suspension
unfortunately the LAL is clearly rated by Pete as a "on road only" suspension (btw the lighter "Flex Air" rides even better ... but is also strictly "on road" rated ... and its low riding aluminum beam would be very exposed to rock damage )


the "Air Leaf" is a lot lighter then the LAL (it uses large high strength aluminum frame hangers and air bag "spoons") and tolerates higher axle articulation and is rated for "off highway" use.

the "Air Trac" is basically identical to the "LA" . the difference is that the AT uses radius rods instead of the LA`s quarter leafs to locate the axle.
the AT has also quarter leafs, but they terminate on slipper pads instead of spring eyes.
this allows the AT to tolerate more flex and also results in its "severe off highway" rating.
if i`m not mistaken the AT has the same travel (and air bags) as the AL
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Old 01-06-2012, 07:58 PM   #25 (permalink)
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Can't the bags on the LAL or AL be changed out to a taller bag?
Of course bag size would have to be figured out before mounting to the frame.. lower/higher the mounting point = able to use taller/shorter bag?

I have been doing ALOT of reading on the inernets about all the various setups, the AL, LAL, Flex Air, Air Trac, some aftermarket setups like silent drive.. but they are way to pricey.. the consensus being the LAL is not a very good setup for anything rougher than flat gravel roads and with any air setup a locking diff is essential for anything off the pavement. I don't have a locking dif but its not often my rig goes off road as its 2wd. I have on occasion been down some rough shit with the trailer to get to the trail which would have been brutal on a air ride I'm thinking.

I am just pretty determined to get rid of these leafs, but looking for the most beneficial and cost effective setup. You can get these LAL's fairly cheap from what I am seeing... still trying to figure out why this swap isnt done more often, if ever, on these F-650/750's. Everyone seems to use the Kelderman rear bag setup with the leaf which mine has and still rides like a pogo in the rear when not loaded.


Edit: This would be the shit if money were no object..

http://www.hendrickson-intl.com/prod...has_single.asp

Hitmoney
i think the Hendrickson "HAS" has also a limited offroad rating ...
if i could afford to buy a new setup like that i would pick the "Primaax" or "Firemaax"

IMHO if i would be you i would check local junkyards and search for a AL or AT.
the downside is riding height; IIRC the Flex and LAL are intended for tall van trailers and ride at a low 8.5" (center axle to bottom of frame rail) but hang very low with exposed airbags.
the AL/AT are intended for skateboards/dump trucks and ride a tall 12.5 ... but have excellent ground clearance (high riding air bags with no crossbar)

i`m kinda in the same boat like you; i`m reusing the AL that i have left over from my Pete (single axle conversion) on my next truck (medium duty IH).
but the riding height and the "stiff" bags (obviously engineered for a heavier truck) are not ideal.
so my solution (after some headscratching )
is to replace the big "weld on" spring saddles (1.5" tall ) on the axles with a lower saddle pad that is integrated/braced into the axle housing (.25" tall)
i also figured out that (with some tweaking) i can mount the spring hangers higher up on the frame rails.
together with slightly shorter bags i`m able to bring the riding height to ~10.5 inches without loosing travel.


however, air springs have a catch; bigger is actually better ...
the more active air volume you have the better the ride
(that is the reason why MCI buses actually use hollow air spring support beams that are open to the air springs to increase air volume = comfort)
so my "trick" is to replace the factory Pete "internal bumpstop" bags ...



with a "non bumpstop" model like this ...



the lack of the bumpstop with its support structure results in a significant larger bag volume that (i hope ) will increase the ride comfort
naturally i will need to add external bumpstops between axle and frame to avoid damage to the bags at full drop

the new airbag also eliminates the two frame holes in the "no drill zone" (Pete frames are drilled for the bag studs before heat treating) ... i would not be comfortable to drill that area of the frame on a retrofit.
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