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Old 01-17-2011, 10:40 AM   #1
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Default HDT suspensions

It appears to me that there are a number of different kinds of rear suspensions on big trucks; traditional leaf springs and some kind of air suspension. Can someone point me to an article or link that explains the difference and possibly the pros and cons.

I'm interested in a HDT conversion to pull my race trailer and would find it helpful if I could raise the back of the truck to lift the front of the trailer up to make getting the low riding race car in and out of the trailer.

Thanks for the help! Dick
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Started looking for 379 Peterbilt TC, 24' to 30' box, bumper pull but ended up w/1999 Liberty Coach conversion of 45' Prevost XLV bus. 1,000sf heated/AC'd race shop w/dump station, 50amp shore power where coach parks. Three NASCAR/ARCA race cars & 26' trailer.
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Old 01-17-2011, 07:32 PM   #2
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I thought most of the trucks now have air bag rear suspensions. I think the steel leaf springs on the drives are mostly gone aren't they? There are several advantages to the air bags. When you load the rear axles with a heavy load it's very easy to adjust the height by adding air. You can also dump the air to drop the back down like when you need to back under a trailer. My rear axle is air ride and it automatically levels the rig. So when I fill up my water and hitch a heavy trailer it still rides at the exact same height. I rarely dump the bags but have a couple times when trying to make sure the tail of my trailer doesn't scrape coming out of a driveway or something. I don't think you'd get a ton of lift by airing the bags way up tho. I've seen Powerhouse Coach offers a option of a high lift air bag for manuvering over stuff. They want several thousand for it tho. What I do when loading the race car is use the leveling jacks on my coach and lift the back of the coach as high as I can with those, leaving the front jacks retracted for max angle. That works pretty good for me. My jacks I can lift the back wheels off the ground with.
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Old 01-17-2011, 10:22 PM   #3
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Lift the back wheels off the ground? Holy smokes! I'm impressed. Do the leveling jacks typically have that much traveling and power? What kind are they?

What kind of race car do you have?

Thanks for the info!
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Started looking for 379 Peterbilt TC, 24' to 30' box, bumper pull but ended up w/1999 Liberty Coach conversion of 45' Prevost XLV bus. 1,000sf heated/AC'd race shop w/dump station, 50amp shore power where coach parks. Three NASCAR/ARCA race cars & 26' trailer.
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Old 01-18-2011, 07:21 AM   #4
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I think my levelers are "Equalizer Systems" brand. www.equalizersystems.com They seem like pretty good levelers. I use some blocks of micro-lam placed under the plates to keep them from wrecking the pavement so much, and it also gives me more lift height.

My son's got a heavily modded '99 Vette fixed roof coupe. He runs in NASA Super Touring 2 I think. He's got a 442ci LS motor, almost 700 crank shaft h/p normally aspirated. Tons of suspension and brakes and aero. He got the car running mid summer last summer so he's still learning it but he took it to Mid America for a practice day and beat up most everybody. I've got a '86 Vette coupe with a 383ci forged 10.5/1 mini-ram trick flow heads, moderate cam, big brakes and lots of suspension mods that I autocross and do some high speed solo NCCC (National Council of Corvette Clubs) and SCCA stuff, and open track HPDE stuff. My son also has an '87 Vette coupe that he gutted out and did big brakes, some suspension, and long tube headers with true dual 3" pipes, no cats. All our cars have 4 point roll bars (he's going to cage his '99 at some point). That '87 he runs 335/30/18 Hoosiers on all four corners. Looks like a steam roller. Sticks like glue. Weighs 2700lbs. He dynoed that and got 330 rear wheel torque so it does pretty well. He's a very good driver. 22 years old and he's been autocrossing since 2 days after his 16th birthday.

Here's some shots of his '99: Welcome to Facebook

Here's a few of his '87: Welcome to Facebook

Here's some random shots: Welcome to Facebook
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Old 01-18-2011, 07:57 AM   #5
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Dick, my Rig has a garage, I have air suspension in the rear. A switch on my dash lowers the rear to allow for easy loading an unloading of the car. We also have Bigfoot levelers, 4 big pads come down remotely and can lift the entire Rig off the ground. G
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Old 01-19-2011, 06:58 PM   #6
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I had the same problem loading my sprint car. The "poor boy fix" was to slide under the truck,remove the 1/4 inch bolt from the back rearend that attaches the ride height rod to the control valve.Push up on the rod and the airbags wood raise the rear of the truck about 8 inches.Car went in the trailer just fine after that. Just need to be careful not to over extend the airbags. Most trucks have the ride height control valve mounted on the crossmember at the rear of the frame. If the truck doesn't have anything covering the rear crossmember you can do it from the top.Only takes about a minute.Just don't forget to reinstall the bolt before you leave!
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