Rear Suspension Height Set

Read the info below then go to Suspension use for an interesting discussion on how to use your active rear suspension system.


So whats the problem Bunky, feel kinda low in the butt?  Butt low.jpg (66796 bytes) Maybe you feel like you're snagged on a "Skyhook". in the air.jpg (68514 bytes)   I tell ya what, lets put you up there with the "big rigs" all up.jpg (62608 bytes) !  Oh, you want to move too, now thats a bit more complicated!  The book says there are specific frame height measurements you MUST have for proper drivability measurement page.jpg (69743 bytes) , what a bummer.  I know what they mean but I don't like it to look low in the back!    I know spring blocks and shackles stink but I liked the way they made my 65 Belair look.  So whats the answer and how can I get the super ride our coaches are noted for and not have it look like I'm packing a load?  Lets talk about why they say what they do.

There are measuring slots on the front and rear of the frame and the front should measure 13 1/8" +/- 1/4" and the rear is to be 11 11/16" +/- 1/4", now you tell me you are worrying about the 11/16" -- bull!  The reality is it is giving you @ a 1" drop front to back to allow the suspension alignment specs to give you proper caster.  Caster is the alignment spec that gives you a light wheel, that also give you an easy straight ahead steer.  If you jack up the rear any amount you will screw up your caster and it may make the coach steer like you are balancing yourself on a basketball.  If you have to stay with your steering all the time, you do not have enough caster.  If you think this the problem, get on an open highway (very flat) and lower the rear of the coach as much as you dare.  If the steering becomes easier then you have proven you need more caster. 

I said all of that to say this, test for proper caster because along with a ride height adjustment, you may also need to adjust your alignment especially if you want to level out or bring up the rear suspension.  Do the test then carry on.

The real limiter of adjusting the ride height is the front suspension, sure being torsion bar you can move the adjuster bolt and raise up and down the torsion pressure but before you break out the wrenches be aware the you must first relieve the pressure on the bolt before you move it.  Replacing stripped bolts also requires the adjuster tool so you may as well get the tool now! I would suggest you keep the front about where they say because too low and you'll bottom out on speed bumps and too high makes the front end look like a DC-3 waiting to take off besides you'll over extend the front suspension on bumps, toe will be grossly off and the tires will look too small!

OK, so you've adjusted the front suspension (don't you love how I glossed over the steps to do the front adjustment!), I won't do that to you, get the torsion bar adjustment tool and bring the measure on the front slots to @ 13- 13 1/2" so If you can't get the coach up that high, your torsion bar may be twisted or the "chunk" where the torsion bar it tied to the lower A arm may be twisting, check that out. If this is the case, call me & I'll hook you up with a guy in the club that rebuilds A arms.

OK, now that the front suspension is "hunky dory", (hey, don't worry bout alignment yet), bring the rear suspension where you want it.  If you're a "spec man", bring the slots on the rear to 11 11/16" or so.   I won't put you in the corner if you are a bit off.  For you free spirits, crank that mother up to what you want it to look like.  Play with it a bit because once we finish this job. it will need to be at whatever you set to keep a good driving feel.  I will tell you this though, if you crank it much above level, you may have to come back and lower your expectations when you find that proper caster cannot be had.

I may need to mention right now that if you deviate from standard spec (and you know I love to when it suits me) you will effect other specs so be prepared to have to "give & take".  OK, using your up/down air ride adjustment on the leveling system, you now have the coach at the level you want, right?  height valve.jpg (69482 bytes) Locate the height control valves back at the air bags for the adjustment.  See the 7/16 nut at the curve of the control valve arm?  Spray it down with penetrating oil and then loosen it.  You will find the stud that the nut it on is in a slot on the arm.  Allow the valve to "pop" to a rest position in the slot.  If it needs to go further than the slot will allow, straighten ot bend the connecting rod from the control valve arm to the boggy arm to allow the height control to rest and center, now tighten the 7/16 nut and you are done!  Test the operation of the height valves by dropping the rear with the "lower" control then set the controls to "travel".  The coach should come up to the level you have set, if it does not, be sure the height valve is at center rest and try your test again.  If this does not work, pull out the wallet and get a new height valve or a stick and mark the level then use the up/down switches to set the ride height.  Hey, do be embarrised to do that, money in the pocket is a good thing!

Now comes the big test, go drive the beast and see how she steers.   If its a handful, manually drop the rear and see if it improves.  If so, stop by the alignment shop and tell them you need more caster and check the rest of it too.   If it drives good, be careful to not over extend your arm while patting yourself on the back on a job well done!

Hope this works for you, for you sticklers for on spec., disregard half of what I just said.  For you other guys, hang some fuzzy dice on the mirror, put a chrome tip on the tailpipe and rock on dude!

The 26 foot, 12,000 pound Antique Hot Rod with Plumbing -- GMC Motorhome