Ride Height Adjustment.

Joe-K · 10-10-2006, 08:08 AM

Just was curious how many folks are checking the ride height of their rig. Especially with the short drive shaft on our pushers, the ride height is critical. If the height is off, the driveshaft U-joints are flexed unnecessarily and are prone to early failure.

Here's how to do it.

The ride height should be checked at each scheduled maintenance interval. This is every six months or 6,000 miles, whichever comes first. The method for checking the ride height is simple.

Ensure that the coach is on level ground, the air suspension is fully inflated and that you have full air pressure in the air tanks (120 psi on the dash gauges).

Always block the tires to prevent the coach from moving any time you climb under your RV.

For the front suspension on an I-beam axle, slide under the coach behind the front tires. Using a tape measure (butt the tape against the lower flange of the frame rail, do not hook it over the edge), determine the distance from the lower frame rail flange to the center of the lower-shock absorber bolt. This dimension should be 10" +- 1/4".

For the front ride height on an Independent Front Suspension (IFS), measure from the center of the upper shock-absorber bolt to the center of the lower shock-absorber bolt. This dimension should be 17.5" +- 1/4".

On the rear suspension, slide under the coach behind the rear axle. Measure the same way that you did for the front I-Beam axle. The dimension for the rear suspension should be 9-3/4" +- 1/8".

Joe-K · 10-10-2006, 08:08 AM

Just was curious how many folks are checking the ride height of their rig. Especially with the short drive shaft on our pushers, the ride height is critical. If the height is off, the driveshaft U-joints are flexed unnecessarily and are prone to early failure.

Here's how to do it.

The ride height should be checked at each scheduled maintenance interval. This is every six months or 6,000 miles, whichever comes first. The method for checking the ride height is simple.

Ensure that the coach is on level ground, the air suspension is fully inflated and that you have full air pressure in the air tanks (120 psi on the dash gauges).

Always block the tires to prevent the coach from moving any time you climb under your RV.

For the front suspension on an I-beam axle, slide under the coach behind the front tires. Using a tape measure (butt the tape against the lower flange of the frame rail, do not hook it over the edge), determine the distance from the lower frame rail flange to the center of the lower-shock absorber bolt. This dimension should be 10" +- 1/4".

For the front ride height on an Independent Front Suspension (IFS), measure from the center of the upper shock-absorber bolt to the center of the lower shock-absorber bolt. This dimension should be 17.5" +- 1/4".

On the rear suspension, slide under the coach behind the rear axle. Measure the same way that you did for the front I-Beam axle. The dimension for the rear suspension should be 9-3/4" +- 1/8".

SargeW · 10-10-2006, 11:24 PM

Good info on the ride height Joe. If it's off a little, how would the adjustment be made?

Joe-K · 10-11-2006, 12:58 AM

Well, Freightliner suggests taking it to a dealer, but the adjustment isn't very difficult.

Most rigs have 3 ride height control valves. Ours has 2 in the rear, and one in the front. The ride height control valves are mounted on the side of the frame rail, and have linkages that connect to the axle. As the distance between the axle and frame changes, the linkage opens and closes the ride height control valves either venting or adding air to the air suspension.

The valve body's themselves have a nut on the side of them that when loosened allows the linkage to be rotated on the valve body. By moving the adjustment, the motorhome body is raised or lowered.

It's best to make adjustments in small increments and be sure to work the suspension by moving the rig after each adjustment to make sure the rig is resting at it's new height after the adjustment.

SargeW · 10-11-2006, 07:56 AM

Thanks Joe,

I'll check the height and see if i'm within specs. I was wondering what determined ride height on our rigs.

Follow up question tho, I am going to add a lift for the Harley in about a year. Is that the same adjustment that may be needed to compensate for the added weight on the rear of the coach?

Jestme13 · 10-11-2006, 10:18 AM

Sarge, I would think if the ride height was correct to start with, it will adjust itself for the added weight of the bike. I'm planning on adding a bike carrier too. But not the heavy lifting type, the bleu ox that allows toad hauling with it is my choice.

Jestme13 · 10-11-2006, 10:21 AM

Great information Joe, thanks.

SargeW · 10-11-2006, 10:53 AM

I looked at that one too Steve. Is that the model that has 3 two inch receivers on the back of the RV that the hitch slides into??

I would like to see it in person, to see how sturdy it is. I also will need to haul the toad as well as the bike. Maybe I'll see it at the RV show here in a week.

JRP · 10-11-2006, 11:00 AM

Sarge,

The Freightliner drwg of those height adjustment vales and linkage arms which Joe is describing, is available for viewing (PDF) at the files section of the Yahoo Group for Freightliner Chasis Owners Club.

FCOC Files

Jim

varmint · 10-11-2006, 09:09 PM

Call freightliner with your Vin # first. Some chassis have different ride height spec. My
XC chassis has a solid front axle, spec.s are:
front 10 1/16 +/- .125
rear 10 1/4 +/- .25

Dane

SargeW · 10-12-2006, 12:56 AM

Thanks for the update. I have the XC chassis as well. I'll check the FL owners site for the diagrams. I registered with them when I first picked up the coach.

Jestme13 · 10-14-2006, 04:56 PM

Yes Sarge, it does have the 3 recievers. I have a bike carrier that uses 1 reciever, I can buy the needed parts to modify it to a Blue Ox configuration for about 1/3 the cost of the whole new unit. My problem is finding a welding shop confident and economical enough to do the job. It is the perfect setup for us.