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| Re: [GMCnet] sreering [message #367466 is a reply to message #367463] |
Tue, 02 November 2021 16:33   |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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I am sorry I did not get back sooner but I have not been home to do it.
Here is what I wrote up while traveling and using someone else's computer.
Here is the problem. The rears once set will automatically adjust the height when weight is added or reduced (changing the height) on one side and not the other. Setting the rear ride height needs to be done correctly first. The sensing switches do not care about how much weight is on the pair of wheels. They only care about changes in height. If one side is 400 or 600 pounds different than the other. The air system will automatically compensate by adding air to the heavy the side bag only.
The front is different. The front will lower or raise when enough extra weight is added to one side or the other. There is no level sensor to automatically add air to adjust for this. So the fronts are a STATIC height adjustment while the rears are a DYNAMIC adjustment constantly changing due to weight changes, or road slope changes, or cross wind changes, etc.
So on initial set up if you find one side in front too low and you adjust the torsion bar, you will be adding additional weight on that wheel. You also will be adding additional weight (downward force) to the one pair of wheels diagonal to it.
Think of the coach as a perfectly flat block of wood sitting on a perfectly flat surface. All 4 corners should see and equal amount of the block's weight. Now slide 4 coins under the 4 corners of the block. The 4 corners should still see a equal amount of weight. Now add a 5th coin to any one corner and you will end up with an increased weight the two diagonal corners of the block and a lowering weight to the other two diagonal corners.
We see this all the time when scaling a coach and adjusting ride heights. Many times we see this diagonal descrepency while weighing random coaches at GMC rallies. This is why we measure every coach's ride height prior to putting them on the scales. By looking at the ride heights and the weights together we can make recommendations to the owner on what to adjust in what order.
I know I did a poor job explaining this but here is what we do when adjusting ride heights.
We start with the rear wheels first. Make sure that the cold tire air pressure is correct for the weight the wheels are carrying. We adjust the rear heights as close as possible. Then drive the the coach on flat roads for about 5 miles, recheck, and readjust as necessary. Sometimes we have to do this up to 4 times to get it within spec while and after driving.
THIS STEP IS IMPORTANT. Next we block the rear frame in place using our pre-cut ride height measurement blocks. (a pair of 2x4s cut to correct frame height.) Put the blocks vertically in place and drop the rear of the coach enough so the frame is applying a couple 100 pounds to the blocks and can not move.
Now go do the fronts. Adjust front torsion bars for the approximate ride height and EQUAL weight (within 100 pounds). Once the weight is equal, adjust the PAIR of torsion bars up and down the same amount of turns for the proper ride height.
That is it. REMOVE THE BLOCKS AND YOU ARE DONE.
Ken B.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Wed, 03 November 2021 07:12] Report message to a moderator |
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