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 > Ride height, weight distribution, and alignment

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JohnnyT

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Posted: 05/31/04 12:52pm Link  |  Print  |  Notify Moderator

I am trying sort out some things in my mind.. Done some research but the more I learn the less I know...

My question is what is the relationship between ride height, weight distribution, and alignment? I am thinking that first one weighs the coach on all four corners sets the tire pressures correctly for the weight and then adjusts the ride height then get the alignment checked and corrected if necessary...

What got me thinking on the subject was a thread that ran a long time ago in which the discussion seem to indicate that adjusting ride height would have a material effect on weight distribution Old Thread

What I am hoping for is a discussion about the sequence I mentioned, along with the mechanics of adjusting ride height, and the effect if any on weight distribution...

JohnnyT


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wolfe10

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Posted: 05/31/04 01:44pm Link  |  Print  |  Notify Moderator

Johnny,

The sequence I would suggest is: Check ride height, weigh, move to distribute weight better if needed, recheck weight after redistribution if needed, set tire pressure, align.

Ride height comes first, as an out of spec setting can transfer literally thousands of pounds to other wheel positions. Picture for a minute the effect of having one side of the rear out of spec by just 2". To see how much extra weight that high side's wheel position is carrying, think about how many of your REALLY STRONG friends it would take to grab onto the bumper on that side of the coach and lift it up 2". The coach with the worse side to side weight distribution RV Safety has ever weighted was an air suspension coach with ride height out of spec. Adjusting the ride height brought it back to reasonable side to side distribution (they reweighted it after doing the adjustment).

If you weigh first, your readings may be way off and very different from what it will be after adjusting ride height.

Weigh next-- 4 wheel position if possible, each axle as a minimum.

Next, if there is side to side or front to rear poor weight distribution, move your stuff around (or for example decide to NOT travel with more than 1/2 tank of potable water and ALWAYS drain holding tanks before driving). Re-weight if you made significant changes. Some coaches NEED much more significant weight transfer. Examples are most (not all) older Safari DP's (very underloaded front axles), recent model National large gas chassis coaches where the rear axle is close to overloaded while quite a lot of CCC remains in front. Consider many things as "movable weights" depending on your skill level and your level of tolerance for less than ideal handling. Moving the house battery bank (4 6 VDC batteries= 250 pounds) from 6 feet behind the rear axle to 3 feet in front of the front axle will transfer around 600 pounds. Same for the generators located all the way in the rear (Safari). With the Nationals, I would move the portable water tank to the center of the forward bay (where Winnebago located theirs on the same chassis for better weight distribution.

These are certainly not the only coaches where there is less than ideal weight distribution, they are just two I have worked with owners to improve.

Next go to your tire manufacturer's PSI vs weight table for your tires and set tire pressure based on heavier wheel position on each axle plus 5-10 PSI extra (MY opinion). Do not go below tire manufacturer's minimum or over the tire manufacturer OR WHEEL manufacturer's maximum recommendations.

Lastly, get a complete 4 wheel alignment done (at least once). After you have verified that the rear axle is tracking straight, I would not pay for any more than a front end alignment on subsequent alignments unless I suspected a problem with the rear axle.


Brett Wolfe
1997 Safari Sahara 3540
EX: 1993 Foretravel 36' U-240


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wolfe10

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Posted: 05/31/04 04:02pm Link  |  Print  |  Notify Moderator

IMO, all coaches with air suspensions should check their ride height at least annually. It only takes a few minutes, and other than a ruler and a flat surface to park on, there is nothing to it.

THE CONSEQUENCES OF RUNNING WITH IT OUT OF SPEC CAN BE SIGNIFICANT. As an example, if say the rear ride height is off by 2" think of the HUGE change in drive line angle you will make on that VERY short driveshaft. Crushing your shocks on extension or compression is also a real possibility. The valves controlling ride height (three on all coaches except Alpine who used 4) are fairly flimsy and can easily get out of adjustment (and can easily be brought back into adjustment).

On edit: Make that first sentence ALL COACHES should check ride height at least annually. Torsilastic suspensions are easily checked and adjusted. Checking a leaf spring suspension will alert you to a weak spring or weight imbalance before it does other damage to the coach or suspension. The few minutes it takes is just good preventive maintenance.

* This post was edited 05/31/04 07:07pm by wolfe10 *

hotjag1

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Posted: 06/02/04 11:03am Link  |  Print  |  Notify Moderator

Brett,

Where are these ride-height adjusters at on a Spartan chassis and what do you do to adjust them?
As usual, I have lots to learn on DP's.


hotjag1
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Carjon

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Posted: 05/31/04 02:54pm Link  |  Print  |  Notify Moderator

JohnnyT I see you have a new Travel Surpreme which would of coarse would have air suspension. The air suspension should keep the ride height the same no matter how much you load into the coach. That is the purpose of the ride height system. Now I should tell you that my coach came from the factory with the adjustment off by 1 1/2 inches and had to be redone. Now having said all that you still need to weigh the coach when loaded and make adjustments to the loading to try to keep the weight with in specs. on the tires. I,ve been told that alignment should be done after the coach is loaded. I havn,t had mine done and after 31000 miles there is no abnormal wear showing up on the tires. Carjon


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mr donut

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Posted: 05/31/04 03:04pm Link  |  Print  |  Notify Moderator

Johnny, great advice so far. Ride height affects geometry which affects alignment.
The best alignment is done last and with everything in the vehicle the way it will travel most of the time. This applies to any vehicle.


George W.
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wolfe10

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Posted: 06/02/04 12:31pm Link  |  Print  |  Notify Moderator

hotjag1,

I have not worked on your model Spartan chassis, but most are very similar. You have a total of three ride height valves. Two on one axle (usually rear) and one on the other axle. Most are adjusted by loosening a hose clamp and sliding the rod. Some are threaded. It will be VERY obvious when you see them. AND they are easy to find. Start at an air bag and trace the air line-- it will lead to the valve. You will need to get your ride height specs from Spartan to know where to measure and what the distance should be. Then, just park on a dead level place and take your ruler under there.

WaterGlide

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Posted: 06/02/04 01:33pm Link  |  Print  |  Notify Moderator

My left front and right rear tires are hotter than the others with equal pressures. This was true with the Michelins and now with the Goodyears on my Spartan Mountain Master Chassis with IFS. I had two blowouts on the left front with the Mcih XRV's and that is when I tripped on the fact that the left front is hotter than all the rest and may be carrying more load. Can't get individual wheel weights here but did get front and rear, front was 950 under and rear was 250 over.
During the old thread I brought up the analogy of having a table where two diagonal legs are longer than the others and therefore carry more load than the others, ie like left front and right rear.

The Spartan has adjustments on the both fronts and only one in the back. I checked them per the specs and they were fine. However, when driving on crowned roads in the right lane the coach leans in that direction and then the ride height adjuster on the right side will reset on push up. The back end measures the ride height on the left side only and will not compensate as much. What this means is questionable.
However, this April I had a malfunction of the rear ride height when a rubber rod end pulled out on the adjuster and the rear end went way up with full air pressure in the air bags, locking the rear end on the upper stop, tried to bounce like a basketball and the dirveshaft was about two inches farther out, not good. I had to make up a new link with a threaded rod and two rod ends from a Hot Rod shop to get them back down. I always thought the rear looked alittle down compared to the front, so I raised the rear slightly. The ride height per Spartan should be 8.25 inches from the rear end weld line to the bottom of the frame rail, I sent it up about 0.6 inches higher and the dirve shaft just had alittle clean shaft showing instead of the two inches when in the up position. Drove about a thousand miles that way and the coach looks better , tire temps are unchanged but the coach only reacts about half as much when semi's are passing me, ie steering wheel correction. As the Semi approaches from the rear in the left lane, I am in the right, the high pressure in front of the truck hits my left rear first and pushes the left rear to the right and makes the coach go left. You have to resist with the steering wheel, then the bow wave from the truck gets to the front and and you have to correct for that, except the front overhang is less, therefore the correction required is less. Anyway, since the rear end is now higher, the high pressure air from the truck can now more easily flow under the higher rear end and the pushing effect is lessened. However, Spartan has informed me that the tolerance on that 8.25 inches is 0.125 inches, so I'll have to lower it somewhat.

In other words, ride height will affect weight distribution and handling, how to adjust is another matter. You need to put scales under each wheel and start adjusting to see waht happens and does a small amount of adjustment affect the weights much, if it does, then crowned roads will also affect the weights on the wheel too.
Heck, now I've got a headache just thinking about it.


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hotjag1

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Posted: 06/02/04 04:19pm Link  |  Print  |  Notify Moderator

Brett,
Thanks for the very clear explanation. If something malfunctions I want to be able to correct it. You have helped myself and others considerably!

CaptEd

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Posted: 06/02/04 09:43pm Link  |  Print  |  Notify Moderator

When I bought my Navigator last December, it leaned to the driver's front. I complained to the dealer and he had the rear adjusted to level, but the front still leaned. Not satisfied, I took it to JOSAM's in Orlando, and they did a ride height analysis. (Cost $168.00) Faxed info to Monaco/Roadmaster and was told it was in specs for its age!! It still leans....

Handling is much better now that I had the shock mounts welded back on. NO ONE discovered this issue until I crawled under to investigate myself. 5 out of 8 shocks were broken off at the top mounts. Roadmaster corrected the problem for me at a cost of $2000.00. Lazydays (the dealer) refuses to reimburse me, and the extended warranty I bought for $5575.00 (from Lazydays) denied the claim. I promptly cancelled the service contract, but lost $2000.00 due to "use". Now I am out $4000.00!!

When I have inquired about alignment for my motorhome, I have been told that unless the tires show uneven wear not to waste the money.

Handling seems to be better fully loaded. As fuel gets low, holding tanks dumped, and passengers off loaded, it tracks the truck ruts more noticeably. All in all, it is far better than my former gasser that headed for the ditch every time an 18-wheeler passed!

Bottom line: With such a dynamic change along a trip, how many would really want to take the time to shift the luggage, etc. to balance the load? It would seem to be an endless struggle to attain the perfect balance. Why bother? Everything will change next fuel stop.

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