p32 chassis sway at speed when passed

[Drjay]

I have a R vision Stratus, I have owned from 2003 when it was new. It was stored for most of it's 10 k miles of life, until I retired last year. After spending a ton of money getting it road ready for travel. I can not figure out why it gets blown off the road when I get passed and then sucked back on the road as the semi goes by. I have replace the original Michelins with Firestones. Replace all of the shocks, all of the bushings, front and back, added a track bar. All of this has only made a slight improvement. At50 mph it is ok but at 65 it is a real problem.
Currently, I have it a local truck shop they have checked the alignment and the steering linkage and all is good. and they think the Firestones are the problem. And want to replace them with Michelins. However, they are only 65% sure that this will cure the problem. He has experience with p32 chassis on van trucks and said that they were tire sensitive.
Any one else have this problem and what was the cure??

[Isaac-1]

I can only tell you my journey to minimizing getting blown around, and which modifications seemed to have helped the most:


I bought my coach in 2016, at about 74,000 miles the previous owner had put about $3,000 worth of suspension upgrades into the coach in the preceding 18 months. These including a Safe-T-Plus steering stabilizer, a pair of super steer bell cranks and a super steer track bar. So I have no experience how bad it was before these were added, though the previous owner claims they helped a lot.


My coach came from the factory with front and rear sway bars



Then I did the following in this order:


Added rear Sumo Springs, they helped some on rear sway, but did not do much for passing trucks


I then in fairly quick progression replaced the shocks with Koni FSD shocks, this improved the ride a fair amount, mostly helped with pavement transitions like going onto a bridge, etc.


Next I replaced the worn rear sway bar bushings and added a Roadmaster Front Spreader bar which changes the front sway bar mounting geometer on wide track front end P32 coaches built after 2001. This mostly helped with body roll, at this point 18 wheelers passing were still a considerable issue, but had been slightly improved.


I had the coach weight for 4 corner weights, and adjusted tire pressure accordingly based on RV tire pressure chart, this was not a big change, only dropping the front tires by 5 psi, enough to feel it, but a small change overall


I then had the front ball joints replaced and upgraded to Super Steer no air bag from springs, again this improved ride quality, softer front end ride feel, but did little if anything for handing

I had a front end alignment done by a local shop at this point, and have never been fully happy with it compared to the alignment done by Josams in Orlando for the previous owner. Unfortunately there are few alignment shops within a couple of hundred miles of here that do motorhome alignments.



Next was adjusting the play out of the steering box, WOW big improvement, as much or more than all the others put together, and significantly improved the feel when big trucks passed me on the interstate.


Finally I added a rear Loadlifter 5000 Airlift airbag kit with in cab compressor control, this was again a BIG improvement on handling in cross winds and when big trucks pass, the key here was the in cab compressor control as it allowed me to increase or decrease the pressure in the rear air bags to match road conditions, ie crank up the pressure to 80-90 psi when on good smooth pavement with cross winds, or lower down to 30-40 psi on rougher pavement as the rear end would get too bouncy then if set at 80-90 psi. Optimal rear end air pressure also varies if we are pulling a TOAD or not, with the Yaris TOAD I usually run around 40-50 psi.

[yeloduster]

Originally Posted by Drjay

I have a R vision Stratus, I have owned from 2003 when it was new. It was stored for most of it's 10 k miles of life, until I retired last year. After spending a ton of money getting it road ready for travel. I can not figure out why it gets blown off the road when I get passed and then sucked back on the road as the semi goes by. I have replace the original Michelins with Firestones. Replace all of the shocks, all of the bushings, front and back, added a track bar. All of this has only made a slight improvement. At50 mph it is ok but at 65 it is a real problem.
Currently, I have it a local truck shop they have checked the alignment and the steering linkage and all is good. and they think the Firestones are the problem. And want to replace them with Michelins. However, they are only 65% sure that this will cure the problem. He has experience with p32 chassis on van trucks and said that they were tire sensitive.
Any one else have this problem and what was the cure??

Before you do anything drastic you should check your tire pressures. Both over and under inflated tires can cause vague steering, limited traction to offset side forces against the motorhome. It would seem strange that the tires are a problem of the magnitude that you expressed.

In the chassis guide Workhorse isn't too helpful with setting airbag pressures. This is a quote from the chassis guide:

"The air bag cylinders should be inspected periodically for signs of deterioration, damage or leaks. To verify possible leaks with the air bag removed from the vehicle, inflate the bag and submerge it in water and check for air bubbles. The standard track suspension system, 4,880 lb. or 5,500 lb. GAWR, utilizes an Airlift Heavy Duty Bag, Workhorse part no. W8803508. The wide track suspension system, 6,000 lb. GAWR, utilized a high-pressure air cylinder from its introduction in Nov. 1999 to Aug. 14, 2001, Workhorse part no. W0001111. Beginning on August 15, 2001 a new coil spring, Workhorse part no. W0000991, was integrated along with the Airlift Heavy Duty Bag, Workhorse part no. W88035508, on all wide track 6,000 lb. GAWR suspensions. The new coil spring originally was blue in color for ease of identification during the change then returned to the standard black starting in the production week of December 1, 2003. Regardless of the spring color the new coil spring is approximately 12% stiffer then the previous spring and is a direct replacement for all P32 chassis. Inflation pressures in either air bag cylinder should be maintained at 50 PSI minimum to avoid chafing. Maximum pressure for the Airlift bag used on the 4,880 lb., 5,500 lb. and the 6000 lb. post Aug. 15, 2001 GAWR suspensions is 90 PSI. The high-pressure air cylinder use from Nov. 1999 to Aug. 15, 2001 on the wide track 6000 lb. GAWR suspensions has a maximum of 110 PSI. Air bag cylinder pressures will vary depending on load and preferred ride quality. Workhorse suggests initially setting the cylinders at 50-60 PSI for the 4,880 lb. axle and 80-90 PSI for the 5,500 lb. and 6,000 lb. axles. Finally air bag pressure should be adjusted for personal comfort and load within outlined recommendations. The general rule is higher inflation pressure firmer the ride quality."

The ride height of the front suspension should be adjusted by setting the airbag pressure. On my older P32 I set the air pressure so that there was 1.75" between the bump stop and the bump stop landing pad while the motorhome was on a level surface. I set the air pressures for the tires according to the GAWR of each axle. I didn't weigh the axles. I had also added stiffer sway bars, a rear track bar, new shocks, etc. At that point I considered the handling as good as a P32 was going to get!

There is very little you can do to make it completely impervious to the buffeting of a large vehicle passing you. It will happen...physics in action. You can't change the laws of physics. A light (comparatively) vehicle like yours with a long, high box on top of it will be pushed around by a heavy (comparatively) vehicle like an eighteen wheeler with a long high box on it.

[Isaac-1]

One thing I forgot to mention, last year I switched to Sumitomo ST719 tires, which handle much better than the Hercules tires the previous owner installed. So much so that I occasionally find myself speeding as I am driving faster than I thought I was.

[paddy_blu]

I have a 32ft fleetwood fiesta. I recently bought it used with 54,000 miles. The front end seemed low. It has new tires on it. I have scheduled to have the front and rear coils replaced. It was recommended to have the coils replaced with sumo coils followed with a front end alignment.
The RV generally drives OK but it gets pushed around by trucks passing. Will that help?

[Isaac-1]

P32 coaches often look low on the front end even when they are correctly setup, there are specific measurements you can take shown in the service manual to tell if the chassis is riding right.

[Mark_K5LXP]

A few years ago when I went to Quartzsite I went to a vendor "seminar" (sales pitch) where they promise that when they're done you will love your P32. I recall the package was around $10K. Was mostly bolt on stuff (shocks, supersteer bits, probably new bushings, track bar, not sure what else). I wouldn't spend that much on my old RV. I've just come to grips with the idea it's a P32, not a Prevost. It's what you get when you make an RV out of a delivery truck. If this were a W22 or W24 one could entertain retrofitting a different suspension but that would be an even more spendy proposition. Given the age of these things and the fact it's an orphan chassis I wouldn't go down that road unless I had tons of money and really, really loved the RV. From what I'm reading some F53 models are nothing to write home about either but at least there are more aftermarket options for those.

The above citation about the airbags is correct. They're not optional, as in something you inflate for the ride height or ride comfort. Per the shop manual they're inflated to a minimum of 50PSI at all times. When I was working on my front end I experimented with different pressures and the ride difference between 0PSI and 90PSI is hardly noticeable. The height difference is 5/8", not something you'd observe just looking at it. My concern is bottoming out and damaging things so my air bags are filled to 90PSI and left there. New shocks have made the most noticeable difference in ride. I'd entertain the addition of a panhard bar as they're not terribly expensive or difficult to install, just hasn't floated high enough on my RV to do list yet. Maybe when I'm back there to do brake and axle service in the next year or so.

Mark B.
Albuquerque, NM

[wolfe10]

What PSI is in the air bags inside the front coil springs?

[yeloduster]

Originally Posted by paddy_blu

I have a 32ft fleetwood fiesta. I recently bought it used with 54,000 miles. The front end seemed low. It has new tires on it. I have scheduled to have the front and rear coils replaced. It was recommended to have the coils replaced with sumo coils followed with a front end alignment. The RV generally drives OK but it gets pushed around by trucks passing. Will that help?

I don't know where you got your quote but there are NO coil springs on the rear of a stock P30/P32. I think I would look for a different shop! In addition, the front suspension design of the P30/P32 is such that Sumo does not make a model for the front of the P30/P32. The front of the P30/P32 has air bags inside the coils on the front springs. These air bags need to be in good condition and properly inflated. See my post earlier in this thread regarding the P30 chassis.

I don't think you need new front springs. Properly inflating the front air bags will be just as good and cost a boat load less money. The rear springs are leaf springs. They may be sagging after years of the motorhome setting on them. Again, I wouldn't replace. The symptom for rear spring fatigue is that the motorhome rear suspension will allow the rear to sag. The rear bump stops my be degraded from the motorhome setting on them. Instead of new rear springs I suggest SUMO springs in the rear. Sumo Part #SSR-290-54.

Spending a boat load of money on new springs will NOT help getting pushed around by big trucks. Things that can make a difference are: Shock Absorbers, sway bars front and rear and a rear track bar.

I suggest that you get the stock suspension in good repair BEFORE considering any after market products. Make sure the shocks are good. Make sure the ball joints and tie rod ends are good. Adjust the bell cranks if necessary.

You don't mention the year of your Fleetwood Flair. The year will tell us a lot about the motorhome and may help us guide you to better wind buffeting resistance.

[Isaac-1]

Originally Posted by wolfe10

What PSI is in the air bags inside the front coil springs?

It depends on how much weight you have on the front end, though for most people it will be in the 60-80 psi ballpark.

[wolfe10]

Originally Posted by Isaac-1

It depends on how much weight you have on the front end, though for most people it will be in the 60-80 psi ballpark.

Yes, sorry I should have been more clear.


Was interested in paddy blu's PSI following some of the mis-information in his post.

[1972VWbus]

It will also be determined by the bags used.

Air Lift 1000 (81560)
Minimum Air Pressure/Maximum Air Pressure
Motorhomes and Commercial Chassis


Min 40 PSI (2.8BAR) / Max 90 PSI (6.2BAR)



Trucks and Passenger Vans



10 PSI (0.7BAR)50 PSI (3.5BAR)



FAILURE TO MAINTAIN CORRECT MINIMUM PRESSURE (OR PRESSURE

PROPORTIONAL TO LOAD), BOTTOMING OUT, OVER-EXTENSION OR RUBBING
AGAINST ANOTHER COMPONENTWILL VOID THE WARRANTY.


1.Check air pressure weekly.

2.Always maintain normal ride height. Never inflate beyond 90 PSI (6.2BAR) for
motorhomes and commercial chassis, 50 PSI (3.5BAR) for trucks and passenger vans.
3.If the system develops an air leak, use a soapy water solution to check all air line
connections and the inflation valve core before deflating and removing the air spring

[Beav12]

I bought my '04 HR Traveler 26RB2 Workhorse from a couple in KS. It drove so poorly his wife refused to ride in it ever again. They (and maybe previous owners?) had done almost everything imaginable to correct it - front springs, tie rod ends, ball joints, control arm shafts & bushings, bellcranks, Konis, rear panhard bar... everything but the front anti-roll bar mount spreader. Actually, I had them install the panhard and Safe-T-Plus Silver dampener before I would buy and drive it back to KY. The last two helped it be manageable to drive, well, driving in traffic was still pretty dicey and even being passed by something like a Ford Explorer took as much planning to steer into, away from and back into, as a passing semi, in order to avoid mangled metal.

BTW, I'm a retired mechanic, fifty years in with more cert's and factory training than I want to shake a stick at. Having done nothing but alignments for six of my early years, my boss, who liked to track such things, informed me that for those six years I averaged 21 alignments/day (x 6 days/week = over 39,000 alignments, not counting those I did during the rest of my career.) Point being, not many can argue with my experience re: suspension woes.

Once home and having a chance to give it more than a driveway inspection I couldn't find anything wrong, other than the crappy four leaf rear springs. I tossed a pair of Sumo springs in (easy and inexpensive) just to see if they would help. They made quite a difference, reducing the side-to-side rolling, but I realize they are more of a band-aid solution. The ride height is in spec, front and rear, but those long, thin, skinny rear springs are pretty sad engineering.

Having grown up with aviators in the family, and having worked in race car shops, I thought I'd give the AirTabs a go as I've seen how well VGs perform in those areas. Well, I wouldn't buy them expecting any MPG returns but they certainly took the white-knuckle, constantly watching for approaching traffic, portion out of the equation and made driving it a one-handed proposition. Broad-siding winds can still toss you around a bit but not nearly as much as they used to do. Now they just make roll more than steer you around.

If it had been built with rear air springs, mounted ahead and behind the rear tires (instead of to the inside of the tires - picture effects of leverage) and didn't have the ceiling mounted bed making it that much more top heavy, it would be better but neither of those things are going to happen. Now I'm mulling over adding a rear Air Lift 88219 kit or having my local spring shop add a leaf, re-arch, whatever. I'll probably make 2-3 trips and see how it does before deciding...

[Isaac-1]

I added reat airlift 5000 airbags about 4 years ago, it helped considerably over the sumo springs I had installed in 2016