[Archived]

The problems we have in our coach is we sit forward of the steer axle so we have no way to sense what is happening with respect to the rear. We can get a sense of what is happening by how the steer axle is moving up and down relative to the chassis because we feel that.

I know the forces in the rear can be substantial because on on trip through NYC we were entering the George Washington Bridge from the NY side and we hit a bump that literally lifted the clothes hangars off the rod in the rear closet and dropped them on the floor of the closet. I felt that bump when the steer axle when over it and it was among the worst we ever experienced. Those are the kind of bumps that break welds if the hitch has much weight on it.

[Corey]

Lots of good info, thanks everyone, gives me a lot to think about.

If someone could clarify since I am no Prevost expert, on my coach, a2002 Xl2 40 foot the rear overhang is short, on a Xl 45 of the same vintage I notice the rear overhang is longer.

At Prevost the other day looking at newer (X3 I think) 45’s the rear overhang behind the axles seems to be shorter, similar to my 40.

So did Prevost update this and change it? Any difference in towing/handling/weight carrying characteristics?

[Peter]

Prevost does not differentiate between 40 and 45 foot coaches for hitch limits.

The X3 compared to the XLII was to make all conversion chassis the same. Prior to the X3 the entertainer chassis and the motorhome chassis had the different wheelbases (and rear overhang).

[Archived]

G-man,

I’m curious, where did Marathon locate the holding tanks in your 40 footer?

[Glenn]

All the tanks are just in front of the drive axle, smaller capacities than on the 45ft according to my owners manual but not by a whole bunch.

I realize that Prevost does not state different capacities, and it makes sense why they would not, but why did entertainer shells differ? Did they know most enertainers made pull a trailer? Sure there has to be something to that.

[Clifford]

The longer wheel base on the entertainer coaches was to provide a better ride and to provide more bay storage space.

As far as entertainers pulling a trailer, that was rarely the case 10 or 15 years ago, but now it is fairly common. But when it comes to overloading the hitch the motor home owners with the tri-axle stacker trailers or the Harley on the bike lift win the prize for excessive loading. Most entertainer coaches are pulling smaller trailers.

[Archived]

Thanks G-man,

I know what you mean about the shorter rear overhang of the 40 footer. All things being equal, the shorter overhang would certainly be capable of supporting greater shear and moment loads; however, I don’t think anyone is going to go out on a limb to publically say how much – you’ll need to consult a PE licensed in your area and supply him with complete chassis drawings, tube sizes, joints and attachment methods, and all the loadings involved including engine, transmission, and accessory systems, then there’s the additional house loads applied by the converter. Since Prevost uses the same tongue and towing weight restrictions as a 45 footer, they must have other concerns probably more related to the handling and braking of the bus and related to the dynamics of the combined bus and trailer two mass system. Your overhang is shorter but your wheelbase is shorter too. I’d be interested to know if the ratio of overhang to wheelbase is the same as, or close to that of, a 45 footer?

[Ron]

I believe the XLII overhang increase on a 45 footer is equal to the width of the rear compartment door that is behind the tag axle on 45 footers. The balance of the extra length is in the bays.

[AL]

I can’t vouch for accuracy, but here’s an article that lists the following wheelbase and overhangs.

XLII-40: front: 68.75″, wheelbase: 279″, rear: 82.75″, storage (below floor): 315 ft3

XLII-45: front: 68.75″, wheelbase: 314″, rear: 107.75″, storage: 407 ft3

Entertainer: front 68.75″, wheelbase: 339″, rear: 82.75″, storage: 433 ft3

H3-45: front: 75″, wheelbase: 316.12″, rear: 107″, storage: 505 ft3

[Archived]

I would imagine as the rear overhang increased the Prevost engineers modified the structure that supports the engine cradle to compensate. I would also surmise they did not modify the structure to carry additional tongue weight, but to maintain the same limitations.

Apart from a better turn radius, I cannot figure out what other motivation Prevost would have for the wheelbase on a 45 footer being different than in an entertainer coach, unless the intent was to use the greater rear overhang to shift more of the weight from the front axle to the drive and tag axles.

According to the Prevost folks at the Tampa Rally the current 19,000 pound steer axle limitation is the limit on X3 coaches (which have the longer wheelbase, and less rear overhang), and to get up to 20,000 pounds they have to add about 1,000 pounds of additional weight, wiping out any gain in carrying capacity. I can bet the X3 shells are giving converters nightmares trying to stay within axle weight limits on the steer. At that point it might be a good thing to hang a motorcycle lift on the rear to counterbalance some of the weight now carried by the steer due to the longer wheelbase.

[Archived]

I think it probably was for better weight distribution. I guess one could argue that fully loaded touring coaches are more uniformily loaded than motorhomes. Motorhome’s tend to have point loads and they tend to be located between the axles in the belly of the beast. As you know, shifting the drive axle forward puts more weight at the rear overhang and less on the steer axle which lessens the bending moment at the center of the coach (and increases the bending moment at the rear overhang). The decreased bending at the center of the coach may also ease slideout functioning. Have you ever sighted down the side of your coach at the belt line? You can see a marked sag in the chassis at midspan of the wheelbase (it’s slight but it’s there) – shift the axles to the outer edges of the chassis and that sag (deflection) get’s a bunch bigger which may cause issues with slide bearings and such. So it’s probably a combination of benefits: less weight on the steer axle, less mid-wheelbase deflection, better point load handling, better turning radius, better slideout functioning, and perhaps more space for a bedroom slide. It’ll be interesting to see how all this is handled in the future with the newer chassis.

Of course, it may have just evolved that way! 🙂

[Archived]

Hey guys, well going with an 18k gvw stacker that will keep me at legal or very close length, I think I can load this one to keep tongue at or very close to Prevost specs, will verify with tongue scale. Also after reading a lot of customer reviews on different RV forums I am going with the AirSafe hitch setup, this should really help alot of abuse from the road being transfered back to the coach…and trailer.

Once I get it all setup, scaled and road tested I will report back!

[Corey]

David,

I posted it at one time (but don’t know where) the data from tests on the Prevost chassis. I know all coaches deflect, but what astounded me about the data I posted was after a simulated multi hundreds of thousands of miles the bus could be supported under the chassis support points and if one support was removed the deflection (or twisting) was negligible. I have seen that in my own garage when I have support stands under the coach and it blows my mind that the engineers made such a strong structure.

But when G man talks about 18K worth of trailer I don’t feel real comfortable. I can think of a lot of instances when that is going to have an impact on the operation of the coach and possibly the structure.

[Sammy]

Jon,

Static deflection measurements are over here on page 50 of the STURRA Altoona Test for the X3-45. The max deflection was 0.137″ with an evenly distributed load of 21750 pounds and a GVW of 60340 pounds. The amount of deflection I’m talking about when sighting down the side of these motorhomes is on the order of 0.100″. Very small, but the human eye is good down to 3 thousandths of an inch!

[Dick]

Someone mentioned the Sherline trailer tongue scale in their post.

https://www.sherlinedirect.com/index.cfm?fuseaction=category.display&category_ID=13&CFID=41723915&CFTOKEN=84777660

I have one, really educated me.

If I remember correctly, the inventer created it after having a problem with his race trailer and trailer hitch.

Good company, good product, American made!