Increasing Towing Capacity

[Sam_Sprott]

Good evening,
Who sets the towing capacities for motorhomes? Why is my 25' class A on a P30 chassis limited to a 3500# tow limit, when a 30' class A on a P30 chassis will have a 5000# limit? Both rigs using the same engine/transmission combo. What are the legal and safety ramifications of exceeding my 3500# restriction if a heavier duty tow bar is installed and auxiliary braking is used on the toad?
My short rig has all the upgrades on the suspension to improve controllability. I have a buddy who had a 36' Dolphin being pulled by a Ford 460 with a 4500# toad. My 25' with a Chevy 454 is restricted to 3500#. What gives??
Thanks,
Sam

[tatest]

Chassis manufacturer sets a GVWR and GCWR for each chassis variation, based mostly on weakest links.

Working with this, the RV manufacturer may put a tow rating on the RV as a whole, based on components installed and the RV structure. It can be less than GCWR - GVWR. Some manufacturers extend frames beyond what was supplied by the chassis manufacturer, others might just build more house back there without extending the frame. That 3500 pound limit came from GM, for many of the smaller P30 ratings.

Comparing a P30 to a Ford chassis, often the Ford will come from the factory with a higher GCWR, in some cases a high enough rating to support a 10,000 pound tow rating, if the RV manufacturer wants to use that.

[n7bsn]

lre01 wrote:
Good frame shop should be able to advise you if they can increase the towing ability and certify it. I never did it on a MH, but on class 8 trucks we had axles added, frames beefed up to carry point loads and hitches installed to pull 20 tons, all with a new door tag to certify the modifications made.

Well, except that the frame is not the only factor effecting tow-rating. Two different P30's might have different brakes, cooling systems, suspension systems, etc.

As noted above, a large number of factors can effect the tow rating

[lre01]

Good frame shop should be able to advise you if they can increase the towing ability and certify it. I never did it on a MH, but on class 8 trucks we had axles added, frames beefed up to carry point loads and hitches installed to pull 20 tons, all with a new door tag to certify the modifications made.

[bsinmich]

I do remember seeing one RV owner who seemed to exceed his tow limits a few years back. It was in the UP of Mich. and he had just gone o ver a dip in the pavement. He had literally broken the back of his MH and it was sitting on the side of the road with the rear end dragging on the pavement and the fiberglass cracked from the wheel up to the roof. That would be one way to total a MH. and probably not get any insurance coverage. In my first MH, a '76 Fireball that was 21'long there was no frame suitable to attach a trailer hitch so I could not tow anything. Many time you will find that a Manuf. will change the specs on a frame from one year to the next. Not all P30s are necessarily the same.

[Francesca_Knowl]

The manufacturer sets the limit based on a number of factors too varied to enumerate here, especially since we're talking about an RV. Those vary so wildly not just from model to model like a car, but from unit to unit due to all the "options" folks add when ordering. Suggest you inquire of the rigmaker directly as to your particular limits.

Per advisability of overtowing, I can only point out that your practical limit is the weakest link in the whole system, whether it's your frame, shocks, axle, braking ability, or simply the point on the frame that you choose to attach your new hitch to. I suggest you examine the rig very closely and identify its weakest point before you proceed.

Per legal ramifications: I'm not of the apocalyptic crowd that sees lawyers lurking at every corner...on the other hand, risk-averse as I am, I see little return in taking a chance on giving one a hook to grab me with while at the same time perhaps damaging a perfectly good RV by exceeding its practical capacity.

[1492]

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