5th-wheel trailer towing specifications

[HINO SG]

Hi.

Couldn't decide which forum to put this in so thought I'd start here.

I have a HINO SG, which is very similar to a Mitsubishi FM. Towing capacity is listed at over 10,000 pounds.

Chassis has a 230" wheelbase, and is bare, working on a design.

Assuming the chassis is loaded to say, 2/3 of max GVW (33,000 lbs) with the weight distributed evenly between the axles, how far behind the rear axle can I consider mounting the fifth wheel hitch without developing dangerous handling characteristics towing a 10k trailer?

 

[HINO SG]

the general idea

http://www.classytrucks.org/Isuzu/Isuzu.Lahore_RV.jpg

 

[cwsqbm]

How far back depends on the tongue weight/pin weight of the trailer. That 10k trailer rating would have been with a certain tongue weight a certain distance behind the rear axle. If the tongue weight of the fifth wheel is twice that tongue weight, the pivot point would need to be less than half the distance from the rear axle. You really want to get it as close as possible to rear axle, as that's the main benefit of a fifth wheel. I'd do more research on sites that focus on converting HDT (there are a lot of them) to tow fifth wheel campers, as they frequently have the fifth wheel behind the axle (after removing one of the rear axles) to get more weight on the drive tires.

 

[HINO SG]

How far back depends on the tongue weight/pin weight of the trailer. That 10k trailer rating would have been with a certain tongue weight a certain distance behind the rear axle. If the tongue weight of the fifth wheel is twice that tongue weight, the pivot point would need to be less than half the distance from the rear axle. You really want to get it as close as possible to rear axle, as that's the main benefit of a fifth wheel.

I may have used the wrong terminology. Don't remember the exact number but the GCVRW was at least 10,000 lbs (I want to say something like 13K) more than the GVW. In my case my 10,000 lb trailer is going to be well within the axle and brake ratings of the truck traveling in a straight line, i.e. barely over the 33k GVW. Won't matter how the weight is distributed. I'd like to retain the load carrying area of the truck w/o a trailer, and also the cost of cutting the frame and building a new bumper (the current ICC bumper is perfectly good).



So, with say, 23,000 lbs distributed evenly on a 230" wheelbase- is there any reason having the 5th wheel pin for my hypothetical 10,000lb trailer 8-9 feet behind the rear axle would cause unsafe braking and cornering conditions? Picture the truck photo in my second post with a longer overhang and the hitch toward the end.

 

[HINO SG]

Also, what is the maximum height for the 5th wheel pin on a typical trailer, and what are typical clearance requirements for the bumper, tailgate of the truck?