RV Design engineers--wheelbase compromise

[DirtRider]

Originally Posted by twinboat

That's you, not everybody is going to load the same way. Really, 2 feet ? Does the include tongue weight, if towing a trailer.

Yep, that calculation included tongue weight. Which has far less effect on anything if the rear axle is closer to the hitch. I agree that I'm probably a unique case, in that I have a small, lightweight C on an E450 with a reasonably long wheelbase. That's my point, I guess. Most C's will be worse than my situation, not better. And everyone will load differently, but no one could put much more weight on their front axle than anyone else. All the differences in loading will be felt at the rear axle. So, why not put more weight on the steer (by extending the wheelbase), and let everyone have a more comfortable drive?

[17 Oaks]

Originally Posted by Chuck Q

I think the short wheelbase is a result of trying to get a tight turning radius. Most folks would tear down the stop lights on a right turn without the short wheelbase.

You GOT IT!s

Closer the axles are the less scrub you have when makes your tires last a lot longer. Spread out the distance of those towed axles and the scrub would eat a set of tires in a few thousand miles.

As for where the axles set that affects Pin/Tongue weight. So you take the weight of the towed unit and the wt capacity of the adds on's. Let's say the built along with a nominal wet weight is 10,000 lbs and the capacity (stuff you add, clothes, dishes etc etc etc) is another 3000 lbs. The bulk of which is in the forward bays (unless it's toy hauler, then the bulk would be rear loaded)

All of this is in some 'fuzzy math calculations that determine where the 2 axles sets go in order to have enough weight at the pin/tongue to insure that the rear end does not violently begin its left-right swing dance going down the highway.

Lots of assumptions are in play and they provide a good margin of error to keep the lawyers off their case when you overload and or have more load in the wrong place as in the rear causing sway.

[DirtRider]

Originally Posted by 17 Oaks

You GOT IT!s

Closer the axles are the less scrub you have when makes your tires last a lot longer. Spread out the distance of those towed axles and the scrub would eat a set of tires in a few thousand miles.

As for where the axles set that affects Pin/Tongue weight. So you take the weight of the towed unit and the wt capacity of the adds on's. Let's say the built along with a nominal wet weight is 10,000 lbs and the capacity (stuff you add, clothes, dishes etc etc etc) is another 3000 lbs. The bulk of which is in the forward bays (unless it's toy hauler, then the bulk would be rear loaded)

All of this is in some 'fuzzy math calculations that determine where the 2 axles sets go in order to have enough weight at the pin/tongue to insure that the rear end does not violently begin its left-right swing dance going down the highway.

Lots of assumptions are in play and they provide a good margin of error to keep the lawyers off their case when you overload and or have more load in the wrong place as in the rear causing sway.

Are you discussing a motorhome, or a trailer? I'm talking about the wheelbase on the motorhome.

[17 Oaks]

Originally Posted by DirtRider

Are you discussing a motorhome, or a trailer? I'm talking about the wheelbase on the motorhome.

It all applies specifically to pin and tongue on 5th/TT on motorhome you the same challenges. On the diesel pushers, you typically find a dual rear axle along with a tag axle. Now you get into a real balancing game of far enough back to handle the weight of a 6 cyl C diesel engine putting out up to 1700+ lbs of torque, huge radiator and everything else, along with prob a rear semi walk-in closet, w/washer/dryer and then some almost 40 feet in front is the drivers seat. In between is a heckuva lot of weight or carry capacity over and above.

That rear axle set is not only a drive set of wheel x 4 but the tag or even full axle set not giving you 8 tires down in the rear has to deal with the scrub of turns.

Its complicated and all based upon each RV mfg their design parameters. Each unit is different by model and by carrying capacity. Vs your typical over the road 18 wheeler where it built to haul the max allowed carry weight of the trailer. And you might have noticed the rear axle sets on some trailers can be moved forward and back depending upon the load to be carried.

Be it a F 150 or a Big over the road rig lot of engineering goes into where those axles set and determining weighting from the pin to the rear axles and everywhere in between...Trust them!