What is the maximum possible, load a typical 18 wheeler can carry

Hello Pedigreed Bulldog -

Thanks very much, that is exactly the type of information I am looking for and it makes sense to me. 113,000 lbs is 33 k over the legal or about 40%. This makes much more sense to me than 100% over load.

I appreciate your help,

Mike

 

Thanks for the reply OFTOTR -

A number of years ago, the Texas State Legislature passed new rules which allowed Department of Public Safety weight enforcement troopers, when they stop a truck, to record tire rating(s) and compare these to their portable scales. This made it much simpler to tell if a wheel / axle group was overloaded compared to the old method of looking at pounds per inch of tire width.

I know that tire load capacities can vary significantly whether we are talking about an long haul truck or a work truck (dump, ready mix, concrete pumper etc.) Long haul trucks on the steer are perhaps 7500 - 8000. The tires on the tandems will be somewhat lower if they are dual tires more like 5000 - 6500; but each wheel position has two tires..... If a truck is running wide base singles, the load capacity must be higher of course.

In Texas, wide base tires are more common on fuel haulers and certain intrastate shippers who understand (in detail) the relationships between engine specs, truck speed, tire rolling resistance, wind resistance and fuel economy. You can gain about 4% fuel efficiency when switching to wide base tires - the dead load weight of a set of wide base tires and wheels is less than dual tires and wheels all around - so you get more cargo capacity to boot.

Fuel tankers who have to worry about roll over on curves - can take advantage of the narrower overall width of wide base tires by spec-ing a wider spacing between their chassis rails which allows them to lower the tank = lower center of gravity = lower roll over potential. I've attended ATA meetings as a member of the old Truck tire impact on pavement damage taskforce and heard testimony by major fuel tanker fleet managers who discussed this in detail.....the lower cg gave them the option of greater safety or more fuel hauling capacity = greater profit at the same level of safety.

We could add to these issues knowledge about the highway route since some routes will have more up and down grades - crest and sag vertical curves (including bridge approaches and interchanges in urban / metro areas.

Major rail companies know the track grades between different points along their routes and take this into account when computing the fuel consumption and wear on the locomotive and rail cars and in determining profitability. I'm not sure if long haul trucking companies do this....maybe the bigger fleets like Swift, Schneider, J B Hunt, Con-way etc.

UT-Austin and Center for Transportation research works with certain fleet operators in Texas to help improve their fleet efficiency.....and of course, we've looked at tires. Some fleet managers know which tires are best to run on each axle position (steer, drive, trailer) and know that tires wear at different rates in different Texas cities.

You wouldn't think tire wear would be that much different, but it is depending on the types of pavement surfaces (tined concrete, coarse surface treatments, dense graded hot mix, permeable friction course hot mix...etc. etc.). Our (UT-CTR) knowledge of the Texas network combined with their knowledge of their fleet adds up to lower maintenance and fuel costs.

Sorry for the long answer.

Mike