Re: RE: 2.5ton vs 5ton axles
jasonjc said:
As per the Memphis Equipment web site 2 1/2 ton ft 11,000lbs rear tandem 28,000lbs 5 ton ft 18,000lbs rear tandem 44,000lbs. I guess that means the 2 1/2 ton is a 13ton???
An interesting thread here, with some interesting info. Per the Memphis data which no one is disputing, the front axle rating is 11,000 pounds, the rear tandem 28,000 pounds or 14,000 pounds per axle.
I guess maybe the rear axles get another 3,000 pounds per axle because of the dual tires. BUT WAIT A DOGGONE MINUTE! I just checked part numbers in the -34P manual (I didn't need to because I already knew the answer but wanted to make sure I am 100% correct), the front and rear axles use the same hub, bearings and brake drums! So how come the rear axle is rated 3,000 pounds greater? Is the front axle derated because it is a steering axle and somehow weaker?
Well, to get back on topic, so the front axle is rated at 11,000 pounds and a single rear axle at 14,000 pounds for a gross rating of 25,000 pounds. Jatonka suggested reducing the axle ratings by 2,000 pounds each which would bring you down to 21,000 pounds. However, you have not mentioned what your rear suspension is like. Assuming it is a simple spring setup like the front with springs equal in capacity to the front springs, I'd suggest rating both axles at 9,000 pounds each for a gross rating of 18,000 pounds. If you used a set of front springs in the rear, you are OK. If you used some other springs and you know the rating of that spring set you can adjust the rear rating up to a maximum of 12,000 pounds. If you don't know the rating of your rear springs you will need to figure it out somehow.
Lets assume you used a set of front springs for your rear suspension, so you can assume a max possible rating of 18,000 pounds. Go weigh your truck. You will need the total weight and the weight on both axles. Subtract the weight of your truck from 18,000 pounds, that will give you one number. Then, assuming the rear axle is centered in the bed and a uniformly distributed load, subtract the weight on the rear axle from 9,000 pounds, that will give you another number. Your maximum load is the LESSER of the two numbers. You cannot exceed either the total GVW OR the individual axle ratings, which is why you use the lesser number.
Here is an example. Lets say your truck weighs 10,000 pounds with 6,000 pounds on the front axle and 4,000 pounds on the rear axle. Subtracting 10,000 from 18,000 gives you a possible rating of 8,000 pounds. Subtracting 4,000 from 9,000 gives you a max rear axle rating of 5,000 pounds. In this case, your load limit is 5,000 pounds, the lesser of the two calculations.
If your rear axle is not centered under the cargo bed, you will need someone with an engineering background to do some moment calculations to determine your capacity. In general, if the axle is rearward of the center of the cargo area, your load capacity will increase as more of the load is being carried by the front axle, up to the point you reach the load limit of the front axle. You may also want to keep in mind that the military reduced the load limit in a Deuce by 50% for off road operations.