Why doesn't the math work?

rhagfo wrote:

wilber1 wrote:
The weakest component will always determine the limit for the complete structure. Only the manufacturer knows what that is. Eg: you can physically put a 5K brake on a 7K axle. You may be able to carry 7K but you can't stop it, therefore your design limit is 5K, not 7K.

To be rated at 7K an axle needs to have 7K of braking power. The rear axle in my 2001, from Dana has a rating of 11,000#, in my truck, it is rated at 6,084# which is the capacity of the stock 245/75-16E tires (The weakest component). This axle has the same brakes as the 2001 3500 axle rated at a bit over 7,000# so brakes not the limit. My 2001 has a camper package and Optional 265/75-16E tires rated at 6,830# for the pair.
So based on the facts stated above I could consider my axle rated at 6,830# as the Camper Package also includes 3500 springs.
I don't need to as I am still 500# under the stock 6,084# rating.

Isn't that what I was saying? I follow your logic but you can consider whatever you want, your axles are still rated at 6084#. Could that possibly be an issue for you? My guess is no but that's just my guess. It's odd that the higher axle rating wasn't included in a factory package that included the higher rated tires. I also believe your GVWR remains at 8800#.


I was thinking along the lines of 5-6 and 7k trailer axles where the brake assemblies are interchangeable. Replacing a 7k brake with a 5k brake would reduce the axle's capacity to 5k, even though it still has the larger structure and bearings that make it able to support 7k.

I don't pretend to know why manufacturers chose a particular GVWR for a vehicle and I'm not about to make assumptions about how they do. Just because some states may legislate a maximum GVWR for 3/4 tons, doesn't mean all states do and all GVWR's are determined that way. 1T GVWRs are increasing with every new truck that comes out. You can say it is all about bragging rights but the engineering still has to be there to back them up.