Originally Posted by Phil57
When I did the research for my upgrade I talked to the front axle manufacturers and was sent the specs for the different axles. The casting for the 10500 lb and the 120000 lb is the same. The brakes and everything else except he air bags were the same. So in case anyone was wondering this is a true 12000 lb axle.
Good info. about the front axle. Do you have any good info. about the rear axle? A couple years ago, I did an extensive research at AccessFreightliner, comparing the parts lists between my 340hp Berk and a 360hp Berk. I found no difference in the axle, shocks, air bags, brakes. Yet, FR specs. the 340hp's rear axle at 17,500lbs and that of the 360hp's at 19,000lbs.
I am speculating that FR does this because if one was to load up their 340hp with 19,000 on the rear and 10,400 on the front (the unmodified front axle), there would only be left 3,600 lbs for the toad - since GCWR is 33,000 lbs. With the modified front axle at 12,000lbs; fully loaded there would only be left 2,000 lbs for the toad.
It should be noted to others reading this, that originally both the 340hp and 360hp Berks had a 10,410 lb. front axle rating. Not sure when and if FR changed over to 12,000 lb. front axles and 275 tires on later models.
Over-loading the front axle is critical because it is the steer axle and it has been found that both the 340hp and 360hp need the 12,000 lb capability Especially models with tile floors; bunkhouse and rear bath models. The 12,000 upgrade to the 340 Berks is doubly necessitated, because it doesn't have much cargo carrying capacity in the first place and especially if you believe the rear axle to be 17,500 lbs maximum.
Besides the axles, the tires are another thing. The original Michelin XRV 255 tires have a combined maximum carrying capacity of 29,630 lbs. With the upgraded Michelin XZE2 275 tires, the maximum load is 35,050 lbs. No Berk would ever be that heavy, but it is a great comfort that there is a greater safety margin with the 275 tires. Also, since like I only run around 83 psi in the rear; the ride is much better.