CAT Scale weights are confusing me.

Atlee wrote:
Why would 3 different trailers that have the exact same tires, and exact same axles have 3 different GVWR?

Why would a 27' 2" long trailer with 3500# axles be only 6500# GVWR, while 28' 8" trailer (albeit with a slide) with the same axles equal 7500# GVWR, while a 29' 3" third trailer with the same axles equal 7000 GVWR.

Would the frame make that much difference?

I've wondered about that too. Doesn't seem to be any standard method for arriving at a GVWR figure. I don't think the frames have much of a bearing, if any. Some TTs have the very flimsy/flexible frame made with I-beams that have 3 pieces of mild steel welded together that look like a regular I-beam. I know of one brand/model with this frame and it has 2 @ 3500 lb axles and a 6800 lb GVWR. Our TT has a custom one-off heavy duty frame with 2 @ 5200 lb axles (and LRD tires) but the factory gave it only a 6800 lb GVWR (which it would normally have for this model) when it ought to be more like 9500 lb GVWR. They simply reduced the CCC to under 1K lbs to account for the heavier frame instead of assigning a new GVWR to it. TT GVWR is typically a few hundred lbs less than the sum of the axle ratings.

The thing about frames is, there are no industry regulations and standards and a TT manufacturer along with the frame manufacturer (mostly Lippert) can build them however they want. The frames themselves have no max. weight rating. If you go to an RV show and crawl under some TTs, you will find that for the same trailer having 2 @ 3500 lb axles, some Lippert frames are stronger than others and some can have reinforcement in the area of the spring hangers. And then there's the same GVWR but with the flimsy/flexible 3-piece I-beam frames. Best frames out there IMO are the ones made in-house by Northwood and the BAL Ultraframe.

Anyway, I note besides all the above posts, the remaining available payload capacity of the truck is 220 lbs with it fully loaded for camping and the TT hooked up. The effect on the tongue wt. with partial or full holding tanks will depend on the location of the tanks. If you're going to do that much, perhaps a tongue scale would help. I think 220 lbs could be eaten up quickly if not keeping an eye on things.

There is no restriction on how heavy TW can be in terms of percentage except you don't want to exceed payload capacity of the TV. In the US & Canada, the required resolution of scales is +/- 20 lbs. I once weighed our TT & TV on the same day at 3 different scales and were all within 20 lbs.