I've recieved a couple of questions lately on the topic and thought it would be worthwhile to pull together all this information spread in different threads and put it all in one post.
Airstream shipped a number of 16' Bambi Airstreams with GVWRs of 3500 lbs and NCCs under 100 lbs. To solve this problem with my 16' Bambi, In February 2007 I made the trek out to Jackson Center to upgrade my Airstream to the 4300lb axle with 15" wheels, 225/75R15 Load Rating D tires, and disc brakes. The axle replacement with wheels and tires cost about 1750.00. The disc brake installation cost 1710.00.
I am very happy with the axle upgrade. I would be completely happy if I hadn't found out while I was there that Airstream is in the midst of switching over to sealed bearings in their new trailers. If anyone else ends up doing the upgrade, check with parts first to see if they can order the new axles.
I am extraordinarily happy with the new tires. They look and feel so much more substantial than the 215/75 R14s - and at 2540lbs vs 1870lbs they provide a mighty margin of safety at any speed.
I am mostly happy with the new brakes. The stopping power of the new brakes is nothing short of amazing - if I slam on the brakes it feels like I dropped an anchor in the road. However, there is a noticeable increase in the delay before the discs activate compared with the drums. Also, because the discs are so much more powerful than the drums it is relatively easy to set the controller too high and get the tires to 'lock' instead of helping to stop the trailer.
In retrospect, knowing more than when I started, I would be inclined to just upgrade the wheels and tires to the ST225/75R15s (raising the max tire load from a nominal 3740lbs to 5080lbs) and not bother with the axle upgrade. I can't speak from experience on this option - but it seems to provide most of the safety increase at a much lower price. Particularly if you have a larger tow vehicle that can handle more of the braking burden.
When I started to look into the issue of dealing with my 51 pound NCC, I emailed airstream and received the following reply. Basically, the axle/wheels/tires seem to be the limiting factor with the 16' Bambi (at least up to 4300 lbs).
Originally Posted by airstream
The Canadian units do have a larger axle as well as 15” tires. It is something that Canadian standards require. The Canadian axle with the 15” tires would give you 800 additional pounds.
Even after weight distribution, a minimum of 200lbs of the Bambi's weight will be carried by the tow vehicle axles. This would make the Bambi's 'real' GVWR 3700lbs even with the 3500lb GAWR axles - thus giving approx 250lbs of NCC (or 450lbs of NCC if you don't fill the freshwater tank).
The standard wheel on a US 16' Bambi is 14" x 6" on 4.5" centers, 5 lug with no offset. So, if you want to upgrade the tires on your 16' Bambi from 215/75R14 LR Cs to 225/75R15 LR Ds without upgrading your axle you need a 15" wheel that matches the pattern above and has sufficient PSI and rim weight ratings.
I found one in aluminum at Eastern Marine - STOCK #: 1350116 @ $82.50 - for details see below.
Trailer Parts Superstore - Trailer Wheel Only: 13" thru 15"