caravan axles.

Are we talking single or dual axle suspension? Vans of that size are made with both.

More important than axle dimension is the type of stubs (and hence bearings) are on the ends. This site will give you the capacity of each of the components in your suspension.

Hi John, Go 50mm Square axle with Parallel bearings as a minimum. Parallel bearings refer to the outer bearing as the same large size as the inner bearing. Bigger outer bearing is rated for higher loads. I recently upgraded my off road trailer to the same as i mentioned above from Alko Melbourne, the complete axle ready to install. I bought 10" electric brakes but you may need 12" as you mentioned. My complete assembled unit was about $1250. If you buy from ebay or the net you may be buying bits and pieces assembled from parts made in several countries that may not be totally compatible. Hope this helps! regards Michael

Phone one of the trailer places, to many experts here!

At least with a trailer place you know you will get the right advice and if wrong someone to fall back on to for help.