Single Axle Car Trailer

Things to consider.
Tandems are a pain in the butt to maneuver by hand, but are the best to tow.
Those skinny single 13" wheels will be outright dangerous at higher speeds with the sort of load you intend towing. Wider, low profile 14's will handle much better, Wide, being the essence.

And if you ding the race car a towing dolly will be no help at all best option dont ding the racecar

Just an update. Almost done the trailer, just needs lights and a deck now.

What I ended up doing was adding 500mm to the rear of the trailer. This meant I could park the car further backwards keeping it within the front of the deck area and it also makes the trailer better proportioned.

In addition to that I did the sums again and found the ideal position of the axle with this extension was 50mm rear of the deck's half way point - exactly where the golden rule says it should be. So that said to me that the trailers proportions were completely out before hand, well for a normal length car they were.

I used drop axles to lower it 100mm. New axle, springs, hubs, coupling, guards and safety chain and dolly wheel. A bit more reinforcing along the sides, triangulating it to reduce flex. Its sitting on 185/60r14 tyres and alloy wheels. I will get some 8 ply tyres for it as these tyres are maxxed out with their weight rating.

I didn't think that Id ever have a ground clearance issue with a trailer, but first config (although awesome looking) gave me only 100mm ground clearance at the back! I moved the axle to below the springs to fix that and its looking much better now. Before hand the dolly wheel was too tall even!

I don't have a pic of the trailer with it raised up a bit but here is what it was looking like last night, it looks far better now.
http://i264.photobucket.com/albums/ii200/morrisman1/P1060552.jpg

Looks good.
Where the drawbar cross's to go under the front deck bar, I would place an extra bar under the draw bar where it cross the front deck bar, BUT only weld the ends of the extra bar & not across that joint.
1" angle iron or 1" x !" box is fine

I have seen a lot of trailers crack the drawbar at that spot.
Because my light weight trailers tend to get a bit of a hiding, I welded in that extra brace to still allow the joint to flex as per normal but it acts as a back stop & as a back up brace if the drawbar should ever crack.

Works well so far, & thats been from a few years ago.

cheers, Im still trying to figure out what you mean though

I am going to weld in some 1.6mm sheet metal along the sides to strengthen it further and prevent flexing of the deck, getting about 7mm of sag at the back with my sentra on it which weighs 1050kg. It got it's WOF today no problems. Tongue loading is about right both loaded and unloaded.

I think putting the sheet metal along the sides will stiffen it up significantly. It will be stitched onto the framework with the mig.

Draw bar rails pass under the front decking bar
At the point that the 2 rails cross, is where they crack a lot

Sheet metal weldedto the sides will leave a damp area between the plates & the welding could over stress & twist the rails slightly

Better to weld in a tapered ladder bar underneath