I have an early (1983) Cobra trailer originally built for a Ventus. It is the smallest (width and height) clamshell I have ever seen. It has been retrofitted for my Pegasus, and if it was 1/4 inch smaller in any dimension, the glider would not fit inside. So, I can't keep a spare inside due to space limitations.

As a result, I built a spare tire carrier that is mounted on the side of the trailer just behind the right fender. I keep a dedicated screw jack with handle and a lug wrench and handle inside the front hatch. The last time I had a flat (actually a tread separation) on the road, it took eight minutes to swap the tire.

I didn't have to unload the fuselage or anything else. I keep a vinyl cover over the spare, but they only last a couple of years. So I spend $20 for a new one when it deteriorates.

Your best insurance concerning flat tires is to not let them get over a few years old. The tread depth may be (and probably is) just fine. What kills tires is age, oxidation (ozone) and ultraviolet exposure. A hundred bucks on a cheap set of radial tires every two or three years is cheap insurance for your $50,000 investment. I also don't bother with "ST" or trailer tires, as they are more expensive and (in my opinion) don't offer any more protection, reliability or longevity.

A lot of this comes from my own experience, as well as from airshow pilot Bob Carlton, who has been dragging glider trailers to airshows around the country for twenty years, logging as many as 30,000 miles or more every year.

Anybody want to buy a slightly used enclosed trailer for a 13 meter glider? Only 650,000 miles. Good tires.