Straps are rubbish and I really wonder why companies still sell trailers/winches with them on.
I use 6mm Dyneema, and have for quite a few years. I get mine from Electric Winches and 4x4 Winch Parts Online | Goodwinch â€“ Leading Winch Suppliers
- the last one for the new trailer was £32 ex vat for 8m of rope and a suitable hook all spliced on, earlier this year. For which price you could buy a £10 winch strap and a couple of gelcoat repair kits for when it breaks...
The Goodwinch blue 6mm Dyneema is rated at 4000kg, the 10mm is rated at 10,900kg so possibly overkill. Other makes will be in the same sort of range. For comparison a quick google shows a typical winch strap is rated at 1500kg.
On all three of the winches I've fitted Dyneema to, there is a hole in the drum where the strap retaining bolt goes through, and to secure it I've just fed the Dyneema through that hole and tied a knot in the end. If you ever need to take it off, cut the knot off, you only lose a few inches of rope. It takes 5 minutes to fit, most of which is winding the rope back on - just as easy as replacing the strap, except it will only need to be done once. I don't know what its useful service life is but the 6mm rope I fitted to my old SBS trailer in 2010 is still fine.