1. Preferred by who? Lots of trailers use biased tires - some even come with them new from the factory. More than half of the 14" ST trailer tires offered by etrailer.com are biased tires. When I look at consumer complaints on vehicletire.com, the only complaints on Kenda tires are for the Karrier ST
Radial! There is not a single complaint about Kenda's biased tires.
Radial and biased tires each have their pros and cons. Every trailer and how it's owner uses it determines what type of tire to use. Perhaps using a biased tire has been overlooked by many TM owners.
2. Does upgrading a 14" tire from Load Range C to Load Range D really reduce tire failure? I have read about many failures of the Kumho Radial 857 14" load range D (65psi) tires and they have the highest load range and speed offered in a 14" radial tire (though this tire is more comparable to an LT tire than an ST since it can be used on light trucks, vans, etc.). What I have not read are any consumer complaints on vehicletire.com of any Maxxis tires (there isn't even a link for Maxxis!). If I go with a radial, I'll use the Maxxis M8008 ST Radial 215/75R14 (Load Range C). A 5-year warranty also says a lot.
For those using 14" tires on their TM's, there are two issues/risks about
rims & psi limitations to carefully consider if using or planning to use a Load Range D tire (unless you want to be or are a test pilot)
:
--- 1. Using a 14" Load Range D tire filled to 65psi on a rim rated to 1870lbs @50psi. Test Pilot! Upgrade 14" rim to 65psi or downgrade to a Load Range C 14" tire.
--- 2. Using a 14" Load Range D tire filled to 50psi on a rim rated to 1870lbs @50psi. The Load Range D tire is producing only Load Range C at 50psi (maybe less!). Will running a Load Range D tire at Load Range C (underinflation) reduce or increase tire failure? Test Pilot! Upgrade 14" rim to 65psi or downgrade to a Load Range C 14" tire.
Running a rim above its max psi limitation could, over time, distort the rim just enough to separate the tire from the rim (blowout) - especially if combined with high temperatures; high speeds; dramatic temperature increase; aged tire; etc. A distorted rim caused by exceeding the rim's max psi limitation might not be noticeable with the naked eye or felt while driving by the seat of one's pants until it's too late.