I'll probably get slapped for this but, concensus of opinion at the delaer where I have my shingle hung is, a darkside tire is noted on the RO if any work is done on the bike and if a trailer hitch is attached it's noted as well.
I've said this before. Under the Magneuson Act, no manufacturer can deny a warranty claim if you use parts not approved or endorsed by the OEM so long as you don't use parts dertimental to the operation of the vehicle, like using K-Mart cheap oil where a JASO-MA oil is specified. There is some common sense involved.
However, it seems apparent that the problems some of us are having are problems that surface after the warranty period has lapsed and at that time, it's the sole discretion of Triumph as to whether you eat the bill or they do. In that respect, I, for one, am glad I never modified the bike (trailer hitch or car tire), which could give Triumph the impetus to deny an after warranty repair. I, for one, would not relish paying for an engine rebuild and the **** bike is too bulky to use as a baot anchor.