The SST seem to be a wheelbase and track that isn't "standard". Have I misinterpreted?

If not - anyone know how the sizing was established? Are they the same as the old Mickey Thompson versions? (I'm sure they are vastly different mechanically)

Sort of wondering how RG decided on this given he (seemingly) could have done any size/spec he wanted.

PS: certainly not criticizing - they seem to be amazing...but, they also seem different than the TT, Dakar, etc.