I think that the 100 B has to do with the Uniform Tire Quality Rating, which includes a speed rating. Not exactly sure, but the 100 probably is the speed rating, and the B is the wear longevity rating. As to the C1 after the rim size, that should indicate a C load rating, but don't know what the 1 is for. Hope this helps.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.