86_OLDS ---------> The T/A stands for Trans-Am.
After the original Trans-Am debut in 1969, it didn't resonate well with the public, only 697 units were built. The 2nd generation T/A was radically redesigned and came back out as a 1970 1/2 model.
Pontiac adopted the name Trans-Am from the SCCA. (Sports Car Club of America). The title Trans-Am was used to title their premier production sedan racing series. The Pontiac Trans-Am didn't fit into the guidelines of the SCCA because they limited the size of their engines to 300 cid or 5 liters. Pontiac's T/A was a 400 cid.
To make a long story short..... The SCCA wanted some type of a reward for the commercial use of their name... Trans-Am. Pontiac and the SCCA agreed on a 5.00 a car royalty. This story is another story all itself.
What does this have to do with the tire? At that time, B.F. Goodrich was marketing their new high performance radial tire called the Trans Am Radial. When the SCCA requested the same royalty Pontiac was paying, B.F. Goodrich declined their offer and shortened the name to the T/A. This legally took them off the hook. The B.F. Goodrich Radial T/A was born.