If 495 rpm was the magical number, then what tire size was that?
10.00x20 tube-type bias ply.
This was the size that the brilliant engineer Dwight Austin used when developing the revolutionary (for it's day) V-drive for the Greyhound-only Yellow Coach 719 introduced in late 1935. Based on his 1932 patent, and originally installed in the Pickwick Nite Coach (see the Santa Fe version below), it was really the beginning of a design concept that basically is still in use today. Granted, 99.9% of North American buses are all T-drive, but Austin's original concept paved the way.
The YC-719 used a GMC 707 cu. in inline 6 gas engine, coupled to a 4-spd manual gearbox, a 4.125:1 rear axle ratio and 10.00x20 tires.
In 1937, YC introduced the 743, which was a mild face-lift of the 719, but more importantly, introduced the venerable 6-71 Detroit Diesel and coach air conditioning. No other changes were made to the drive line specs with the change to the Detroit, as the 707 operated w/in the same RPM range.
IIRC, the 12R22.5 (or it's bias-ply equivalent) size became the stock OEM installation when GM introduced the 40-foot 4903 in 1968, but am not sure. All of my 4108 and 4905 sales literature indicate 12R22.5 as the stock tire.
How's that for historical GMC coach trivia? Hehehehe. . .
FWIW & HTH. . .