These guidelines are from AACA, not from Coker Tire and are subject to change.  For exact judging guidelines or specific questions, please see the AACA website . 

- Prior to 1915, tires must be matched in pairs (front and rear), but spares need not match anything on the vehicle except each other. (If there’s more than one size spare,they will naturally differ.)

- The following items are accepted for judging without penalty under the “Grandfather Clause”, due to their initial acceptance in
the beginning of the judging program.

• Whitewall tires. Must be proper size designation and proper style.
• 1941 Last use of double whitewall tires.
  

- Tires on all vehicles must be as specified by manufacturer. They must be nearest the correct size if the correct size is not available. Tubeless tires with a tube will be allowed without removing the wording on vehicles that did not come with tubeless tires. Tubeless tires were introduced in 1955 for cars and light trucks and in 1956 for heavy trucks.

- The following identifies the first year of tire sizing for the various designations. IT IS IMPERATIVE THAT THE TEAM ASK FOR DOCUMENTATION FOR ANY TIRE THAT IS QUESTIONED BY THE CHASSIS JUDGE OR DOES NOT MEET THE FIRST YEAR OF MANUFACTURE GUIDELINES LISTED BELOW. Some manufacturers offered a radial tire - for specific vehicle(s) - as a factory authorized option to the standard issue ply tire. The use of red line radials on a vehicle should be accompanied with documentation. It is advisable to seek documentation from the vehicle owner when a tire size or type is in question. This is especially so in cases of limited production, specialty vehicles, and foreign made vehicles.

• Letter Size Tires, ie G78-15, GR78-14, etc 1967
• Metric Size Radials, ie 185R14, 175R13, etc. Domestic Cars. (Factory documentation is required for any vehicle with radial tires prior to the years listed below.)  Some domestic manufacturers offered these tires as early as 1967, such as Buick and Oldsmobile. It is possible that others may have offered them as well. BEFORE taking any deductions, ask the owner for documentation (Note: European built vehicles can be much earlier, seek documentation) (Japanese vehicles 1967, possibly earlier - seek documentation).
• Low Profile Metric Radials, ie 195/70R13, 195/70VR14 Domestic Cars as early as 1976. European Cars 1969*. Japanese Cars 1975* (Factory documentation is required for any vehicle with radial tires prior to the years listed below.) *Also refer to above note when judging foreign made vehicles.
  

- Valve stems must be metal prior to 1930 and must be the same as originally supplied on the vehicle. Documentation may be required. Fords will have metal valve stems through 1934. Rubber valve stems may be used on any vehicle, prior to 1935, that was originally equipped with metal
stems, if completely covered with authentic valve cover, atop a retainer nut fastened to the rim. In all cases, it must appear as original equipment.

- Plastic valve caps will receive a one point each deduction if used on any vehicle prior to 1951. “Red Crown” valve caps are not accepted on any vehicle. Red plastic valve caps (not “Red Crown”) will be accepted
on Whizzer motorbikes.

- Wheel weights will be considered a safety item; therefore there will be no deduction for wheel weights if installed in a workmanlike manner. They may be painted.

 For a complete copy of the AACA judging manual see  http://www.aaca.org/publications/2006judgesmanual.pdf