Tire Classification Types Dragging  Chattering or Squealing  $^{ }$Aircraft Tires and Tubes 13-75 Type VIII aircraft tires are also known as three-part  nomenclature tires.  [Figure 13-127]  They are inflated to very  high-pressure and are used on high-performance jet aircraft.  The typical Type VIII tire has relatively low profile and is  capable of operating at very high speeds and very high loads.  It is the most modern design of all tire types. The three-part  nomenclature is a combination of Type III and Type VII  nomenclature where the overall tire diameter, section width,  and rim diameter are used to identify the tire. The X and  “–” symbols are used in the same respective positions in the  designator.  Aircraft tires may be tube-type or tubeless. They support the  weight of the aircraft while it is on the ground and provide  the necessary traction for braking and stopping. The tires also  help absorb the shock of landing and cushion the roughness  of takeoff, rollout, and taxi operations. Aircraft tires must  be carefully maintained to perform as required. They accept  a variety of static and dynamic stresses and must do so  dependably in a wide range of operating conditions. Brakes may chatter or squeal when the linings do not ride  smoothly and evenly along the disc. A warped disc(s) in  a multiple brake disc stack produces a condition wherein  the brake is actually applied and removed many times per  minute. This causes chattering and, at high frequency, it  causes squealing. Any misalignment of the disc stack out  of parallel causes the same phenomenon. Discs that have  been overheated may have damage to the surface layer of  the disc. Some of this mix may be transferred to the adjacent  disc resulting in uneven disc surfaces that also leads to  chatter or squeal. In addition to the noise produced by brake  chattering and squealing, vibration is caused that may lead  to further damage of the brake and the landing gear system.  The technician must investigate all reports of brake chattering  and squealing. Type VII tires are high performance tires found on jet aircraft.  They are inflated to high-pressure and have exceptional high  load carrying capability. The section width of Type VII tires  is typically narrower than Type III tires. Identification of  Type VII aircraft tires involves a two-number system. An X  is used between the two numbers. The first number designates  the nominal overall diameter of the tire. The second number  designates the section width.  [Figure 13-126] Type III tires are common general aviation tires. They are  typically used on light aircraft with landing speeds of 160  miles per hour (mph) or less. Type III tires are relatively low-  pressure tires that have small rim diameters when compared  to the overall width of the tire. They are designed to cushion  and provide flotation from a relatively large footprint. Type  III tires are designated with a two-number system. The first  number is the nominal section width of the tire, and the  second number is the diameter of the rim the tire is designed  to mount upon. [ Figure 13-125] At all times, the technician should perform inspections to  ensure the proper parts are used in the brake assembly.  Improper parts, especially in the retraction/adjuster  assemblies, can cause the brakes to drag. A brake may drag when the return mechanism is not  functioning properly. This could be due to a weak return  spring, the return pin slipping in the auto adjuster pin grip,  or similar malfunction. Inspect the auto adjuster(s) and  return units on the brake when dragging is reported. An  overheated brake that has warped the disc also causes brake  drag. Remove the brake and perform a complete inspection  as discussed in the previous section. Air in the brake fluid  line can also cause brake drag. Heat causes the air to expand,  which pushes the brake linings against the disc prematurely.  If no damage has been caused when reported, bleed the brakes  to remove the air from the system to eliminate the drag. Type I tires are manufactured, but their design is no longer  active. They are used on fixed gear aircraft and are designated  only by their nominal overall diameter in inches. These are  smooth profile tires that are obsolete for use in the modern  aviation fleet. They may be found on older aircraft. A common classification of aircraft tires is by type as  classified by the United States Tire and Rim Association.  While there are nine types of tires, only Types I, III, VII,  and VIII, also known as a Three-Part Nomenclature tires,  are still in production.  Aircraft tires are classified in various ways including by:  type, ply rating, whether they are tube-type or tubeless, and  whether they are bias ply tires or radials. Identifying a tire  by its dimensions is also used. Each of these classifications  is discussed as follows. Brake drag is a condition caused by the linings not retracting  from the brake disc when the brakes are no longer being  applied. It can be caused by several different factors. Brakes  that drag are essentially partially on at all times. This can  cause excessive lining wear and overheating leading to  damage to the disc(s). 