Tire/Wheels - Eliminating Vibrations
89audi08Applies To: ALL
Subject: Eliminating Vibrations
(Supercedes Product Circ. 88-02, dated 11/30/88)
Number: Group:
89-03
November 2, 1989 44
Suspension ^ Wheels
Wheel imbalance generates dynamic forces that can cause vehicle components such as steering gear, wheel suspension components and body to resonate. This, in turn, leads to vibrations of the steering wheel and the vehicle itself.
When vibrations of this type occur, use the following procedure to determine the source of the imbalance.
^ check tire pressures and correct if necessary
^ check surfaces of tires for scuffing, flat spots or other damage
^ road test vehicle to determine type of condition and speed range
^ check suspension components for damage or wear
Note
If a component is replaced or if tires are worn unevenly, check and align front suspension as necessary. Road test vehicle again after alignment.
^ check wheel mountings
^ center boss of hub or brake drum must protrude beyond, or be flush with, center collar of wheel. If not, replace wheel.
Wheel and tire runout, checking
^ set up dial indicator so roller is just making contact with center of tire tread or tire wall
^ rotate wheel slowly by hand and read needle deflections off meter
^ mark location of maximum radial runout on tire
Radial Lateral
Tire with wheel 0.8 mm 1.2 mm
(0 032 in.) (0.059 in.)
^ if runout figures are within limits, balance wheels/tires (see next page, Wheels/tires balancing)
^ if runout figures are outside limits, rotate tire on wheel
^ deflate tire and push tire beads down into wheelbed
^ rotate tire 120~ on wheel
^ inflate tire and remeasure radial runout if maximum figure is still outside limits, rotate tire a further 120~ on wheel and remeasure radial runout if outside limits, check lateral and radial runout of wheels (see next page)
Wheel runout, checking
^ dismount tire and mount wheel in balancing machine or on vehicle
^ measure radial and lateral renout at points shown
Radial Lateral
(H) (S)
Steel wheel 0.6 mm 0.8 mm
(0.024 in.) (0.032 in.)
Alloy wheel 0.5 mm 0.5 mm
(0.020 in.) (0.020 in.)
Note
Peak readings, up or down, which are caused by small imperfections on the wheel surface, can be ignored.
^ if maximum values are exceeded, replace wheel and recheck runout of wheel and tire assembly
^ balance tire and wheel assembly
Wheels/tires, balancing remove existing balance weights before balancing
CAUTION
Wheels MUST be mounted with same centering method as on vehicle (i.e. bolted to hub/arbor) and centered on a cylindrical (not conical) surface.
^ maximum permissible residual imbalance = 5 grams
Wheels/tires, balancing (continued)
Note
For on-the-vehicle balancing of the driving wheels, the wheels must be driven by the engine so that wheel speeds are synchronized.
CAUTION
For on-the-vehicle wheel balancing of Quattro models, both axles of the vehicle MUST be raised and the parking brake released. If not, damage to the Torsen center differential will result.
Wheels, installing
^ install wheels and tighten lug bolts with point of maximum radial runout at top
Note
If tire wear is approximately equal, the wheels with the lowest amount ot radial runout and the smallest balance weights should be installed at the front.
^ repeat road test of vehicle
If vibrations are still present, the radial and lateral oscillations of one or more tires are too high. These oscillations cannot be measured with normal workshop equipment. For such cases, the front tires, rear tires or all four tires should be replaced.