How To Adjust Wheel Bearing Clearance?

Whether the axial clearance of automobile hub bearing (also known as pretightness) is adjusted properly or not will directly affect the sliding performance of automobile, increase fuel consumption, and even endanger driving safety.  If wheel hub bearing adjustment too tight (that is, the axial clearance is too small), increased rolling friction resistance, reduces the vehicles glide performance, fuel consumption increase (increased about 2.1 ~ 8%), driving bearing overheating, the grease outflows, destroyed the bearing lubrication condition, serious when bearing caused by high temperature sintering, make hub disassembly difficulty;  If the wheel hub bearing adjustment too loose (that is, the axial clearance is too large), the driving wheel deflection of produce and put the first failure, increase the tyres and related parts is not normal wear and tear, when the steering knuckle or half axle sleeve pipe thread and nut thread due to wear and tear that both fit clearance at the time, not may cause “flywheel” phenomenon, endanger safety.Therefore, in the warranty work, we should pay attention to the adjustment of hub bearing axial clearance.  

At present, there are mainly two ways to adjust the axial clearance of automobile hub bearings in the instructions and materials of various manufacturers:  

The first is to use the torque of 196~245 N.M(20~ 25kGF. m) (the value is CA141 car, each manufacturer has different provisions on the value), adjust the nut tightening, in the tightening process should be to the positive and negative direction of the wheel, in order to make the bearing roller correctly contact with the inner and outer four cone surface,  Then return the adjusting nut about 1/6 to 1/4 turn.  

The second is to use a spanner about 400mm or 500mm long to turn the adjusting nut until the hub can no longer be turned, and then back 1/4, 1/5, 1/6, 1/7, 1/8 turn.  

The two methods introduced above can only be applied to newly produced or overhauled vehicles within 2~3 two guarantees, and the second method is basically used around the country at present.  

When vehicles use after a period of time, the adjusting nut and the steering knuckle or axle fitting clearance between pipe thread will gradually increase, this gap is greater than 0.50 mm, while the change the new nut, but due to the steering knuckle or half shaft sleeve pipe thread has wear (knuckle or half axle sleeve pipe thread is not damaged, generally does not change), and zhejiang screw type lie thread machining precision,  There is always a certain limit between them, if you adjust the axial clearance of the bearing according to the two methods introduced above, when the lock nut is tightened outside, it is bound to make the axial clearance of the bearing too small, or even no, so that the wheel hub rotation heavy, increase the driving of the car.  

Resistance, and the lubrication surface of the bearing roller and the outer seat ring is destroyed, shortening the service life of the bearing.  In addition, when the internal and external tapered bearing wear face wear or more severe, the rear axle shell casing pressure fashionable size error, adjusting nut and the contact surface grinding of bearing inner race out deeper annular groove, even if the adjusting nut and tighten, the axial push-pull wheel with both hands, will still feel gap and wheel for bearing axial clearance is too large.  Therefore, the two methods introduced above still cannot make the axial clearance of the hub meet the requirements.  

So, how to adjust to ensure the necessary axial clearance of hub bearings (namely, tightness)?  According to our practical experience.  To rely on experience and then cooperate with the technical requirements of manufacturers according to different situations to adopt different adjustment methods.  

• (1) For the new factory or overhaul in 2~3 two protection vehicles, can be adjusted according to the manufacturer or the method of all kinds of information.  
• (2) to adjust the business mother and steering knuckle or half shaft sleeve pipe thread fit clearance or larger because of the gap of more than 0.50 mm in vehicles with new nut, first the adjusting nut and tighten, tighten while rotating wheel, so that the bearing roller correctly with the inner and outer conical surface contact, and then return the adjusting nut to 1/4 to 1/2 turn, axial push-pull wheel with both hands,  There should be a slight feeling of gap.  When the outer locking nut is tightened, the adjustment nut also produces a slight displacement along the axial direction inward, so that the axial clearance of the bearing just meets the requirements.  
• (3) for the inner and outer cone bearing not damage more serious, the rear shell face wear or error causes such as the size of the casing pressure trendy hub after adjusting nut twist exactly, wheel hub is still axial clearance, should according to the different situation, serious parts or replacement of the wear between the wheel and inner and outer bearing seat with a certain thickness of ring gasket (usually around 0.5 mm).  Then adjust the axial clearance of hub bearings according to the requirements of point ②.  

Several problems should also be paid attention to when adjusting hub bearing clearance:  

• (1) The operation method of tightening hub bearings should be changed to adjust the tightness of the right amount. After adjustment, the vehicle should check the temperature of the hub frequently when driving at the beginning, and the overheat should be adjusted again, not forced driving.  
• (2) For the replacement of the new nut, should check its side for burr or protruding, in case of improper assembly.  
• (3) The torque value used by the wrench should be in accordance with the manufacturer’s regulations, and the super long steel bar or crowbar should not be used arbitrarily.  In particular, it should be emphasized that the lock nut is not the tighter the more reliable, so that the adjustment nut and the lock nut can be adjusted with each other to achieve the ideal effect.  

Matters needing attention:  

Hub bearings worn or damaged hub bearings or hub units will make your vehicle in the road of driving inappropriate and costly failure, or even harm your safety.  Please pay attention to the following items in the use and installation of hub bearings:

1.To ensure maximum safety and reliability, it is recommended that you check hub bearings regularly regardless of the age of the vehicle — watch for early warning signs of bearing wear, including any friction noise during rotation or abnormal deceleration of the suspension combination wheels during turns.  

For rear-wheel drive vehicles it is recommended that the front hub bearings be lubricated when the vehicle travels to 38000 km.  When replacing the brake system, check the bearing and replace the oil seal.  

2.If you hear the noise from the hub bearing part, first of all, it is important to find the location of the noise.  There are many moving parts that may produce noise, and some rotating parts may be in contact with non-rotating parts.  If it is confirmed to be noise in the bearing, the bearing may be damaged and needs to be replaced.  

3.Because the working conditions of bearing failure on both sides caused by the front hub are similar, it is also recommended to replace in pairs even if only one bearing is damaged.  

4.hub bearings are more sensitive, in any case need to use the right method and appropriate tools.  In the process of storage, transportation and installation, the parts of bearings should not be damaged.  Some bearings require greater pressure, so special tools are needed.  Be sure to refer to the car manufacturing instructions.