Wheel Fixings - Meritor TM Series Service Manual

9 Wheel Bolt Replacement

WHEEL FIXINGS

Currently there are three different types of wheel mounting in
common use:
1. British Standard system using 7.8" BSF thread and 80 o conical
seatings, (usually with L.H. and R.H. threads)
2. DIN metric system with M22 threads and spherical seatings .
3. ISO system again using M22 threads but locates the wheels by
the centre bore on a spigot on the hub.
It is imperative that trailer manufacturers and operators ensure that
the wheels and wheel mountings on the axle are compatible before
assembling wheels to the axles and tightening to the recommended
torque settings.
The achievable clamp load can vary considerably for a given applied
torque depending upon a member of variable factors such as the
surface condition of the bolts and nut threads.
To ensure accurate and positive location of the wheel, all mating
surfaces should be free from dirt, excessive paint, rust and damage.
The only satisfactory method of maintaining the correct torque
figures, which are based on coated and lightly oiled threads, is by
using a correctly calibrated torque wrench.
All Meritor HVS axles with DIN and ISO fixings have RIGHT HAND
THREADED BOLTS ON BOTH SIDES OF THE AXLES. Adhesive labels
are available to highlight this.
If inspection reveals damage to bolts, cones or wheels, replacement
is recommended. THIS CONDITION IS USUALLY DIRECTLY RELATED
TO IMPROPER TIGHTENING.
The wheel bolt . being a safety critical component . should only be
replaced with ORIGINAL Meritor HVS PARTS.
Fig. 9.1
Meritor HVS TM Series Axle
41
NOTE:
Detail of the Meritor CVA service tools refered to in this
section can be found in Section 12 Service Tools.
REMOVAL AND REFITTING OF WHEEL BOLTS
(REFER TO WHEEL BOLT CHART FIG. 9.3)
Meritor HVS bolts are pressed into the hub and drum assembly and
retained by serrations and the press fit in the hub.
Damage to wheelbolts is caused by:-
. Loose wheel nuts
. Over tightened wheel nuts
. Mismatched wheel and fixings
. Cross threadings
. Mismatched bolts and nuts
Removal
They should be carefully pressed or hammered out using the wheel
bolt removal tool (Meritor HVS Part No. MST 3211) (Fig. 9.1).
IMPORTANT
ALL MATING SURFACES SHOULD BE CLEAN, DRY
AND FREE OF BURRS PRIOR TO REASSEMBLY.
Refitting
Care should be taken to align the serrations of bolt and hub. They
must be driven FULLY home with the wheel bolt driving tool (Meritor
HVS Part No. MST 3210) (Fig. 9.2), using the sequence as for wheel
nut tightening. Ensure no gap exists between hub, drum and
wheelbolt head. When fitted the anti-lock Exciter Ring is retained by
the wheel bolts. When driving the wheel bolts home great care
should be taken not to damage the Exciter Ring.
Fig. 9.2