You can't Ian, it's very difficult to see pads on most cars and now manufacturers are redesigning callipers where you can barely see the pads even with the wheels removed. You have to take the callipers right off to see the pads. I'll take some pictures next time I come across one like it.
3.5 Mechanical Brake Components 3.5 - page 1
Information
Method of Inspection
Reason for Rejection
It is acceptable to fit cable expanders to reduce maladjustment.
A visual and physical check must be carried out on all mechanical components that are visible and accessible.
1.
Check the mechanical brake components for:
a.
chafed rods or levers
b.
frayed or knotted cables
c.
free rotation of clevis joints between cables and levers (this includes cable linkages between brake pedals and remote mounted servos)
d.
security of cables, rods and clevis joints
e.
a corroded or damaged rod, lever or linkage. Wear in eyes of relay levers, clevis joints, stationary pins or pivots
f.
abnormal movement of levers, indicating maladjustment or excessive wear
g.
security and excessive wear of brake linings/pads
h.
contamination of brake discs and drums by leaking brake fluid, oil or grease
i.
the condition and security of brake drums and discs
j.
presence and security of brake back plates, wheel cylinders and calipers
1.
a.
A brake rod or lever reduced in thickness by more than 1/3rd
b.
a brake cable:
knotted or,
with wires broken so that the cable is weakened significantly
c.
seizure of clevis joint pivots which causes strain or wear to cables to an extent likely to lead to premature failure of the cable
d.
a cable, rod or clevis joint insecure
e.
serious weakening of any part due to excessive wear, damage or corrosion
f.
abnormal movement of levers indicating maladjustment or excessive wear
g.
a brake lining or pad insecure or less than 1.5 mm thick at any point
h.
a brake disc or drum contaminated by brake fluid, oil or grease
i.
a brake disc or drum in such a condition that it is seriously weakened or insecure
j.
a brake back plate, wheel cylinder or caliper securing device loose, missing or excessively deteriorated
Tony.