mot testing

And limitations of the Mot inspection.

Nowadays we’re seeing more vehicles at Mot time that haven’t had a service in the previous 12 months, the customer using the Mot inspection as a “service”. Unfortunately this can lead to problems as on an Mot test we’re not permitted to dismantle anything to check any items not visible.

Twice recently I’ve advised brake pads wearing thin, but not able to fail the item as the parts of the brake pads visible were not less than 1.5mm thick . Most manufacturer’s service limits are at 3mm for brake pads. In both cases the pads not visible were below 1.5mm, in one case the brake pad was touching and scoring the disc.

In this case both pads are just below 1.5mm, however the pads from the inner side of the caliper have worn lower and one was scoring the disc.

In many cases the condition of brake pads can only be truly assessed with the wheels removed, rather than relying on the tester being able to peer past a wheel trim or through small holes in the wheel rim.

With wheels removed  the condition of all the brake pads can be checked.

In this case the slight pitting of the outer face of the disc indicated problems in that the outer pad wasn’t moving and being pressed onto the face of the disc, the caliper was sticking and allowed the inner pad to wear down to score the disc. In this case the caliper was only functioning at approx 50% of it’s efficiency and had to be replaced.  In fact this particular vehicle had had an advisory that the pads were wearing thin at it’s last mot, had they been replaced then the caliper may have been able to be lubricated and thus saved the expense of replacement.