Mot Advisories

[edam]

I had a MOT Advisorie for Worn brake discs, but not excessively, 300 miles ago. As Im not doing much driving at present do they need to be changed by the next MOT?

[Mr Onion]

I would, but then I would have changed them on the Advisory Notice.

Brakes and Tyres are the only things preventing you going straight to the scene of the accident. Never skimp

[edam]

As the car had only done 900 miles since the previous MOT ,which had no adviseries, im a bit suspicious.

[TnTkr]

You can get the brake discs checked or measure the thicknesses yourself.

[Lord Voltermore]

Much of the UK MOT test is subjective - ie some things are not actually measured  with instruments, but it is the opinion of the experienced  tester that there is some wear, free play etc that is either unacceptable  and  fails  or  is acceptable at the time of the test  but may require attention sooner rather than later.  Ther 'advisory' alerts the owner to the neeed to 'keep an eye' on the situation,  but is also used by some testers to 'cover their backs'

MOT tests are overseen by VOSA  who sometimes carry out checks to ensure the efficiency of testers  , or mediate in disputes about whether a car should have passed or failed the test.   Advisories are sometimes used by the tester to prove to VOSA that they did indeed spot there was some wear, or other anomaly but decided it was acceptable at the time of testing. . I did once hear of an advisory being given to the effect that at the time of the test the car was fitted with wheels and tyres  that, although legal  for a pass , did not appear be its usual set.

Brake discs do have a minimum recommended thickness that can be measured with calipers. But worn discs also typically develop a  lip of unworn metal around their outer perimeter  where the brake pads dont quite reach. A tester might just conclude from the presence of a lip  that there has been some disc wear without actually measuring it. It may still be well within acceptable tolerance.   Discs are sometimes failed/advisories because they are  excessively grooved or rusty  .(some grooving etc is considered acceptable. ) This  could be mis described.  This type of disc  damage/ rusting  is quite common on  cars that are driven infrequently and on short journeys. 

Incidentally 'sloppy' mechanics sometimes also estimate  brake pad wear without bothering to use instruments.  And this can be deceptive as the metal backing plates of pads are sometimes dipped in black  paint  which depending on the pad maker may extend partially up the lining material.  Mechanics will sometimes 'estimate'  the remaining thickness of pad lining material  to this paint  line   rather than its actual thickness. 

But ultimately its best not take risks with brakes, or speculate on whether they really need doing  or  'how long have I got' . I'd get them checked independently.       

[NoelM]

Brake discs do have a minimum recommended thickness that can be measured with calipers.

lol measured with a micrometer not a caliper lol

[Lord Voltermore]

 

[edam]

I did not get the discs changed and when it went in for a new MOT it passed with no advisories !!!

[2robbie2]

Personal experience has taught me to never take any advisory or service feedback on brake pads at face value unless I have seen them for myself (unless I know/trust the person who has looked at them).

In mid-2024, I had all my brake pads changed with Honda OEM parts at 31,500 miles (they were the original pads - 4.5 years old). The works were carried out by a local Honda specialist and I saw them all in-situ (and took away the old ones).

I subsequently took my car into the local Honda dealership for its 5th service in December of the same year (just 6 months and 6,500 miles later). You can imagine my surprise when I was informed that my front brake pads were 50% worn and those on the rear 40%! I immediately questioned them on this and they took me out to see the mechanic who proceeded to take off the wheels, following which he measured them with the brake pad thickness gauge and then apologised saying he had just estimated the wear by looking through the holes in my steel wheels and had clearly made a mistake.

[Kremmen]

I had similar at a Citroen main dealer

Told me my brake pads needed changing or they would not last till the next service. As the main dealer was only a 3 min walk from  my office I popped in and asked to be shown as the car had only done 10k

Again ..... very sorry, mechanic wrote down wrong reg No

[ColinB]

I recently had cause to check the MOT history of a vehicle. It failed in 2024 with one major defect (different sized tyres on the front), one minor defect (deteriorated dust cover on suspension ball joint) and two advisories (superficial cut on one tyre, and a slightly distorted road wheel).

At the retest 11 days later, everything seems to have been fixed because the only thing recorded was an advisory for front brake pads wearing thin. The car had covered 200 miles between tests.

How likely is it that the pads had worn that much in that short time? If it had been driven that hard that quickly then it was without MOT and hence was uninsured. Or did the garage make up the brake pad advisory to drum up business?

[Sean Regan]

It's a problem sometimes with main dealers.
I had a part replaced after an "advisory," following a service on the CRV I had at the time
The following year, at the next service, it was on the service report as needing to be changed.
When I asked why it needed to be changed again, I was told that someone had neglected to take it off the service record when the work was completed.

[Lord Voltermore]

I recently had cause to check the MOT history of a vehicle. It failed in 2024 with one major defect (different sized tyres on the front), one minor defect (deteriorated dust cover on suspension ball joint) and two advisories (superficial cut on one tyre, and a slightly distorted road wheel).

I think this illustrates how you need to consider MOT failures  and advisories on their merits. An odd sized wheel/tyres  is a major defect but easily fixed by fitting the correct size. Deteriorated dust cover is minor defect but may require expensive repairs.    Advisory of superficial cut might get ignored and not  noticed by the next MOT tester, yet might deteriorate  and become dangerous.   Distorted road wheel ,especially if there is also a substituted second wheel/ replacment tyre , might indicate a major kerbing collision  , with potential for distortion and damage to suspension etc which might not get noticed on an MOT.   But if the distorted  wheel , incorrect size  and cut tyre are all one and the same wheel, there may be no cause for concern beyond checking the same wheel is not still being carried as a spare.