Wait for brakes light ON to change brake pads, bad idea ? is it too late already if warning lights turns ON ?

[190]

It is checked but I think it is only commented on as an advisory if the pads are worn.

There must be a minimum of 1.5mm of friction material remaining to pass.

They don't remove the wheels for an MOT inspection so they can't measure them, instead it's subjective observation that often results in an advisory. Same for disc thickness. I had an advisory at the last MOT for front disks and thought they might have been trying it on but when I measured them last week they were only 0.1mm above minimum thickness. Well done MOT tester and new discs on order next week.

Avoiding an advisory on your MOT history might be good reason for not allowing pads to get down to the wear sensors. I noticed my rear pads are down to 4mm which is well above min thickness but perhaps not far from an advisory so I will be changing those too.

 

[DSM10000]

They don't remove the wheels for an MOT inspection so they can't measure them, instead it's subjective observation that often results in an advisory. Same for disc thickness. I had an advisory at the last MOT for front disks and thought they might have been trying it on but when I measured them last week they were only 0.1mm above minimum thickness. Well done MOT tester and new discs on order next week.

Avoiding an advisory on your MOT history might be good reason for not allowing pads to get down to the wear sensors. I noticed my rear pads are down to 4mm which is well above min thickness but perhaps not far from an advisory so I will be changing those too.

They must have a way of measuring otherwise how can they state that the pads are below 1.5mm?

 

[190]

They must have a way of measuring otherwise how can they state that the pads are below 1.5mm?

The MOT manual doesn't say how but it does say:

(a) Brake lining or pad: (i) worn down to wear indicator (ii) worn below 1.5mm

Major Dangerous

Oddly it says this about disc thickness:

A brake disc or drum must be significantly worn before you should reject it. Being worn below the manufacturer’s recommended limits is not a reason in itself.

It seems to me there is a lot left up to the subjective assessment of the tester,

 

[DSM10000]

The MOT manual doesn't say how but it does say:

(a) Brake lining or pad: (i) worn down to wear indicator (ii) worn below 1.5mm

Major Dangerous

Oddly it says this about disc thickness:

A brake disc or drum must be significantly worn before you should reject it. Being worn below the manufacturer’s recommended limits is not a reason in itself.

It seems to me there is a lot left up to the subjective assessment of the tester,

Perhaps the testers have Calibrated eyeballs!

The part about disc thickness is rather arbitrary.

What is "significant"and how is it deteniined?

 

[GP801]

Some personal experience here. A few months ago the pad warning light came on in the 124 the day before heading to Italy. Roughly 1,000 miles in total. Took it to local guy who does the MOT. He found it really difficult to tell how much was left on the pads but as a general rule the warning comes with roughly 10% left so his opinion was ok to do the trip and get them changed in Italy. Managed to book it in for 3 days after our arrival. Journey was uneventful. Hardly touched the brakes. However the pads were completely shot. So much for the 10% theory. Amazing what a difference new pads made to the braking feel.

 

[Petrol Pete]

Here is a photo of the Akebono Carbon Ceramic pads I have on my car. Akebono give you a choice of brake pad wear sensor positions. My guess is that a track day Hoon would want to know earlier rather than later of excessive wear on the pads than a day to day road driver might . I fitted my sensor closer to the back plate .

Not sure about this 1.5mm thing the MOT is on about . At that point you are close to losing a pad on to the road , especially with worn discs (depending on calliper design) and is way past the minimum thickness I would ne comfortably run .