Minimum pad thickness

[Altamar]

My story starts with the usual one of a MB dealer saying my front pads are 90% worn and in the opinion of the technician the discs should be done at the same time. That'll be the best part of £500 sir.

I politely refused and have today checked the car myself.

The discs are well over published minimum thickness criteria, so I won't be changing them this time.

The pads (which started life at 12mm) were just over 5mm remaining (so not 90% worn then?) but I can't see any suggested minimum online.

So, my question is whether there is a recommended minimum thickness for pads?

I suspect the answer is different if you are a technician being encouraged to up-sell, but I would be interested to hear from owners/engineers who have evidence based rationale please.

I know I could wait for the warning light to come on (which it seems to do at around 2mm BTW) but I try to take a planned maintenance approach.

Thoughts?

(Oh, and before anyone says it I know it's not just MB dealers who try to up-sell pads and discs. Honda have done the same with my wife's car recently)

 

[EmilysDad]

https://www.mot-testing.service.gov.uk/documents/manuals/class3457/Section-1-Brakes.html#section_1.1

MOT says it's a fail at 1.5mm remaining. (section 1.1.13)

 

[Blobcat]

If everything is wearing evenly I wait for the warning and book it in or DIY it then.

 

[EmilysDad]

If everything is wearing evenly I wait for the warning and ....

how confident are you that the sensor works?

 

[Blobcat]

how confident are you that the sensor works?

Very

 

[M80]

Minimum this and that are for guidance imo.
With brakes the risk is skinny discs and low pads can't handle the heat generated and distort or break up.

I would be happy to let my pads run down to 2mm,
in fact if i inspect and I see the pads are below 4mm I remove the sensor and tie it back, and programme a change for 2k miles ahead or so.

 

[LostKiwi]

The guy who does my MOTs and I were discussing this the other day.
He says that when he does a service he looks at the pads and discs and makes a call on whether they will get to the next service and still have 2mm based on what he knows of the car and customer. If not he recommends they be changed solely on the basis of minimum inconvenience to the customer but he also advises they will last X many miles in his opinion and let's the customer decide.
For an MOT on the other hand it's just "Are they legal today?" and if so it's a pass (with a possible advisory if marginal).

So recommending a pad change at a service may not be just upselling.
In the OPs case claiming 90% worn is just a barefaced lie.

 

[Altamar]

https://www.mot-testing.service.gov.uk/documents/manuals/class3457/Section-1-Brakes.html#section_1.1

MOT says it's a fail at 1.5mm remaining. (section 1.1.13)

And that's what the Forum is for... Thanks #Emily'sDad for providing exactly the type of independent criteria my original post was seeking to establish.

 

[Altamar]

The guy who does my MOTs and I were discussing this the other day.
He says that when he does a service he looks at the pads and discs and makes a call on whether they will get to the next service and still have 2mm based on what he knows of the car and customer. If not he recommends they be changed solely on the basis of minimum inconvenience to the customer but he also advises they will last X many miles in his opinion and let's the customer decide.

And if the garage had said something like this they would have built up far more trust in my mind. By saying the pads are 90% worn when I can easily check just destroys trust.

Of course the problem for the garage is that if they say the pads are ok today but bring the car back in x thousand miles and we will check them again, they know there is no guarantee that I will bring it back or indeed that they will get the work in the future.

I should also have said this was on the SL which only does about 4k miles a year so in all probability won't need new pads before the next service!

So short term potential gain for them if I had just said yes vs destroying trust with customers who actually know a bit about cars.

 

[Altamar]

Minimum this and that are for guidance imo.
With brakes the risk is skinny discs and low pads can't handle the heat generated and distort or break up.

I would be happy to let my pads run down to 2mm.

... and that is why I posted the question originally.

I too let them go to 2mm (monitoring regularly in fairness) but it always brings a disapproving look and a shake of the head from a mechanic friend of mine!!

I just wanted to check if I was doing something stupid and/or dangerous.

 

[Blobcat]

... and that is why I posted the question originally.

I too let them go to 2mm (monitoring regularly in fairness) but it always brings a disapproving look and a shake of the head from a mechanic friend of mine!!

I just wanted to check if I was doing something stupid and/or dangerous.

No, you're contributing to saving the environment and valuable resources by using them as designed rather than replacing too soon.

 

[curious]

When I had the C-class, the main dealer rang me after the car was in for a service saying the pads and discs need replacing since "they're down to the metal".
If that's the case then replace them was my response. Unfortunately for them, I'd inspected them myself the day before when I had the wheels rebalanced. Nowhere near down to the metal.
Before paying I requested the old discs and pads. The person who retrieved the old items obviously wasn't aware of the the prior phone conversation.
After a bit of silliness on their part I had free discs and pads.

 

[kid-jensen]

Dealers (and Halfords) are always playing on the owners fear of safety-related parts (particularly to women owners).

Your best defence is to know what the (rough) measurements are, then you can make your own mind up.

There's always the Audio warning as a back-up.

 

[umblecumbuz]

Of course, this standard upselling technique is to prepare owners for the electric revolution.
No longer will you need to take your car into the Dealer for gearbox or engine oil and filter changes, or for many other works that are now commonplace.

Dealers will have to drum up work somehow, so the ritual pad and disc change will become even more important to them. While your electric car is in their clutches, they will recommend wiper blade servicing, pollen filter changing and a thorough valet. That's about all that will be needed.

Maybe they haven't worked out yet that even discs and pads will last far longer with electric cars due to the inherent strong 'engine' braking effect.

Oh dear, poor old Dealers. Maybe we should have a whip round for them.

 

[LostKiwi]

Oh dear, poor old Dealers. Maybe we should have a whip round for them.

Or not.....

 

[Blobcat]

Of course, this standard upselling technique is to prepare owners for the electric revolution.
No longer will you need to take your car into the Dealer for gearbox or engine oil and filter changes, or for many other works that are now commonplace.

Dealers will have to drum up work somehow, so the ritual pad and disc change will become even more important to them. While your electric car is in their clutches, they will recommend wiper blade servicing, pollen filter changing and a thorough valet. That's about all that will be needed.

Maybe they haven't worked out yet that even discs and pads will last far longer with electric cars due to the inherent strong 'engine' braking effect.

Oh dear, poor old Dealers. Maybe we should have a whip round for them.

They'll be recommending changing brushes on the brushless motors

 

[ioweddie]

At least Dick Turpin had the decency to wear a mask

 

[Blobcat]

At least Dick Turpin had the decency to wear a mask

I prefer to get kissed first...

 

[malcolm E53 AMG]

Everything is subjective with brakes, how hard do you brake, how many miles between services etc.

I’ve never seen a percentage ruler lol what you should do is ask how many millimetres are left on the pads. Sytner have just done a service/video on the 4 series and funnily enough they use millimetres to indicate wear on brake pads and tyres.

2mm was what I used to work to when doing my own servicing but really you need at least 5mm or more depending how many miles you do between services

 

[John Laidlaw]

In ye olde days it was 1/8” wasn’t it? Which is 3mm but 1/16” as last gasp ....
Anyway nowadays it’s brake warning light then within next 500 miles