Brake pad life

There's two major factors that have changed over the decades - the pad material (the non-asbestos pads are much more abrasive than the old asbestos ones), and the weight of the average car.

That does sound like a low mileage given your description of how you drive. I would expect to get 30-40K minimum out of a set of front pads, and that's replacing them well before they get down to the metal. I tend to view disks and pads as a service item though, replacing both together, but then I don't have a lathe to skim the disks!

I could be mistaken, but I think disks are relatively cheaper (at least on mass production cars) than they were years ago.

Biggles

a focus usually needs disks and pads every 36k no matter what make they are.

I'm absolutely not an expert in metallurgy, but my understanding is that discs should only be refinished by grinding, not turning. The surface finish when turned will increase pad wear.

I've ran two Focuses over the last 14 years. The first, a 1.8, was driven fairly hard. Pads lasted 20K, disks 40K. I tend to replace things like brake parts before they wear though, and might have squeezed a bit more out of them.

As an aside, I changed the rear shoes for the first time at 100k, although they were still within wear limits.

Pads and discs on the current 1.6 *seem* to be lasting a bit longer, but my usage has changed too much to make a firm comparison.

FWIW, having used both OEM and non-OEM (but branded), the genuine ones have a noticeably longer life. Whether there is a cost benefit in OEM is unsure.

SHHHH! Don't mention that here!

Chris

Dave Baker put finger to keyboard:

21k does seem very low. Have they both worn at the same rate? Presumably you've checked the calipers aren't stiff and causing binding.

I suspect the caliper may be getting sticky. The pad that is knackered is the inside one and the outside one still appears to have a few mm of meat left on it although it's hard to see exactly with the wheel still on until I strip it all down. I'll be giving everything a good polish up with wet&dry and slapping plenty of copperslip on the slidy bits before it all goes back together anyway.

Would have been nice not to have had to mess with it for another 10k miles but given the discs have now run two complete sets of pads when they probably should have been changed along with the first set it doesn't owe me much. £60 on brakes after 9 years of ownership and the car itself now 12 years old is still just about within budget.

It'll be interesting to see how thick the discs are when I get them off. They were close to the 2mm notional wear limit when I skimmed them 9 years ago but there's a huge chunk of safety margin in those limits and I don't pay them much heed. Another 1mm a side off them won't have hurt them any. Mind you I once saw a Pug 205 with the discs near as dammit down the ventilation slots and just about ready to burst. I've even heard about them bursting in use on that model if they've been used for too long which must be an interesting experience if you're hurtling down to a tight corner when you nail the brakes.

I actually am an expert in metallurgy, tribology and machinging practices and I can tell you that OE brake discs are fully lathe machined in production with carbide tooling in exactly the same way as I refinish mine and that the surface finish so achieved is both near as dammit identical to a ground finish with the right speeds and feeds and in any case utterly irrelevant after a few miles when the pads have worn that top few thou of surface away and created a new finish all of their own.

When re-maching engine flywheels you can come across rock hard carbide inclusions generated by the heat of friction which can defeat lathe tooling and require grinding through but the material used in brake discs doesn't generate such carbides, or at least not to the same extent, and actually cuts as clean as a whistle old or new. Soft grey cast iron is a lovely material to machine with sharp tooling.

However I can be damn sure that better grades of material for discs would last many times longer and that the materials used today are to actually make them wear out fast so you have to buy new ones at each pad change. I could spec disc material that would last almost the life of the car with the right pads but the car makers rely on future servicing revenue rather than any profit on the actual sale of the new car to a huge extent.

My front pads on the Leon lasted to about 80K. Almost certainly the originals, as I bough the car with 19k on it. The rears lasted less- about 65K I think, for the first set, but seized rear calipers haven't helped. I try to be light on brakes and anticipate, and my driving does involve a fair amount of motorway.

Discs on the Berlingo lasted, apparently, until about 83k, and they were well knackered by then. No idea how many sets of pads it's had, but there was about 1/2 a pad left on each one when I changed the discs and pads a couple of months ago. It had had an advisory for disc thickness on it's last MOT, and they were well worn out.

How many miles?!

I've known a set of pads to be toast within 6k miles.

I read somewhere that the change to non asbestos pads in the '80s meant a change in the disc material too which resulted in a shorter life for the discs.

However, the brakes on the average car are rather better now than they were in the asbestos pad days. Even although they may not last as well.

The rear shoes on my BMW are original, and have done about 100,000 miles. But they are the handbrake ones and it's an auto so they don't tend to do much, as I never stop the car with them.

The point of this is that how long brakes last depends on use.

JCB stopped grinding hydraulic rams many years ago. The introduction of CNC and carbide tipped wiper tools meant they got a better than ground finish from a lathe.

In the mid 90's Norton motorcycles stopped using a very expensive epitrochoid grinder for finishing the rotor chambers and used CNC. Then they could make any size they wanted and not the fixed size of the grinder.

On my 1.6 Focus the rears are original at 97K miles. The first front pads lasted around 30K and the car is still on its second set. With the last MOT (this month) I had an advisory about the front disks being lipped. The lip is insignificant compared to what I've had on previous cars.

On my previous car, a Citroen ZX I was lucky if I got 30K miles before the disks started to warp requiring a pad and disk replacement each time.

Maybe for some OE disks but I'm not 100% convinced for all. I've seen crosshatching by the use of rotary / blanchard grinding on quite a few.