Rear brake pads wear

Linas.P · April 29, 2017

Today I was replacing my winter tires, back to summer ones. I have to say few times I wanted to punch the guy scratching around my (not) so recently refurbished alloys, but one fair point he made was that my rear pads are low.

To my surprise indeed there were like 5mm left, so not a tragedy but they were replaced just 12k miles ago when I was replacing all rotors and pads.I would expect to replace front pads before rear ones i.e. last time when I was replacing front ones I had ~40% thickness left on the rear (still replaced them anyway) furthermore, I tend to belive that front pads were replaced once in the mean time. So my expectation is those rear ones can usually outlast 2 sets of front ones, but now my front ones are like 9mm and rear ones already 5mm. Callipers seem to be OK, have them inspected and greased maybe 4k miles ago and the only issue was one of the front pins was slightly loose. The pads themselves are brembo "low dust"... so theoretically they should be harder and last longer and maybe wear rotor a bit more.

What you get out of your rear pads? And maybe you have a brand to recommend...

madasahatter · April 29, 2017

It depends on your driving style i imagine. I am of the understanding autos go through pads quicker than manuals. Having said that when i changed my

winters over i thought my rears seemed low. I purchased some brembo pads but have not fitted them yet. Rear discs are original no lip on them at 57,000

miles. Pagid pads were fitted same as the front also new discs at front. So i have only covered circa 8,000 miles in my ownership.

Linas.P · April 29, 2017

That is true regarding pads wearing quicker on AT, but that is mainly front pads, not the rears. Last time when I have replaced all rotors and pads I realised my rear rotors were barely worn, tracking back through the history it seems last time they were replaced was at 61k miles due to corrosion and I tend to believe they have not worn at all after 90k miles. I still have rear rotors and rear pads from last time, but in other hand my current rotors are not worn either, only the pads! Some kind of mystery...

J Henderson · April 29, 2017

Do you have solid or vented discs?

Linas.P · April 29, 2017

Solid

madasahatter · April 29, 2017

1 hour ago, Linas.P said:

Solid

Yes solid rear discs look like brand new in wear . Grey coating on the inside i bought similar for a Vrs i had from germany were brilliant discs.

They look like originals i have seen on eBay, not cheap but quality never is.

Shahpor · April 29, 2017

Well, according to a couple of my Lexus Visual Safety reports, my rear pads haven't worn down in almost 10k miles. Having said that, I did have one seized rear caliper, so I wouldn't expect much wear from that one.

I currenly have 3-4mm on mine, so it is time for a change, and I would also appreciate any recommendations.

Lexus want £125 to do the rear pads, but I am assuming I can get it done cheaper from a local indy. I know it is pretty straightforward to do myself, but I don't have any tools or space to do it.

These are the ones I have seen:

http://www.carparts4less.co.uk/cp4l/c/Lexus_IS_2.2_2008/p/car-parts/brake-friction/car-brakes/brake-pads/?101824689&1&2e6dd3bbdabce8dbbcb508fe58074a77d461b9b6&000036&awc=6409_1493504259_5e4e74b856962636f167d91869ac5fc7&utm_source=Skimlinks&utm_medium=affiliate&utm_term=cp4l+homepage&utm_content=awin+traffic&utm_campaign=Editorial+Content

Glover · April 29, 2017

Brakes and tyres will generally wear quicker on the driven wheels and if those wheels are also the steered wheels the tyres will wear quicker than wheels which are the driven wheels but don't steer . Hence I'd expect the rear brakes on a rear wheel drive car to wear quicker than the front brakes and the front tyres on a rear wheel drive car to wear slower than those on a front wheel drive car. As the IS is rear wheel the wear characteristics that Linas has experienced seem correct i.e. rear brakes wearing out quicker than fronts although whether they should have worn that quickly is another thing and depends on driving style, type of journey e.g. mainly motorway or mainly city etc.

By the same token brakes and tyres on a front wheel drive car will wear quicker but the rear brakes and tyres will (or should) last a lot longer as they are not under power or steered. Hybrid drive cars will have different characteristics for brake wear as the regeneration, rather than the brakes, takes out some of the initial momentum.

There's not a direct correlation between wear on FWD and RWD; FWD will be far heavier on their driven wheels because they are also steering but will be lighter on their rear wheels because they aren't driven nor do they steer. RWD will have less wear on their front wheels because they aren't driven but because they steer they experience greater wear than the non-driven wheels on a FWD car.

So in a nutshell the back brakes and tyres of a FWD car (undriven) should last longer than the front brakes and tyres of a RWD car (undriven but steering) and the rear brakes and tyres of a RWD car (driven) will last longer than the front brakes and tyres of a FWD car (driven and steering).

I hope all that makes sense and apologies for a very long post!

johnatg · April 30, 2017

I don't see why brake wear should depend on which wheels are driven - you don't brake and apply power at the same time (unless you're doing a bit of fancy rally driving!). Front brakes wear quicker than rear brakes because they do more work due to weight transfer (unless you make a habit of driving fast and braking hard backwards!), regardless of which wheels are driven.

Linas - are you sure the caliper pistons are moving freely and retracting properly? (Caliper pistons should move back a smidgen when the brakes are released)

I'd expect rear brake pads to last twice as long as front pads on an IS250 (and the discs should last longer too, although corrosion can be a problem particularly if the car is not used every day.)

madasahatter · April 30, 2017

7 minutes ago, johnatg said:

I don't see why brake wear should depend on which wheels are driven - you don't brake and apply power at the same time (unless you're doing a bit of fancy rally driving!). Front brakes wear quicker than rear brakes because they do more work due to weight transfer (unless you make a habit of driving fast and braking hard backwards!), regardless of which wheels are driven.

Linas - are you sure the caliper pistons are moving freely and retracting properly? (Caliper pistons should move back a smidgen when the brakes are released)

I'd expect rear brake pads to last twice as long as front pads on an IS250 (and the discs should last longer too, although corrosion can be a problem particularly if the car is not used every day.)

I believe you are right 75% front brake force 25% rear. That is why larger calipers and discs are normally on the fronts. Also nearly all fronts are vented.

http://knowhow.napaonline.com/front-brakes-vs-rear-brakes-whats-the-difference/

Glover · April 30, 2017

Well that's something I've learnt. Thanks for putting me right guys and a very useful link.

Linas.P · May 2, 2017

On 4/30/2017 at 9:11 AM, johnatg said:

Linas - are you sure the caliper pistons are moving freely and retracting properly? (Caliper pistons should move back a smidgen when the brakes are released)

2

Yes they do retract and has ~0.5mm gap when retracted (more or less, visually I would say is less than 1mm). One other thing which strikes me is that my rear rotors are almost untouched i.e. if I would have seized rear callipers I am sure it would feel quite a lot of heat coming from them and they would wear rotor as well ... so it is kind of paradoxical front rotors are quite obviously "lipped", I have not measured them, but I would say it is 0.5mm (meaning they are 33% worn) front pads has ~10mm left, which is as well ~33% (I believe new ones were 14 or 14.5mm), rear rotors are untouched, similar to previous one I have replaced, but pads are worn by more than 50% (I believe new ones were 12mm).

I was thinking maybe that is related to EPS kicking in, because my winter rears were quite slippy, but then I would see wear on rotors as well.

To conclude, I can not find anything wrong with rear callipers or anything else on the car, so it was either bad batch or brembo rear pads should be avoided ( these particular ones: https://www.amazon.co.uk/gp/product/B00AJU1ZP0/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1)

madasahatter · May 3, 2017

On 29/04/2017 at 7:04 PM, madasahatter said:

It depends on your driving style i imagine. I am of the understanding autos go through pads quicker than manuals. Having said that when i changed my

winters over i thought my rears seemed low. I purchased some brembo pads but have not fitted them yet. Rear discs are original no lip on them at 57,000

miles. Pagid pads were fitted same as the front also new discs at front. So i have only covered circa 8,000 miles in my ownership.

Well fitted the new pads today, and really was not much wrong with the old ones. Very deceptive still no harm done, another grease of the sliders.

Noticed pins get covered in a lot of brake dust. Cleaned them again with a bit of 240 grit paper. Wonder if that is the pagid pads? See how the brembos

perform against them.

is200 Newbie · May 3, 2017

7 hours ago, madasahatter said:

Well fitted the new pads today, and really was not much wrong with the old ones. Very deceptive still no harm done, another grease of the sliders.

Noticed pins get covered in a lot of brake dust. Cleaned them again with a bit of 240 grit paper. Wonder if that is the pagid pads? See how the brembos

perform against them.

If the rubber boots that fit over the pins are working as they should be on the calipers then the pins should not be exposed to any sort of dirt and that includes brake dust. The rubber boots should be tight and flexible and should expand the full range of motion of the pin without popping out of the groove that it sits in.

What grease are you using for the pins?

If you have had to use grit paper to clean them then if the rubbers are shot you may run a higher risk of them rusting if, like you say, dirt (brake dust) and water is getting in. Using a grit paper would have scored the pin surface.

Are you talking about the slide pins or the brake pad securing pins?

madasahatter · May 4, 2017

4 hours ago, is200 Newbie said:

If the rubber boots that fit over the pins are working as they should be on the calipers then the pins should not be exposed to any sort of dirt and that includes brake dust. The rubber boots should be tight and flexible and should expand the full range of motion of the pin without popping out of the groove that it sits in.

What grease are you using for the pins?

If you have had to use grit paper to clean them then if the rubbers are shot you may run a higher risk of them rusting if, like you say, dirt (brake dust) and water is getting in. Using a grit paper would have scored the pin surface.

Are you talking about the slide pins or the brake pad securing pins?

The brake pad pins all rubbers are fine on the sliders. I check them twice a year when changing wheels over. The calipers move easily by hand.