Brake pads last longer than discs

[wharfhouse]

Had my 130k mile service done yesterday on my 2014 IS 300h. On the health check it was noted:

- Front discs worn/lipped - will require replacement at next pad change - pads 9mm remaining

- Rear discs are heavily worn and badly surface corroded - recommend replacement with rear pads - pads 8mm remaining

I had my front discs and pads replaced at 80k miles as the front wheel bearings had to be changed and so made sense at the time as the discs were quite close to minimum thickness. The rear discs/pads have never been replaced though.

It's interesting that given the 8/9mm of pads remaining (which is some 80% of what they start off with when new I believe), particularly on the rears, it appears the discs are actually what seem to wear down or corrode (with age) before the pads are worn out. In previous cars one could usually get a couple of pad changes out of one set of discs. 

There was no hard sell from the dealer to change the discs - just pointed it out on the report (as did the tech in the video they sent) and let me know a cost should I want it done. The fronts I will leave for the time being (as the last set did 80k miles) but will need to consider if I get the rears done - can't complain at 130k miles but just wondering if others have done their rears on the IS 300h and if so what sort of mileage?

[Linas.P]

They are not very pushy because this is typical up-sale for older cars. Experienced that myself many times. 

"Lipped" is usual catch phrase, but in fact it means nothing, how much lip is too much and how much is acceptable? The answer is rather simple - the only thing that matters is minimum thickness of the disc, and that is all - if it is close to minimum thickness or below it, then it is worn out and needs to be replaced, however if there is still 1mm of thickness left (0.5 per side) and you already have good pads with 9mm, then I would leave them until next service... as replacing discs requires replacing pads and you would be throwing away nearly new pads. Make no mistake - they measure thickness and if it is below, then instead of warning they would put it as "red - below minimum thickens, requires immediate replacement", if they not saying that, then it means you still have life in them.

Rear discs being corroded has less to do with wear, but more to do with lack of it. This can be caused by car just sitting, or maybe you have issue with the callipers, just not applying pressure on one or both sides. It is not unusual for rear discs to corrode before wearing out and I guess in hybrid it is even more of an issue (because rear brakes don't do much most of the time). Especially is callipers are stuck/seizing the discs would corrode, but I would assume Lexus would pick-up on it if that would be the case.

Now when it comes to IS300h it has same issue as older IS250s had and that is in my opinion "excessive" brake wear because "undersized" brakes for heavy car. IS300h being hybrid should be little bit better with some regen braking, but it is even heavier car. So in my experience the discs would last ~1.5set of pads, which is below average. I assume in IS300h discs last longer, but ratio would be the same i.e. on IS250 they would only last 30-40k and pads would last 20-30k, on IS300h it is likely be 40-60k and pads 30-40k, but effectively you would still be expected to replace discs before you need to replace second set of pads. I kind of doubt that you worn out disc with just 1-3mm of pad (I believe new they are 10mm, or maybe 12mm). So again I assume you probably still have life on front discs, even if there is little bit of lip. 

[Las Palmas]

1 hour ago, Linas.P said:

Rear discs being corroded has less to do with wear, but more to do with lack of it. This can be caused by car just sitting, or maybe you have issue with the callipers, just not applying pressure on one or both sides. It is not unusual for rear discs to corrode before wearing out and I guess in hybrid it is even more of an issue (because rear brakes don't do much most of the time). Especially is callipers are stuck/seizing the discs would corrode, but I would assume Lexus would pick-up on it if that would be the case.

Now when it comes to IS300h it has same issue as older IS250s had and that is in my opinion "excessive" brake wear because "undersized" brakes for heavy car. IS300h being hybrid should be little bit better with some regen braking,

The corrosion on rear callipers is normal on many cars as front is where most of the braking power come from. On a hybrid even more as the regen braking of the engine take a good part of wear of the brakes.

[wharfhouse]

4 hours ago, Linas.P said:

They are not very pushy because this is typical up-sale for older cars. Experienced that myself many times. 

"Lipped" is usual catch phrase, but in fact it means nothing, how much lip is too much and how much is acceptable? The answer is rather simple - the only thing that matters is minimum thickness of the disc, and that is all - if it is close to minimum thickness or below it, then it is worn out and needs to be replaced, however if there is still 1mm of thickness left (0.5 per side) and you already have good pads with 9mm, then I would leave them until next service... as replacing discs requires replacing pads and you would be throwing away nearly new pads. Make no mistake - they measure thickness and if it is below, then instead of warning they would put it as "red - below minimum thickens, requires immediate replacement", if they not saying that, then it means you still have life in them.

Rear discs being corroded has less to do with wear, but more to do with lack of it. This can be caused by car just sitting, or maybe you have issue with the callipers, just not applying pressure on one or both sides. It is not unusual for rear discs to corrode before wearing out and I guess in hybrid it is even more of an issue (because rear brakes don't do much most of the time). Especially is callipers are stuck/seizing the discs would corrode, but I would assume Lexus would pick-up on it if that would be the case.

Now when it comes to IS300h it has same issue as older IS250s had and that is in my opinion "excessive" brake wear because "undersized" brakes for heavy car. IS300h being hybrid should be little bit better with some regen braking, but it is even heavier car. So in my experience the discs would last ~1.5set of pads, which is below average. I assume in IS300h discs last longer, but ratio would be the same i.e. on IS250 they would only last 30-40k and pads would last 20-30k, on IS300h it is likely be 40-60k and pads 30-40k, but effectively you would still be expected to replace discs before you need to replace second set of pads. I kind of doubt that you worn out disc with just 1-3mm of pad (I believe new they are 10mm, or maybe 12mm). So again I assume you probably still have life on front discs, even if there is little bit of lip. 

Yes agree - for the front discs it's ambiguous just to say lipped without any measurement. The fact that they say "will require replacement at next pad change" when there is still 9mm left on the pads means that replacement is either a long way away or more than likely when the discs reach minimum thickness which as you say should be a red mark at a future service. The last set of discs/pads did 80K miles (and weren't actually worn to minimum) so given I have been driving the same I expect to be looking to change the fronts around 160K miles.

The rears were more interesting since I've had the car from 2 years old (when it had 40k miles on it) and I've put 90k miles on in just over 6.5 years (which includes a lot of motorway driving, so not so much use of the brakes) so it's been well used and never sitting for long and the discs themselves are bright and evenly worn where the pads contact (and there is a lip which I'd expect) and I've not had anything like a sticking calliper. The rest of the disc (other than the contact area) is however heavily corroded and in the contact area there are dark spots which I understand are corrosion in the disc material. Given that the pads are original and still have 8mm remaining, it means the rear disc condition itself based on age rather mileage will be the deciding factor of when to change rather than the disc thickness or the pads being worn out.

In previous (non-hybrid) cars I have generally got through two sets of pads per set of discs - so the pad thickness was always the leading factor for changes. Being a hybrid I can understand that the pads can last longer, but I was surprised that I don't still get through two sets of front pads before a disc change, though your experience of 1.5 sets of pads per disc concurs with the discs and pads being changed together on the front for an IS. More understandable that the rears having much less use in a hybrid means they last a lot longer, but interesting that it has got to a point where there is plenty of pad life left but the discs become the deciding factor.

As for the pad thickness left front and rear, this is as measured by Lexus at the service - it did surprise me they said there was so much pad thickness left given the mileage, but I haven't personally checked that myself.

 

[wharfhouse]

4 hours ago, Las Palmas said:

The corrosion on rear callipers is normal on many cars as front is where most of the braking power come from. On a hybrid even more as the regen braking of the engine take a good part of wear of the brakes.

Agreed, though with past non-hybrid cars I had two pad changes at the rear before I had to change the discs - that's why I was quite surprised when they said they recommend rear discs to be replaced when the original pads still have so much life left in them - so wondering when others had changed the rear discs on hybrids.

[Linas.P]

That is why I prefer getting "coated" aftermarket discs - coating does not help braking or anything else, but it prevents discs from corroding in places where pad does not touch them.

And as you said yourself - I would probably leave them as they are. If there is still thickness left (in the rear) then rust is more or less cosmetic thing. Again if they were below certain thickness or unsafe Lexus would have market them red and insisted on replacing them, if they marked them yellow then it means they are decent enough. 

[wharfhouse]

8 minutes ago, Linas.P said:

That is why I prefer getting "coated" aftermarket discs - coating does not help braking or anything else, but it prevents discs from corroding in places where pad does not touch them.

And as you said yourself - I would probably leave them as they are. If there is still thickness left (in the rear) then rust is more or less cosmetic thing. Again if they were below certain thickness or unsafe Lexus would have market them red and insisted on replacing them, if they marked them yellow then it means they are decent enough. 

Yes, I will have an MoT in September so I think will leave it until then and see what they report on the rear discs at that time.

[Las Palmas]

5 hours ago, wharfhouse said:

Yes, I will have an MoT in September so I think will leave it until then and see what they report on the rear discs at that time.

Maybe your garage just want a bit of extra money a bit sooner than needed for the car.

[wharfhouse]

8 hours ago, Las Palmas said:

Maybe your garage just want a bit of extra money a bit sooner than needed for the car.

I don't think so as they weren't at all pushy about it - just went through the report and told me the cost if/when I should decide to have them done. I've never found my dealer trying to sell me what wasn't needed - in fact on a couple of occasions they actively suggested not doing some things I'd enquired about and was happy to pay for.