How long, on average should rear brake discs last?

[MrsS]

I’m asking because my 2019 (Oct) CHR hybrid has just had its two year service. I’ve done 8,150 miles.  And yet apparently my rear brake discs are excessively scored and need replacing.  I’m totally flabbergasted that they need replacing after so few miles.

I’m not a speed demon, in fact my kids say snails drive faster!  I don’t ride the breaks are break excessively.  

I wondered if anyone else had experienced this? 

[Stivino]

Take the back wheels off and have a look, measure the thickness, take some pictures. 

If that is beyond you, get a second opinion. 

[Cyker]

It can be an issue on hybrids and EVs as the brakes get much less use than on normal cars, and they rust to buggery because they aren't being 'cleaned' by the brake pads squeezing them enough, and the rears are particularly prone to this as they do very little braking under normal circumstances anyway.

I heavily doubt they actually need replacing tho'; You'd have to check with the garage to see how thick they are and what the minimum thickness is first - If they're near the minimum thickness then they have worn down and need to be replaced anyway, but I'd be very surprised if they were anywhere near minimum thickness.

You might be able to clear the rust by just braking a bit harder in normal use to force the car to use the friction brakes more.

The ghetto way to fix it is just get up to speed on a quiet fast straight road and do a few hard stops - The pads will polish up those discs pretty quick and they should soon be all shiny again!

A less dodgy way is to find a garage that will skim the discs for you - Good ones won't even need to remove the brake disc, as they use what's basically a portable lathe; EBC brakes sometimes come with a leaflet advertising Pro Cut lathe disc skimming services.

If you google for something like skim brake discs and your area might find some local garages that do it, or even a mobile service!

Example of the skimming process:

 

[Roy124]

Mrs S said scored which implies ridges so skimming or replacement might be necessary. 

"This is where score marks are apparent on the surface of the disc's friction surface. They can be caused by several reasons including, brake over use, poor brake disc material, corrosion of the disc surface, incorrect or unsuitable pad material or contaminated pads."

I would put money on contamination. 

This is quite informative :

" https://www.dixcel.co.jp/en/popup/pop_exchange.html"

[TonyHSD]

Hi, the problem with your brake discs is caused by rust as a result of very light use due to regenerative braking and low mileage., this is also the reason why some manufacturers like Vw are moving backwards to use drum brakes in their latest Evs. I do believe that all you need is some diy cleaning and lubricating the slider pins and all will be back to normal. Happened to all hybrids owners who doesn’t drive a lot or every day. Here an example what happens to a brand new rear brake discs and pads in one year time with  minimal use during lockdowns. First picture February 2020, second picture March 2021 , I did clean them and back to new condition. Brakes need cleaning and lubricating every two years and it will last probably the lifetime of the car or at least 100000+ miles. You can request a car mechanic to do this cleaning for you. No need to replace them. 👍

[Cyker]

Yeah, that's what some garages will claim is scored and need replacing, but to me that's absolutely fine; A few firm brake events will clean that up!

One of the few good side-effects of driving around pedestrian lemming central is I get to exercise the friction brakes on a semi-regular basis!

[Roy124]

Even drum brakes need to be used.  SAAB introduced a split hydraulic disk brake system with the handbrake operating on a rear drum.  The handbrake also suffered from lack of dynamic use and the drum got rusty. 

[Starensis]

Mine is almost 4 years old and done 23k, discs are not pitted or worn.

[Red_Corolla]

25 minutes ago, Roy124 said:

Even drum brakes need to be used.  SAAB introduced a split hydraulic disk brake system with the handbrake operating on a rear drum.  The handbrake also suffered from lack of dynamic use and the drum got rusty. 

Same thing happened with the shoe-in-disc setup on the Volvo I had.

The real advantage of drums is that they need to be removed along with the wheel in order to be inspected, ergo they are less scrutinised. Discs are an easy target, if you can forgive my cynicism. I think another reason why we see drums less now is because a disc setup with a little motor to do the parking brake is simply cheaper than a traditional handbrake lever and Bowden cables.

[Cyker]

Maybe from a manufacturing point of view but not from a repair point of view

I just hope that is covered by the Toyota Relax warranty if it does fail, and they don't try to wriggle out of it by saying the brakes are a wear item...!

 

[Stivino]

46 minutes ago, Red_Corolla said:

The real advantage of drums is that they need to be removed along with the wheel in order to be inspected, ergo they are less scrutinised.

I think you meant disadvantage.

And that’s not necessarily the case, most drum brakes have a removable rubber grommet in the backplate that can be removed to enable the shoes to be inspected.

[AndyRC]

Had a good look at ours , which has 3500 miles on and the rears were way more rusty than I would like.  Did over 100 miles cross country and used the brakes as often and as hard as possible and I’ve got rid of the worst of the rust, I reckon it’s going to take a few hundred miles of pretty hard braking to get the rears as polished as the fronts.  

[TonyHSD]

3 hours ago, AndyRC said:

Had a good look at ours , which has 3500 miles on and the rears were way more rusty than I would like.  Did over 100 miles cross country and used the brakes as often and as hard as possible and I’ve got rid of the worst of the rust, I reckon it’s going to take a few hundred miles of pretty hard braking to get the rears as polished as the fronts.  

You can switch to neutral N instead of hard braking and do a few continuous moderate slow downs from 50mph to 20mph and repeat, this will work better and faster to cleaning the rust off. Make sure no tailgaters behind 😉👍

[Big_D]

After reading this thread, I did some hard braking today. Surprisingly,my mpg improved !!

[AndyRC]

11 hours ago, TonyHSD said:

You can switch to neutral N instead of hard braking and do a few continuous moderate slow downs from 50mph to 20mph and repeat, this will work better and faster to cleaning the rust off. Make sure no tailgaters behind 😉👍

I’m guessing that If you’re in Neutral it will switch  all of the regenerative breaking off and you are just using the brakes ? 

[TonyHSD]

1 hour ago, AndyRC said:

I’m guessing that If you’re in Neutral it will switch  all of the regenerative breaking off and you are just using the brakes ? 

Yes that’s correct. 
Toyota hybrids because of the regenerative braking very rarely can get the brakes to warm up over 30C° and with the time moisture finds it’s way into the slider pins, no heat means can not evaporate and the slider pins get rusted  got stuck and then even after many hard braking the discs can’t clean off the rust as the callipers can’t move and outer pads can’t press onto the disc surface with enough force. Going into N may help unstuck the slider pins but best way is to be dismantled , cleaned and lubed with silicone grease. All that can happen on only 2 years old cars if not been used regularly or mostly on short town drives. 

[TonyHSD]

7 hours ago, Big_D said:

After reading this thread, I did some hard braking today. Surprisingly,my mpg improved !!

That’s no surprise because if you have done all that in D drive not N neutral you had regenerated more power into the Battery and then used to help the ice. I noticed that 10 years ago on Prius when needed to get to my pick up at no time and had to drive a bit more spirited with shorter more progressive brakes instead of a long regenerative ones. I had recommended few times here in different posts previously that if you are not about to keep rolling then shorter braking is better for the discs and for the energy recovery. 👌✅

[Cyker]

Yeah I've been finding that braking slightly harder to get it to at least 2 blocks of regen gives better energy recovery than gentle braking/coasting to a stop, but at the same time timing your coasting so you don't have to stop at all saves more energy than stopping, even with regen. Either way, good strategies for getting those high mpgs!

 

[Spo2]

On 1/29/2022 at 6:20 PM, TonyHSD said:

You can switch to neutral N instead of hard braking and do a few continuous moderate slow downs from 50mph to 20mph and repeat, this will work better and faster to cleaning the rust off. Make sure no tailgaters behind 😉👍

You mean like coasting in N and let the car slow down from 50mph to 20mph without braking?

[TonyHSD]

27 minutes ago, Spo2 said:

You mean like coasting in N and let the car slow down from 50mph to 20mph without braking?

No, no., you have to use the brakes but continuously  with moderate pressure. The idea is to let the pads squeeze the discs from both sides and while the car is in motion it’s like you are polishing the surface on lathe, cleaning the rust evenly. , kind of a new bed in process. You can do either way as long as the slider pins are free and can move will clean the discs with the time, if the discs doesn’t clean after let say 100 miles of driving you may need to clean and lube the sliders, because when they get stuck outer pad can not move and squeeze the disc, only the inner pad is working. 

[AndyRC]

There is really a case for drum brakes on the rear of hybrids, it would be perverse that you have to change the discs and pads through lack of use 🤔. I read that Porsche developed a special coating for steal discs on their EV range to avoid this sort of problem. 

[forkingabout]

I don't want drum brakes on the rear of a vehicle plus they wouldn't work with the current electric parking brake set up - the manufactures would have to go back a step to a motor pulling on mechanical cables which brings back more failure points.

Drum brakes are a pain as the automatic adjustors never work & you would still need to remove the drum at least every year to clean inside them then manually adjust the shoes & try to balance both side up. 

 

[TonyHSD]

27 minutes ago, AndyRC said:

There is really a case for drum brakes on the rear of hybrids, it would be perverse that you have to change the discs and pads through lack of use 🤔. I read that Porsche developed a special coating for steal discs on their EV range to avoid this sort of problem. 

Indeed, I had to change twice full set of discs and pads because of rust as a result of lack of use, Porsche perhaps can use ceramic discs as their customers can afford one 😉👌. The major problem with Toyota hybrids brakes is the callipers slider pins get moisture trapped in because the brakes are always cold and this moisture can not evaporate and with the time and little use the pins get rusty too, then stop moving and this is what cause the rust on disc surfaces. When the pins does not move only the inner pad provides braking force to the disc and clean up the rust from inside but not outside, then reduced brake performance which you can’t probably notice because of the help of regenerative braking, mot advisory then failed ….. I never seen a rusty brakes on ph Priuses in London, they drive every day in town and use the brakes properly. Their discs are shiny as on the non hybrid cars. 👍

[AndyRC]

I think if you’re doing highish mileages and using the car regularly than there probably won’t be a problem, but many folk don’t use their cars every day. It’s definitely one to keep eye on if you’re a hybrid owner. An awareness of the issue and making a positive decision to use the brakes hard when the opportunity arises should help 🤔

[Sooty]

Another way of cleaning the rear discs is to find an empty space and drive in reverse quite fast and brake hard. This will force the rear brakes to act and also help to free of any "sticking" calliper slide pins.