Brake discs

[Mitsyphev]

Hello.
I have a September 2015 PHEV (facelift) which has just had an MOT and a 50000 mile service. The car has only done 29500 miles, but in the MOT advisory notes, under work required in the near future, it states that the front and rear discs are worn and will need replacing. New pads would be fitted at the same time bringing the total bill to just under £1000. I have driven many makes of cars and have never had one that required the discs being replaced at such a relatively low mileage. Also, you’d think that with regenerative braking reducing the load on the brakes the discs and pads should last longer than average. Has anyone else had a similar experience?

 

[jaapv]

Never heard of it. 130.000 km and still on the original pads and disks, and plenty of use left in them on mine. Are you the original owner? Otherwise there is reason for grave doubts about the mileage.
How come you have a 50.000 miles service at less than 30.000 miles?

 

[richr]

The discs on mine are lipped and probably will need replacing in the next year. It’s on 60,000 miles. I guess the previous owner (I’ve only done 2500 miles since purchase) liked to brake hard and didn’t use regen and smooth driving to slow down.

 

[jaapv]

Well, yes, if you brake mostly mechanically, two tons will throw some strain on the brakes.

 

[AndyInOz]

Very interesting, mine are still on the original pads, and very little signs of wear.

Just goes to show that driver behaviour affects the outcome a lot.

I would imagine that the brakes would show a lot more wear if the original owner did a lot of towing.

Did the car have a tow-bar when you bought it?

 

[Mitsyphev]

A 50,000 mile service was due because the car is 4 years old.
My wife and I are very sedate drivers. When I was younger and drove more enthusiastically I still didn’t have any premature wearing out of brake discs. As I originally said, I have driven many makes of vehicles, over forty years, and I have never had to replace discs - this is odd.

 

[Steel188]

My car recently had the big 100k mile service (at 106,000) and I have been told that I will need a complete brake rebuild at my next service (12500 miles here in UK) in 3 to 4 months.

They were last rebuilt at 60k with a set of front pads at 30k and 90k

For a two tonne motorway cruiser this seems perfectly reasonable to me as, where safe and legal to do so, travelling at the speed limit is the only choice I will make.

 

[Mitsyphev]

I forgot to say. Yes, owned from new and I did, very occasionally, tow a small trailer with light load.
I have been wondering about three possible contributory factors:
1. We don’t use the car everyday and rust does appear on the discs, as is normal, but maybe longer periods of disuse allows a bigger build up of rust and therefore a faster erosion of the disc??
2. The car has been back to the garage for the brake recall a couple of times. Could the calipers have been sticking on? Didn’t notice worsened fuel economy or drag.
3. We live at the top of a hill. When the car is fully charged and regenerative braking is off/minimal I have to apply the brakes all the way down the hill.

Since brake wear is not a warranty issue I am going to have to bite the bullet and pay to have the work done. Very disappointing though, especially after the rust issue I reported on last year.
Thanks for all your replies.

 

[michael8554]

Do you mean £1000 for the whole service, or for the brakes?

Premium discs and pads would cost about £250, just the parts no fitting.

I wouldn't normally recommend a QuikFit type solution, but a potential £500 to £600 saving.......?

 

[greendwarf]

I forgot to say. Yes, owned from new

3. We live at the top of a hill. When the car is fully charged and regenerative braking is off/minimal I have to apply the brakes all the way down the hill.

Sounds like the answer, to me.

BTW - presumably (thinking of another post today) you would have used engine braking on earlier cars down your hill - which is, of course, not available on a PHEV with a full battery.

 

[Mitsyphev]

The service and MOT were about £380. The brake work quote was just under £1000. I will get quotes from some of our local garages, ones with good reputations!

 

[ThudnBlundr]

Modern non-asbestos pads are much more aggressive than they used to be, so every car now needs the disks replaced much earlier than they used to. Lack of use will mean rust build-up on the disks. When you subsequently brake, that rust has to go somewhere and is forced into the pads and disks, wearing both much more than usual.

That said, £1k does sound excessive!

 

[STS134]

I forgot to say. Yes, owned from new

3. We live at the top of a hill. When the car is fully charged and regenerative braking is off/minimal I have to apply the brakes all the way down the hill.

Sounds like the answer, to me.

BTW - presumably (thinking of another post today) you would have used engine braking on earlier cars down your hill - which is, of course, not available on a PHEV with a full battery.

It's just poor design by Mitsubishi.

1. If the battery is full, this isn't a pure BEV. There IS somewhere you can dump extra energy: into the ICE! The ICE has a dedicated cooling system that's designed to dissipate far more energy than comes out of driving the vehicle down even a steep hill, and when the battery is full, what Toyota does is draw power from MG2 just like it always does, but instead of charging the battery with it, it will use the power to spin MG1 and turn the ICE, with a closed throttle, to dissipate extra energy.

2. Mitsubishi needs to provide a charge limit setting like Tesla does. If you live at the top of a hill or you do not need the full range on any given drive, you should be able to set the limit at say 50%, 60%, 70%, 80%, or 90%. Not only would this save the batteries, but it would also prevent excessive brake wear in this scenario (along with dumping power into the ICE when the battery is full).

 

[Mitsyphev]

Good points made - previous cars would have used engine braking and yes, Mitsubishi should have allowed the user to select the charging limit. I suppose by careful choice of timer settings I could arrange to have only 90% of a full charge thereby enabling the use of regenerative braking.

 

[jaapv]

A charge limit would certainly make sense. However, using the ICE for braking poses a problem - the Mitsubishi does not have a CVT like the Toyota.

 

[STS134]

A charge limit would certainly make sense. However, using the ICE for braking poses a problem - the Mitsubishi does not have a CVT like the Toyota.

I'm not sure why this would be a problem. Toyota doesn't really have a CVT, what it has is what they call an eCVT, but in reality is a planetary gearset that functions as a "power split device". Here's a good video explaining how the thing works:
https://www.youtube.com/watch?v=E_xCssR8qQI

What Toyota does is draw power from MG2, and shunt it to MG1, which forces the sun gear to turn quickly, and drives the planet gears. They also keep the throttle plates closed, so that the engine pulls a vacuum, and power is dissipated into the ICE.

I think it's actually far easier to do engine braking on the GKN "transmission" in the Outlander PHEV. There is a single ratio clutch that connects the ICE directly to the front wheels, which is irrelevant in this scenario, because it is not used. There are drive motors attached to the wheels, which function as generators to slow the car down. Normally, the power they generate is dumped into the battery. There is also a generator attached to the engine. When the car operates in series mode, this generator turns mechanical power from the ICE into electricity, which is used to power the drive motors. When the car is in parallel mode, this generator is also sometimes used to charge the batteries to increase load on the ICE and put it into a more optimal place in the specific fuel consumption map. The generator is also used as a motor to start the ICE.

So instead of using the thing as a motor to start the ICE, use it as a motor to drive the ICE, by shunting power from the drive motors (which are operating as generators), and fully close the throttle plates. This should accomplish the exact same thing that Toyota does, and it shouldn't be hard. All of these components already exist.

 

[jaapv]

So braking will generate petrol? :mrgreen: :lol:

 

[michael8554]

I believe that Mitsu don't ever put the ICE immediately on load, they run it up for a while to distribute oil etc.

So although engine braking would be handy in this zero B mode scenario, it would not be immediate.

Maybe starting the descent in SAVE would work instead?

 

[STS134]

I believe that Mitsu don't ever put the ICE immediately on load, they run it up for a while to distribute oil etc.

Oh, that aspect of the Outlander PHEV really pisses me off. Despite the fact that Mitsubishi claims that they designed the ICE to be able to generate power from a cold start immediately, if the ICE is cold, it will run for exactly 48 seconds before load is put on it, if the total power demand does not exceed 60 kW. The ICE will only go under high load immediately if you demand in excess of 60 kW of power. Now if Mitsubishi's claims are true, why would they do this? This is the problem with all series-parallel PHEVs: in order to get maximum power, they require the ICE. But at the same time, unlike HEVs, they do not warm up the ICE because they're trying to not waste gas warming it up if they don't have to. But the problem is, they'd need an algorithm that can predict the future in order to know when they should warm the ICE and when they shouldn't. I think in a PHEV, you really need the motors and batteries to be capable of providing maximum acceleration on their own because it's annoying as hell that I can only use half the power of this thing while still keeping it in EV mode.

So although engine braking would be handy in this zero B mode scenario, it would not be immediate.

It would be immediate. The engine isn't "under load" in the usual sense when doing engine braking. Instead of driving something else, it is being driven by something else, and it's turning mechanical energy into a small amount of heat by pulling a vacuum and dissipating energy as internal friction.

Maybe starting the descent in SAVE would work instead?

SAVE mode would do exactly the same thing as Normal mode or EV mode on a long descent. The battery will still charge. The only difference is that when the battery drains to the level it was at before you pressed Save, the ICE will start to maintain it at that SoC level. And if the battery is 100% full, Save will not do anything until it reaches 90% of so.

 

[Tai626]

Welcome back to forum, STS.
With Trex and Anko out, I am missing all the technical jargon here in forum.

I do agree with you that we only get half of power in EV mode, however, we are getting almost all the torque right out of bat ( from standing still to around 30mph, I think)

Back to the OP (I think the disc for that kind of money is too expensive!): it should be fairly easy for Mitsubishi to limit the 80% or even 50% state of charge for folks who lives in the top of a hill. Besides the safety, it also can be used to preserves the battery in the storage voltage. With the Watchdog reading voltage from batt during the charging and an intelligent outlet, we should able to do that.

Tai