MG ZS EV brakes and tyres after second service

[Lovemyev]

Mine does a lot of town work so unfortunately its front brakes are down to 70% according to dealer 2nd service.

To be honest, I would take that 70% with a large pitch of salt to be honest.
Why - Well it is extremely difficult to accurately measure the true amount of wear on the front pads, without removing them and comparing them with a brand new set from the stores.
The wear is SO small, that the tech is likely to "guest-o-mate" the percentage of wear status..
I had this with my previous VW PHEV when it was submitted for its regular service checks.
On the first service the pad wear was reported as 95% and on the second service it was down to 90%.
All sounds about right - Yeah ?????.
On the third service it went back to 95% !!!!!.
When I challenged the senior Tech on this figures, he explained that the wear was SO small, they use their judgement and make a "Stab In The Dark" approx figure.
He went on to say, that customers are very unlikely to want a FULL ON 100% accurate figure.
Should they wish that, then removing the pads and comparing them to a brand new set, is the only true way of doing it.
But, this would be chargeable to the customer and totally unnecessary in his eye's.

 

[Gadget Geek]

To be honest, I would take that 70% with a large pitch of salt to be honest.
Why - Well it is extremely difficult to accurately measure the true amount of wear on the front pads, without removing them and comparing them with a brand new set from the stores.
The wear is SO small, that the tech is likely to "guest-o-mate" the percentage of wear status..
I had this with my previous VW PHEV when it was submitted for its regular service checks.
On the first service the pad wear was reported as 95% and on the second service it was down to 90%.
All sounds about right - Yeah ?????.
On the third service it went back to 95% !!!!!.
When I challenged the senior Tech on this figures, he explained that the wear was SO small, they use their judgement and make a "Stab In The Dark" approx figure.
He went on to say, that customers are very unlikely to want a FULL ON 100% accurate figure.
Should they wish that, then removing the pads and comparing them to a brand new set, is the only true way of doing it.
But, this would be chargeable to the customer and totally unnecessary in his eye's.

They could use a thickness gauge to measure them. Any self respecting mechanic should have one in his/her tool box.

 

[Lovemyev]

They could use a thickness gauge to measure them. Any self respecting mechanic should have one in his/her tool box.

They could, but access is tight to make an accurate measurement anyway and removing the road wheels is never going to happen, due to the time and cost factor that will be pushed onto the customer.
When the wear is really minimum, then a estimated guess is close as they feel necessary.
If on Tech suggest 90% and then in twelve months time another Tech estimates 80% ( but it is slightly out ) then it matters not really I guess.
At 80 or 90% the pads are pretty much brand new anyway.
In truth, they are checking with one eye on a view towards replacing them ASAP to generate some extra work .
Disappointed at how slowly they are taking to wear out ?‍ !.

 

[Alb]

It's usually easy to measure thickness for the parts you can access but don't lose sight of the fact that wear is often uneven across the pad and may not be the same for inboard and outboard pads.
The bit you see can see may look (and measure) just fine but the bit you often can't could be down to the metal.
Here's an example of some rear pads I replaced on another car. The one on the right is the outboard (visible) pad and the one on the left is the inboard (not visible) pad.

 

[Lovemyev]

It's usually easy to measure thickness for the parts you can access but don't lose sight of the fact that wear is often uneven across the pad and may not be the same for inboard and outboard pads.
The bit you see can see may look (and measure) just fine but the bit you often can't could be down to the metal.
Here's an example of some rear pads I replaced on another car. The one on the right is the outboard (visible) pad and the one on the left is the inboard (not visible) pad.
View attachment 6617

Yeah - I have seen and dealt with type of issue on many occasions myself .
Single piston type calliper in this case by any chance @Alb ?.
As I am sure you know already, but for the benefit of others.
This type of of uneven wear pattern is usually caused by either a sized piston in one side of a dual piston calliper or corrosion / crud build up on the sliding mechanism of single piston type calliper set up.
The correct brake pad lubricate is never used to assembly these pads in the factory anymore.
Brake services are common place on EV's now, due to the lack of use of the friction brakes, due to the effects of Regen braking.

 

[Alb]

Single piston type calliper in this case by any chance ?

Yes, the sliding mechanism was seized in this case
When the overall wear rate is low, you will run into this type of problem long before your pads actually wear out. You can keep on top of it by routinely stripping, cleaning and lubricating as necessary but this isn't actually part of any official service routine.

 

[Lovemyev]

Yes, the sliding mechanism was seized in this case
When the overall wear rate is low, you will run into this type of problem long before your pads actually wear out. You can keep on top of it by routinely stripping, cleaning and lubricating as necessary but this isn't actually part of any official service routine.

No your right !.
Wheel removal never happens anymore, unless there is a problem that necessitates them to be removed.
Back in the day, all four wheels where removed and brakes checked, every 12,000 miles while being serviced.
Visual inspection ( where possible ) at every 6,000 miles service points.

 

[Alb]

You can see from my picture that this had been going on for a while but it was not picked up during the (Main Dealer) service or at MOT time.

 

[Lovemyev]

You can see from my picture that this had been going on for a while but it was not picked up during the (Main Dealer) service or at MOT time.

Yeah - It would take a while to produce that amount of wear on that single pad.
Calliper had been sticking for a while.
I am surprised that it was not picked up at the time of service, mind you if it was on the blind side, it makes it easy to miss I guess ?.
You can’t beat wheel removal to be honest, otherwise it’s a bit of a half arsed job.
With the rears ( the more common area ) a typical symptom that you have a problem developing, is when you release the foot / handbrake, and you get that high pitched squealing noise from the binding pads, just as you pull away.
Pads removed and the crud cleaned from the sliding surface, then a full clean down.
Slide pins etc checked and lubricated.
Pads cleaned and lubricated, then reinstalled.
Probably out last the car !.

 

[Steptoe]

Interesting thread re. sliding callipers and uneven pad wear as this is something I've always obsessed about, however after maintaining my own vehicles for the last 50 years I'm now reluctantly thinking about hanging up my overalls!

One of the reasons for buying an ZS EV with a 7 year warranty is to avoid the need to deal with oils and filters but I'm still worried about the sticking pads issue as I find the wheels very heavy to remove and refit

As mentioned, cleaning and lubricating pads are not a routine servicing item so I'm hoping that the low pad wear means that, even if the pads and carrier coalesce into a solid block, braking effort will still be sufficient to pass future MOT's!

However the electric handbrake is another matter and it would be useful to have inspection and lubrication of this as a specific item on the service sheet.

 

[Alb]

I wonder how my MG5 will compare with my other car which is still on the original front pads and discs at 12 years old!

 

[Alan]

I wonder how my MG5 will compare with my other car which is still on the original front pads and discs at 12 years old!

probably pretty well I would think

 

[Kithmo]

It must be 20 years since I last changed brake pads on any of my cars, I tend to change cars more often than I used to.
Last time I saw a car dealer remove and lubricate brake pads was when SWMBO bought a 12 month old Ford Focus in 2003 from The Car People in Wakefield. They did the first, 12 month, service on it before we picked it up and made an excellent job, it was more like a major service with all the stuff they did on it, better than Ford's own services.