The Leaf's MOT is up at the end of the month and at the last one brake discs were marked down as having corroded.

I bought discs and pads (not too bad- £93 for a pair of TRW discs and £40 for Nissan pads). Then I broke my shoulder.

Today was sunny so thought I ought to get on with it.

The 'inside' face of both discs were very badly corroded, maybe a third of the 'braking surface' was in use and 'shiny', the outer third and inner third was just a rusty mess. I've never seen this before, I have seen some ingress of rust onto braking surfaces but not that much. I don't much understand why it's rusty and hasn't been cleaned up by the pads (which were only maybe 1/3 worn but the profile clearly matched the disc).

The discs themselves (once rust cleared off) were about 24mm thick. The replacements were 28mm... I think a decent sized lathe could have faced them off and saved 93 quid...

All I can think was that because most braking is regenerative and the discs don't come into play as much as on a (non-hybrid) ICE vehicle then the discs don't get hot enough to evaporate water which just sits there and rusts?

Anyway... electric cars do need *some* maintenance it seems.

Stephen Packer <stephen.packer@gmail.com> wrote:
> The Leaf's MOT is up at the end of the month and at the last one
> brake discs were marked down as having corroded. I bought discs
> and pads (not too bad- £93 for a pair of TRW discs and £40 for
> Nissan pads). Then I broke my shoulder.
>
> Today was sunny so thought I ought to get on with it.
>
> The 'inside' face of both discs were very badly corroded, maybe
> a third of the 'braking surface' was in use and 'shiny', the outer
> third and inner third was just a rusty mess. I've never seen this
> before, I have seen some ingress of rust onto braking surfaces but
> not that much. I don't much understand why it's rusty and hasn't
> been cleaned up by the pads (which were only maybe 1/3 worn but the
> profile clearly matched the disc).
>
> The discs themselves (once rust cleared off) were about 24mm thick.
> The replacements were 28mm... I think a decent sized lathe could
> have faced them off and saved 93 quid...
>
> All I can think was that because most braking is regenerative
> and the discs don't come into play as much as on a (non-hybrid) ICE
> vehicle then the discs don't get hot enough to evaporate water which
> just sits there and rusts?
>
> Anyway... electric cars do need *some* maintenance it seems.

Around here, trying to find a shop that has a brake lathe is difficult.
The high cost of skilled labor (yes, I know it's not terribly difficult
to run a brake lathe) has made it uneconomical, more profit to fit
new parts.

And supposing you do find one, it's probably still cheaper to just
replace the rotors. Last set I bought for my Corolla were considerably
cheaper than 93 quid.

But it does irritate me that I'm scrapping a perfectly servicable pair
of rotors.

--
FJR1300A, GL1000, KLR650A6F, EX250J9A, DR200SE, Vespa Ciao

On 10/1/2021 9:23 AM, Stephen Packer wrote:
> The Leaf's MOT is up at the end of the month and at the last one brake discs were marked down as having corroded.
>
> The 'inside' face of both discs were very badly corroded, maybe a third of the 'braking surface' was in use and 'shiny', the outer third and inner third was just a rusty mess. I've never seen this before, I have seen some ingress of rust onto braking surfaces but not that much. I don't much understand why it's rusty and hasn't been cleaned up by the pads (which were only maybe 1/3 worn but the profile clearly matched the disc).
>
Perhaps a change in the disc alloy?

--
The erstwhile Thomas
FJR1300, R1200GS, ST1100 (in memoriam)

On Friday, 1 October 2021 at 18:49:26 UTC+1, Turby wrote:
> On 10/1/2021 9:23 AM, Stephen Packer wrote:
> > The Leaf's MOT is up at the end of the month and at the last one brake discs were marked down as having corroded.
> >
> > The 'inside' face of both discs were very badly corroded, maybe a third of the 'braking surface' was in use and 'shiny', the outer third and inner third was just a rusty mess. I've never seen this before, I have seen some ingress of rust onto braking surfaces but not that much. I don't much understand why it's rusty and hasn't been cleaned up by the pads (which were only maybe 1/3 worn but the profile clearly matched the disc).
> >
> Perhaps a change in the disc alloy?

I think it's a steel of one sort or another, what surprises me is that the corroded and pitted part wasn't just brushed clean by the pads.

I guess that the pads only come into play once the regenerative braking has 'done its thing' and just slow the car from 10mph or so and thus don't really get a lot of heat into the discs so the water doesn't evaporate. Or something. And I guess it's only on the inside because there's less 'wind' than on the outside blowing the discs clear?

Fuck knows.

On 01/10/2021 19:03, Stephen Packer wrote:
> I think it's a steel of one sort or another, what surprises me is that the corroded and pitted part wasn't just brushed clean by the pads.

I thought decent quality cast iron.

Stephen Packer <stephen.packer@gmail.com> wrote:

> I guess that the pads only come into play once the regenerative
> braking has 'done its thing' and just slow the car from 10mph or so
> and thus don't really get a lot of heat into the discs so the water
> doesn't evaporate. Or something. And I guess it's only on the
> inside because there's less 'wind' than on the outside blowing the
> discs clear?
>
> Fuck knows.

If it were mine, I'd be doing regular hard stops to force the
mechanical brakes to get exercised. A small cost in lost energy but
as least it would keep the discs de-rusted for the most part and
ensure good engagement between the pads and the disc for when you
have a real emergency.

--
FJR1300A, GL1000, KLR650A6F, EX250J9A, DR200SE, Vespa Ciao

On Friday, 1 October 2021 at 19:25:40 UTC+1, Mark Olson wrote:

> If it were mine, I'd be doing regular hard stops to force the
> mechanical brakes to get exercised. A small cost in lost energy but
> as least it would keep the discs de-rusted for the most part and
> ensure good engagement between the pads and the disc for when you
> have a real emergency.

It barely gets used really, just shopping. About 2.5k in the last year.

I suspect it needs a harder foot as you say.

On Friday, 1 October 2021 at 19:24:41 UTC+1, AJH wrote:
> On 01/10/2021 19:03, Stephen Packer wrote:
> > I think it's a steel of one sort or another, what surprises me is that the corroded and pitted part wasn't just brushed clean by the pads.
> I thought decent quality cast iron.

You're right. My mistake.

In which case I'd hate to machine it to skim it; cast iron makes a real fucking mess (in my very limited experience)

On Fri, 1 Oct 2021 18:25:38 -0000 (UTC), Mark Olson
<olsonm@tiny.invalid> wrote:

>Stephen Packer <stephen.packer@gmail.com> wrote:
>
>> I guess that the pads only come into play once the regenerative
>> braking has 'done its thing' and just slow the car from 10mph or so
>> and thus don't really get a lot of heat into the discs so the water
>> doesn't evaporate. Or something. And I guess it's only on the
>> inside because there's less 'wind' than on the outside blowing the
>> discs clear?
>>
>> Fuck knows.
>
>If it were mine, I'd be doing regular hard stops to force the
>mechanical brakes to get exercised. A small cost in lost energy but
>as least it would keep the discs de-rusted for the most part and
>ensure good engagement between the pads and the disc for when you
>have a real emergency.

Hmmm. That sounds like a plan.

--
Colin Irvine
FJR1300A

Stephen Packer <stephen.packer@gmail.com> wrote in news:4b2144c5-9829-4a5a-
8a11-d352a95d7e89n@googlegroups.com:

> On Friday, 1 October 2021 at 19:25:40 UTC+1, Mark Olson wrote:
>
>> If it were mine, I'd be doing regular hard stops to force the
>> mechanical brakes to get exercised. A small cost in lost energy but
>> as least it would keep the discs de-rusted for the most part and
>> ensure good engagement between the pads and the disc for when you
>> have a real emergency.
>
> It barely gets used really, just shopping. About 2.5k in the last year.
>
> I suspect it needs a harder foot as you say.

like any low mileage car, it needs an Italian tune up

On 10/1/2021 12:26 PM, Stephen Packer wrote:
> On Friday, 1 October 2021 at 19:24:41 UTC+1, AJH wrote:
>> On 01/10/2021 19:03, Stephen Packer wrote:
>>> I think it's a steel of one sort or another, what surprises me is that the corroded and pitted part wasn't just brushed clean by the pads.
>> I thought decent quality cast iron.
>
> You're right. My mistake.
>
> In which case I'd hate to machine it to skim it; cast iron makes a real fucking mess (in my very limited experience)
>
If you're just taking rust off, wouldn't emery cloth on a rotating disc
work?

--
The erstwhile Thomas
FJR1300, R1200GS, ST1100 (in memoriam)

On Friday, October 1, 2021 at 8:26:24 PM UTC+1, stephen...@gmail.com wrote:
> On Friday, 1 October 2021 at 19:24:41 UTC+1, AJH wrote:
> > On 01/10/2021 19:03, Stephen Packer wrote:
> > > I think it's a steel of one sort or another, what surprises me is that the corroded and pitted part wasn't just brushed clean by the pads.
> > I thought decent quality cast iron.
> You're right. My mistake.
>
> In which case I'd hate to machine it to skim it; cast iron makes a real fucking mess (in my very limited experience)

Most grades of cast iron machine very nicely once you've got beneath the casting scale. Admittedly
you'll have black bogies for a couple of days afterwards, but that's not a major problem. (I probably
should wear a mask when machining it...).

--
WUN

On Fri, 1 Oct 2021 13:57:56 -0700 (PDT), WUN <nigel.eaton@gmail.com>
wrote:

>Most grades of cast iron machine very nicely once you've got beneath the casting scale. Admittedly
>you'll have black bogies for a couple of days afterwards, but that's not a major problem. (I probably
>should wear a mask when machining it...).

Swarf seems to fly off in a spray IMLE. Though the scale, I read, is
very abrasive on slideways.

--

-Pip

On 01/10/2021 21:57, WUN wrote:
> On Friday, October 1, 2021 at 8:26:24 PM UTC+1, stephen...@gmail.com wrote:
>> On Friday, 1 October 2021 at 19:24:41 UTC+1, AJH wrote:
>>> On 01/10/2021 19:03, Stephen Packer wrote:
>>>> I think it's a steel of one sort or another, what surprises me is that the corroded and pitted part wasn't just brushed clean by the pads.
>>> I thought decent quality cast iron.
>> You're right. My mistake.
>>
>> In which case I'd hate to machine it to skim it; cast iron makes a real fucking mess (in my very limited experience)
>
> Most grades of cast iron machine very nicely once you've got beneath the casting scale. Admittedly
> you'll have black bogies for a couple of days afterwards, but that's not a major problem. (I probably
> should wear a mask when machining it...).
>
I think it is the scale that is the problem - or at least the rust that
develops on it is actually harder than the brake pad material?
Either way, the SO's van had a similar problem a few years ago and,
realising it was actually rust that was the problem, I removed it with a
coarse file. Followed occasionally by a finer one. This solved the
problem until pad wear 'caught up' and all was shiny again :-)
HTH

--
The Deuchars BBB#40 COFF#14
Yamaha XV750SE & Suzuki GS550t
http://www.Deuchars.org.uk

On Saturday, 2 October 2021 at 11:13:14 UTC+1, ChrisND @UKRM wrote:

> I think it is the scale that is the problem - or at least the rust that
> develops on it is actually harder than the brake pad material?
> Either way, the SO's van had a similar problem a few years ago and,
> realising it was actually rust that was the problem, I removed it with a
> coarse file. Followed occasionally by a finer one. This solved the
> problem until pad wear 'caught up' and all was shiny again :-)
> HTH

I suspect you're right, the rusty section on the discs had a corresponding
wear on the pads, so the pads were coming into contact with the rust and
were abraded by them.

I think the problem is caused by the fact that the brakes very rarely get used
apart from bringing the car to a stop from low speed. At higher speeds it
uses the motor to recharge the battery so I guess the brakes don't ever get
properly hot.

I suspect I'll end up keeping this car for 'a while'[1] so I've put the discs away
and will ponder how I can get the rust off and maintain 'flatness'. Certainly
won't fit on my lathe or mill.

[1] Until it's fit for the scrap yard.

On Friday, 1 October 2021 at 23:15:46 UTC+1, Pipl wrote:
> On Fri, 1 Oct 2021 13:57:56 -0700 (PDT), WUN <nigel...@gmail.com>
> wrote:
> >Most grades of cast iron machine very nicely once you've got beneath the casting scale. Admittedly
> >you'll have black bogies for a couple of days afterwards, but that's not a major problem. (I probably
> >should wear a mask when machining it...).
> Swarf seems to fly off in a spray IMLE. Though the scale, I read, is
> very abrasive on slideways.

I bought a backplate for my ML10 and had to machine a step into it to locate a chuck. Maybe I ought to
have taken bigger 'bites' but the surface came off as a black powder that got *everywhere*. I had ended
up wiring a vacuum cleaner pipe to the cross-slide to try to suck up most of it. Filthy job.

Stephen Packer <stephen.packer@gmail.com> wrote:

> I suspect I'll end up keeping this car for 'a while'[1] so I've put the discs away
> and will ponder how I can get the rust off and maintain 'flatness'. Certainly
> won't fit on my lathe or mill.

https://www.hunter.com/brake-lathes/bench-lathe/#overview

Might not be a cost-effective solution (in your lifetime).

--
FJR1300A, GL1000, KLR650A6F, EX250J9A, DR200SE, Vespa Ciao