From: Chris Whelan on
On Wed, 12 May 2010 01:20:25 +0100, The Other Mike wrote:

[...]

> Now he takes it for the MOT and its failed on front brake imbalance!
>
> FFS, what more can I do?
>
> Could it be a master cylinder problem?
>
> Or a sticky caliper piston?
>
> Or something else?

Not the same thing, I know, but last year my Focus failed on rear brake
imbalance. I got the fail notice together with an offer to have a look,
and see how expensive the repairs would be! I had fully overhauled the
brakes less than 3K miles previously.

I booked a re-test for the following day, took it back without doing
anything, and it passed. They declined my request to see the actual
numbers.

They were a local garage, 10 minutes walk away, and had done all my MOT's
for years. Needless to say, I won't go there or recommend them again.

My new(er) Focus needed a test last week. Through someone who worked in
the trade, I found a testing station 20 minutes drive away that only does
tests.

I got chatting to the tester; he had worked at the place that had failed
the other car, but eventually left. One of the reasons was that he was
under constant pressure to fail more cars...

The second bay at the test centre was testing a MB A class. The guy
testing that kept driving it on and off the brake rollers, and re-doing
the test. "My" tester explained that the rollers weighed the car, and if
you didn't drive on them carefully, the weight, and hence the efficiency
recorded, would be wrong. Less scrupulous places could easily have just
taken the first figure as a fail.

Perhaps you might be able to find a testing only type of place for the
future?

> ...and if so how the hell do I diagnose an imbalance that I can't detect
> when I'm driving the bloody thing?

As far as I can see, only by paying in one way or another.

Chris

--
Remove prejudice to reply.
From: Chris Whelan on
On Fri, 14 May 2010 23:25:26 +0100, JReynold wrote:

[...]

> Similar to the way the AA/RAC force people to
> sell batteries to everyone - as featured on BBC Watchdog.

It wasn't the AA, just the RAC.

The only thing AA patrols are encouraged to sell is membership.

Chris

--
Remove prejudice to reply.
From: Duncan Wood on
On Sat, 15 May 2010 08:03:48 +0100, Chris Whelan
<cawhelan(a)prejudicentlworld.com> wrote:

> On Fri, 14 May 2010 23:25:26 +0100, JReynold wrote:
>
> [...]
>
>> Similar to the way the AA/RAC force people to
>> sell batteries to everyone - as featured on BBC Watchdog.
>
> It wasn't the AA, just the RAC.
>
> The only thing AA patrols are encouraged to sell is membership.
>
> Chris
>

It's just the idiot morphing again.


--
Duncan Wood
From: Chris Whelan on
On Mon, 17 May 2010 01:15:52 +0100, Duncan Wood wrote:

[...]

> It's just the idiot morphing again.

Thanks for the heads up; hadn't spotted him this time.

Chris

--
Remove prejudice to reply.
From: The Other Mike on
Thanks for all the advice, a follow up to my previous posting,

Yes it was an independent garage, they do very little other vehicle
work besides welding so nothing to gain from failing it on the brakes.

I road tested it again and found a panic stop from 40mph caused the
drivers side front wheel to lock up right at the end of the stop if I
didn't modulate the pedal pressure. From speeds less than this there
was no locking. There was certainly no evidence whatsoever of any
pulling.

So I removed the calipers from their mounts and exercised the
hydraulics against a G clamp, the pistons moved ok and I checked that
they returned with thumb pressure I couldn't find any seal kits
locally so didn't bother disturbing the dust covers and hydraulic
seals any more than looking under the dust seal - there was no
corrosion.

I removed the sliders and flushed them through to remove all traces of
grease, no wear was evident, no damage to the sliders either so I
relubed with copious amounts of CV joint grease, the sliders seemed a
bit more free moving than before.

I checked all areas of the caliper that the pads were bearing on and
removed a small area of corrosion maybe the size of a drawing pin head
and maybe 1/16" thick. Ran a smooth file over the metal bits of the
end of the pads to remove any burrs. A few blobs of copper grease on
the sliding areas and back out on the road to retest.

It was still locking at the end of a panic stop but the road was now
slightly damp so I'm not sure it was representative.

In desperation we took it back for a retest (free) and it passed.

The previous imbalance was 30%, the new imbalance is 17% (which I
presume is still high?) In hindsight I might have tried using a
rotary hone on the discs and rubbing the pads on some glass paper.


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