w211 ovality, help please.

[whitefang]

Hi all,
good evening hope all is good.

Im looking for a bit help again please.

Car W211 e220 cdi, failed a NCT (ireland) test or MOT (england) test.

6% imbalance on the brake ovality.

I take it its the front.

The hand brake / park brake was ok.
About 1+ (i can get the date if needed.. the car is my fathers & he keeps a personal record of date & part change) the front disc , pads, was changed, & he's a clean worker, copper grease on things.

could you please advise were to go looking / checking.?

thanks all.

 

[Petrol Pete]

OP , forgive me but I don't understand the term '6% imbalance ovality' ...? Is the brake force imbalanced , 6% more on one side than the other ?

 

[whitenemesis]

Ovality is the proportion of the minimum and maximum brake force on one full wheel rotation at a brake force of 25%

Normally only relevant to drum brakes?

Could now mean the relative brake force range on a disc, perhaps due to 'warping '?

 

[Muckypaps]

It’s really a question that you should have asked the tester.

 

[whitefang]

hi all, sorry i just relpying now.

prteol pete, sorry, 6% imbalance, i think it was between the braking front & rear. & the brake test's are all smack on & well within tolerance's. sorry for my crazy statement in post ''1.

whitenemesis, yeah, ive seen a few folk saying something about 25% ... & warping, but i'd rule out (not 110% tho) but the pads & discs have been new for about less 10 months.

muckypaps, dad said that he spoke to the tester, & the tester said no idea about the fault, that a machine test's the car & the machine as failed the test. I see the point of the tester saying that, as he just test's or operates the machine, but perhaps the tester should have a bit more knowledge of the test, & but if the car now went to a garage to be done, all they can do is change everything & charge a fortune.

thanks for the help & input.

yeah....
the weekend, we removed both sides (1 at a time), the brake caliper...pads...disc...the guides... & cleaned everything up.
after taking the caliper off, pads out, & then what il call the pads guide ...
the photo below is not our car but its a w211 picture from the internet.

on the picture, there is 2 bolts with rubber gaters, when this is off the car you can actually slide the bolt part in & out. the 1 bolt part was a little hesitant.
could this be the issue for ovality.?

the bolts parts can be replaced, (the other picture is the replacement part).

thanks all.
talk to you all later.

 

[whitefang]

Hi all .. morning.

I'm sorry for very late reply with update on the above problem.
I like to say the final out come, as I did ask you all for help.

The car passed the test (nct). & we did was remove the brake discs,, the pads & the caliper runners with the little guide's (above). Cleaned it all up, even tho it wasn't that bad. Alittle copper grease & back together, & yeah pass.

Sorry for the late reply. & Hope this does help you folk a little.

Thanks all, drive safe. Talk to you soon.

Thanks.

 

[m80]

In case you didn't realise you need keep copper grease away from rubber. It will cause it to swell and then grab.
Red rubber grease is the stuff around rubber.