Technical grinding on front discs?

[SamuraiDragon]

took the car for a quick drive eariler and as it was a short drive, i didnt bother turning on my stereo... as a result of this, i could hear a light grinding noise comming from the front drivers side brake disc ( may have been from both sides but hard to tell from one side of the car)
it sounds like something metal is rubbing on the disc(s).
now, i did change the brake discs and pads myself (1st time ive done it) and all seemed to be fine - new pads seemed a little tight and very slightly rubbed against the discs, but i put this down to the fact they were new and maybe i didnt push the pistons back quite enuf? but it was that slight (could still rotate the disk by hand relatively easily by hand without the weight of the wheel to help, but it wasnt "free" spinning) i left it as they would wear away a little through use. The old discs were pretty worn as well, didnt look like they had ever been changed in 10 years.
anyways, driving round a corner, i heard this grinding noise... from what i could hear, it only happened when i turned a corner (either way) but only sometimes... has anyone come across this before? is this something i have done wrong in my inexperience, or could it be something else? and more to the point... is this something of a concern?
ramblings over. any help would be much appreciated. thanks.

 

[DaveMcT]

Check the wheel bolts are all tight as they also hold the discs. Then:

• Brake pad sticking in lits slides in the caliper but unlikely as its been done recently.
  The slides were cleaned and thinly copper greased?
• A stone stuck behind the weather shield or the shield itself is loose - easy to leave one of the tags hanging when putting the caliper back on.
• Sticking caliper piston. See if the disc gets hot even when brakes not being used.

 

[SamuraiDragon]

Check the wheel bolts are all tight as they also hold the discs. Then:

• Brake pad sticking in lits slides in the caliper but unlikely as its been done recently.
  The slides were cleaned and thinly copper greased?
• A stone stuck behind the weather shield or the shield itself is loose - easy to leave one of the tags hanging when putting the caliper back on.
• Sticking caliper piston. See if the disc gets hot even when brakes not being used.

yes, slides were wire brushed and copper greased.
unlikely to be a stone as its only when i turned. wheel bolts shouldnt come into play either as the steel wheel alignment spikes were also screwed in tight.
what are the weather shield "tags"? - although, the shield could be the cause in one way or another.. it sounds like a thin piece of metal is rubbing against the disc, but would turning affect them more?
how do u go for a drive and not use the brakes? but, how can u solve a sticking caliper piston incase this is the cause?
id just like to point out that, with the exception of the first few miles of use, the brakes have been pretty good once they started to bed in. not quite there yet, but definitely quite responsive.

 

[Adrian Bravo]

If its a constant sound check the splash plate behind the disc has not been bent against the disc. Seems to happen a lot when people turn the wheel by grabbing the disc, its only thin bendy metal.

 

[SamuraiDragon]

i didnt touch anything but the disc.... but i could have knocked it when i fitted the caliper mounts or whatever they called.... just seems odd that its only when turning... thats what i cant get my head around.

 

[shadgrind]

i didnt touch anything but the disc.... but i could have knocked it when i fitted the caliper mounts or whatever they called.... just seems odd that its only when turning... thats what i cant get my head around.

Hi, I believe that it looks like your pistons are sticking in the callipers. it will be worse under turning as you put strain laterally on the disc. Really sorry but it seems to me unless they do a rebuild kit for your callipers then you need new ones.

What probably happened is that the dust seals perished and some grit got in and scored the pistons.

 

[Ffoxy]

Hi, I believe that it looks like your pistons are sticking in the callipers. it will be worse under turning as you put strain laterally on the disc. Really sorry but it seems to me unless they do a rebuild kit for your callipers then you need new ones.

What probably happened is that the dust seals perished and some grit got in and scored the pistons.

Before doing this be mindful that most disc brakes appear to sound as if they are grinding from cold... particularly after rain! After washing your car & wheels, take a peek at how quickly surface rust appears on the usually shiny brake disk... it's scarily fast... minutes... even seconds sometimes.... that can cause a grinding that goes away after a short drive.

 

[SamuraiDragon]

having a quick peak and feel about the brakes, it does seem the the weather shield was very close to the disc. bent it away slightly so will keep a close eye and ear out for any more grinding. im not that worried (at the moment) as they work well now after a little bedding in. will report back if it hasnt sorted it.

 

[SamuraiDragon]

Before doing this be mindful that most disc brakes appear to sound as if they are grinding from cold... particularly after rain! After washing your car & wheels, take a peek at how quickly surface rust appears on the usually shiny brake disk... it's scarily fast... minutes... even seconds sometimes.... that can cause a grinding that goes away after a short drive.

they are brand new discs, only about 60 miles done on them, they are not polished, but have more of a matt look to them, either way, they work and show no signs of rust at all, even after rain etc.

 

[DaveMcT]

Sticking pads/pistons generally dont make any noise - just the disc gets stinking hot.
But if it gets really hot the wheel bearing grease will soften and that can make some nasty noises. The bearing will be grinding (worn out) a few thousand miles later.

My bet is on the splash shield. Its held on by the caliper bolts so can accidentally be left loose or its just got a bit bent.