New brakes groaning on full lock in reverse

[visor_down]

Hi
Have fitted new discs and pads on the front a few weeks ago and have since found when parking that there is a groan (sounds bit like a fog horn!) when on full lock in reverse.
Doesn't seem to be the power steering (didn't have the 'problem' before the new brakes) and if I apply the brakes whilst reversing the noise stops, which makes me think it is the brakes.

Anyone know what might be causing this? It resonates through the car and it definitely wasn't present before the new brakes. There is no noise from the brakes when braking and the contact points of the pads and the sliders were coated with mintex ceratec.
Cheers

 

[DrNik]

normally cheaper end market brakes make some noise, but are there supposed to be anti squeal shims or clips missing, now i know this is a silly question but you did put the pads in the right way, ive had to look at a car that was grinding even after someone fitted new pads the wrong way round, maybe driving a good 50 miles of stop start should bed them in, normally copperslip or equivalent on the backside of the pad stops it from vibrating in the caliper

 

[visor_down]

Thanks for reply, sorry should have given more detail, they are well bedded in with about 800 miles on them. It's a Focus ST with the volvo running gear, the new discs and pads are OEM and are pretty well regarded for road use from what I hear. Not sure you can fit these the wrong way round they have different clips on the back of the inner/outer pads.
It is only on full lock (or slightly off it) in reverse that it does it, in my mind can't think what would cause the brakes to droan/groan only in this circumstance.

 

[shenion]

I have seen dust shields rub the rotor only on full lock. Often get bent when doing brakes.

 

[MattF]

Not sure if your vehicle has them, but have you checked it's not something totally unrelated like steering stops?

 

[visor_down]

Thanks for suggestions so far, will check those out.
Google throws up some similar posts, but in relation to VW's, apparently down to worn ARB mounting bushes, don't see how they would cause these symptoms but their description of the sound is spot on like blowing on a beer bottle or running finger round rim of wine glass, so will check that out to.
Maybe a coincidence but definitely only started after new brakes

 

[normspanners]

One way to test if it is the brakes is to jack it up remove the wheels push the pistons and sliders back so that the pads are completely clear replace the wheels then do the maneuver again. this will prove if it is the brakes, you could clamp off the rubber hoses release each in turn pump up the pedal before moving then try again, that will prove which wheel has the problem then check the noisy wheel more closely.
It sounds to me like a sticking slider and the discs havnt fully bedded in and still has the cast rough in reverse under a microscope a bit like a saw tooth, thats causing a vibration in the sticking pad.

 

[mike 109444]

As the pads are probable not swappable within the caliper try swapping the "set" of pads from the left to the right and vis versa. Could be the pads have worn slightly tapered shaped and are acting like a wedge when the back lash is taken up in reverse.