car mechs.. quick q on brake rotors

[bugjuice]

couple of months ago (few thousand k's), I replaced all 4 corners with new pads. Nice easy job, drove it easy for around 100ks and all was sweet. Stops well and good feel back. Lately, there's a grinding coming from the brakes like there's no meat left (altho there's hardly much worn) when braking moderately (not really any when light or hard), and there's a strange (to me)wear pattern appearing on the disc. I don't know if it's an indication of what's going wrong, or nothing to do with anything, but just wanted some views.

There's no pitting in the disc (still smooth to touch), and before the pad change, the rotors were like every other car in that they were silver and had no discolouring etc of any sort. And no, it's not a stone caught in the caliper. I know how bad they sound, and it's not that sound..

Any clues on if this is an issue or/and what's causing the grinding noise? The front pair are obviously more 'this condition' than the rear, but the rear are coming along nicely. Doesn't seem to have affected the braking performance either and made a clean bill of health on a WOF last week..
I can't get the wheel off yet, I don't have enough leverage on the locking nut, so have to get my wrench back, so I can't check out the caliper or pad surface..

Any ideas?
btw, the car is a '98 subaru impreza wagon 2ltr auto with about 160,000 on it.

[onearmedbandit]

I'll let imdying know about this thread, worked fulltime at a brake specialist for a number of years (now in pc's) and still works there on Saturdays. He should be able to give you an idea.

[Smee]

Dude, I changed the pads on my car (4 disks) about a year ago and I got the same problem. My brakes have a "grinding noise and feel". Not any squeiling (spelling). To begin with I thought they were just wearing in and glazed. But it hasn't gone away after a few thousand K's. So I asked a few people and they all reckon it was the compounds the pads are made from - short of replacing the pads with another make theirs not much I can do. Hope this is some help.

[bugjuice]

yeah, i had wondered if the compound might be wrong.
but the pads are OE replacements, and the guy who handed them over said he'd handed a hundred sets over and never had one back.. Starting to wonder if this'll be the first..

[N4CR]

Hmm, workmate had a similar problem and was told to get his discs skimmed. Don't know if this will help you though. Motu might know

[Motu]

Yeah,an ongoing problem in the brakes game - pad material is no longer asbestos,and brakes were designed around asbestos....kinda like trying to make your motor run on something other than petrol which it was designed for.If we have bad noise issues I'll fit the softest pad I can get.We do EVERYTHING on a brake job so they won't come back,and yet still they do - one on friday,another on tues.

What I did with these two was remove the rotors and go over the surface with an abraisive disc (Ryloc) to take out any spiral grooving from machining,the same to the pad surface,the rotor washed in hot soapy water,the pads and all other hardware in brakeclean.Then I sprayed the rotor with some crap I got last week that stops noise,I've used this stuff before and really don't know if it works or not.Then all assembled with stop squeak on the pads,high temp grease on all moving points.

I do all this for free of course,like all come backs (JDO - job done over) You'd wonder how I survive in this game eh?

[bugjuice]

What I did with these two was remove the rotors and go over the surface with an abraisive disc (Ryloc) to take out any spiral grooving from machining,the same to the pad surface,the rotor washed in hot soapy water,the pads and all other hardware in brakeclean.Then I sprayed the rotor with some crap I got last week that stops noise,I've used this stuff before and really don't know if it works or not.Then all assembled with stop squeak on the pads,high temp grease on all moving points.

thanx
so that isn't really going to fix it long term, is it? cos the problem is still there that they're asbestos free pads, but the discs are designed for use with. So the expensive fix is to get new discs, the lesser expensive is to find different pads, or the cheaper fix is just do nothing, cos it'll still work until it wears down and remember to get better pads next time?

Speedy - yeah, so what? If I want manual and fun, I have two wheels (and sometimes one) for that

[imdying]

Yep, I'd be machining those rotors, they're looking unhappy. Just make sure you give them a nice wash down with brakekleen, or at least some hot soapy water before you refit the pads. High temp grease on the slides, and a little on the piston face, pad shims, back of pad. Then give it a 1000kms to bed in. I assume you brought the cheapest shittiest pads you could find? We only fit Bendix pads if we can, and like Motu, always the softest compound we can. By doing these things, we hardly ever have come backs.

[marty]

i put some ferodos on the front of the daimante 5000kms ago, and they are nearly fucked. worst pads i've ever had. there is also now a slight shimmy under medium braking - possibly from a warping of the disc. this weekend i'm replacing them with oem pads (will get a refund from ferodo - 15000km warranty) and i'll run the DTI on the discs. it's only $200 for new pads and disc skim, so that's next week's job.

[Motu]

Did you have the discs machined when you fitted the Ferodo's? If not they may not honour the warranty...they won't for us,but we are only trade.One of the worst brake noises I've ever heard was on my own Diamante - machined rotors and Remsa pads,the noise was horendous,you could feel it through the whole car.I checked them several times,but as there was nothing wrong just told my wife to ignore it - sure freaked out passengers! Replaced them 6 mths ago with cheap Chinese rotors and some softer pads,Mintex I think - no noises at all.

[imdying]

Once had a bad set of Bendix Metal Kings, had a big lump of something in them... murdered the poor customers discs. It was like a stone, or a hard piece of compound metal that somehow made its way through the manufacturing process. Sticks in my mind because problems with Metal Kings are so damn rare (well, except for people bitching about brake dust).

[bugjuice]

Yep, I'd be machining those rotors, they're looking unhappy. Just make sure you give them a nice wash down with brakekleen, or at least some hot soapy water before you refit the pads. High temp grease on the slides, and a little on the piston face, pad shims, back of pad. Then give it a 1000kms to bed in. I assume you brought the cheapest shittiest pads you could find? We only fit Bendix pads if we can, and like Motu, always the softest compound we can. By doing these things, we hardly ever have come backs.

nah, they weren't the shittiest pads - I do want the car to stop! But I can't remember the flavour tho. I might get them skimmed back and get some new pads. I kept the shims on the backs of the pads, it was all reassembled how it was dissasembled. I've done pads on cars for years, but just hadn't come across that wear pattern. Every other time I've done brakes etc, I've not had any probs.

[Motu]

Tell us about it! We've ALL being doing brakes for years with no problems - just slap in new pads,don't clean nothing,never machined rotors,pads were pads,they were all the same - and never a come back.The noisy brake problem has come at the same time as the customer has been given too many rights,the garage may have to do the job several times until they sort it out...all for nothing of course.Now my suppliers carry a dozen different materials,and pricing - so I can choose the best compromise for my customers.Some are understanding,some a right pain in the arse.

[bugjuice]

lol.. sounds like a special club..

[imdying]

VN commodores, warping a set of rotors inside of 10000kms from new (Holden mechanics got extremely good at machining rotors), Cortinas that would never stop squeaking no matter what was done. Brakes have been ghey things to work on for years