did you EVER had a warped disc ?

Thing is, when people talk about judder under braking, couple of people appear telling the disc is warped. Heck, I phoned two OPCs with mine ( plus a couple of indys ) and ALL of them told that most likely the disc is warped. Or both. Ive been reading Carrol Smith good material on brakes and brake myths and theres a sentence that is on the back of my head > When a driver reports a vibration under hard braking, inexperienced crews, after checking for (and not finding) cracks often attribute the vibration to "warped discs". They then measure the disc thickness in various places, find significant variation and the diagnosis is cast in stone. With one qualifier, presuming that the hub and wheel flange are flat and in good condition and that the wheel bolts or hat mounting hardware is in good condition, installed correctly and tightened uniformly and in the correct order to the recommended torque specification, in more than 40 years of professional racing, including the Shelby/Ford GT 40s – one of the most intense brake development program in history - I have never seen a warped brake disc. Im happy to swap the disc(s) if it cures the problem.. but confused now. How many of you had juddering or vibration, people told you that was warped discs, replace them and then problem was solved. Or not? All the best ps : by the way, his webpage can be found ( where I extracted that text ) here : http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml#

I have had only 1 warped disc in my history, that was with cheap sports x-drilled discs by G-force on my Astra GTE 16v but I reckon that was down to poor installation. Since then I have had some pretty fast cars with no issues, i.e 1967 Mustang GT500, Honda S2000, 350Z, Boxster & now 911. So I feel warped discs to be somewhat rare but not unheard of.

Interesting read, and it does make more sense, un-even brake ware ion the pads causing the issue as they are not flat to the disk. Maybe you could get the disks skimmed and replace the pads as well. I would be interested to hear about this one. I have warped brake disks before but I think that was due to a sticking caliper causing excessive heat during a spirited drive.

I find it very hard to believe that it is possible to warp a cast iron disk. I am absolutely certain that the "warped disk" problem is pretty much always caused by uneven deposits of pad material on the disk. In turn this is caused by sitting with your foot on the brake with hot disks/pads - e.g. on track days. Of course whichever it is (assuming for the moment that it is possible to warp a disk) then changing the disk is going to fix the problem.

You can't warp them, that is just the "feeling". It's uneven pad deposits. When brakes work, a thin layer of pad material is applied to the disc and the pad interfaces with this. When you get the "warped" feeling you are getting patches of disc with pad material and parts without. This happens when you overheat the pad material and it comes away in uneven deposits. I believe the reason it does it in patches is due to surface temp differences between the vaned sections and solid sections. I have actually seen on discs of a previous car the uneven deposits on my discs in patches around the disc. The general fix is a skim which people thing "trues" up the disc which in fact only removes all the pad material giving you a clean slate to start again with. Get a pad that works at the temperature you work at and you won't have this problem ever again. Jeff

I think you are right, hence why I suggested maybe skimming the disk thus removing the deposits. Though I will be watching this thread, I bet many a person has been "ripped off" by a garage or two saying they had warped there disks... I am intrigued to know though how deposits would build under normal road use, I know from doing the odd track day that you leave the car on the flat without the brakes on when not on track. I wonder if stopping at traffic lights etc is long enough to start the deposits building, also when coming back from a spirited drive it might be an idea to leave the car parked in gear for 30 mins to an hour to let the disks cool down slowly. even after a spirited drive brake disks get hot to the touch. I mean if you run a turbo'd car you don't turn it stright off do you, you let the turbo cool down a bit or take it easy for the last few miles etc. Not that simple to do that with brakes on the road as you still need them, junctions, traffic lights, roundabouts etc....

Skimming discs? Hi, Have just come back from a weekend in France ( via the tunnel avoiding the striking Frenchies ) and after about 1000km+ of relatively high-speed driving over 2 days my 996 has developed the same shudder under braking.... Obviously, I'd like to avoid the cost of new discs / pads / fitting kit etc ... is brake skimming undertaken by most garages (tyre fitters?) or do I need to find a specialist? Thanks Tim :nooo: nb: Quick bit of reasearch seems to indicate I'm not alone in getting the juddering brake problem: http://www.telegraph.co.uk/motoring...seen-on-TV-wear-and-tear-Give-me-a-brake.html

Ironically you also get uneven deposits when the car has been parked for a week or more in winter especially if it has been raining or been washed. Pads stick to disc car can't move so you increase the power and some of the pad material stays on the disc when it is finally freed. Happened to me ....

Would a quick sand with some wet n' dry sort this out as a preventative option?

I use some stuff called "Muck-off" to clean up the motorbike when it's got a few deposits. Maybe it would work on the discs? :?: (not)