allegro Posted October 8, 2001 Share Posted October 8, 2001 I have an SLR and have done only 4K miles. I'm not heavy with my brake foot, but appear to have picked a judder. WARPED DISC. Is this common question.gif I have not seen any other threads regarding this subject. Is it an expensive repair once I have found which is the offending corner. Andy Mac Out of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
ashaughnessy Posted October 8, 2001 Share Posted October 8, 2001 Normal discs are cheap but the vented ones are expensive. Also, you'll probably have to do both sides to avoid an imbalance, which would make it doubly expensive. I had a warped disc recently, but with an older car with plain discs and the standard brakes, not the big brake setup. The standard discs were only £14 each. If your discs are very new, maybe you'll get away with just replacing the warped one. What kind of judder is it? Anthony Link to comment Share on other sites More sharing options...
R2D2 Posted October 8, 2001 Share Posted October 8, 2001 Have you checked the wheel bearings and the wheel balance? They could both be contributing to a wheel wobble under braking. I would also check for glazing of the pads before I bought new discs. If everything else seems Ok you need a dial gauge so that you can check the disc runout as this is the only way to be sure that your discs are warped. If you have more than 0.2 mm I would think the discs certainly need changing. If they are in good condition the runout should be less than 0.05mm. 0.1mm is marginal, disc manufacturers would tell you that they need changing some pepole would tell you not to bother. If the discs are warped after 4k miles I would also look for another problem such as a lazy piston in one of the calipers. Link to comment Share on other sites More sharing options...
allegro Posted October 8, 2001 Author Share Posted October 8, 2001 Anthony As I slow down, I can feel vibration. As I come to a stand still under very light breaking I can feel a definate variation in deceleration as the wheels turn. At very low speed, under very light breaking, I can not think of anything else it could be. Andy Mac Out of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
EFA Posted October 8, 2001 Share Posted October 8, 2001 Allegro, If you have the AP racing front discs I would say this is very strange. If you have not had your car from new I would say its possible you have an aftermarket disc which is not of anything like the same quality. I have been unable to break (geddit?) the discs on my car except whne I fitted a pad metal side to the disc! Evven then I had to do 300 miles before it became noticeable! I would suspect your pads - what are you using and how much material is left on them?? If they are worn thin they can overheat which will give some strange effects caused by gassing. Be aware an AP disc is and AP disc and anything which LOOKS the same may not be. For you pleasure I can inform you the AP discs are around £130 each! Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
ashaughnessy Posted October 8, 2001 Share Posted October 8, 2001 Yep, symptoms definitely sound like a warp. You should also notice it if you jack the car up and spin the wheels round. The warped one will catch on the brake each revolution. Overheating can warp them, but as they are designed to cope with higher than normal temperatures you would think they'd be OK. Anthony Link to comment Share on other sites More sharing options...
allegro Posted October 8, 2001 Author Share Posted October 8, 2001 The discs are the original AP units supplied new from Caterham. I do not know what type/manufacture of pad it is but will jack the car up and put a guage on the discs to confirm. What typical mileage would you expect to get from a set of pads.question.gif I drive the car quite hard, but not as hard as some. ( This is probably not a question for you Arnie teeth.gif I suspect you have to change yours more often then I change my under pants ) Andy Mac teeth.gifOut of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
EFA Posted October 8, 2001 Share Posted October 8, 2001 Andy, The pads last variable lengths of time depending on use, but none seem to wear out quickly. If you have the original pads (Mintex 1136 compound) they will wear quite quickly if you drive the car hard, so its possible they are failry worn. I'd look at this first - Any pad with 2mm or less material on it is suspect. Does the judder appear at high or low speeds, heavier or lighter braking??? I think it very unlikley you have warped a disc. Be aware that early AP discs were prone to cracking so have a good look, I dont know where the cracks occurred though - perhaps someone else on here can advise??? Or Darren in Caterhma parts should know. Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
allegro Posted October 8, 2001 Author Share Posted October 8, 2001 Arnie I have a judder under heavy breaking at speed and a definite break on / off feel at low speeds with very light breaking. The variation in breaking happens to coincide with the wheel rotation. I will do further investigation tomorrow evening. Andy Mac teeth.gifOut of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
wg_mulholland Posted October 8, 2001 Share Posted October 8, 2001 I believe they (like almost all competition discs) were prone to radial cracks. Link to comment Share on other sites More sharing options...
Rob Walker Posted October 9, 2001 Share Posted October 9, 2001 I had terrible brake judder following fitting the AP big front brake package. I was convinced that the Alcan discs were warped as the problem had only developed since upgrading and I could measured .020" run out on the discs. Caterham sent me a new set of discs but when I fitted them the run out was still present. I retfitted the solid stock discs and the runout was still present. Turned out that my hubs had the runout not the discs. The remedy was to mark the disc and the hub so that they could go back in the same position. Then rotate the disc and mark the high spot on the disc, it is then easy to carefully remove a small amount of metal off the hubs disc supporting luggs in the behind the high spot on the disc using a very fine flat file until you have the disc running true. I used engineers blue to finish off and ensure that any high spots had been removed from the disc supporting luggs on the hub and that the disc was now seating flat on all four luggs. A tiny bit of course valve grinding paste also helped to remove the high spots off the hub. You could also take the hub to your local engineering shop and have the offending face skimmed up. Or buy some new hubs. Link to comment Share on other sites More sharing options...
stevefoster Posted October 9, 2001 Share Posted October 9, 2001 Get a dial gauge on them and see. A light skim may be all that is required. Link to comment Share on other sites More sharing options...
Andy G Posted October 9, 2001 Share Posted October 9, 2001 Anthonyor anyone else who can help, I have just knackered my front discs at an airfield day I am looking to replace them with "ordinary" discs as the car is an 89 Xflow so does not need anything too esoteric. You mention a price of about £13 per disc is this from Caterham or are there cheaper of the shelf alternatives? As I am not technically minded ( someone else is repairing the car!) so any assitance would be gratefully received. Link to comment Share on other sites More sharing options...
R2D2 Posted October 9, 2001 Share Posted October 9, 2001 If you have a Triumph PCD (Ital axle) any supplier of Spitfire components will have discs such as Moss Europe, Rimmer Bros. etc etc. I just fitted Red Dot Grooved discs which are standard sized, they cost about £100 + VAT and were in stock at Halfords! Link to comment Share on other sites More sharing options...
deanteam Posted October 9, 2001 Share Posted October 9, 2001 I don't think that the discs are dependent on the PCD's are they? Link to comment Share on other sites More sharing options...
ashaughnessy Posted October 9, 2001 Share Posted October 9, 2001 Cheaper than £13 each? You must be desperate :-) I got mine from Caterham but I think they are just "off-the-shelf", as Chris Flavell suggests. I would think the wheel stud pitch would be important because the discs have the holes for the wheel studs in them. I'd buy them from Caterham to avoid getting cheap pattern replacements instead of original equipment ones. Anthony Link to comment Share on other sites More sharing options...
R2D2 Posted October 9, 2001 Share Posted October 9, 2001 Deanteam, quite right about PCD, late in the day no brain! Link to comment Share on other sites More sharing options...
elie boone Posted October 9, 2001 Share Posted October 9, 2001 Chris, are you happy with the Red Dot discs ? BTW. Ital or Ford it is the same disc. Link to comment Share on other sites More sharing options...
R2D2 Posted October 9, 2001 Share Posted October 9, 2001 Elie, I used to have standard discs with Mintex C1144 and the brake pedal was just like treading on a dead cat. I also used to get inconstent braking with pulling to the left or right depending on the phase of the moon. I fitted the Red Dot discs after you suggested them and cahnged the pads for EBC green Stuff and I now have an excellent pedal, much better feel and consistent braking. The only thing I haven't done is given them any serious trouble in the Welsh Mountains, but so far a great improvement. Edited by - chris flavell on 9 Oct 2001 20:50:15 Link to comment Share on other sites More sharing options...
EFA Posted October 9, 2001 Share Posted October 9, 2001 Well at least we all now know what treading on a dead cat must feel like. Fat Arn The NOW PROVEN R500 Eaterid=red> See the Lotus Seven Club 4 Counties Area Website hereid=green> Link to comment Share on other sites More sharing options...
elie boone Posted October 10, 2001 Share Posted October 10, 2001 Chris, With new discs and pads it is easy to warp a disc, best is to take it easy for the first 50 miles or so. You can shim them, i think 1mm. Link to comment Share on other sites More sharing options...
allegro Posted October 12, 2001 Author Share Posted October 12, 2001 Right The discs have been checked by Caterham and are apparently within tolerance. But it is possible to feel a slight warp at slow speed with a small amount of pressure on the brakes. So although this is not a problem, it is bloody annoying. Can somebody tell where in the Reading area I can get my discs accurately skimmed. And how much should I expect to pay. Thanks Andy Mac teeth.gifOut of Control RED SLR teeth.gif Link to comment Share on other sites More sharing options...
R2D2 Posted October 12, 2001 Share Posted October 12, 2001 Andy, I think expressions such as "in tolerance" are a real cop out. Just in tolerance is almost as bad as just out of tolerance. I would ask what the tolerance is and what the discs measured. At least then you could have an objective argument. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted October 12, 2001 Share Posted October 12, 2001 eek.gif Are we supposed to be imagining a dead cat before or after it has gone runny? eek.gif Link to comment Share on other sites More sharing options...
R2D2 Posted October 12, 2001 Share Posted October 12, 2001 Just after rigor mortis has set it would be best I think. Link to comment Share on other sites More sharing options...
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