mccallm Posted May 23, 2008 Report Share Posted May 23, 2008 Hi All, I have a vibration on braking at speed, the kind of thing you get from distorted brake discs. I have checked the brake discs and there is distortion of about 30thou is this enough distortion to cause the vibration. What are acceptable tolerences for brake disks. Thanks Mark Quote Link to post Share on other sites
CP62 Posted May 23, 2008 Report Share Posted May 23, 2008 Hi All, I have a vibration on braking at speed, the kind of thing you get from distorted brake discs. I have checked the brake discs and there is distortion of about 30thou is this enough distortion to cause the vibration. What are acceptable tolerences for brake disks. Thanks Mark Hi Mark, 30 thou sounds an awful lot - you should get the discs skimmed (if not worn significantly) or replace them. The runout and thickness limits will be in a Haynes or Standard Triumph manual - I will check tonight and post unless someone gets there first! All the best, CP62 Quote Link to post Share on other sites
mccallm Posted May 23, 2008 Author Report Share Posted May 23, 2008 Hi Mark, 30 thou sounds an awful lot - you should get the discs skimmed (if not worn significantly) or replace them. The runout and thickness limits will be in a Haynes or Standard Triumph manual - I will check tonight and post unless someone gets there first! All the best, CP62 Thanks for the reply. I have some replacement standard discs, but I asked the question because the offending items are drilled and grooved and not very old. I understand the std are OK with a well maintained brake system any way. I can get them skimmed if I'm not happy with the standard discs. Mark Quote Link to post Share on other sites
Richard Crawley Posted May 23, 2008 Report Share Posted May 23, 2008 The max disc run out is .002” so a reading is .030” is very bad. If it is really that bad it & not caused by burs it probably means the discs are junk as the maximum you can skim them is .060”; the finish also has to be pretty good as well! Before you skim or junk them, remove the discs & check there are no burs on the mating surface & remove any you find with a file. This cured the problem for someone posting similar problems only recently. You could also try putting the disc back in a different location. I’m also in the camp that believes the standard discs & brakes are more than adequate for a road car when properly set up. Quote Link to post Share on other sites
vanflyer Posted May 23, 2008 Report Share Posted May 23, 2008 I'm with Richard on this one, the standard style of disc is more than adequate to lock up all of the wheels if you stomp on the brakes.I replaced my front discs with solid Brembo discs, If I recall they were $150.00 for the pair here in Canada so I can't imagine that they would be much more in the UK Quote Link to post Share on other sites
mccallm Posted May 23, 2008 Author Report Share Posted May 23, 2008 Thanks for the replies, I have changed other to the standard discs now, unfortunately the rain has now appeared so I can't take her out for a test drive. Let's hope we get some dryer weather this weekend. If your interested there are free tickets available for the Formula Ford festival at Castle coombe in October, all you have to do is register on the Castle coombe web site and while I'm at it there are free tickets to the renault day at Silverstone just go on the renault sport website, The last Three years has been at Donnington it's a great day lots going on and good racing from most of the Renault championships. They normally get the Renault F1 on the track as well. Mark Quote Link to post Share on other sites
mccallm Posted May 24, 2008 Author Report Share Posted May 24, 2008 Hi, Took the car for a test run, its still the same, I went back in the garage to check my vernier gauge ( the one I checked the disc alignment with) it's in mm not Thou, so I am assuming it was 0.3mm DOH! So now I know it's not the front it must be the rear, I have pulled on the handbrake while moving and can feel some uneven braking. Is it likely that the drums are distorted, it was standing for a number of years but I can't remember whether the handbrake was on or off when we first moved it. If I need to replace the drums what's the best option am I likely to get good second hand ones or am I best to shell out for new. If anyone has good second hand I would be interested. Mark Quote Link to post Share on other sites
Richard Crawley Posted May 24, 2008 Report Share Posted May 24, 2008 Hi, Took the car for a test run, its still the same, I went back in the garage to check my vernier gauge ( the one I checked the disc alignment with) it's in mm not Thou, so I am assuming it was 0.3mm DOH! But that’s still .012” & 6 x more than the permitted run out! I still reakon the problem’s at the front somewhere, the rear drums & shoes are quiet large & rarely give problems. Can I ask how you are checking the disc run out with a Vernier gauge? It’s usual to use a dial indicator gauge but there are other ways of doing it. Quote Link to post Share on other sites
marvmul Posted May 25, 2008 Report Share Posted May 25, 2008 Sometimes, air in the brake lines can cause vibration, at a higher frequency than distorted disks. Disks can get deposits of the brake pad material : when the distribution is uneven, vibration can be the result. Quote Link to post Share on other sites
mccallm Posted May 25, 2008 Author Report Share Posted May 25, 2008 Hi, I have replaced all the components on the front, bushes ,springs,shocks,calipers discs,bearings,etc and have only done 150 miles since. If I brake slowly it's OK to start then towards the end of braking is when the on off feeling comes. I've just put these new discs on they can't be distorted as well. Yes, it was a dial gauge I used. Mark Quote Link to post Share on other sites
PILKIE Posted May 25, 2008 Report Share Posted May 25, 2008 (edited) Hi Mark. One thing you should check is that the front wheel bearings are tight enough! Have you used a nyloc nut or a castellated nut and splitpin? Nylocs can work loose and shouldnt be used! "unless the vehicles manufacturer states it,even then I dont trust them" I've set mine by gradually tightening up,while spinning the wheel slowly to even out the pressure,then slacking of till the smallest amount of movement can be felt by wobbling the wheel,then nipping up just enough to fit the split pin. A bit too much slack in them will not be detectable when you check for run out on the discs,but will show up under braking as what you describe! Some cars are more sensitive to this than others. I had this problem on a Dolly Sprint,and many a head scratching hour or more!! I fitted new discs,pads,it took me a while to suss it out!! Dave Edited May 25, 2008 by PILKIE Quote Link to post Share on other sites
marvmul Posted May 25, 2008 Report Share Posted May 25, 2008 Mark, is the brake pedal feel hard or spongy? Did you use silicone brake fluid? Then lots of bleeding is necessary, with days between. All items that have to do with disc run out or distorted, wheel bearings etc. will cause a slow vibration, with every turn of the wheel. Do you feel the vibration in the pedal? It can be difficult to find the cause. When nothing obvious is found, put the old pads in it, and even the old disks or thorougly clean the new one's. If that makes disappear the vibration, properly bedding in new pads again (or, if possible, shaving the new ones you have) will cure the problem. Uneven deposits of pad material is not easily noticed, it is felt in the brake pedal though. Quote Link to post Share on other sites
Andy Moltu Posted May 26, 2008 Report Share Posted May 26, 2008 Are you sure the hub was perfectly clean before you bolted the discs on? It seems strange to have 2 sets of distorted discs. Quote Link to post Share on other sites
mccallm Posted June 5, 2008 Author Report Share Posted June 5, 2008 Hi, Thanks for all the feedback. I have stripped the front hub and cleaned it ( off side is fine) , even took the bearings out and made sure they are seating properly, but still have play in the disc. I marked the high point on the disc and the hub refitted the disc turned 180 degrees to original, the high point on the disc is now on the opposite side to previous but on the same side on the hub this means the hub is out doesn't it ? I don't quite understand, if this is the case, how this wasn't an issue before. Am I missing something? Mark Quote Link to post Share on other sites
chrismitchell Posted June 5, 2008 Report Share Posted June 5, 2008 (edited) sounds crazy but maybe one of the bearings is off-centre? By that I mean a manufacturing fault. Edited June 5, 2008 by chrismitchell Quote Link to post Share on other sites
TIMS Posted June 5, 2008 Report Share Posted June 5, 2008 Mark At any time in all of this have you had the stub axle out of the vertical link, or even replaced the stub axle? I ask as there was a thread a while back which revealed that a "new" stub axle was infact bent, if I remember correctly. With an out of place, (I.E. not at 90 degrees to the vertical link) or bent stub axle you do not have a hope. Just a thought. Regards Tim Quote Link to post Share on other sites
mccallm Posted June 5, 2008 Author Report Share Posted June 5, 2008 Thanks for the suggestions. I thought about the bearing so have bought a replacement shall try and see, I'm running out of ideas. I know the stub axle is OK, I put the off side hub on the near side to see, checked the run out and it was OK. Mark Quote Link to post Share on other sites
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