Ian C Posted July 17, 2002 Share Posted July 17, 2002 What's that then? Had my MOT today. For all those concerned, I have both the CW decat pipes installed. I swapped the centre section for a stock catted up one, and it passed OK. So you can all stop worrying. I also got notified that the front right inner pad was worn, and it was causing 'brake runout'. I pretended I knew WTF that meant at the garage The other thing I noticed instantly was the brake pedal feel was back to how I thought it should be. Good bite, minimal initial travel. Before it seemed to have a (relative) lot of travel before much happened, and about three 'stages' of feel. Strange but true. I know the garage didn't do anything like change the fluid or owt as they didn't bill me for it So what did the MOT do to make the brake pedal feel good again?! And why would the low brake fluid light start flickering on under high acceleration as a result of this? I feel it's all interlinked (I've topped up the brake fluid to stop the light flicker), but what, for future reference, tidied up the brakes and resulted in a slight dip in fluid level??! -Ian Quote Link to comment Share on other sites More sharing options...
matt Posted July 17, 2002 Share Posted July 17, 2002 Originally posted by Ian C What's that then? but what, for future reference, tidied up the brakes and resulted in a slight dip in fluid level??! -Ian Probably the mechanic givin the brakes a good stamping on the 35 mile 'test' drive afterwards......... :p and freein up a slightly stickin piston or somethin.......... The low fluid light might mean you need some new pads:baa: Quote Link to comment Share on other sites More sharing options...
Digsy Posted July 17, 2002 Share Posted July 17, 2002 There was a thread of Mycroftian proportions about brake runout a few months back. Its the measurement of how far away from true flat (i.e. warped or worn) your brake disc is. There's limits specified for it in the service book. Although how a worn pad could be causing this, and then how it could be rectified without fitting new discs I can't explain! Maybe it was the mechanic getting his terms muddled up? Quote Link to comment Share on other sites More sharing options...
Ian C Posted July 17, 2002 Author Share Posted July 17, 2002 I check the mileage these days, after a 75-mile hike on the MkIII appeared once... The mechanic didn't say swapping the pads would fix the runout, just that the runout may have been caused by it. i guess if the outer pad is pressing a lot harder than the inner one it could eventually distort the pad a bit. May explain the slight judder I'm starting to get during high speed braking. I figured the discs are on their way out because of this anyway. Any idea why one pad would wear faster than the other? Sticking pistons? It's only 29,000 miles old... I'll give it a set of discs and pads after 10 of the Best -Ian Quote Link to comment Share on other sites More sharing options...
Digsy Posted July 18, 2002 Share Posted July 18, 2002 Sticking piston if you have UK brakes or a sticking slider pin on J-spec (I would imagine). Quote Link to comment Share on other sites More sharing options...
Ian C Posted July 18, 2002 Author Share Posted July 18, 2002 Best I twat it one with a big spanner when I swap the pads, then! UK spec, of course, dahling. -Ian Quote Link to comment Share on other sites More sharing options...
Digsy Posted July 18, 2002 Share Posted July 18, 2002 If he measured your runout, maybe you could ask him what is actually was? Something doesn't sound right here... Quote Link to comment Share on other sites More sharing options...
Need4Speed Posted July 18, 2002 Share Posted July 18, 2002 Brake run-out is caused by the disc being out of true either due to warping or (less likely) the disc carrier or hub/flange being bent. You would notice general vibration under braking, even light braking, and a juddering in the pedal. The effect on pads would be to wear both pads, and they would sit further away from the disc than if it were running true. This would cause a long pedal. It sounds to me like you had a sticking piston. This would also explain the low fluid level warning as once the brake was operating correctly the piston would have moved to the correct position; ie pad just touching disc, thus lowering the fluid level in the master cylinder reservoir. The "three stages of feel" of your pedal was caused by the working side of the caliper bending the disc until it met the pad on the seized side. You symptoms and result all make sense to me although run-out is not strictly the correct wording. Still if it's sorted... Consider putting new pads in as the ones you've got will be worn unevenly. Quote Link to comment Share on other sites More sharing options...
Need4Speed Posted July 18, 2002 Share Posted July 18, 2002 Just an after thought, is your car j-spec, because the most common cause of your problem is a seized sliding caliper. Quote Link to comment Share on other sites More sharing options...
Ian C Posted July 18, 2002 Author Share Posted July 18, 2002 John, It's a j-spec import but with UK-spec brakes on it. Your explanation makes sense, I'll know what to look for next time the brakes feel wierd like that -Ian Quote Link to comment Share on other sites More sharing options...
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