Euan, Brake fade is caused by a small layer of gas that forms between the rotor and the pads. The gas layer is very thin but it acts like a cushion that prevents the pads from gripping the rotors.
The cause is heat and this is why you experience brake fade going down a long hill. You apply the brakes and with each cycle, the rotor & pad surfaces get hotter & hotter until you finally cross a threshold, some of the compounds inside the brake material turn into gas & create the cushion and you have no brakes. Race car drivers cross drill & mill slots their rotors to help bleed off the gas. They also run special metal brake pads that don't off gas like composite brake pads do. This is why you can actually see rotors glow dull red in some night time races & they still have brakes. The one advantage of modern ceramic pads is that they also off-gas less. This is the real reason they reduce brake fade. Your solution is to install a set of ceramic brake pads but also to change your driving habits. You need to slow down and shift into second gear and let the engine do most of the braking so that you have brakes when you need them. Thanks, Tom Hargrave www.kegkits.com 256-656-1924 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Euan Sent: Sunday, November 30, 2008 7:20 PM To: Mercedes Discussion List Subject: [MBZ] W123 brake fade Colleagues Brake fade may be familiar to most you as a concept but this weekend, I encountered it for real. And not for the first time. My 5-spd manual 1985 300TD suffers brake fade quite conspicuously on long winding descents, even at relatively slow speeds. The speed is slow because I descend in 3rd gear, usually adopting the truckies' practice of braking the wagon on the engine with short, periodic use of the brakes to bring speed down further. I do not ride the brakes all the way down hills. This weekend I had four souls on board. Not a big load by any means. So, what's causing this? The rotors are MB standard issue (not machined down at all). The pads are (to my knowledge) MB-approved (that is, not some after-market crap by Kamakusa) but soft rather than hard compound. I experimented with harder pads once but removed them as unsatisfactory (noisy and less efficient, if I recall correctly). Is there anything else I can check? Thanks Euan 1985 300TD 5-spd manual 213K mi CHCH NZ _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com No virus found in this incoming message. Checked by AVG. Version: 7.5.552 / Virus Database: 270.9.11/1820 - Release Date: 11/29/2008 6:52 PM No virus found in this outgoing message. Checked by AVG. Version: 7.5.552 / Virus Database: 270.9.11/1820 - Release Date: 11/29/2008 6:52 PM _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
