Re: Front drum part number
Posted: May 7th, 2013, 7:52 pm
If you look at most mass produced drums the adjustment and weep holes are broached and not necessarily drilled. By rounding the sharp edge on both ends of these holes you will reduce the tendency to act as stress risers or crack starters.
It is not the heat checking cracks that cause the drum failures demonstrated by the radial cracks around the spindle area or bearing races. Nor is it a disparity of heat ranges. It is my humble theory that the vibrations and pulsing caused by heat checked drums that is stressing the attachment area surrounding the spindle and causing those cracks. If you look at most front drums there are radial curved casting webs winding out from the race bosses. These are designed to strengthen the connection between friction area of the drum and the spindle area which is fighting those twisting forces. A pulsing drum is just too violent to resist failure and overwhelms those extra casting reinforcements.
There have been several threads about vibration and tramping under braking on this forum. I believe these negative actions are also generally triggered by drum vibrations.
As I adjust my brakes and sneak up to a rubbing point, I listen to hear if the duration, or amount of time the shoe is rubbing, is very short. If your shoe just hits one small area, chances are the drum is no longer true and could be prone to having vibration issues. I have found a great machine shop that turns my drums just slightly enough to make them round again and minimize this issue. I ask for a slow cut, which will give a very fine finish and would never take my drums to "Brakes are Us".
It is not the heat checking cracks that cause the drum failures demonstrated by the radial cracks around the spindle area or bearing races. Nor is it a disparity of heat ranges. It is my humble theory that the vibrations and pulsing caused by heat checked drums that is stressing the attachment area surrounding the spindle and causing those cracks. If you look at most front drums there are radial curved casting webs winding out from the race bosses. These are designed to strengthen the connection between friction area of the drum and the spindle area which is fighting those twisting forces. A pulsing drum is just too violent to resist failure and overwhelms those extra casting reinforcements.
There have been several threads about vibration and tramping under braking on this forum. I believe these negative actions are also generally triggered by drum vibrations.
As I adjust my brakes and sneak up to a rubbing point, I listen to hear if the duration, or amount of time the shoe is rubbing, is very short. If your shoe just hits one small area, chances are the drum is no longer true and could be prone to having vibration issues. I have found a great machine shop that turns my drums just slightly enough to make them round again and minimize this issue. I ask for a slow cut, which will give a very fine finish and would never take my drums to "Brakes are Us".