Cross-drilled rotors can't be turned????
07-15-2003, 06:19 PM
#16
Intermediate
Join Date: Jan 2002
Location: Dallas,TX
Posts: 49
Likes: 0
Received 0 Likes
on
0 Posts
I don't think buying new rotors with every pad change is necessary but you should turn the rotors. Like Loren posted, you have about 2mm of rotor thickness to work with, and if machining drops them below that tolerence, then replace them. Frugal is not cheapskate, but safety should never be compromised.
07-15-2003, 07:56 PM
#17
Nordschleife Master
Thread Starter
Yup, That's what the service GM is saying. My rotors are worn. New pads will wear the rotors down beyond minimum before the new pads need replacing. He said they can be turned, but he wouldn't recommend it for my rotors. Guess I've been doing too much threshold braking.
07-16-2003, 06:11 AM
#18
Drifting
Join Date: Jun 2001
Location: Houston, Texas
Posts: 3,199
Likes: 0
Received 0 Likes
on
0 Posts
I've worked on cars for many years, you definitely do not need new rotors with every pad change/ brake job. As long as they are in spec it's ok to use the original rotors. It's not a question of someone being cheap or being a sucker, it's very straight forward. If they are, or soon will be, out of spec then replace the rotors and if not then go ahead with a simple pad change.
07-16-2003, 06:50 AM
#19
Burning Brakes
Join Date: May 2001
Location: Washington, DC
Posts: 1,163
Likes: 0
Received 0 Likes
on
0 Posts
During DE seasons I go through 3 sets of front pads before the rotors need to be replaced, which is about twice a season for me (fresh at the start and replaced about half way through). Maybe with normal street use, pads and rotors would need to be replaced at the same time but this is not the case with mostly track use.
Karl
Karl
07-16-2003, 09:26 AM
#20
Nordschleife Master
Thread Starter
What do they mean when they say rotors are glazed? I know it has to do with overheating, but what else? Does the pad material get melted into the rotor? Does the rotor surface get so hot that it gets polished so smooth that brakes don't work well?
07-16-2003, 01:23 PM
#21
Burning Brakes
Join Date: May 2001
Location: Washington, DC
Posts: 1,163
Likes: 0
Received 0 Likes
on
0 Posts
Yes, the rotors overheat and the pad material bonds to the rotor, causing it to get a blue tint and lose a significant amount of friction. Glazed rotors have to be surfaced or replaced.
Karl
Karl
07-16-2003, 03:21 PM
#22
The blanchard griding does ring a bell. It was discussed by a few engineers in the 928 areas. Remember that the nice round curve from the surface of the rotor to the hole will be "edged" just slightly if it is "ground" or "turned". I supposed from many readings of many performance books that an edge is a stress riser, "problem" waiting to happen.
07-16-2003, 06:25 PM
#23
Pro
Join Date: Apr 2003
Location: Northern VA
Posts: 620
Likes: 0
Received 0 Likes
on
0 Posts
That's a great point. Any perforated rotor must have the edges of the holes beveled. This reduces rotor stresses/cracking, and also can keep the pad material from "catching" and tearing free of the pad surface. This was an issue with some GM disc brakes in the late 80's/to mid 90's.
J
J
