The cylinder heads and throttle bodies are aluminum, rotors are cast iron. In the days of cast iron heads, you rarely saw a warped head, even after severe overheating.
Again, I do not mean that rotors do not warp, just that shuddering brakes are not always due to warped rotors. There are other causes. I happen to believe that most shuddering is not because of warped rotors, but other causes. You clearly do not share this opinion. As I pointed out, hard stops are free, if they take care of the problem, as they usually (but not always) do. then its worth a try.
I still have to disagree. In the old days with many cast iron heads it was automatically assumed by many back yarders and even shop mechanics that the heads were not warped because they’re cast iron.
The vast majority of DIYers did not even check them for warpage.
How many even owned a precision straight edge?
A guy I knew (good mechanic but now deceased) used to do head gaskets and engine work on iron head Fords and Chevys all the time and he just would not ever check a head for warpage no matter what.
Generally they were lucky; sometimes they weren’t.
The throttle body I mentioned is a carb throttle body from the 70s and 80s era Subarus. It is cast iron, prone to warpage, and I can’t even count how many of these I filed down flat to stop them from sucking air. The cast iron would warp around .003 of an inch and the upper float chamber body would warp sometimes as much as .020. (pot metal)
I agree somewhat with the part about cast iron heads and blocks being aged, but that does not make them a constant. A friend of mine (machinist of 45 years) used to machine blocks and heads that were cast on-site where he worked. The block and heads were piled outside for 2 years before machining and allowed to ripen like a tomato.
However, after countless heating and cooling cycles of a running engine cast can still change its shape.
I’ve rebuilt several small block Chevys in which the original cast exhaust manifolds would not even go back onto the heads. Once the mounting bolts were removed, the manifolds curled almost a 1/4" after the bolts were taken out. This would allow a couple of bolts located together to go back in but not all of them as the holes became progessively more off-center.
When I see a rotor wobbling on the lathe, or the car, and a dial indicator says it’s out of whack, then I believe the indicator any day of the week.
I’m going to be back on the lathe some evening this week and may just make a cut or two on half a dozen rotors just to see whats up. Will post a pic of them for analysis.
Rotors can and do warp. All machined iron parts are subject to possible warping if not properly heat treated.
However, pulsating can also be caused by glazing or material deposition…sometimes by the tech not cleaning the disk surfaces with a cleaning solvent prior to installation.
In short, not all pulsating is caused by warpage, but warpage can cause pulsating.
Just for hoots this evening, I made a few quick cuts over half a dozen rotors off the top of the pile.
Most of them are tolerable and will probably clean up within the limits.
The middle one on the bottom row is not as good as it appears to be in the pic - that metal is absolutely cooked, and cooked deep. It’s headed to the scrap pile.
Just another reason why I say warped rotors are as common as fleas on mangy dog.
