with Clem. That is exactly the kind of thing the Stop Tech articles talk about. Basically the pad ends up depositing material unevenly on the rotor. They mention this happening when the pads/rotors haven't yet bedded in and stopping with the brakes hot and leaving them in one spot. Some material sticks. I think it's the same idea here, but moisture/whatnot end up causing the same deal.

 

No expert here but I had issues with replaced rotors on the rear. Probably were true out of the box but bolted to my spindles they no longer were. Had them turned on the car and it took a lot of material off before they were true. I believe this cndition trashed one of my relatively new calipers which is now drawing in air somehow. Point is, in my opinion, until turned on the car you will never know if the end result is correct.

 

Andre, also, I'm no expert, but I don't think that turning a rotor on a car is a good solution to an out of true problem in any case. It is just masking a larger problem with the spindle being out of true if you ask me. Best to correct the real problem. A small amount of runout is acceptable. Some people even shim the rotors, though I've heard mixed opinions about doing that and again is is masking a potentially larger issue. I did it on mine, so go figure

Also, the Corvette brakes are very well known for getting air back into the system, especially when out of true. The best solution I've seen to that problem is to remove the springs from the calipers. Old Corvette calipers are the only design I have ever heard of that have springs behind the pistons. They aren't necessary and can be easily removed if you take your time.

-dath

 

the rear rotors on corvettes were trued on the spindles when new,that is why they were rivited to the spindles from the factory.

 

Clem - Yeah, I guess you're right about that. Just seems like a poor design if you ask me, but the rears certainly don't see as much abuse either. Doing something like unevenly removing material seems like it would invite rotor warping if they were to warp.

-dath

 

Okay... I took the time to go scan the article.
The only part I have a problem with is...

" I have never seen a warped brake disc."

I have a pile of them in my shop.... anyone is welcome to come take a look.

The material written there seems technologically competent. I work in research now (closed my machine shop and moved south to warm weather & sunshine). I work in "Materials Research", teaching PHD candidates how to bridge the gap between "ivory tower" theory and backyard mechanic applied theory.

Recently, I had a student connecting an aluminum panel to a steel frame. The hole on the panel was clear (no threads) and the frame was steel, to be tapped for 8-32 machine screws. He messed up the tapped threads, so we had to up the size to 10-32 for the tapped hole. I told him to drill the hole oversize so I could re-tap the frame to 10-32. He drilled the frame instead of the panel. So now we had to start all over again at a different location. He was supposed to drill the panel being attached, not the frame where the threads were.

This is the "disconnect" between theory & practice which I deal with daily. It's my job.

" I have never seen a warped brake disc." smacks of the same disconnect.

I have absolutely seen all of the things that are written in that blog.
No issues with what they say.... except for the point on warped rotors.

When I buy Vette rotors, I pre-mount them with -0- bearing clearance and check them with a dial gage. I have found new rotors, which have never had a brake pad touch them, with up to .014 runout. So, although the brake pad deposition theory has merit, saying that rotors never warp, and all runout is caused by metal/pad deposition, is Bull tocky.

I have done the same check with an AMMCO brake lathe... and found even the best rotors can have runout, right out of the box. I worked in an auto parts store before I had my own shop... and I sold many, many Delco and Bendix rotors. We had a shop right next door to our store, who was our biggest brake parts customer. They refused to accept any NEW rotors from us unless we first turned them on our lathe. Reason: warped NEW rotors were causing them to have call-backs on their brake jobs.

I currently own 4 Mustangs... I go through rotors and pads at a high rate. I have bought several different grades of rotors, and have checked them out of the box.... they have runout. Current manufacturing technology is no better than it was 30 years ago in rotor machining. The materials may be better, but the manufacturers are not doing any better -statistically- in the machining department.

I had a 1966 Ford Ex-NYS State Police car with Kelsey Hayes Factory disc brakes which were only available on Police cars for that year. The rotors not only warped, the webbing between the plates separated while I was driving the car.

I don't disagree with the general content of the article... but rotors do in fact warp. I have had customers come to me with cheap rotors and ask me to do a brake job. I accommodated them, but gave no guarantee on the rotors. They came back to me within 2 weeks complaining of brake pulsating.... the rotors were warped.

How do I know it was warping and not material deposition? Because I am the one who physically examined the pads and measured rotors, and I am the one who did the hands-on machine work.

It's real easy to sit in a lab and theorise about how things "should" work on paper... yet a whole other ball game when you actually implement your ideas.

I'm clueless as to why they say " I have never seen a warped brake disc." The man needs to get his hands dirty.

Send 'em over to my place.... I'll give them a proper education.




On the gunk in your master cylinder... can come from a number of places. We can guess all day long, but the only way I could be sure would be to see the car in person. There are several good responses above. They are viable.

New or rebuilt master cylinders for C3's will be sitting on the shelf for some time before they are sold.... they are no longer a high-volume turnover product. Hence, they may rust before they get sold. I disassemble and inspect ALL master cylinders I install.

The brake switch/valve can hold gunk and it can feed back to the master cylinder after a brake job. I have seen this happen.

I have disassembled brake switches to learn and to run tests... they were full of residue, even after thorough flushing.

The only way to do a good job on a C3 is to completely disassemble all of the components and MANUALLY clean them out. Flushing is marginal, at best. Any one who is competent and confident in their ability to do a C3 brake job, should not be the slightest bit hesitant to remove the entire system and manually clean it out. It's not rocket science, and it's not difficult.

This is especially critical when switching from DOT3/4 to DOT 5, or from DOT 5 to DOT3/4, but recommended for any quality C3 brake job.

I hope I answered the question and didn't cloud the issue.

 

Very interesting tom, Thanks for the insight.

I have seen warped rotors, and rotors that felt warped but wern't.
My 92 saturn warps it's rotos if you drive it hard and over heat the brakes, They look fine but the runout has increased.

My 97 Caravan eats rotors, I see metal redopisits and big chunks missing from the rotor surface makes the brakes pulsate like mad

 

I just bought the car so I don't have any bills or proof to take back to a shop.

There is clearly rust on the outside of the brake M/C...which can happen on the surface in just a month...new M/C's NEED to be painted. The previous owner of my car took it to the shop and had a new M/C installed without painting. Now there's rust running down the brake booster as well as covering all of the M/C. It doesn't look like the brake system was taken care of properly...it could just be the lines IF the previous owner did what he said with new calipers.

You should pull the M/C and get all the rust off of the outside and paint it. You should also replace all of the brake lines because it looks like they have rusted from the previous owner(s) not flushing the brake fluid at least ever 5 years. Proper Maintenance involves more than just gas, oil, & water.

 

Hey Tom, thanks a bunch for your reply. What you said makes perfect sense to me. I didn't mean to spout babble that wasn't 100% true when I originally said what I did, I believe I was mistaken. I know what they are saying *CAN* cause brake pulsing is also true, so I think it would be fair to say that they discount a possibility too quickly. Also, I believe the people at that site specialize in high performance brake systems for racing, but I'm not possitive. It may be a slightly different ball game out there in whatever kind of car the author is used to working on. Some cars are more likely to see one problem than the other I imagine.

-dath

 

Yes.. that is exactly what I thought after reading the info... it had a narrow focus. Interesting stuff, but a bit too quick to generalize on the warping issue. I learned a long time ago not to believe something simply because it is written. That is why I spend so much of my free time "testing" the theory. I need to get a life.

 

Yeah, I myself also need to get a life. . . I spend too much of my free time surfing the web and bugging all of you around here for more information

-dath

 

Well, I haven't had time to look at the brakes, but I did change the fluid in the master cylinder and it looks a lot better.

Thanks to all for their info

Kilroy1024