What's new
What's new

OT sort of. Machining brake rotors.

newt

Aluminum
Joined
Jan 17, 2005
Location
Jackson, MS
I bought a car a while ago and noticed that the brake pedal has a lot of pulsating in it. I know that it is the warped rotors but my question is do I have to replace the pads, they are brand new, when I turn the rotors or not? The pads were replaced by the dealer but they neglected to turn the rotors :rolleyes: , I personally looked at them a while ago. If I turn the rotors with out replacing the pads what would happen? Is it possible that there is that much warpage in the pad? :confused:

Thanks in advance. Newt
 
I'm not telling you this is right, but it's my way.

When time to do a brake job, if there are pulsation issues, buy new pads and new rotors.

I chalk up the savings to my labor alone.

Something about reducing the thickness of the rotors tends to increase the thermal problems IMHO because of the reduced mass.

The other issue is that I don't have to leave the car pulled apart for a day or more while I find a shop to turn the rotors, just go buy the parts, change them, and go drive around some more.

-Matt
 
The pad just goes along for the drag. So long as the surface of the pad is still fairly smooth, I would just reuse them after you fix up the rotors. Pads don't cause pulsation, AFAIK.
 
I'm with Matt...just replace them if possible.

I spent many years doing brake work, and as vehicles became lighter, so did their component parts.

Many manufacturers went to composite rotors on light-duty vehicles (CI braking surface with a stamped steel center section). These can be a bear to machine on the equipment used in a typical automotive shop.

There are lots of setups that can be used to reduce or eliminate chatter, but most do not produce adequate results as far as surface finish and parallelism.

Some manufacturers (notably GM) specify replacement rather than resurfacing, and I tend to agree based upon customer satisfaction and experience.

If your rotors are full cast, it might be worth a shot to have them turned if you can find a competent shop (about a 50-50 coin toss around here).
 
Matt and Wilbilt you would replace both and not just the rotors? Why? I do not mean to seam like a tight wad but if the pads are like new why replace them when I could get another 40K+- out of them? What would be the down side of just replacing the rotors? :confused:

Newt
 
I dunno Newt, I guess you don't have that much to lose, just change out the rotors and see what happens.

The worst case is that you'll get pulsation again...it's not like the brakes will fail or something like that.

-Matt
 
Newt, if the pads are new or nearly so, I wouldn't worry about it.

If they have more than a few thousand miles on them, I would replace them if installing new rotors.

The pads wear into the surface finish of the rotor. If they have worn into used rotors, there will be high spots on them in reference to a new rotor.

The high spots will concentrate heat in areas, and may well cause the same distortion problems you are experiencing with the old rotors.

The same problem occurs when installing new pads on used (or unsuccessfully refinished) rotors.

Just my opinion, YMMV
 
awake ,

I would think the answer is yes. Most HSMs would in all likelihood take more time and care on the job than auto techs in a production environment.

I once resurfaced my truck flywheel at work on a brake lathe with acceptable results. It took two setups as the diameter was larger than the lathe was designed to handle. Even with the interrupted cut, it worked out OK, but I wouldn't want to do it on a daily basis.

Brake shops base their bottom line on low overhead and high volume. If a tech can save a problem rotor but take half the day doing it, it isn't gonna fly.
 
At the risk of revealing my vast ignorance ... can a HSM turn brake rotors with, say, a 12" or 14" lathe?
In a word, NO! Many, if not most, HSMers do not have the necessary expertise or equipment to return brake rotors to the required degree of flatness and parallelism. Playing with brake parts is NOT something to be done on a trial and error basis.
That being said, if you have a good tenth indicator; your lathe has flood coolant, and you have the understanding of how rotors must be turned... You are taking your, and your family's lives in your hands. You must be absolutely sure that you know what you are doing.

RAS
 
Awake, yes you can but the setup can be a -ss ache. On the other hand I bought aftermarket roters for my daughters Toyota and had pulsation problems with them. Checked the roters on the surface plate and found them to have a bit of runout.

I did then take a light skim cut in the lathe to true em up. And have had no problems since.
 
Rotors and pads are so inexpensive these days that it pays to do it right and make it all new. If you use old pads on new rotors, you'll just screw-up your new rotors. As far as turning rotors on a regular lathe, sure, you can do it. But it is better to replace them IMHO. Brake lathes cut both sides of the rotor at the same time. Keeps things even. Also, many times there are hard spots that a tool bit will not remove, it leaves high spots that will need to be ground.
Just replace this stuff, you shouldn't skimp on brakes. Matt and Wilbilt had it right the first time.

Wayne
 
Many, if not most, HSMers do not have the necessary expertise or equipment to return brake rotors to the required degree of flatness and parallelism
RAS, with all due respect,

neither do most ASE Certified brake technicians.

IMHO, HSMs work to a higher degree of accuracy and have more pride in the finished product than what I have seen in production brake shops.

That's my take on that subject, and I'll leave it at that.

Will
 
RAS, with all due respect,

neither do most ASE Certified brake technicians.

IMHO, HSMs work to a higher degree of accuracy and have more pride in the finished product than what I have seen in production brake shops.

That's my take on that subject, and I'll leave it at that.
That wasn't really my point. In brake shops, the machine does the work; just know the procedure to set the rotor up, and the machine does what it is supposed to do. I am not saying that HSMers are a slack lot; I'm just saying that brake rotors are not to be taken lightly. I have turned both drums and rotors in a conventional lathe, but, as Scott said, the setup can be a PITB. If one is not TOTALLY sure of their abilities, it's not something they should attempt. Since awake asked if it was possible to do, on a typical HSM lathe, that tells me that he is not sure. In that case, I still give a resounding 'NO'.

RAS
 
In a word, NO! Many, if not most, HSMers do not have the necessary expertise or equipment to return brake rotors to the required degree of flatness and parallelism. Playing with brake parts is NOT something to be done on a trial and error basis.
That being said, if you have a good tenth indicator; your lathe has flood coolant, and you have the understanding of how rotors must be turned... You are taking your, and your family's lives in your hands. You must be absolutely sure that you know what you are doing.

RAS
Wilbilt pretty much beat me to it. You seem to not know the huge tolerance that rotors have, they are not trued to the 'tenth,' that's a joke. Chuck up some brand new rotors, you will find them out up to .010 or so.

Actually, rotors can be out quite a bit, that's why the calipers are designed to 'float,' so you don't feel it in the pedal. If the caliper mountings (pins, slides, etc) are rusted or froze then any warpage is felt in the pedal.

Hanz
 
turn the rotors on your lathe, scuff the pads with som 80 grit and go on your way. the only trick is to make sure your turn the friction surface parallel to the surface the rotor squares up on, on the hub,make sure all the "sliding" points the caliper mounts to, are clean and lubed, happy motoring
Jim
 
Wilbilt pretty much beat me to it. You seem to not know the huge tolerance that rotors have, they are not trued to the 'tenth,' that's a joke. Chuck up some brand new rotors, you will find them out up to .010 or so.

Actually, rotors can be out quite a bit, that's why the calipers are designed to 'float,' so you don't feel it in the pedal. If the caliper mountings (pins, slides, etc) are rusted or froze then any warpage is felt in the pedal.

Hanz
LOL! Actually, I am very aware of the tolerances allowed on OEM rotors and drums. When I turned mine, I didn't allow myself those tolerances. Again, you are missing the point I am trying to make: ANY MACHINING OF BRAKE PARTS SHOULD NOT BE TAKEN LIGHTLY. If the person who posed the question of whether he could turn rotors on his lathe does not already know the answer to that question, then he shouldn't attempt it. It is only a very short step from "if ten thou is ok, thirty thou isn't much worse...". It's fine, for a beginner to make useful bits for around the house repairs; the house won't kill you, if the door latch fails.

RAS
 
Maybe I'm revealing some ignorance, too, but aren't rotors supposed to have both sides turned at the same time? I thought brake lathes were set for this for more than just speed.
 
I turned some rotors on a lathe once. I thought I had a good setup but the pedal was pulsing like crazy. I tried again, same thing. :rolleyes: I then had a shop turn them. I put that on my list of things to not waste my time on.
 
Maybe I'm revealing some ignorance, too, but aren't rotors supposed to have both sides turned at the same time? I thought brake lathes were set for this for more than just speed.
That is exactly right. This ensures the parallelism of the two surfaces. Flatness is also a factor; if the rotors are 'coned', or 'caved', the pads have a very small surface to bear on, until they wear in to the rotors.

RAS
 








 
Back
Top