RotorJoe

Like the title states. I am replacing my brake pads all the way around. I have slotted and cross drilled rotors and would like them to sty thick and last a long time.

Is it absolutely necessary to turn the rotors everytime you replace pads? I have heard of some that do and some that don't.

Please all opinions and experiences are greatly appreciated.

Thanks

alberto_mg

it is not necessary, but it has been my experience that it feels better when you do.

macdaddy

If they are not scored, just scuff both surfaces of the rotor with coarse emery cloth. This is especially important if you are going from high temp (track) pads to low temp (street) pads, not as big a deal if you are going from low tempt to high temp pads.

DamonB

I don't turn my rotors unless there is scoring that I can feel.

adam c

iTrader: (2)

It really depends on wear. If they have 20K on them they will almost certainly need to be turned. 5K of really hard miles may produce as much wear as 20K of normal miles.

If they are very smooth, and you have ZERO warping, they are probably fine. If you feel any warping when applying your brakes, get them turned.

RotorJoe

Hey thanks alot guys. You guys make me feel better about not turning them before either. The disks are not damaged and I don't have any abnormalities in the pedal. I am going from the Hawk HP pads to EBC red in the front and EBC green in the back. I wore through the Hawk HP pads in about 10,000miles. Wow. But then I have a heavy foot which requires a heavy brake too. Plus the Hawk HP's created too much dust and that is a PTA to clean off of my blitz rims.

Thanks Again

RotorJoe

Well just an update. My McGard lug key broke and I was only able to remove one rim. I took the car over to my Dad's house and we welded on blots to the keyed lug tell we could remove it.
I am contacting McGard and giving them the key code so they can send me a replacement key.
So I was only able to do the front pads, but those needed it the most. The rear can wait tell I get the replacement key.
The brakes feeel good, no vibration or weird pedal feel. Still letting them seat and brake in but otherwise they feel good.
What a PTA and thanks again.

GTRay

the skinny on turning rotors...

for slotted rotors i normally don't turn them. the slots are typically cut to a calculated depth and when you turn the rotor you diminish the effectiveness of those slots. the drilled holes on the other hand i don't worry as much about, keep cutting until you hit the specified limit.

i realize that these rotors are expensive pieces of equipment but we all have to realize that not only do they have to do the same job that mom's minivan has to do when the stop pedal is kicked they have to do it at MUCH greater levels of stress.

i typically cut rotors for two reasons.
1) new pads are being used. new pads don't like sloppy seconds :-) new pads will ALWAYS perform better and last longer when they are broken in with a freshly machined rotor.

2)there is a variation in rotor thickness that causes a pedal pulsation. you WILL NOT feel a WARPED rotor through your brake pedal. a warped rotor causes thin and thick spots to develop in the rotor and that is what you feel in your pedal.

one of the dangers of having rotors turned OFF of the car on a bench lathe is that the person operating the lathe doesn't go through all of the steps to do it right. 7 out of 10 times i garuntee that if the propper procedures are not followed then the operator of the lathe will actually cut more lateral runout into a rotor than what it began with (lateral runout is the measure of the warpage of the rotor - and warpage leads to variable disc thickness which leads to poor performance and pulsing pedals). if you are going to have your rotors turned make sure that it is done while they are on the car if at all possible with a machine that bolts to the hub and spins the hub. the machine we use is the ProCut and it garruntess .002" maximum lateral runout, bench lathes even when used properly have a difficult time matching that kind of accuracy and control.

Ray

adam c

iTrader: (2)

I had badly warped rotors in my Accord, and very slightly warped rotors in my FD. In both cases, I could feel the warp in my brake pedal. The Accord was much worse.

GTRay

read the post again. it's not the warping that you are feeling. it is a variation in the thickness of the rotor. hydraulic brake calipers are designed in such a way that you will not feel a warped rotor. Calipers are designed to float and compensate for warping in the rotors.

what you felt was the rotor causing the pads to seperate and contract due to thin and thick spots that developed as a result of a warped rotor scrubbing on the pads while the brakes were not being used.

warping is what leads to rotor thickness variations.


Ray

RotorJoe

Thanks again.

Pads are on. Did not turn the rotors. Because of the slots (thickness and depth of slots) and the fact that (with my luck) a monkey **** will mess them up. Just like the dip **** cutting my key at homedepo.

Went to local tire shop and they pulled of my rim locks free of charge. Please don't steal my rims. Those things are not going back on.

Otherwise all is good.
And Thanks

adam c

iTrader: (2)

Ray,

It's possible that the problem with my FD brakes is as you have described. The brakes on the Accord were so badly warped that it is not possible to be as you have described. The warpage was definitely what was coming thru the pedal. I had a thorough discussion about it with my brake mechanic.

GTRay

the only way for this to occur is for the rotor to be warped beyond the point where the caliper slide can compensate. this is a very easily confused subject even for experienced brake technicians. the warp would have to be so significant that you could see it with your bare eyes and the rotor not moving - that is EXTREME. I concede that it is possible for this to be the case but it's HIGHLY unlikely and would require a such a dramatic lapse in judgement by a brake tech to allow the brakes to leave the shop in the first place that he should invariably lose his job as a result of it.

did the term "variable thickness EVER come up in your conversations with your brake tech? does your brake tech know what bariable thickness is? is your brake tech certified?

Ray

DamonB

I have several issues with this. Issue #1 is that even a sliding caliper is going to vibrate like hell if the rotor were distorted or non-uniform in any manner and you will certainly feel it. Issue #2 is that since the pad linings cover a good portion of the rotor when the distorted (warped, varied thickness, whatever) area of the rotor passes between the pads they will in fact be pushed apart and then relax after the "bad" portion passes and this will be felt as a pulse in the pedal along with vibration in the car.

Issue #3 is that the front calipers on all FC's and FD's (and every other caliper I know of with opposing pistons) do not slide as they are solidly mounted in place to the spindle. Only the single piston rears are on sliders...

Can't feel a warped rotor? Bologna.

As for machining rotors off the car that is a non issue and I would insist off the car is the preferred way unless the machinist is an idiot. If the machinist were an idiot then I would insist that no matter how he does it he will screw it up. The brake rotor registers to the spindle by its inner face around the bolt circle and so as long as the rotor is mounted from here and the cutting head is true to that reference plane your rotor will be cut just fine.

If you choose to turn the rotor on the car (I've never heard of that. Would like to see it.) You are now merely driving the spindle somehow and your cutting head is not referenced to the inner face of the rotor. This leads to the possibility of runout since the cutter is not registered to the same surface the rotor will be registered on the car. There's no way to eliminate that without actually clamping the rotor to the machine and driving it in the exact way the spindle does.

adam c

iTrader: (2)

First of all, the brakes on my Honda didn't leave his shop that way. They arrived that way. They left with new rotors because the old ones were so badly WARPED that they could not be machined.

Secondly, I have issues with your insinuation that my brake tech doesn't know his job. He has at least 20 years more experience working on brakes than you have (since you are only 23 years old), and has earned my trust by working on many cars for me over the years, including my race car. He is a respected mechanic in my community, and frequently does brake work on the local city police cars. HE knows what he is doing.