Rotors Re Surfaced Twice in 20k Miles?

My rear rotors were pulsing under braking at only 20k miles. I assumed they were warped. They were not but the pads were almost totally gone. The rotors were only out .002" which is well within the factory spec and the industry standard of .005" but I beleive they were the cause of the shimmy/pulsing feel when braking. I had a auto parts skim cut only .010-.015" off of the rotors and the shimmy/pulsing feel when braking was gone. I did replace the rear pads when the rotors were cut but I don't think the pads were the issue. I don't see how a worn pad can cause the pulsing problem but I know a warped rotor can or an uneven surface profile could cause the pulsing.

I have just over 60K miles on my 2009 FX35. The shimmy/pulsing feel when braking returned somewhere around 45-50K miles with plenty of rear pad remaining. I check the rear rotors a few months ago and they were warped no more than .002" , same as before, but they are producing the shimmy/pulsing feel when braking. It is my opnion the OEM rotor material is not what it needs to be to stave off this problem. IMHO the problem is a surface hardnesss change across it's surface due to wear. The rotors are not warping but over time the pulsating comes back.
 
There is a legal minimum thickness. Whatever that is, the shop cannot exceed it.

I once owned a brand new Jeep Cherokee Laredo 4x4. At 6k miles the rotors needed to be turned because they had warped. However, they were already at their minimum thickness from the factory. The mechanic explained to me that these rotors were a composite iron and aluminum and that's what was causing the warping under heat. That cost me $800 for new rotors all around.

Then 6k miles later the rotors were warped again. I traded in the vehicle at that time.
 
Thanks guys for the replies! So far I havent had anymore problems with the brakes or steering but I only have put a couple hundred miles on it since I got it.
 
Here are my notes from my service records I keep on my 2009 FX35. I do all work I can do myself. Been working on cars and other rotating equipment for over 40 years. I'm a machinary millright. IMHO......The FX brakes, while very strong, have a poor service history due to reoccuring pulsating issues both on the front and rear brakes, but mainly on the rears and long before the fronts begin to show this same problem. This is because Infiniti over works the rear brakes IMHO. While I like the system design where it applies quite a bit of initial pressure to the rear before activating the fronts, thier design puts the rears through much more operational service than most cars designs. In addition, the Anti-Skid feature of our rear brake system adds addtional work load and wear to the rears. That's why we're having problems and why the rear pads wear out so fast relitive to the fronts compared to any other conventional car brakes system design. Pulsating brakes complants have been documented many times on this and other FX forums. Bottom line is this, brake pulsing on the FX will continue even after the rotors are resurfaced and in a relatively short period of time of doing so. This IS NOT because the rotors are too thin or due to over tightening lug nuts. Overtighting lugs can cause rotor warp if the area underneth the rotor is unsupported by the wheel axle hub, but this IS NOT the case on the FX. Pulsation reoccurs for me at only about 11,000 miles and only from the rears. In my case on my car..........Rotor warp on the FX is NOT the cause of pulsing brakes. It is inferior rotor material which allows surface imperfections to form over time from operational use (service miles driven). In normal disc brake systems, a warped rotor of more than .010-.020" CAN CAUSE and is the minimum warp threshold of when pulsations can begin to be felt. This can occur on any car but this is not the issue on my FX and with many others as proof by the forum postings. Rotor warp is not the most common cause of pulsation brakes on the FX..........inferior rotor material is.




1-17-12 39774 Rear Brake Pad Replacement
Pads purchased from infinitipartsusa.com Front and Rear pads $ 152.40
PepBoys machined both rear rotors. Total $ 30.39
I replaced rear pads with OEM pads #D4M60-EG50C and turned rotors at PepBoys. The OEM pad thickness was not measured before installation. I wish I had done that. It was my intention to do so but I forgot to measure them prior to installation. The pads had approximately 1-2mm material remaining when they were replaced. The rear pads are known to wear much faster than the front on the FX35 so this is not unusual pad wear. Rotor warp was only .002” on left and .004” on right which is within spec but something could be felt as “pulsing” when the brakes were applied. The “pulsing” may be due more to hard spots in the rotor more than actual warping. Pulsing has stopped since the brake work has been done. Rotor thickness after turning was .609” on left side and .613”on right side. They were not measured prior to turning. OEM new rotor thickness is believed to be .630” (16mm?). Minimum spec thickness is .551” (14mm).

1-28-12 40020 Front Brake Pad Inspection
Only the left front wheel was removed for inspection. The L.F. front pads were inspected for wear but not removed from the caliper. They have approximately 6mm of material remaining which is more than half of the original pad thickness. The OEM pads measure 10.6mm thick. That equals 56% of the pad remaining. The OEM pads are part # D1060-EJ20A and I have already purchased these (see 1-17-12 notes) and they remain in my stock awaiting installation when the original pads wear out or the rotors warp to a point they need to be turned. The original pads should last to approximately 62k miles at the current wear rate. The rear pads are known to wear much faster than the front on the FX35 so this is not unusual pad wear. The rotor was checked for run out and it measured only .001” run out.
I attempted to install the Doran #12706 size M10x1.0x 31.4mm long (Speed Bleeder # SB1010S ) on the front calipers but these are too short in the thread length. I need Speed Bleeder # SB1010 or Doran #12709 size M10x1.0x 34.4mm long, which equals the OEM length. The left front caliper fluid was flushed until clear with Valvoline synthetic DOT 3&4 fluid. I will purchase the correct Speed Bleeders and install at a later date.

2-27-13 50911 Front Brake Pad Inspection
Both front wheels were removed for inspection. The right front pads were inspected for wear and removed from the caliper. The right front outer pads (on the non-piston side of the caliper) have approximately 6.3mm of material remaining which is still quite a bit. The piston side pads measured 4.6mm. The left front pads were inspected but not removed or measured. They have approximately the same remaining pad as the right side. New OEM pads measure 10.6mm thick. The OEM pads are part # D1060-EJ20A and I have already purchased these and they remain in my stock awaiting installation when the original pads wear out or the rotors warp to a point they need to be turned. The original pads should last to approximately 62k miles at the current wear rate. The rear pads are known to wear much faster than the front on the FX35 so this is not unusual pad wear for the FX35 but the rear pad wear is accelerated wear if compared to most disc brake powered cars. The rotors were not checked for run out but there is a slight oscillating bump feel (warped rotor?) when the brakes are applied. It is unclear which wheel(s) are responsible.

5-5-13 54545 Brake Comments
The brakes are generating a much more pronounced oscillating/pulsing feel (warped rotors or hard spots?) since the 2-27-13 review. It is unclear at this time which wheel(s) are responsible. It’s time to inspect the brakes and I suspect the rear rotors are warped or hard spots have developed again that is generating the pulsations.

11-16-13 61887 Rear Brake Pad Inspection and Rotors Turned
BrakeCheck machined both rear rotors. $ 52.71
I pulled the rear wheels to inspect the pad thickness and determine why the brakes are pulsing again only after 11,137 miles since the 2-27-13 front brake inspection, which is when the pulsing was first noticed after the rear pad replacement on 1-17-12 . Today the pads were not replaced as they still have quite a bit of pad remaining and are wearing evenly relative to the backing plate surface. The pads have approximately 5mm material remaining on the Left Rear and 4.5mm remaining on the Right Rear. These pads have 22113 miles on them since their 1-17-12 install date. The rear pads are known to wear much faster than the front on the FX35 so this amount of wear for the miles accumulated is not unusual pad wear.

Upon disassembly, rotor warp was measured as only .002” on left and .004” on right which is well within spec.. Curiously the rotors are warped exactly the same amount as they were as noted on the 1-17-12 pad install date. Even though I can feel pulsing as the brakes are applied, I don’t believe this slight amount of warpage is the cause because the rotor warpage is within book spec. and pulsing doesn’t generally occur with this little amount of warpage in most disc brake systems. The “pulsing” may be due more to hard spots developing on the surface of the rotor due to operational wear or inferior rotor material more than actual warping.

During test drive after reassembly, the pulsing has been eliminated by the machining of the rotors as was the case on 1-17-12 by turning the rotors. The pads were changed as well at that time but I don’t feel that was a contributing source for the reduction of pulsing under braking. I believe the OEM rotor material is inferior and cannot hold up well for very many miles after the rotors are machined before pulsing creeps back in at approximately 11,137 miles as noted above.

Rotor thickness today prior to turning was .606” on Left Rear and .610”on Right Rear. The rotors have only worn down .003” due to normal abrasion wear since they were installed after machining on 1-17-12. Rotor thickness on that day after turning was .609” on Left Rear and .613”on Right Rear so they are wearing evenly on both sides of the car. OEM new thickness is believed to be .630” (16mm) but has not been confirmed. Minimum OEM spec thickness is .551” (14mm) as stamped on the each rotor. Today after turning, the rotor thickness before installation is .6000” on Left Rear and .613”on Right Rear. I had a specific discussion with the BrakeCheck technician prior to turning about removing only what would be needed to get a good surface profile. He did a great job of removing the least amount of rotor material to obtain a flat consistent surface.

He only removed a total of .006” on the Left Rear and .005” on the Right Rear. I think that proves the fact that the reoccurring pulsations that the FX35 experiences are a result of surface abnormalities due to normal operational wear of inferior rotor material, rather than a warping condition. Prior to machining the rotors, slight raised imperfections could be felt on the rotor surface as a random pattern across the entire surface. It is unclear if these raised areas are a result of inferior rotor material as a base material precipitating out of the substrate or a random buildup of OEM pad material over time. Under a 10 power loop, they appear to be actual in and part of the substrate of the rotor material which supports my claim of inferior base metal material. Without destructive testing of the rotor to determine the actual cause, I cannot actually determine why the raised areas are occurring but this appears to be the cause of the reoccurring pulsing problems plaguing the FX35.
 
Well documented and My opinion.
I think the warped rotors are caused from heat and that in turn forms hard spots on the rotors. When you only machine a total of .005-.006" from each rotor then the hard spots will not be removed and the warped rotors will come back quickly. The quality of the material in the rotors is inferior.
 
GEE50FX said:
Well documented and My opinion.
I think the warped rotors are caused from heat and that in turn forms hard spots on the rotors. When you only machine a total of .005-.006" from each rotor then the hard spots will not be removed and the warped rotors will come back quickly. The quality of the material in the rotors is inferior.
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A rotor can warp if it gets hot enough from braking use to releive the internal stresses within the steel. All metals have internal stress as a result of the manufacturing process. This causes the rotor to change it's physical shape (warp) enough (although only thousands of an inch) to cause the pusling brake issue. Cryrogenically treated rotors don't suffer from this issue because they are stress relieved by vertue of that process. This type of stress relieving is used in many manufacturing processes such a rifle barrels. When I finally replace my FX rotors, and I know I will sooner than later, they will definitly be Cryrogenically treated rotors from a quality manufacturer.

While I'm not a metalurgy major, I have seen this same sort of problem that plauges the FX rotors with other machinary in the rotating equipment industry. The surface imperfections (hard spots) I spoke of previously are actually rising out of the rotor surface as a result of the softer surrounding material wearing away from around the hard spot. When enough material gets worn away, you have a protruding irregular hard spot that is above the rotor surface. The irregular formations of these high hard spots across the rotor surface are the source of the pulsing brakes. While machining the rotors will restore a flat surface and produce smooth non-pulsing brake action for a short period of time, the problem will eventually return because these flaws in the steel are throughout the part.
 
Anybody (or after market OEM) try annealing the cast rotors before turning them true? This would provide a more homogeneous material matrix and should soften up the "hard" spots on the surface of the rotor? In the day we always annealed all cast iron parts prior to finish machining (v belt pullies, diesel engine flywheels, water pump impellors, etc.) as well as welded steel assemblies such as stub shafts ( round steel shaft welded into a large disc allowing a shaft drive from a small engine flywheel, etc.)
 
This sounds like the exact same problem the first gen had when it was released with single piston front calipers until they changed that sometime in 2005/2006 to two piston front calipers. At the same time the front rotors increased in size and I believe this fixed the issue. But now we see this happening in the 2nd gen and my only thought is that the stock rotors are too small for the FX and that's the key cause for warped rotors. Fact is the more leverage your brakes have over the weight of the car, the less you'll have issues like this. If you have brakes that pass the "standard" then our type of driving even in traffic on hot days is going to warp rotors without a doubt.

To correct this issue, I would not bother with the stock rotors but goto something like brembo but I'm sure there's members on here who have far more experience in the brakes department so I'll let them chime in. I myself have warped rotors on the front end and they were perfect until I had to brake hard because someone cut me off...that shouldn't be the price you pay in a 3 second hard braking situation.
 
Don't our rear rotors engage first to mitigate brake dive while stopping? Since the rears are so small, that could lead to the warping if there were already an issue with the rotors.
 
Yes that's true, the rear engages first though only for a short while until the fronts engage right after and it takes over most of the braking. Ive never heard of rears warping...like ever! On my first gen I still had my factory rotors, only changed pads and they never warped.

The only other thing that will warp rotors for sure is water...so if you go to wash your car at a drive through or even at your house without letting the brakes cool, guess what.. warped rotors :) I know because I went through it. Plus if you over tighten your lug nuts, you don't give the rotor much space to expand hence it will expand elsewhere and warp.

But brakes are a cash cow for the dealer, they warp, you pay to get them back to normal and its not cheap. Quality rotors don't warp that easily and they use a dense iron composition so they can handle more heat and harder to warp.

shadow191 said:
Don't our rear rotors engage first to mitigate brake dive while stopping? Since the rears are so small, that could lead to the warping if there were already an issue with the rotors.
Click to expand...
 
True, I never had an issue w/ my rear rotors (swapped at 50K just to go drilled/slotted). Just throwing ideas out there since the rears were turned twice. Could also be incompent/lazy dealer. First tech turned the rear rotors on a hunch and then the owner came back for the same issue so the 2nd tech just assumed that was the problem again.
 
There has been a lot of discussion by me and others here about rotor warp. I just want to remind the group................... My rear rotors WERE NOT warped enough to cause pulsing brakes because they were only a couple thousands out. Once the irregular rotor surface was restored to an consistant even finish by vertue of machining, the pulsing stopped, even with old used pads reinstalled on the rears.
I'm would expect some owners are truely having warping issues on thier cars, but for me durring the two times pulsing issues occured on my car, warping WAS NOT the cause of brake pulsing. For anyone experiencing pulsing brakes, if you take your car into someone to repair it, have them first dial indicate the rotors to see how warped the rotors are.........if any at all. I expect a lot of the pulsing issues we are hearing about is due more to an unever surface wear (as was the case for me) rather than actual warping.

Unfortunatly most brake techs I've talked too really don't know how to machine a rotor correctly. :eek.:
Don't let the brake tech remove all of the remaining life out of your rotors by over machining them! Most of them always take too much material off the rotor when machining and that's doing you a dis-service. Have them mic the rotor before and after machining and tell them you expect them to only remove AS LITTLE AS NESSARRY to obtain a flat surface. Doing this will allow you to keep plenty of remaining rotor material for longer service life and this will help keep the brake pedal from falling too low to the floor when braking.
 
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1-28-14 Update

I inspected my front brake pads yesterday and there is a little over 3mm remaining material with 65K miles on these OEM original pads.
At the current wear rate.............I should be able to go approximatley 75K miles before I need to change them, but I will change them at 70K miles to make sure I don't plow into the rotors. FYI..............These pads have their pad material glued to the backing plates so there are no worries about pad rivets digging into the rotors. These are the original pads on the fronts and I've never machined the rotors yet. They are not warped at all. The only pulsing brake issues I've had with this car is from the rear brakes. By the time I need to replace the front pads, the rears will be very close to being worn out again. My brakes are wearing the rears out almost twice as fast as the fronts. Most of my driving is normal city of Houston stop and go driving.
 
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ive ran 80k miles on oe rear rotors and 3 or 4 pad changes and im still happy with them.
 
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