Anybody know where the silver shims in this picture go? How are they supposed to be oriented? I'm guessing they're supposed to be on the piston side of the rotors. But which is for the right side and which is for the left? Does the cut out part of the ship go up and toward the back of the car or down toward the front?

http://i237.photobucket.com/albums/f...o/CIMG2181.jpg

 

Nevermind the last question. I see it in a pic in the manual. Thanks for viewing, though. Oh, and in case someone else is wondering, the pieces I was asking about are inner brake shim covers and the gaps are toward the top in the picture.

 

Sorry for reviving such a relatively old post, but I would like to contribute from my own experience.

- Instead of turning rotors when you get a vibration from rotor runout, indexing the rotors to a position of minimal runout can temporarily reduce or eliminate the brake vibration for another thousands of miles before you turn them. Let's say, my existing rotors now have 10,000 miles on them and runout has gotten to 0.007", causing a very slight vibration. I would index them and achieve back to 0.0015". Yes, I REALLY did that, from ~0.007" to 0.0015" on my G35 on BOTH front rotors. I saved $40 on resurfacing and extracted another 10,000 miles out of them before they had to be resurfaced. This prolonged the life of my rotors because I did not shave any metal out of it, I restored trueness by simiply rotating them!!!

- Rotors that are not perfectly true can work to your advantage if your hubs have a slight runout. If your hubs have a little bit of runout from age and wear, a tiny amount of rotor runout will allow you to index them and balance out the runout on both items.

- The quality of the lathe can greatly determine your rotor runout. Many people incorrectly suspect that their hubs or rotors are junk because the shop that resurface the rotors have done such a poor job on them. Dirty or rusted mounting points, or even a piece of hair could have a profound effect on the trueness of the rotors!!! The diameter of a hair is approximately 0.004". If that is stuck on your rotor, then you MAY have that kind of runout.

- Clean not only the hubs and the back side of the rotors before mounting, but also the mounting surface of your wheels!!! You will notice smoother braking and smoother ride by cleaning the backside of the wheels during a brake job.

- When indexing rotors, tightening a couple of lug nuts or torquing all five to specification made no difference whatsoever. I did many experiments and found that there was no observable difference between torquing all five lugs or just tightening two. Even if there was a difference, it wasn't detectable by the typical dial gauge used for rotor indexing. Furthermore, the FSM only instructs to use two or more lugs when measuring rotor runout. Statistically speaking, whether you use all five lugs or just two, that woudn't change which position you use: you only have five positions to choose from (or four if you have 4 lug hubs).

- The FSM suggests a runout of 0.0014" for the G35 (0.0028" for most other Nissans such as the M45, Maxima, etc). This specification is for installing new rotors. As the rotors go through regular usage, they would NOT remain at 0.0014". However, you want to maintain runout to a minimum as you install new rotors, so that you will have more headroom before you experience vibrations from runout. As you use your brakes, runout develops from normal use. Typically, 0.005" of runout is still tolerable for used rotors and can still be used without having any other work performed as long as you are not getting vibration. If you measure excessive runout from your used rotors after 10,000 miles, don't panic, that is not an indication of underlying problems. It's just regular wear. Don't turn or change your rotors just yet, try indexing them to gain more life from them before turning or replacing your rotors. Save your time and money.

- Excessive runout doesn't always cause vibration. Sometimes excessive runout is experienced through uneven pad wear. On a S550 I worked on, the rotors had about 0.01" of runout, but no brake vibration whatsoever. Don't you wish all cars are like that?

- Some skeptics may argue that indexing used rotors is not a good practice because the FSM doesn't mention it anywhere. The FSM would NEVER advise technicians to index rotors to restore trueness. They advise the technician to turn them. This is because machine work translates to revenue for the dealer. Indexing rotors does not generate as much revenue. Many people, including myself, have saved a considerable amount of money just from indexing rotors at home.

Finally, indexing both new and used rotors depends on a lot of variables and requires a lot of luck. You can have brand new hubs and rotors and still not achieve rotor trueness. This is why manufacturers have on-car lathes to correct such phenomenon in the assembly lines.

 

Thanks for posting that, Tyau. I always thought it odd that the instructions in the braking manual only have two lugs on for measuring runout. I put all five on when I measured just to be sure. But when and if my braking gets shaky again, I will definitely try the indexing first. Hopefully, though, they don't. I have probably 14K or 15K miles on my front rotors and they're still fairly smooth. I was convinced that the cheap Chinese-made rotors I had from NAPA were just impossible to true up. I had them turned like twice. Once at Pep Boys and then I went to a Nissan dealer and they were still vibrating. That's when I bought OEM rotors from everythingg35.com or whatever they're calling themselves now and things have been fine since.

 

When you keep runout to a minimal when installing new rotors, they would last longer before needing another indexing or resurfacing.

Sometimes a perfectly true rotor can still have vibrations, caused by hot spots and disc thickness variations, as pad deposits stick on one spot of the rotor, causing uneven grab as the material heats up. Higher quality rotors are slightly better at preventing this.

Keep in mind that when you are Measuring runout, you're only measuring the out side. The inside is not measured or indexed. So in essence, your rotors are only true to one side.

 

Actually, I measured on the inside and outside. The possible deposit of brake material onto the rotor is just what made me measure both sides just to check and see if the runout matched both sides. You know, if the high on one side matched the low on the other and vice versa. I actually found that it did, but I was still unsure if the rotors were just garbage or if the two shops I went to for machining were unable to get them flat or if the hubs were untrue. But like I said before, I just went ahead and got new rotors since I was getting pads anyway. And I think they were probably right at the minimum thickness. (Since I'd had them turned twice already, of course.)

 

You actually went the extra mile to measure the inside as well!!

Glad the new rotors are working fine for you. I am surprised that the FSM doesn't have a specification for hub runout. The FSM never instructs for the replacement of hubs when rotors are untrue. I wonder what the hub runout tolerance is.

I just reindex my front rotors on my G35. They were not vibrating, but one of the rotors was at 0.006" of runout. After reindexing the rotors back to 0.001 for both, the difference in smoothness is profound. And I wasn't even experiencing vibrations before.

 

Yeah I didn't mind going that extra mile considering that the vibration was buggin the heck out of me and none of the "professionals" could seem to eliminate it and were seemingly pretending it wasn't there or that I was "feeling things." So I went online and found a runout meter and measured myself every which-way I could find to measure.

I should probably check it now but I'm afraid because if I decide to do this indexing on mine, as things go for me, I'd get rough vibration again.

 

With about 15000 miles on your new rotors, it may be a good idea to index them to make sure you are getting the most life out of them before you resurface them, even if vibration isn't felt yet.

Rotor resurfacing can mess up rotors if done on rusty or contaminated equipment, or even having a thin layer of rust on the rotor hate itself. Some high end machine shops would clean out the rotors before resurfacing them, but others don't. So that may contribute to the vibration. I wouldn't be surprised that NAPA rotors are actually junk though.




Does anybody here stock up on brake rotor shims at home just in case???