Hey Daniel B.M. I,ve noticed that in the FSM for resurfacing rotors it states to do so on the car with on brake lathe. Although I,m sure it probably helps prevent runout but I,m wondering if doing so would be noticeably any better than taking the rotors in and having it done. If on the car method is better, can I rent the lathe to do so myself? FYI I do know that it will be necessary to check for runout and rotor thickness but if they are within spec, just curious if either way is better. Thanks in advance.

 

Despite the FSM recommendation, my local Nissan dealer resurfaces rotors off the car. I've heard ardent advocates for both methods, and don't have a personal preference. I'll judge the quality of the job by the result rather than the kind of machine which generated that result.

A perfectly flat rotor would still exhibit runout if mounted on a slightly bent hub. An on-the-car lathe would eliminate the rotor runout but you still have a slightly bent hub... and the wheel mounted on that hub will wobble as the car goes down the road. In this scenario, the on-the-car method just compensated for a problem but did not correct it.

 

Makes a lot of sense to me. Appreciate your input on this. While I,ve got you, when driving I hear what sounds like maybe a bad wheelbearing. While on a smooth surface the noise is consistent. Hit a bump as the car is on the way up (and before the car levels out) it quiets until the car is back to it,s normal travel range. In other words as it bounces it gets quiet,gets loud, gets quiet etc.etc. Could a bent hub or warped rotor also cause this. Thank you in advance!

 

A mysterious symptom. The wheel bearing would be my first guess. Try to gather more clues by jacking the front and spinning the wheels by hand. Listen for bad sounds. Grab the tire at the top (12 o'clock) and shake inward (toward the engine) and outward (toward yourself), listening for clunking sounds and the feel of looseness. Examine the CV joint boots for damage which could hint at trouble with the joint itself. I call this kind of investigation "looking for clues at the scene of the crime".

[Edited by Daniel B. Martin on 12-20-2000 at 09:01 PM]

 

Oh I HOPE you are wrong in talking about my CV joint being bad. Before I went on vacation, I noticed grease on my wheel. Bad boot. I had just replaced the inner/outer boots about 3 months prior. I obviously fouled(I,m being nice with my F words) it up when I installed the shaft. After the second boot it was then that I noticed the noise during our 1500 mile trip. It has not got any worse but it is not going away either. Don,t quite know how long the joint was exposed but I will say the rim was a !@#$%^&*()_+ to clean. If it is the joint (oh please no) how do I check it? And please give me an acceptable (cheap,easy,cheap) answer! TYIA

 

Though I'm sure I will be quoted something to the contrary out of the "Haynes Manual" I will offer my two cents on this.
Don't have your rotors turned on the car unless absolutely necessary. They make those machines for cars which have rotors that are difficult to remove, such as late '90's Accords. Unless the brake lathe the shop is using has the optional electric motor (which almost doubles the cost - a lot of shops don't spring for it) to spin the hub, the other way to do it is to put the car in gear and let the drivetrain spin the hub. You also have to stop the opposite side wheel from spinning to make sure all power is going to one side. It is very difficult to maintain a constant rate of speed which results in a lousy cut. That's very important. Trust me - nothing beats a good Ammco brake lathe with the proper cone and chuck adapters. Besides, why are you turning the rotors anyway? Do you have runout or deep grooves? It's not necessary you know. Also, they're so damned cheap now anyway that I would just replace them if I came up with a warped one. If it's warped now, it will warp again after you cut it.

 

I was not predicting a bad CV joint, just mentioning it as something which could make noise. However, the repair history which you now reveal is a cause for concern.


The usual test for a bad CV joint is to go to a quiet parking lot and drive the car slowly (3 mph) in tight clockwise circles, and then tight counterclockwise circles. Do this in a forward gear, and also in reverse. A bad joint will usually make distinct rhythmic clicking or snapping sounds. Snap, snap, snap!


If I were Santa Claus you would get one!

Seriously, you have to do more diagnosis to identify the source of the sound. It might be a wheel bearing, or a CV joint, or ??? Loose lug nuts?


[Edited by Daniel B. Martin on 12-21-2000 at 10:56 AM]