Rotor wobbles, how to fix?

[jedi_sol]

Ever since i bought the Q, whenever i apply the breaks, i hear this faint grinding or rapid knocking noise coming from both front wheels along with a slight vibration on the steering wheel and pedal. It noise becomes even more pronounced if i am doing the automatic creep with the brakes lightly applied.

Upon closer inspection of the rotor, i noticed a lot of resistance on about 3/4 rotation when i turn the rotor and the last 1/4 rotates freely. On the 1/4 section where it rotates freely, i notice that i can jiggle the entire rotor very slightly. And when i jiggle it, it makes the same grinding noise as when i apply the brakes. On the 3/4 section where there is resitance, i cannot jiggle the rotor at all.

Any ideas on how to fix this? might be a warped rotor? get them Resurfaced? or get new ones?

thanx,james

[Q45tech]

Important to spell brakes correctly because you are forever in Google

The decision depends on the rotor thickness, how much above minimum.The reason there is a minimum is that with wornout pads, there is a point where the brake caloper piston seals will over extend and fail [leak].Also the rotor mass determines the rotor and pad temperature: About half the mass is in the wear area, so the minimum thickness reduces the rotor weight by ~10%, so the pads get hotter by 10%.

For perfection you must measure [and correct] the flatness of the wheel hub flange as a perfect rotor on a warped/corroded/rusted flange will magnify the flange warp by 2 x [5 vs 11]. Rarely done because it takes too much time and owners don't ask and won't pay.

Time to future warp depends, but the closer to perfect you start with the longer it takes.

Another thing to remember is the thickness of the pad [9mm=0.35"] is all the insulation between the hot rotor and the piston and thus the brake fluid..............Why one would always change pads EARLY with at least 3mm remaining.

Don't assume that a full brake refurbishment at a dealer [much less some brake shop] returns the brakes to as NEW! Too many shortcuts are used to keep the prices down.

The dealer pays $35- $40 per set of pads vs some breako outfits $8-$9.

[maxnix]

Important to spell brakes correctly because you are forever in Google

.....

The dealer pays $35- $40 per set of pads vs some breako outfits $8-$9.

I think Dennis means "Brake-o"

In any case, check your ball joint and bearings also. Sometimes the best cure to rotors wering rapidly out of specification is found in replacing the out of specification hub and bearing.

[elwesso]

Dennis, what do you suggest be done to the hubs to make rotors better... Can the hubs re redone to ensure they dotn have runout?

[Q45tech]

Measuring the hubs is tough until you polish them to remove the rust.

You can grind them down in .00005" increments. Tough to decide the high spot or if bearings are wobbley.

Important to determine whether the hubs or the brand new rotor is at fault.Since you are trying for 0.001" at the rotor outer edge.

Measure first to decide what's necessary. If the runout is 0.003 or 0.006 use:http://www.brakealign.com/pages/product ... fs...e.pdf

BA402xx Nisssan part # for Q, G35, I30, M35-45 [xx=03=0.003"].

Brand new hubs are true until the first rotor warp, that cannot be said if the hub or bearings are replaced...........why I say refurbished brakes are not as brand new............actually things [hubs] stay in spec for the first 60k or so.

Luckily the extra volume of lines and ABS system isolates the brake pedal so mild warping is damped and it has to get bad >0.003 before an experienced driver feels it . I have trued rotors that were warped 10 times more than that before some [totally numb] drivers noticed. Made my partial jump out of my mouth on each application.

[jedi_sol]

Thanx for the quick replies guys. A few more questions.

1)Does this problem have to be dealt with immediately? Or can it wait? i still have the plenum job to do...

2)This might be relevent, but it only makes the sounds while going forwards, NOT in reverse. Any thoughts on this?

James

[maxnix]

Thanx for the quick replies guys. A few more questions.

1)Does this problem have to be dealt with immediately? Or can it wait? i still have the plenum job to do...

2)This might be relevent, but it only makes the sounds while going forwards, NOT in reverse. Any thoughts on this?

James

1.) Depends on your tolerance factor and how much more you want to eventually replace as the increased wear of other suspension components takes its economic toll.

2.) No. It's still has a problem regardless of direction of travel.

[elwesso]

1.) Depends on your tolerance factor and how much more you want to eventually replace as the increased wear of other suspension components takes its economic toll.

2.) No. It's still has a problem regardless of direction of travel.

agreed..... However, id personally rather see you do the plenum before fixing the rotors..