Sean73 Posted August 8, 2005 Share Posted August 8, 2005 I am trying to finish up my rear disc conversion. My dial gauge shows a .015" runout on the left and right rotors. The rotors are new Brembos. The runout seems to be coming from the stub axle flange. Perhaps the rear wheel bearings aren't seated perfectly square ( I recently changed these to 280Z stub axles)? They are torqued down to 220 ft-lb, so it seems everything should be seated ok. Is it worth pulling apart the stub axle, or should I just have the rotors turned on the car and be done with it? .015" seems like a lot, since the FSM specification is .003. Any advice greatly appreciated. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 8, 2005 Share Posted August 8, 2005 0.015" is a lot. Enough to notice. Are your axle flanges flat? Does the runout peak at one spot, and the lowest point 180 degrees around? That would be an indication your stubs or flanges aren't flat, or aren't in the bearings right. Otherwise it's probably your rotors. I bought a set of Toyota rotors (OEM, off brand) that were out more than that. I had to have them turned (later realizing I should have returned them instead). Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 8, 2005 Share Posted August 8, 2005 I had this problem with a front hub and was considering turning the hub. Ended up just buying another set of hubs. I suppose you'd have to remove the stub axle and the lugs to turn it though, and by that point the machine work would probably cost more than another stub axle... Interesting idea about turning the rotor on the car, but that doesn't take care of the fact that the wheel isn't going to turn straight. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted August 8, 2005 Share Posted August 8, 2005 How much material can you turn off the rotor and still be safe? If the run out is due to a crooked axle, then wouldn't you have to turn 15 thou off of both sides? Seems like it would be better to shim the rotor. But then the center of the wheel would still be spinning about a cone. Wouldn't the tire then oscillate up and down as it spins? Maybe too small to notice. Should be relatively straight forward to calculate if one knew how far from the center of the axle axis (the radius) you measured the run out. Quote Link to comment Share on other sites More sharing options...
jt1 Posted August 8, 2005 Share Posted August 8, 2005 Mark the point of highest runout on the rotor and stub. Then remove the rotor, rotate it 180 deg, and check it again. This should show whether the runout is in the rotor or the stub axle. You might also try torqueing the lug nuts in stages. Sometimes pulling them down at once will introduce runout in an otherwise straight setup. Putting a wheel on can also make a difference, since it spreads out the clamping force of the lugnuts. If you can get to the rotor to check the runout from the backside, check it with a wheel on. John Quote Link to comment Share on other sites More sharing options...
Sean73 Posted August 8, 2005 Author Share Posted August 8, 2005 On one side, the runout is definitely coming from the stub axle. I get .005 runout on the stub axle flange. Some simple trig indicates this translates into .013 runout at the end of the rotor. I need to check the runout at the inner companion flange and see if indeed the entire stub axle is wobbling. If so, I guess it needs to come out (what a bitch). Maybe I will try retorquing the stub axle nut first. Also, I'll try taking the measurment with the wheel mounted and see if that makes a difference. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 8, 2005 Share Posted August 8, 2005 If you can spin it and it doesn't slide in or out, then the flange is bent. It would take something pretty severe to bend the shaft where it is supported by the wheel bearings (not to mention it would quickly kill the wheel bearings. The flange is exposed to all kinds of stuff like parallel parking and backing into the curb, etc. Quote Link to comment Share on other sites More sharing options...
zgeezer Posted August 9, 2005 Share Posted August 9, 2005 I had similar problem with rear disk conversion. Pulled both stub axles, cleaned [really cleaned] the mounting side of the stub axle flange and then retorqued the bearings to 225#. Problem solved. g Quote Link to comment Share on other sites More sharing options...
Phantom Posted August 9, 2005 Share Posted August 9, 2005 Nissan dealerships have a machine that will turn the rotors on the car. I had run-out on my front disk conversion. I took it to my local Nissa dealership, they turned the rotors and now more problem. Quote Link to comment Share on other sites More sharing options...
Clifton Posted August 10, 2005 Share Posted August 10, 2005 .015" is alot. If the stub is out even .004" it would throw the outer edge of the rotor off 4 times that. Apparently bent, or run out in stub axles are fairly common. I know Dave at AZC turns every stub before reassembling his strut assemblies. I didn't do mine and I do have a little run out on the rear. I didn't check if it was the rotor on stub, it wasn't too bad. Quote Link to comment Share on other sites More sharing options...
Sean73 Posted August 10, 2005 Author Share Posted August 10, 2005 Update - After taking a bunch of measurements, It turns out to be about .007 runout on the stub flange. If I measure just the inner circle of the flange, I get about .002. So, the distortion gets worse further out from the center. It would seem this thing is bent. I had thought of turning it on a lathe, but I wonder if the stub axle is just going to break on me later anyway. Now I am seriously considering the billet stub axles, but thats going to set me back $$$ Quote Link to comment Share on other sites More sharing options...
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