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Brake rotor runout spec?

JoshHefnerX

JoshHefnerX

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Just swapped out axles on my truck, Getting some bounce and low speed, one of the things I found was that one of the rotors up front (brand new) has some runout in it. You can hear it grab as you spin the tire. Measured .006 runout. May have happened when I pressed the lugs in... (may just be cheap rotors, no idea...)

Cant seem to find a good spec on this, seen anything from .0015 to .005.

D60 axle w/ jb8 brakes.

Anyone have a spec on what's allowable runout?
 
JoshHefnerX said:
Just swapped out axles on my truck, Getting some bounce and low speed, one of the things I found was that one of the rotors up front (brand new) has some runout in it. You can hear it grab as you spin the tire. Measured .006 runout. May have happened when I pressed the lugs in... (may just be cheap rotors, no idea...)

Cant seem to find a good spec on this, seen anything from .0015 to .005.

D60 axle w/ jb8 brakes.

Anyone have a spec on what's allowable runout?
Click to expand...

I wouldn't worry about it. Theyll wear in. In all reality 6 thou is probably pretty decent. The rotor is probably flatter than that but the mounting surface is pretty rough.

Cheap rotors are usually ok but they often wear in a weird fashon or warp early on. I put some cheapies on my tundra and 10000 miles later I have the shakes.
 
Not sure I want to leave it, I'm tracking down several bounces/oscillations and noises, and one of them sounds kinda like a brake rotor... I swapped out much of the drivetrain, so I'm trying to get this as 'clean' as I can to narrow down where my problems may lie...

Tires, wheels, axles, entire brake system rear driveshaft (no front at this point) and sye on the t-case...
 
Good link! Looks like .004 runout. So I have to see if I can exchange that or if it will have to be turned down...
 
I would just have them turned on the hubs. You will go through a lot of work trying to get less runout than that by swapping rotors (and rotating it to different positions on the hub.

I just went through this a couple times on mine, in the end, having the lugs torqued on the studs WHILE being turned made the difference.
 
black dawg said:
I just went through this a couple times on mine, in the end, having the lugs torqued on the studs WHILE being turned made the difference.
Click to expand...

That's a good one. Just talked to parts place they were willing to turn it for free. maybe I'll put a couple of washers on there and torque them before taking it in.
 
Yeah, I would try taking the rotor off and putting it back on in different positions first. If the runout gets worse or better, then some of the runout is in the hub its self.
I have seen hubs warped that much.
If that is the problem, you need to find someone to turn it on the hub like black dawg said. That way you would a rotor that is actually not flat, but that ran flat because of the hub.
Which is what you ultimately want, a rotor that runs true. A perfectly flat rotor on a warped hub will act warped.
 
Fordum said:
Yeah, I would try taking the rotor off and putting it back on in different positions first. If the runout gets worse or better, then some of the runout is in the hub its self.
I have seen hubs warped that much.
If that is the problem, you need to find someone to turn it on the hub like black dawg said. That way you would a rotor that is actually not flat, but that ran flat because of the hub.
Which is what you ultimately want, a rotor that runs true. A perfectly flat rotor on a warped hub will act warped.
Click to expand...

This guy nailed it. I'd turn the hub long before the rotor. Atleast chuck it up in a lathe and put an indicator on it.
 
yes, nothing wrong with truing up a hub...it can be surprising how crooked they can be. My point was that very few new rotors are flat, add this to a maybe crooked hub...... just turn the works together like it will be installed on the truck.
 
I was amazed when I threw my dana 60 dually hubs on a lathe. Probably out .08" in concentricity and out easily .005" on mount surface.
 
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